User Guide to the RAPID Measurements in the Cluster Active
Contents
1. esa m Date Project Cluster Active Archive User Guide to the RAPID Measurements in the Cluster Active Archive CAA prepared by Patrick W Daly and Elena A Kronberg Version 3 0 Cluster Active Archive User Guide RAPID CAA EST UG RAP 3 0 2011 05 01 Page 1 of 31 CAA EST UG RAP esa Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 2 of 31 Table of Contents Reference Documents 3 List of Acronyms 3 1 Introduction 4 2 Instrument Description 4 24 The IES Instrument s omo Ro eoo momo Ru UR beg Y GRON OR e oO de RU Ue EON 4 2 3 The IIMS Instrument 2 24 54 ox o EO mon ds 4 2 3 SpimnSectonzati on sce vxo eR Rn RR eR n RR a n ri 3 Instrument Operations 8 3 1 Telemetry modes ees ee 8 3 2 Operations on IES electrons les 8 3 3 Operations on IIMS ions 9 4 Measurement Calibration and Processing procedures 11 4l Electrons ood Rem ds RR ee Se Nur eU Web me d 11 A 11 4 3 Standardized Energy Channels 12 4 4 Phase Space Density Conversion 14 5 Key Science Measurements and Datasets 14 5 1 Particle Distribution lt lt s pes lees 14 2 27 AUKA utpote Eos ve VS opes Oe cdd e e Ere2. 0 86430 0 09930 0 86976 0 49232 0 03377 0 01970 0 10302 0 99448 Let us calculate the flow direction for detector 2 sector 3 both counting from 0 which from Eqn 8 gives us 50 and 78 75 and from Eqn 10 0 1494 07513 c 0 6428 We now apply Eqn 11 to get 0 49308 0 86430 0 09930 0 1494 0 6395 0 86976 0 49232 0 03377 0 7513 0 5216 0 01970 0 10302 0 99448 0 6428 0 5648 Cluster Active Archive User Guide RAPID esa Date Project Cluster Active Archive CAA EST UG RAP 3 0 2011 05 01 Page 31 of 31 The flow vector on the right is in GSE coordinates and corresponds to 05 55 61 and gse 39 20 the same values that are listed later in this record for this detector sector combination 11 13 14 15 TT 61 47 32 69 52 89 TA 72 94 09 70 30 32 34 35 98 TT 57 37 59 50 31 70 16 90 04 109 93 129 78 149 50 168 38 77 52 56 72 44 92 34 112 24 132 11 151 85 170 56 52 54 41 74 34 94 28 114 23 134 14 153 98 172 91 64 55 61 75 59 95 58 115 56 135 54 155 48 175 04 08 103 33 106 17 108 36 110 55 113 39 118 67 139 22 07 81 48 83 98 85 97 88 02 90 78 96 19 121 48 04 60 17 62 01 63 52 65 10 67 31 71 90 99 59 59 39 20 40 17 40 97 41 83 43 05 45 71 67 78 D 4 Things to Note The rotation matrices given in t
3. 100 171 Figure 11 Example of a CAA RAPID summary plot Panels 1 4 show from top to bottom differential fluxes of ESPCT HSPCT ISPCT He and ISPCT Panels 5 7 display several instrument settings Cluster Active Archive User Guide RAPID CAA EST UG RAP esa Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 21 of 31 Cal subset for ions for internal RAPID usage the data at CAA always have the value 2 Spectrum correction how the varying energy thresholds between detectors spacecraft and for electrons inte gration times are corrected to a uniform set of values The pedestal shift for electrons is also corrected with spectral shifting Possible values are for no correction 2 and 3 for power law fitting between two adjacent channels With 2 the pedestal shift is the spin average while for 3 it is done for each sector So far only 2 is used Background subtraction 0 for no subtraction 3 for removal of solar noise on SC3 Section 4 1 Caveat e In January 2009 an error was discovered in the ion geometry factors for 2006 and later As a result the 2006 ion flux products HSPCT ISPCT_He ISPCT CNO I3D H I3D CNO have been redeliv ered to CAA To distinguish the corrected datasets from the previous ones the dataset version number for ions now begins with 3 For other products and for ion data from 2005 and earlier the initial digit remains 2 for now 5
4. Page 13 of 31 CAA EST UG RAP QS a Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 14 of 31 4 4 Phase Space Density Conversion Conversion factors between differential flux and phase space density are listed in Appendix C 5 Key Science Measurements and Datasets 5 1 Particle Distribution Key science measurement for the RAPID instrument are particle distributions in the following units Raw Count Rate These are raw data in units of 1 s with no corrections calibrations suppressions whatsoever only the accumulation time is employed to convert from counts to rates This accumulation time is well defined but not trivial to determine hence it is included as a record varying parameter in every count rate dataset The original number of counts can thus be reconstructed if wanted The dataset names of the raw data products have an ending suffix _R see Appendix A for a complete list of datasets Number Flux Processed data in units of differential particle flux 1 cm sr s keV See ICD for more details Standard Deviation For both fluxes and raw count rates the standard deviation is also included in each record in the same format and array size as the data This is obtained from both the Poisson statistical error of the counts plus a factor for the data compression uncertainty the former normally dominates For measured zero flux the standard deviation is also set to zero although it should really
5. RAP SUMPLOT D in the 6th panel IIMS Modes A This information is also available in the Status product SETTINGS Section 5 3 3 3 20 Damage of the central ion head e The central ion head on all 4 spacecraft deteriorated within the first months of the mission most likely sunlight saturated the time of flight system The result is that ion distributions are not available within 30 of the ecliptic plane This is often referred to as the donut effect hole in the middle How this caveat affects the 3 D distribution see Figure 7 For the omni directional flux products the donut effect is taken into account Cluster Active Archive User Guide RAPID CAA EST UG RAP esa Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 10 of 31 Cluster RAPID 5 C3 5 amba 2001 09 28 02 30 00 07 00 00 Time resolution spin 3 Electrons 103 4 1 1 1 ET E me 104 PS o gt 10 103 2 2 mm s E a AutoSW 4 ON 50 1505 4 505 4 F 2 us F 5 8 Serial Parallel IFFT A 3 HV off HV ok ENA gt BM BM3 NM3 Bf a tf i i ee z 64 E gt 44 L 54 STA ST DEF L o L 0230 0300 0330 0400 0430 0500 0530 0600 0630 0700 Xose 2 63 3 19 3 63 3 90 3 96 3 78 3 35 2 74 1 99 1 18 Re Yos 0 98 0 36 0 28 0 90 1 47 1 95 2 31 2
6. gt di Under Range 30 keV CNO1 H1 He1 10 I T T T 1 25 2 50 5 00 10 00 Time of Flight ns 20 00 40 00 80 00 Figure 4 The RAPID ion classification system Every ion event occupies a point in the 256x256 energy TOF space which is divided into areas for different ion species and up to 8 energy channels For events of internal energy lt 30 keV no energy signal is produced In this underrange region species determination is done solely with TOF and the fact that the energy is below this threshold The opening angle for a single ion detector is also 60 but unlike for the electrons the subdivision into four 15 slots is done by determining the location of the start signal This of course has an efficiency associated with it The start and stop signals are used to measure the time of flight TOF over the 32 mm separation This time plus measured energy locate the event within the energy TOF space of Figure 4 which then determines the species and energy channel The number of events in each of the species channel bins in Figure 4 is read out and reset once per sector 1 16 spin Only the hydrogen helium and carbon nitrogen oxygen CNO data are delivered by RAPID as part of the regular products the silicon iron channels are also available but only in the direct events product see ICD 2 3 Spin Sectorization For both IIMS and IES the azimuthal distribution of particle fluxes is ob
