CAA 6 th Cross Cal Meeting RAL, th Oct 2007 RAPID/IES Calibration Status J.A. Davies

CAA 6 th Cross Cal Meeting RAL, th Oct 2007 PEACE/RAPID Cross Cal PEACE/RAPID Kappa fitting undertaken for a number of intervals The original study found that the fit is very sensitive Two similar distributions result in significant differences in the cross cal parameter. Tried using two kappa distributions (e.g. result of W-P interactions) We always find that the gap between energy ranges hinders direct comparison.

CAA 6 th Cross Cal Meeting RAL, th Oct 2007 PEACE/RAPID Cross Cal Questions highlighted at October Cross-Cal Should we be using the kappa fitting technique to determine the cross-cal parameters or just as a verification of the cross cal from other techniques? Answer: For normal science data, only the latter! Do the new PEACE inter-anode comparisons make any difference? Answer: Does not resolve the differences. Can we use the IES test-mode histogram data to look for intervals where IES and PEACE have an energy overlap ~19 keV. Answer: Yes, but this is proving more complicated than expected! Anything else we can try? Answer: Looking back at ground cal and commissioning data and also looking at cross cal with other spacecraft under special circumstances

CAA 6 th Cross Cal Meeting RAL, th Oct 2007 PEACE/RAPID Cross Cal Difficulties with cross-cal include Pile-up in IES (only important in high count rate regions) Multiple (kappa) populations give too many possible fitting options No energy overlap between PEACE and standard IES products Some hints of inaccurate e-cal in top PEACE and bottom IES channels Instruments on different spacecraft give similar results so any discrepancies likely to be systematic. Bad E cal? PEACE IES Distributions from C2 and C4 look very similar in both PEACE and IES

CAA 6 th Cross Cal Meeting RAL, th Oct 2007 PEACE/RAPID Cross Cal Can we use the IES test-mode histogram data to look for intervals where IES and PEACE have an energy overlap ~19 keV. Answer: In theory yes, but need to consider a number of factors! Using PEACE 3DXnP product and then spin averaging to give distribution best matched to IES histogram data. Only about 20 events over the entire mission when the count rates in IES high enough during histogram intervals. PEACE data on C1 and C3 is usually windowed such that highest energies are not returned (is 3DR an alternative?). PEACE inter-anode recalibrated data only just available. Currently working with two plasma sheet intervals & and a higher count rate interval at the edge of the ring current

CAA 6 th Cross Cal Meeting RAL, th Oct 2007 PEACE/RAPID Cross Cal Issues with using histogram mode data include: Pile-up in IES (as with normal data) Pedestal subtraction issues Energy efficiency fall-off Very limited dataset E fall-off important for direct comparision in the energy overlap range. (n.b. occurs above pedestal subtraction effects) Property of the detectors Will be the same for all detectors May depend on look direction (but second order effect) Expected to be stable with time Four sample averages (dE ~8.8keV) pedestal removed Histogram point (dE ~2.2keV) pedestal removed Histogram points without pedestal being removed Power law tail Fall off in energy efficiency? IES BM Clean data from nearby spin

CAA 6 th Cross Cal Meeting RAL, th Oct 2007 PEACE/RAPID Cross Cal Energy fall-off seen in commissioning and ground cal data. To first order can be expressed as a linear energy loss, increasing with decreasing energy. E loss ~ 14 – 0.08E (E in keV) Currently investigating if this is sufficient to explain in-flight data or if there is an additional count rate efficiency term. This will allow (almost) direct comparison with PEACE for those few events where we have data.

CAA 6 th Cross Cal Meeting RAL, th Oct 2007 Investigation of possible Ground Level Event by Bern Blake Medium energy electron precursor due to neutron decay Should produce a flat spectrum which would be easier to assess inter-calibration between PEACE and RAPID Only a few of these types of event have been identified The current study concentrates on an event on

CAA 6 th Cross Cal Meeting RAL, th Oct 2007 RAPID-IES for Possible precursor signature X-ray signature detected in IES Sun sector

CAA 6 th Cross Cal Meeting RAL, th Oct 2007 ACE supports idea that we are seeing precursor electrons before main energetic component Similar signatures seen in HEO data J.B. Blake

CAA 6 th Cross Cal Meeting RAL, th Oct 2007 J.B. Blake Unfortunately spectrum does not match what is expected in theory

CAA 6 th Cross Cal Meeting RAL, th Oct 2007 Started PEACE/RAPID comparison for this interval…

CAA 6 th Cross Cal Meeting RAL, th Oct 2007 PEACE/RAPID Cross Cal Moments: IDL Software developed for production of RAPID partial moments. Works using the CAA datasets (Cn_CP_RAP_E3DD) Comparison with PEACE using data from CAA (C2_CP_PEA_MOMENTS) Using Cluster 2 data from 2003 tail season. This provides intervals of NM3 data when RAPID is effectively in Burst Mode and returning full 3D electron distribution for extended periods. Also PEACE moments currently only delivered to CAA for C2. The software is being extended to also include the PEACE 3D data products (Cn_CP_PEA_CP3DRH_PSD) to give total electron moments. Focus is on hot plasma so only considering E>100eV to avoid SCP and photo-electron effects. Corrections from the cross-calibration analysis are not yet finalised and so are not included in the current CAA products.

CAA 6 th Cross Cal Meeting RAL, th Oct 2007 PEACE/RAPID Cross Cal Partial Moments PEACE RAPID PEACE RAPID

CAA 6 th Cross Cal Meeting RAL, th Oct 2007 PEACE/RAPID Cross Cal Next steps: Complete the assessment of energy fall-off using ground cal and in-flight data. Look for differences in the off-axis detectors in each head. Further investigation of precursor events to see if they can help with cross- calibration (also scientifically interesting!). For 20 identified intervals investigate near energy overlap region to obtain relative PEACE/RAPID cal as a function of time. Complete development/testing of IDL S/W for combined PEACE/RAPID moments from 3D electron data. Assess RAPID contribution to total moment sums in regions of hot plasma.