7. sential that the RAPID Team process this initial data set into more usable format showing physical parameters in physical units and make them available to the scientific community The RAPID team delivers about 50 different data products per spacecraft for each day of observations This User s Guide explains how to exploit the CAA RAPID dataset how to select the right products for various applications as well as which problems might be encountered and what the user must watch out for It is intended to be concise and uncomplicated therefore only the main products will be discussed here A complete description of the RAPID CAA data products is given in the RAPID Interface Control Document RAP ICD and the data quality issues are described in the RAPID Calibration Report RAP CR e For emphasis important caveats are bulleted and placed inside a gray shaded box 2 Instrument Description The RAPID experiment is described in Wilken et al 1997 as well as in the Flight Operational Manual RAP FOM The first results are presented in Wilken et al 2001 The RAPID instrument uses two different and independent detector systems for the detection of nuclei and elec trons The Imaging Ion Mass Spectrometer IIMS and the Imaging Electron Spectrometer IES 2 The IES Instrument One of the three IES detector heads is shown in the left side of Figure 1 Each functions as a pin hole camera with 3 microstrip detectors to locate the incoming
8. 3 D electron product is available in nominal mode It is the same as the burst mode distribution but for energy channels 1 and 3 only For CAA this product is also provided in burst mode by simply extracting it from the existing burst mode distribution The array size is 2 16 9 for energy azimuthal direction polar direction e Dataset title Electron 3 D distribution standard L3DD Cluster Active Archive User Guide RAPID CAA EST UG RAP QS a Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 15 of 31 Burst mode There is one full 3 D electron distribution per spin with 9 polar directions 16 azimuthal sectors and 8 energy channels The polar directions 0 2 and 6 8 those closest to the spin axis Figure 2 really have only 8 azimuthal sectors per spin the CAA products artificially double this to simplify handling the data as a rectangular array of size 8 16 9 e Dataset title Electron 3 D distribution E3DD Nominal mode Counts are summed over the whole spin so angular information is limited to 9 polar directions thus this is often called 2 D data as reflected in the CAA product name There are also only 6 energy channels the top two corresponding to the upper 4 in burst mode The array size is 6 9 e Dataset title Electron distribution spin averaged detector E2DD6 Sparse 3 D This product exists only until May 2004 the CAA data files are empty after this when i
9. 53 2 64 2 65 Zese 4 96 4 11 3 12 1 99 0 76 0 53 1 78 2 93 3 94 4 82 R 570 5 21 4 79 4 48 4 29 4 28 4 44 4 74 5 15 5 62 UT of 2001 Sep 28 Figure 5 Demonstration of how changes in the IES integration times can produce erroneous changes in the electron fluxes if the automatic switching occurs too late times are denoted by red arrows For example at 04 32 integration time second from the top panel switches from 5 us to 2 us and produces the sudden sharp change in the electron intensity Another example one can see at 05 49 when integration time was erroneously switched from 2 us to 50 us and than back to 5 us producing a sharp intensity drop for the time of the too long integration time Cluster R APID S C4 T ango Cluster RAPID S C2 Salsa 2004 01 20 18 00 00 22 00 00 2004 01 20 18 00 00 22 00 00 Time resolution spin Time resolution spin a Electrons Electrons 10 n 1 n 1 1 1 103 1 104 8 104 3 5 10 9 5 10 z 1 102 x 102 492 5 E 1 5 v 5 E 10 c E 5 3 109 10 a x E r 1 1 1 1 1 8 107 19 Autosw 4 OFF HIST H Autosw J ON OFF HIST z n z L z z L E sour Integration time is not switched E sou 1 Integration time is switche 150 4d r 15 5 H Esu 4 F Esu 4 L 2u 4 F 2us 4 L Seid IFFT g s Seid Pale
10. 6 Quality flag Every CAA RAPID data product contains the quality flag In fact this is the calibration version for a given calibration set constant number The user should see the caveat files for detailed issues 6 Recommendations Most straightforward to use are the omni directional particle fluxes for ions and electrons A summary of the RAPID Datasets at the CAA is listed in Appendix A A guide on calculations of the RAPID partial moments can be found in Appendix B Conversion factors between differential flux and phase space density are listed in Appendix C 6 1 Usability issues Regions where the instrument operates well These are plasma sheet magnetosheath magnetopause cusp bow shock upstream region in cases where for ions the main plasma flow direction does not coincide with the look direction of the dead sensor Regions where there are issues The radiation belts is a region where a user must be careful with the data anal ysis In this region the pileup problems can lead to the flat spectrum see Section 3 2 1 and Figure 6 Also here often appear problems with the auto switching of the integration time and as a sequence erroneous jumps in the fluxes see the same section and Figure 5 Additionally at 3 5 L shells more energetic ions and electrons can penetrate the IES instrument see Figure 12 The IIMS instrument is not so sensitive to the penetrating particles because of time of flight filtering The pileup effects f
11. ae 0 i 10 9 E 5 107 bs x 5 lt 10 T 2 a c 10 00 01 02 03 04 05 06 Xose 4 13 3 50 2 85 2 19 1 51 0 82 0 12 Yose 11 47 10 78 10 03 9 22 8 35 7 40 6 37 Re Zose 10 07 10 22 10 31 10 33 10 28 10 14 9 90 Re R 15 81 15 26 14 67 14 02 13 33 12 58 11 77 Re Hours of 2003 Oct 29 Figure 13 An example of the effects which produce penetrating particles during the Halloween solar proton event Electrons do not show sensible measurements Ion intensities increase with the energy when they expected to decrease towards the higher energy channels Cluster Active Archive User Guide RAPID esa Date Project Cluster Active Archive Appendices A Summary of RAPID Datasets at CAA CAA EST UG RAP 3 0 2011 05 01 Page 24 of 31 Note the dataset IDs marked with are available both as differential fluxes and as counts sec with suffix _R Table 3 A summary table of RAPID datasets in dataset id is for R in raw count units Dataset title Dataset ID Science Particle Distribution Electron omni directional distribution ESPCT6 Electron 3 D distribution standard L3DD6 Electron 3 D distribution best Proton omni directional distribution HSPCT Proton 3 D distribution standard I3DM_H Helium omni directional distribution ISPCT_He Helium 3 D distribution standard I3DM
12. deposited in the detector and is recorded Cluster Active Archive User Guide RAPID esa Project Cluster Active Archive Table 1 The standardized RAPID energy channels Doc No Issue Date Channel Hydrogen Helium CNO Electrons BM NM 1 27 7 64 42 29907 83 8 40 79 407 2 75 3 137 8 274 4 50 5 50 5 3 92 2 172 3 414 68 1 68 1 4 159 7 235 1 498 94 5 94 5 5 374 351 638 127 5 127 5 6 962 737 948 175 9 244 1 7 1885 1689 1414 2441 8 2539 3365 Upper 4007 3799 4046 406 5 406 5 Lower thresholds all units keV Energy gap between hydrogen amp 2 Helium channel 1 contains hydrogen suppressed CNO channel 1 contaminated at times suppressed d Temporary pseudo value see RAP CR 8th channel not accessible for hydrogen and helium Incoming lon 3 Microstrip 1 7 TUE 7 solid state detectors Electrons Energy and direction Collimators CAA EST UG RAP 3 0 2011 05 01 Page 5 of 31 Time of flight measurement Start Stop Energy measurement in solid state detectors Figure 1 Left One of the three IES heads containing three solid state detectors to determine the direction of the incoming detected electron to within 20 Right One of the three SCENIC heads making up the IIMS part of RAPID Shown is an incoming ion that triggers a start signal at a foil which also serves to determine the fine direction and a stop signal when it enters
13. energy or in practice the geometric mean of a given energy channel for more details see chapter about phase space density and d E is the energy width of an energy channel Using these relations we can derive the moments as functions of measurable quantities B 1 Density For the density the zero order moment calculated from the 3 D data the following formula can be used A E keV 0 2284 10 m amu A sr s keV 3 ien visi D See 1 In case of using omni directional flux gt Ag gt Ad sind 47 4 0 Note The central head on the ion detector is damaged therefore one can not use 3 D data for calculation of the ion number density B 2 Velocity The components of the bulk flow velocity the first order moment are expressed as 1 5 1 1075 A0 sin 0 AE keV j cm 7 am 4 cos o f sin keV j cm sr s ke 1 Vy kms 10 ea 2 Agsing gt sin 0 AE keV 268 15 5 6 E 1 V km 51 2 10 X Ag X AG sinb cos X AE keV j cm sr s keV n cm 2 gt 2 Note For calculation of the bulk velocity the only 3 D data can be used as one needs the direction information for this Therefore the bulk velocity can be calculated only for electrons as ions have lack of measurements in the central head Cluster Active Archive User Guide RAPID CAA EST UG R
14. mode RAPID borrows extra bandwidth from the non functioning CIS instrument so that the data are in BM format even though the spacecraft telemetry mode is NM The times for NM3 can be found under the following link http caa estec esa int caa rapid docs xml Note NM3 was an attempt to improve the angular resolution of the electron 2 D data in NM It became unnecessary after May 2004 when the new L3DD product became available on all 4 spacecraft see Sec tion 5 1 1 page 14 and Table 2 The telemetry modes can be checked in the RAPID Quicklook Plots described in Section 5 4 and available at http caa estec esa int caa quicklook xml by selecting plot C RAP SUMPLOT D in the 6th panel IIMS Modes TM Alternatively this information is also contained in the CAA Status product SETTINGS see Section 5 3 3 2 Operations on IES electrons 3 2 1 Integration time The RAPID detectors do not accumulate counts all the time there is a dead time that leads to a duty cycle of less than 100 The total energy deposited by electrons during the so called integration time is accumulated and then read out over the next 50 us this is so called dead time which is fixed for all integration times The integration time switches automatically between values of 2 5 15 and 50 us depending on count rate It is vital that at most one electron per interval integration time is detected otherwise it is the summed energy of multiple electr
15. obsolete Pedestal determination for electrons how the pedestal Figure 3 is determined 0 for no correction 1 for the stepping method the only method used at the moment Cluster Active Archive User Guide RAPID esa Doc No Issue Date Project Cluster Active Archive Diff flux 1 cm sr s kev Int Time Cluster RAPID SC1 Rumba 2005 01 25 12 00 00 18 00 00 Time resolution 1 min 3 Electrons 10 1 1 1 1 L 1 1 1 1 1 n 1 L 1 1 L L 1 1 1 X Protons L L 1 1 1 1 1 1 L 1 1 1 L 1 1 1 1 i 1 1 1 L SS CNO 1 1 n 1 1 1 1 1 1 1 1 1 1 1 1 1 n 1 1 1 1 1 1 1 2 j Sw i I ii j 5 i n 1 gt D LIE UTI c amp j 4 L 1L 1 1 1 1 1 1 L 1 1 1 1 L 1 1 1 AutoSW ON OFF HIST 50 us 15 us 4 Wl UT 5 us 4 2 us 4 H A S B Serial Parallel IFFT 3 HV off HV on HV a NM BM BM3 NM3 40 gt 8j X 6 gt 4 2 STA STO DEF 0 et 12 13 14 15 16 1 18 Xgsp 2 84 4 03 5 15 6 20 7 48 8 11 8 96 RE YGsE 8 16 7 10 7 92 8 63 9 24 9 76 10 21 2658 657 6 44 6 18 5 84 5 44 4 98 4 48 R 9 44 10 40 1129 12 13 12 91 13 63 14 30 RE Hours of 2005 Jan 25 Generated 2009 Jun 26 17 10 13 V2 3 Data Vers 2120 E amp 3220 D CAA EST UG RAP 3 0 2011 05 01 Page 20 of 31 103 102 101 100 104 103 102 101 100 4071 402 101 100 4071 101
16. particles to within 20 Not shown is a foil between the pin hole aperture and detectors that removes any ions up to 350 keV A single head covers an acceptance angle of 60 in all a total of three heads span the entire range of 180 with 9 pixels middle of Figure 2 in one half plane During one spacecraft spin 4 s this plane rotate through 360 during which time 16 measurements are made one speaks of 16 spin sectors which are synchronized to the sun right side of Figure 2 A 3 D distribution thus consists of 9 polar x 16 azimuth directions The 3rd dimension energy is determined by the charge deposited in the detector by the absorbed electron which is proportional to that energy minus a constant The accumulated charge is swept out and converted to a digital signal at regular intervals Because of background currents 0 energy corresponds to some finite signal called the pedestal 8 energy channels are defined in terms of the 256 bin numbers relative to the expected location of this pedestal Figure 3 see Table 1 for the measured energies 22 The IMS Instrument A single ion detector head is illustrated on the right side of Figure 1 there are three ion heads in total The entering particle first traverses collimating plates penetrates a thin foil that emits electrons to generate a start signal and then strikes the solid state detector where electrons emitted at the surface produce a stop signal The particle energy is
17. the solid state detector where its energy is measured The stop and start signals are detected by multichannel plates MCPs not shown Cluster Active Archive User Guide RAPID esa Project Cluster Active Archive Spin Spin Doc No CAA EST UG RAP Issue 3 0 Date 2011 05 01 Page 6 of 31 Spin axis points southward o RAPID at 60 167 deg from Sun at start of Spin Sun Sensor N M Offset 26 367 deg Figure 2 The IIMS and IES polar segments relative to the spin axis left and center and the RAPID sectorization relative to the sun right Note that the spin axis actually points towards the Z GSE axis southward Pedestal Electron Line Electron energy relative to pedestal PHA T T T T T T T T Ch 0 N N 45 N 135 255 0 300 0 200 Energy keV Figure 3 The IES pulse height analysis The analog signal reflecting the electron s energy on top of a background pedestal is digitized from 0 to 255 and then sorted into broad energy bins that must be set relative to the pedestal Cluster Active Archive User Guide RAPID CAA EST UG RAP QS a Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 7 of 31 RAPID Classification Scheme CNO7 H7 H6 Over Range 1500 keV 1000 1 H6 SiFet 100 Measured energy keV
18. to GSE rotation EFLOW GSE IFLOW_GSE SC GSE rotation matrix Provided in the same files as the flow directions is the actual 3 x 3 rotation matrix to do a general transformation to GSE from the RAPID spacecraft frame 0 angle to spin axis sector x22 5 See Appendix D for usage e Dataset title Electron Ion Flow direction matrix RAPID to GSE rotation EFLOW GSE IFLOW_GSE Pitch Angles For each of the electron and ion polar azimuth flow directions the angle to the magnetic field pitch angle plus a magnetic azimuth is provided this is done for each spin e Dataset title Electron Ion pitch angle assignment matrix EPITCH IPITCH What is necessary in order to plot 3 D angle angle plot e One can create angle angle plots from 3 D distributions in any units E3DD L3DD I3DM_H I3DM He I3DM CNO I3D_H I3D He I3D_CNO EPADEXm IPADEXm e EFLOW GSE or IFLOW_GSE the rotation matrix for rotation from SC to GSE coordinates e Spin resolution or 5VPS FGM magnetic field vector in the case the magnetic field direction will be plotted see white and red dots in Figure 10 5 3 Status The key two datasets for knowing the instrument status are CAVEATS and SETTINGS The CAVEATS dataset text contains warnings or information on data gaps Some of these are generated automati cally by the processing software while others are copied from a master list maintained by the RAPID Team The daily caveat files contain only those cave
19. 3 2 2 Histogram mode Histogram mode is a test mode that is commanded about once month A fixed integration time is selected his togram mode activated the counts in all 256 energy channels are read out for all 9 angular detector strips uncom pressed and then regular operation is resumed Times when IES was switched to the histogram mode will be reflected in the Quicklook Plots plot C CG RAP SUMPLOT D 5th panel AutoSW A complete list of times when histogram mode occurs is given in the table at http caa estec esa int caa rapid docs xml 3 3 Operations on IIMS ions 3 3 1 IIMS instrument modes In the usual serial mode each ion head accumulates for a fixed 60 ms within each of the 16 azimuthal sectors one after the other This means the duty cycle depends on spin rate For example for a nominal 4 s spin each of the 16 sectors requires 250 ms so each head accumulates for only 24 of the time During the remaining dead time the counts from the previous sector are processed and other housekeeping tasks are performed There is also a parallel mode that was used occasionally in the solar wind early in the mission in this mode all three heads accumulate simultaneously for 180 ms per sector In the first few months of the mission before the main patch was uploaded the accumulation times were 65 and 195 ms for serial and parallel mode respectively The IIMS instrument modes can be checked on then Quicklook Plots plot C CG
20. 3 D distribution expanded see Figure 7 which will show the partial distributions in a time sequence as they were accumulated This bug affects only the ion data in nominal mode and only spacecraft 1 3 4 4 3 Standardized Energy Channels A uniform set of energy channel definitions is essential for any physical analysis of the data Hence the variations in the spectra among the sensors are corrected to bring them effectively to such a standardized set The correction is applied to the each ion and electron sector The official values now used for the CAA products are listed in Table 1 The algorithm used for this correction is to fit the data between adjacent channels to a power law which is then integrated over the energy shift region with the resulting flux subtracted from the one and added to the other channel as shown in Figure 8 For the electrons there is a further adjustment to be made because the pedestal that defines the energy origin can move in a way that depends on count rate its location is monitored by some additional diagnostic channels The spectral shift introduced by this effect can be deduced and then also corrected for as part of the energy channel standardization Note that the spectral correction is applied only to flux data not to the raw count rates since they are to remain as original raw data Cluster Active Archive User Guide RAPID CAA EST UG RAP esa zs Date 2011 05 01 Proje
21. 72 4 244 3 2 197 10 3 287 2 2 991 x 10 5 599 8 8 953 x 107 508 6 1 689 x 107 6 1340 4 005 x 107 1100 7 806 x 10 7 2748 1 954 107 2533 3 392 x 10 3 8 4007 1 340 x 107 3799 2 261 x 10 3 Oxygen Electrons 1 151 6 9 066 x 107 43 40 5 369 x 107 2 337 0 4 079 x 107 58 64 4487 10 3 454 0 3 028 x 107 8022 3 872 x 107 4 563 6 2 439 107 109 7 3 517 x 10 5 777 7 1767 x 107 149 7 3402 x 10 6 1157 1 187 107 207 2 3 556 x 107 7 1931 7 117 1072 286 6 4 080 x 107 8 3267 4 207 1072 369 8 4 883 x 10 Table 4 Conversion factors from differential flux j cm s sr keV to phase space density f km s3 The ratio f j is listed to obtain f multiple the j value by this ratio Cluster Active Archive User Guide RAPID CAA EST UG RAP esa Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 29 of 31 D RAPID to GSE Rotation Matrix In Section 5 2 the products EFLOW GSE IFLOW GSE are described which give the GSE coordinates for each of the 9 x 16 electrons or 12 x 16 ions detector sector combinations in the 3 D datasets shown in Figure 2 These detectors and sectors are fixed in the spacecraft coordinate system and must be transformed to GSE by means of the rotation matrix included in the two datasets Note that e The GSE coordinates given are the polar angle from the Z axis 0 180 and the azimuthal angle f
22. 97 RAPID The Imaging Energetic Particle Spectrometer on Cluster Space Science Reviews 79 399 473 Wilken B et al 2001 First Results from the RAPID Imaging Energetic Particle Spectrometer on board Cluster Ann Geophys 19 1355 1366 List of Acronyms BM Burst Mode Cluster high telemetry rate CAA Cluster Active Archive CEF Cluster Exchange Format CAA format CR Calibration Report DPU Digital Processing Unit EDB Experiment Data Block GEI Geocentric Equatorial Inertial coordinate system GSE Geocentric Solar Ecliptic coordinate system ICD Interface Control Document TES Imaging Electron Spectrometer part of RAPID IIMS Imaging Ion Mass Spectrometer part of RAPID MCP Multichannel Plate NM Nominal Mode Cluster low telemetry rate RAPID Research with Adaptive Particle Imaging Detectors Cluster Experiment SCENIC Spectroscopic Camera for Electrons Neutral and Composition part of RAPID TOF Time Of Flight Cluster Active Archive User Guide RAPID CAA EST UG RAP esa zs Date 2011 05 01 Project Cluster Active Archive Page 4 of 31 1 Introduction The RAPID experiment Research with Adaptive Particle Imaging Detectors on board Cluster measures 3 D en ergetic electron and ion fluxes in the energy range above 30 keV Since the raw data delivered by the instrument are of no use without detailed knowledge of their construction functioning calibrations and limitations it is es
23. AP esa Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 27 of 31 B 3 Pressure The diagonal terms of the kinetic pressure tensor the second order moment are the following Py nPa 0 731 1075 m amu gt cos gt sin gt A E keV 15 1 P nPa 0 731 10 5 m amu gt sin RN sin 0 gt A E keV _18 1 6 nPa 0 731 10 5 m amu Ag gt A0 sind cos 6 AE keV E keV cm 257 s keV For the isotropic pressure 2 4x 30 731026 1075 m amu gt A E keV E keV j cm sr s keV 7 E Note For calculation of the pressure tensor the only 3 D electron data could be used An isotropic pressure can be derived from both electron and ion omni directional fluxes Cluster Active Archive User Guide RAPID esa Date Project Cluster Active Archive C Phase Space Density Conversion Factors CAA EST UG RAP 3 0 2011 05 01 Page 28 of 31 A set of fixed conversion factors between differential flux jand phase space density f based on the mean energies E of each channel is listed in Table 4 More details on its calculation can be found in RAP CR Chan E fli Eg f j Protons Helium 1 4223 1 271 x 107 64 18 1 338 x 107 2 83 32 6 445 x 107 154 0 5 576 x 10 3 121 3 4426 10 3 201 2 4 269 x 10
24. IFFT ga LM HV off HVon HVok 3 HVof HVon Bms E O BM3 2 10 10 x 89 F 84 E Z s 6 L gt 4 gt 4 T 5 STA sto DEF L el STA DEF E I IF 1800 1830 1900 1930 2000 2030 2100 2130 2200 1800 1830 1900 1930 2000 2030 2100 2130 2200 Xa 1 82 2 21 2 71 3 06 3 21 3 14 2 89 2 49 1 99 Ry Xese 1 67 2 26 2 75 3 09 3 22 3 15 2 90 2 49 1 99 Re Yose 3 55 3 52 3 34 2 96 2 40 1 69 0 86 0 00 0 87 Re Yose 3 56 3 52 3 33 2 95 2 39 1 67 0 85 0 02 0 88 Re la 3 55 2 45 1 25 0 02 1 29 2 47 3 50 4 36 5 05 Re Zore 3 50 2 40 1 19 0 08 1 34 2 51 3 54 4 40 5 08 R 5 28 4 83 4 48 426 4 21 4 34 4 62 5 02 5 50 R 5 26 4 82 4 48 4 27 4 23 4 36 4 65 5 05 5 53 Re UT of 2004 Jan 20 UT of 2004 Jan 20 Figure 6 Left An illustration of what can happen when the integration time fails to switch As the intensities increase the count rates in the lowest channels are too low since multiple low energy events count as a single high energy one Right For a comparison the same time period and the same region measured by another Cluster spacecraft where the auto switching was working properly Cluster Active Archive User Guide RAPID CAA EST UG RAP esa Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 11 of 31 3 3 3 Loss of Ions on SC1 since March 16 2007 e On Ma
25. _He CNO omni directional distribution ISPCT CNO CNO 3 D distribution standard I3DM_CNO Pitch Angle Electron Pitch Angle distribution standard PAD_L3DD Electron Pitch Angle distribution best PAD_E3DD Proton Pitch Angle distribution standard PAD_H Helium Pitch Angle distribution standard PAD He CNO Pitch Angle distribution standard PAD_CNO Ancillary Caveats CAVEATS Instrument settings SETTINGS Summary Plot SUMPLOT_D Electron Flow direction matrix RAPID to GSE rotation EFLOW_GSE Ton Flow direction matrix RAPID to GSE rotation IFLOW_GSE Electron pitch angle assignment matrix EPITCH Ion pitch angle assignment matrix IPITCH Particle Distribution Electron distribution spin averaged detector E2DD6 Electron 3 D distribution sparse 2001 Feb 2001 May EPADEX1 Electron 3 D distribution sparse 2001 May 2002 Jul EPADEX2 Electron 3 D distribution sparse 2002 Jul 2004 Apr EPADEX3 Proton 3 D distribution sparse IPADEX Helium 3 D distribution expanded I3D_He CNO 3 D distribution expanded I3D_CNO continued Cluster Active Archive User Guide RAPID Issue Date esa Project Cluster Active Archive Table 3 RAPID datasets continued Doc No CAA EST UG RAP 3 0 2011 05 01 Page 25 of 31 Dataset title Dataset ID Diagnostics Direct Events DE Ion diagnostics SGL1 count rates nominal mode SGL1 Ion diagnostics SGL1 count rates burst mode SGL1_BM Ion diagnost
26. amp e dtes 18 9 3 oy tote dom ble eee ten Boe id ee oe ee aoe Bae ay doe ae ay ed eo doe be a 18 54 Graphical i25 226 EEA ee RUE GR 9 Robb RA ew ee eee ea 19 5 5 Dataset Version s pa e sosi 6 eps bee ep o ROO S OR RUE RR m FOROR 19 6 Quality Mag ee Rem oso Ow vesc eoe uU He e oce e e e eoque a 2l 6 Recommendations 21 6 Usability ISSUES 21 Somos bee ee REE ue s eue E PH ood SR 21 A Summary of RAPID Datasets at 24 Partial moments 26 B l sch xk eom kN SR RAS hem m EE AUS Pede s 26 wAR Ou AIT 26 B3 Pressure x 66 2 42 6 BS aed ENS ewe EXPE SOE WE Wb ed deus 2T C Phase Space Density Conversion Factors 28 D RAPID to GSE Rotation Matrix 29 D 1 The RAPID Spacecraft Frame gt s s se ee les 29 D 2 The Rotation Matrix 29 D3 Example ninaa uot d EERE dedu UE mue Vedere b xus 30 DA Things to Note 2e eae ES EAS ee ee SALUS 31 Cluster Active Archive User Guide RAPID CAA EST UG RAP QS a Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 3 of 31 Reference Documents RAP GSE Daly W 2004 Converting from RAPID Coordinates to GSE RAPID Report DS RAP IN 0019 Issue 1 1 Max Planck Institut f r Sonnensystemforschung Katlenbur
27. ats that are relevant to that one day Each caveat text has an associated time range which is always truncated to fit within the time limits of the given file This means it does not represent the true overall time limitation of the text In such cases the text itself specifies when the warning starts and stops The SETTINGS dataset contains a subset of the housekeeping data 11 variables in all for the most important aspects of the instrument status including telemetry mode multichannel plate voltages electron integration time ion accumulation mode These variables are described in RAP ICD as well as by the dataset metadata Cluster Active Archive User Guide RAPID CAA EST UG RAP Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 19 of 31 RAPID L3DD Ct 04 14 RAPID LSbb CE Dp 14 South Tall Tail Sun Sun jew from North View Figure 10 Left 3 D electron distribution from L3DD data in GSE showing 9 polar directions and 16 azimuthal sectors Right The same data but in a bispherical view whereas the left spheres on both plots show northward flow and the right southward White dots indicate 90 to the magnetic field and the red dot and red star mark the calculated direction magnetic field vector 5 4 Graphical RAPID summary plots are available for differential fluxes In Figure 11 we present an example plot of Cluster 1 From top to the bottom omni direc
28. be that for a single count to express the uncertainty level However such a procedure would lead to errors when summing over longer times Recall that errors are combined by summing the variance i e the sum of the squares of the standard deviations Time Tag The record time tag refers to the middle of the record interval the time half interval for each record is also given Note that the record interval and the accumulation time are two separate things data are accumulated over a certain interval but not necessary for 100 of that time 5 1 1 Electrons The electron distributions as delivered directly by IES exhibit some importance differences between the nominal telemetry mode NM low bit rate and burst mode BM high bit rate see Section 3 1 All the above products have a time resolution of one spin i e 4 s Here we list only the datasets in particle flux The datasets in raw count rates have an additional suffix _R in their names as indicated by the in the names below They can be downloaded as well but their use is advised only for experts as these datasets are not calibrated and corrected Omnidirectional Omnidirectional electron fluxes are created artificially for CAA from the 3 D 2 D data by summing up over the polar and azimuthal angles It always has the 6 energy channels of nominal mode array size 6 e Dataset title Electron omni directional distribution dataset id ESPCT6 Electrons Lite Since May 2004 a new
29. bins 0 180 are available in burst mode 8 energy channels and after May 2004 in nominal mode 2 non contiguous energy channels The distribution is provided once per spin e Dataset title Electron Pitch Angle distribution standard best PAD L3DD PAD E3DD Ions Differential fluxes in 9 pitch angle bins 0 180 and 8 energy channels Cluster Active Archive User Guide RAPID CAA EST UG RAP QS a Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 18 of 31 Ion pitch angle distributions are provided for SC2 over 1 spin every 32 8 spins NM BM SC1 SC3 SCA BM over 8 spins once every 8 spins SC1 SC3 SC4 NM 8 spins with asynchronous sectors over 24 or 40 spins a result of the bug illustrated in Figure 7 e Dataset title Proton Helium Pitch Angle distribution standard PAD PAD He 5 2 Auxiliary Some additional datasets are provided to assist users with the interpretations their derivation requires detailed knowledge of the RAPID location on the spacecraft the spin axis and sun sensor Thus all this is worked out for the user as separate products Flow directions For each of RAPID s 9 x 16 electrons and 12 x 16 ions polar azimuth directions the GSE coordinates of the flow vector at their centers are provided Since these values change very slowly they are only given once per hour e Dataset title Electron Ion Flow direction matrix RAPID
30. ct Cluster Active Archive Angle to Spin Axis RAPID I3DD E1 H SC4 2008 02 13 12 40 21 12 41 27 12 42 00 12 43 05 12 44 11 1 j 1 0 60 5 jp 120 120 180 180 r 90 180 270 360 90 180 270 360 c 12 44 44 12 45 49 12 46 22 12 47 28 12 48 33 1 1 B 1 5 1 toee le 60 60 e E 120 120 120 L120 120 4 le le oo o 180 e 180 180 T T 180 hr 180 L T 0 90 180 270 360 0 360 0 90 180 270 360 90 180 270 0 60 Li l 120 180 360 120 180 0 90 180 270 Angle from sector 0 Figure 7 Example of the 3 D ion timing problem Rows 1 and 3 show the partial distributions the dataset called as the ion 3 D distribution expanded at the CAA while rows 2 and 4 are the merged full distributions the ion 3 D distributions standard at the CAA The red oval at the lower right indicates a spurious anisotropy that is really time aliasing ul power law y Figure 8 Shifting the energy threshold between two channels the differential flux in two channels is fitted to a power law that fit is integrated over the energy shift E E shaded area and the result moved from one channel to the other Cluster Active Archive User Guide RAPID
31. e above products have a time resolution of one spin 4 s 5 1 2 Ions The ion distribution products delivered directly by IIMS can be summarized as follows Omnidirectional There is an omni directional base product for H with 8 energy channels Since these events do not depend upon the efficiency of the directional signal mentioned above they are not identical to the sum of the 3 D data Array size is 8 frequency is once per spin There are also omni directional He and CNO spectra at a rate of one per 4 spins their array sizes are 8 e Dataset titles Proton Helium CNO omni directional distribution HSPCT ISPCT He ISPCT_CNO 3 D Data The merged full distributions of ion fluxes for 3 species H He CNO in 12 polar and 16 azimuthal directions over 8 energy channels Array size is 8 16 12 RAPID EPADEX E1 SC2 2004 02 15 22 00 01 Angle to Spin Axis xna 180 Angle from sector 0 Figure 9 An example of the sparse 3 D electron distribution in s c coordinates Black diamonds indicate 90 to the magnetic field and the red dot and red star mark the calculated direction magnetic field vector taken from FGM Therefore the data obtained in the direction perpendicular to the magnetic field are seen along the black diamonds the data in second direction perpendicular to the first are seen around the red dot and star and eventually the data accumulated in the parallel or anti parallel to the spin axis direction are se
32. en in the polar sectors 0 0 20 and 8 160 180 Cluster Active Archive User Guide RAPID CAA EST UG RAP esa Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 17 of 31 Each distribution is accumulated over 8 spins except on spacecraft 2 where they are accumulated over a single spin Because of the limited telemetry rate for RAPID only a fraction of accumulated data can be transmitted to the ground In burst mode one can transmit one full distribution over 8 spins wheareas in nominal mode it requires 32 spins This is a result of the limited telemetry rate for RAPID There are thus data gaps between the delivered accumulations Note that the proper distributions are the partial ones described next The merged ones are reconstructed from them for the convenience of the users but may exhibit time aliasing problems as shown in Figure 7 The merged distributions are only provided as fluxes not as count rates e Dataset titles Proton Helium CNO 3 D distribution standard I3DM H I3DM He I3DM_CNO The partial distributions of ion fluxes for 3 species H He CNO in 12 polar and 16 azimuthal directions over 8 energy channels Array size is 8 16 12 As mentioned in Section 4 2 the I3D distributions for SC1 3 4 in NM have a bug in accumulation time and therefore for each time tag corresponding 3 D distribution is not full In order to indicate how the partial distributions are to be me
33. g Lindau Germany http www mps mpg de dokumente projekte cluster rapid rap to gse pdf RAP ICD Daly P W M hlbachler S and Kronberg E A 2011 Cluster Active Archive Interface Con trol Document for RAPID Report CAA RAP ICD 0001 Issue 4 0 Max Planck Institut f r Sonnensystem forschung http www mps mpg de dokumente projekte cluster rapid rap caa icd pdf Hapgood M A 1992 Space Physics Coordinate Transformations A User Guide Planet Space Sci 40 711 717 RAP CR Kronberg E E and Daly P W 2011 Calibration Report of the RAPID Measurements in the Cluster Active Archive RAPID Report CAA EST CR RAP Issue 2 0 Max Planck Institut f r Sonnensys temforschung Katlenburg Lindau Germany http www mps mpg de dokumente projekte cluster rapid caa rap cal pdf RAP FOM 2000 RAPID Flight Operations User Manual Version 3 0 Max Planck Institut f r Aeronomie Katlenburg Lindau Germany http www mps mpg de dokumente projekte cluster rapid Rapid_ flight man30 pdf Wilken B Axford W I Daly P Daglis I G ttler W Ip W H Korth A Kremser G Livi S Vasyliunas V M Woch J Baker D Belian R D Blake J B Fennell J F Lyons L R Borg H Fritz T A Gliem F Rathje R Grande M Hall D Kecskem ty K Mckenna Lawlor S Mursula K Tanskanen P Pu Z Sandahl I Sarris E T Scholer M Schulz M S rass F and Ullaland S 19
34. he two products are identical for the same spacecraft and time It is only the array sizes of the resulting flow matrices that are different for ions and electrons We have assumed here that the spin axis is identical with the body reference axis of the spacecraft Strictly speaking this is not true and the attitude files also contain information on this deviation However these are very small 0 05 and so have been neglected The rotation matrix is very nearly diagonal meaning that its inverse transpose is not obviously different This means that if one applies it in the wrong direction a common and understandable error the result does not appear immediately as nonesense It is for this reason that we provide the correct results and also emphasize how the matrix is to be filled and applied Cluster Active Archive User Guide RAPID
35. ics SGL2 count rates SGL2 Ion diagnostics SGL3 count rates SGL3 IES pedestal counts in nominal mode PED_NM IES pedestal counts in burst mode PED_BM IES pedestal positions in nominal mode PEDPOS_NM IES pedestal positions in burst mode PEDPOS_BM IES Histogram data HIST Miscellaneous Housekeeping data HK Preliminary Energetic Electron Proton and Ion Flux spin resolution C n PP RAP Preliminary Energetic Electron Proton and Ion Flux I minute resolution C n SP RAP Cluster Active Archive User Guide RAPID CAA EST UG RAP esa Date 2011 05 01 Project Cluster Active Archive Page 26 of 31 B Partial moments The moments of the velocity distribution function f v of a given particle species are calculated as 1 where v denotes n fold dyadic product a tensor of rank n and d v is the volume element in velocity space Therefore the zero first and second order moments will be correspondingly the number density the bulk flow velocity V and the pressure tensor P It is common to use as the measurable quantity for particle counters the differential flux j for particles of energy E within a solid angle dQ The relation between the distribution function and the differential flux is v 2E JE 2 f0 fo 2 m m Since d v f d 49 f dvv and v 2E m then fdo fdo sino dEV2E m where dQ f 40 sin0 Here E is the effective
36. ion of the spin axis as given in the attitude files varies very slowly is updated every few days e The spin phase corresponding to the occurrence of the sun pulse also in the attitude files can vary slightly Cluster Active Archive User Guide RAPID CAA EST UG RAP esa Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 30 of 31 Spin axis Ww Look Direction Figure 14 The RAPID spacecraft coordinate sys tem fixed to the spin axis 10 and the start of the 16 spin sectors An arbitrary look direction has angular coordinates and Sector 0 0 u The coordinates for the spin axis are converted to GSE using standard algorithms e g Hapgood 1992 and references therein We can then determine the GSE coordinates of both the spin axis and the RAPID sector 0 0 which is sufficient to generate the rotation matrix M its columns are simply the three vectors 0 0 expressed as GSE cartesian coordinates The flow vector Fgse is then Mi Mis a Fose Mo b 11 M3 M32 M3 c or generally Fose M Note the minus sign to convert from look to flow direction The components of M are given in the files by row i e as M11 M12 M32 M33 D 3 Example As an example let us take a record from EFLOW GSE for SC1 on 2001 08 22 It starts with the time stamp and the 9 values of M 2001 08 22T03 30 44 501Z 0 49308
37. lizing them such that on the long term they all have the same average values see RAP CR The user must realize that these inter spacecraft inter head cross calibrations are therefore only approximate and can deviate on any particular day This could lead for example to an assymetry between ion head 1 and 3 e First energy channel He CNO These channels are included in raw count rates but they are replaced with fill values in particle flux datasets The lower part of Figure 4 shows the underrange region where no energy signal is received 30 keV ion classification is done solely on TOF information and the fact that the energy is so low These events contribute to energy channel 1 The species determination is not so precise low energy hydrogen enters and dominates the helium channel 1 which is therefore suppressed and the CNO channel 1 often exhibit signs of contamination as well most likely from low energy helium For more detail see RAP CR Accumulation problem for the 3 D ions SC1 3 4 NM There is a bug in the onboard programming that causes the 3 D ions to be accumulated at different times in different sectors A presentation of this bug is shown in Figure 7 Therefore the users dealing with the ion 3 D distributions standard i e the merged full ion 3 D data see Figure 7 should be aware that it could have spurious anisotropy due to different accumulation times In suspicious cases it is advised to check this using the ion
38. ons that is registered Thus the integration time should be as short as possible On the other hand it is desirable to have a long integration time to improve the duty cycle The maximum duty cycle of 50 is achieved with an integration time of 50 us This is the usual case except during times of high count rates Caveats e There can be jumps in the flux values at such erroneous switching times as the pile up effects i e more than one count per interval are suddenly removed This problem is most serious before January 25 2002 when the automatic switching was occurring too late After this date the timing of the auto switching was improved by modifying the parameters involved The problem is thus reduced but not entirely eliminated Cluster Active Archive User Guide RAPID CAA EST UG RAP QS a Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 9 of 31 Corrections for this are not possible the user must be careful with such jumps An example on switches of the integration time and its effects can be seen in Figure 5 e From January 18 to February 20 2004 the automatic switching on SC4 was turned off by error the integration time remained fixed at 50 us Figure 6 The information on integration time switches can be found in the Quicklook Plots by selecting plot C CG RAP SUMPLOT D 5th panel Time This information is also available in the Status product SETTINGS Section 5 3
39. rch 16 2007 the MCPs SC1 started behaving strangely with loss of time of flight signals Some weeks later the voltages became unstable so they were shut down As a result there are no ion data from SC1 since this date 4 Measurement Calibration and Processing procedures Before raw data become scientifically valuable they need to go through various treatment procedures and become reprocessed Imperfection of some corrections lead to caveats which the user should be aware of 4 1 Electrons e Spectra correction Since the pedestal position see Section 2 1 moves with time aging temperature and even raw count rate its position is constantly monitored and corrected for in the data A consequence of this is that the different electron detector strips effectively measure different energies Efforts are made to correct for this as described in Section 4 3 However the corrections are not always perfect and the user should be aware of this For diagnostics when pedestal is an issue see RAP CR e Pedestal noise correction on SC4 Pedestal contamination affects the electron omni directional distribution To correct for this we re move the noisy strips from both the omni directional and 3 D data Correction as always is made for the fluxes only never for the raw count rates For more details and examples see RAP CR e Solar noise correction on SC3 Sunlight enters the IES head 1 on SC3 and produces noise in the data This solar noi
40. rged to regenerate the full distribution a record key variable named Rec Key is provided for each record This is an integer with the following values Value Meaning Sectors included 11 Rec 1 of 1 0 15 all 21 Rec 1 of 2 2 7 22 Rec 2 of 2 0 1 8 15 31 Rec of 3 2 3 32 Rec 2 of 3 0 1 4 11 33 Rec 3 of 3 12 15 Note that the value 11 is provided for burst mode and SC2 for which no splitting is done each record is a complete simultaneous distribution e Dataset title Proton Helium CNO 3 D distribution expanded I3D H I3D I3D_CNO Sparse 3 D As for the electrons there is a sparse 3 D hydrogen distribution available every spin with 3 polar directions per sectors which vary with the magnetic field It too is expanded to fill the complete 3 D array with fill values for those directions not measured The array size is 2 16 12 As of May 2004 this product exists only in burst mode e Dataset title Proton 3 D distribution sparse IPADEX 5 1 3 Pitch Angle Distributions The pitch angles for electrons and ions are delivered based on the 5 vectors per second 5VPS FGM data Each distribution is accompanied by the GSE components of the magnetic field averaged over the data interval plus a quality flag This flag is derived from the normalized variance of the field such that it is 1 for steady constant field and 0 for extremely variable Electrons Differential fluxes in 9 pitch angle
41. rom the X axis C180 180 e The direction refers to the flow directions of particles detected i e it is opposite to the direction in which the detector is pointing e The direction corresponds to the middle of each sector detector range The rotation matrix alone would be sufficient to generate all the flow directions however the results are given as a convenience to the user and to eliminate many of the intrinsic ambiguities A description of how to apply the rotation matrix properly is found in RAP GSE and a summary is given here D 1 The RAPID Spacecraft Frame Let us define the RAPID coordinate system to be relative to unit vectors along sector 0 0 0 along sector 4 0 and w along the spin axis Figure 14 The look direction for the middle of detector d in sector s has the angular coordinates d 4 0 5 5 0 5 2 8 8 where D 15 12 for ions and 9 for electrons The vector L for the look direction is L 00 c 9 where the cartesian coordinates are a sin0cos sinOsin 10 cos D 2 The Rotation Matrix The 3 x 3 matrix for rotating from the RAPID system to GSE is given in each record of the EFLOW_GSE and IFLOW GSE products This matrix is determined using the following factors e The location of RAPID on the spacecraft fixed e The position of sector 0 0 relative to the sun pulse has an ideal value but can vary given in the RAPID housekeeping data e The GEI locat
42. rom both penetrating particles and high count rates can be detected and will be flagged in future Solar Proton Events can also produce penetrating radiation that distorts the instrument s behavior see an ex ample in Figure 13 Cluster Active Archive User Guide RAPID CAA EST UG RAP esa Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 22 of 31 180 E oes ud O 5 135 1 um o o X 2 oU gt 90 us 5 Sn E uo oU 45 um 9 zt 2 o 777 970 PC T Tm 05 00 05 15 05 30 05 45 06 00 06 15 06 30 06 45 07 00 UT of 2008 04 27 Figure 12 An example of the electron data contamination in the radiation belts In the pitch angle distribution of the electrons one could see stripes denoted as the noise in one detector The fact that this noise appears only in the radiation belts implies that the contamination is from penetrating particles The sharp enhancement of the electron flux at the integration time switch is not related to the contamination problem Cluster Active Archive User Guide RAPID i Doc No CAA EST UG RAP esa Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 23 of 31 Cluster RAPID SC4 Tango 2003 10 29 00 00 00 06 00 00 Time resolution 1 min Electrons 10 104 gt a gt D 102 c 103 Protons gt 102 E gt 10 o e 10 1071 gt 1 10 P 3 o
43. se is very strongly dependent on solar aspect angle SAA A correction is made to both 3 D and omni directional flux data For more details about this correction and examples see RAP CR e Inter spacecraft cross calibrations Large differences between the electron detectors on different spacecraft are not expected and spot checks have confirmed this expectation 4 2 Ions e Time varying detector efficiencies The start and stop signals are generated by MCPs whose performances change considerably over time Thus the overall response including the TOF efficiency is monitored continuously and the calibration files regularly updated The user must realize that since these parameters are based on long term averages over weeks or months there can be deviations on any particular day See more details and diagnostics in RAP CR Cluster Active Archive User Guide RAPID CAA EST UG RAP QS a Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 12 of 31 e Absolute fluxes may be overestimated As illustrated in RAP CR Section 6 1 comparisons with the CIS CODIF instrument indicate that at times when the TOF efficiencies are fairly low the derived geometry factors might be underestimated hence producing fluxes that are too large Inter spacecraft and inter head cross calibrations Efforts are made to cross calibrate the ion detector performances over the 4 spacecraft and all the functioning heads by norma
44. t was replaced by Electrons Lite see above To compensate for the missing 3 D data in NM this additional product called EPAD electron pitch angle distribution contains fluxes from 3 polar directions for azimuthal 16 sectors but only for two energy chan nels One direction is perpendicular to the magnetic field in that sector the 2nd is 90 to the first the 3rd is either parallel or anti parallel to the spin axis The other 6 directions are given as fill values An example of the angle angle plot created with this product see in Figure 9 The definitions of the two energy channels have changed several times over the first years of operation Table 2 A summary table of characteristics for different datasets Species Dataset title Dataset name Nominal mode Burst mode Electrons Electron omni ESPCT6 6 energy channels 6 energy channels directional distribution Electron 3 D L3DD 9 polar x 16 azimuthal 9 polar x 16 azimuthal distribution standard 2 energy channels 2 energy channels Electron 3 D E3DD 9 polar x 16 azimuthal distribution best 8 energy channels Electron distribution E2DD6 9 polar x 1 azimuthal spin averaged detector 6 energy channels Electron 3 D EPADEXm 3 polar x 1 azimuthal 9 polar x 1 azimuthal distribution sparse 2 energy channels 2 energy channels Ions Ion omni directional HSPCT 8 energy channels 8 energy channels distribution ISPCT_He ISPCT_CNO Ion 3 D dis
45. tained by sorting the counts into 16 sectors during one rotation of the spacecraft right side of Figure 2 The spin phase relationship between the sun sensor pulse and the start of sector 0 the start of a new spin is fixed so that the RAPID detectors are looking into the direction of the sun at sector 13 326 or about one third into sector 13 This relationship has been set in agreement with the other experiments so that all start a new spin simultaneously Cluster Active Archive User Guide RAPID CAA EST UG RAP QS a Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 8 of 31 3 Instrument Operations 3 1 Telemetry modes The Experimental Data Block EDB contains the compressed science data produced by the Digital Processing Unit DPU One EDB is generated per spin 4s The data structure varies with the telemetry mode The RAPID telemetry formats are NM Nominal mode is active most of the operation time of the instrument with 1024 8 bits second BM Burst mode allows four times more data downlinked than NM The principal difference between BM and NM is a higher sampling rate for the 3 D ions and an enhanced 3 D electron products BM3 This mode lasting 5 minutes once a day is intended to read out scratch memories of some instruments For RAPID BM3 simply forms a data gap during this time NM3 Nominal mode 3 is a special mode on SC2 only used between July 2003 and April 2004 in this
46. tional differential energy flux spectra of electrons hydrogen helium and CNO with 1 min time resolution for January 25 2005 within a 6 hour period from 12 00 to 18 00 UT are shown At the right hand side of each plot panel a colour bar defines the colour code of the spectra This range is autoscaled which has to be considered when comparing several plots The second part of the plot panels 5 7 reflects the IES and IIMS instrument settings For more information about instrument settings and their meaning see the description in Section 3 and RAP ICD At the bottom of the summary plots orbit information in GSE coordinates is given The Summary Plots can be downloaded from CAA as part of the RAPID ancillary data or viewed under the CAA Quicklook plots They may also be obtained from the MPS web site at http www mps mpg de cgi rapid sumplot cgi 5 5 Dataset Version Currently RAPID data at CAA are of the 2nd release with upgraded calibrations over those of the Ist release The calibration version can be found in the data files There is a metadata parameter called DATASET_VERSION which for RAPID is a 4 digit code which is slightly different for electrons and ions Calibration version Pedestal determination e Cal subset ions Spectrum correction Background subtraction xX X X X Calibration version has the value of 2 or 3 see caveat below for the current calibration data or 1 for the old calibrations of the 1st release now
47. tribution I3DM_H 12 polar x 16 azimuthal 12 polar x 16 azimuthal standard I3DM He 8 energy channels 8 energy channels I3DM_CNO Proton 3 D distribution IPADEX 3 polar x 1 azimuthal 3 polar x 1 azimuthal sparse 2 energy channels 2 energy channels Ion 3 D distribution I3D_He 12 polar 16 azimuthal 12 polar x 16 azimuthal expanded I3D CNO 8 energy channels 8 energy channels The product is available since May 2004 The product ceases after May 2004 Particles are registered in only 3 of 9 directions as determined by onboard magnetic field measurements 4 After May 2004 this product is available only in burst mode Expanded 3 D distributions are split into partial distributions according to different accumulation intervals Cluster Active Archive User Guide RAPID CAA EST UG RAP esa Issue 3 0 Date 2011 05 01 Project Cluster Active Archive Page 16 of 31 hence 3 separate products must be given distinguished by m 1 2 3 m From To 1 May 2001 2 May2001 July 2002 3 July2002 April 2004 The above dates are approximate and vary slightly for each spacecraft The data files are empty for the times for they do not apply No energy corrections are applied for this product Strictly speaking this product exists only in NM in BM it is emulated from BM and it contains 9 polar directions e Dataset title Electron 3 D distribution sparse EPADEXm All th
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