CIS Calibration Status Lynn Kistler, Chris Mouikis Adrian Blagau Iannis Dandouras, Alain Barthe 22 th Cross-Calibration Meeting, Tenerife, November 2015

CIS Instrument Status RumbaSalsaSambaTango * 1 : Not operational since 25 Oct * 2 : Not operational since 11 Nov * 3 : to be switched ON, if necessary * 4 : Magnetospheric modes only, since April 2011; operations reduced to 1 hour / orbit since October 2012 * 1 * 3 * 2

CODIF Calibrations New CODIF Calibrations, by Lynn Kistler (March 2015):  Changes to SC4 O + and He + HS and LS “absolute efficiency”.  Changes to SC3 O + and He + HS “absolute efficiency”  SC4 absolute efficiency checks (no change to SC4 H + absolute efficiency for )  Changes to SC4 H + and O + anode efficiencies  SC4 He + anode efficiencies  Comparisons with Van Allen Probes / HOPE measurements  Calibrations are now updated up to January 2014 CODIF in-flight calibration articles, by Kistler et al., and by Mouikis et al. in the G.I. special issue.

Start/Stop and single position efficiencies all show very stable behavior since the MCP HV increase in The observations are consistent with no change. Stop eff. Start eff. Single Position eff. CODIF Calibrations

Plasma Pressure Mag. Pressure Total Pressure Pressure Balance Checks Pressure balance in the plasma sheet still looks very good through the end of CODIF Calibrations

CODIF Cluster 1, 3 and 4 total H+ efficiencies evolution, normalised to the start of the mission. CODIF Calibrations

Oxygen Efficiencies  Decided to assume that the O + efficiency change tracks the H + efficiency change. Note that that was approximately true in the early mission, when the O + beams were used.  Revised efficiencies shown with dotted line. CODIF Calibrations

Statistical Study of Ion Composition – implications for the calibrations Lynn Kistler, Nov 12, 2015

Results with New CODIF Calibration Files Last delivered calibrations (March 2015) contained significant changes to how the O+ and He+ changed with time. We have also improved the subtraction of spillover from H+ into He+. Using these new efficiencies and background subtraction, we have performed an extensive statistical study of composition as a F10.7 and Kp in the inner magnetosphere from (Kistler and Mouikis, 2015) We have compared the results of this analysis with the results of Young et al., 1982, at geosynchronous orbit, covering the energy range keV. These comparisons show good agreement, but one additional adjustment to He+ was required. The reason for this adjustment was tracked down to a decision made in early calibration files. Kistler, L.M. and C.G. Mouikis (2015), The inner magnetosphere ion composition and locatl time distribution over a solar cycle, J. Geophys. Res., Under Review.

Comparison with Young et al., 1982, Kp: 0-2 These show the comparison using the same energy range and similar L-values and geomagnetic conditions –E-range keV –L=6-7 –Kp=0-2 Young et al., 1982 Fit to CODIF data Maggiolo and Kistler, 2014 (1-40 keV,L=7-8)

Comparison with Young et al., 1982, Kp: 2-4 These show the comparison using the same energy range and similar L-values and geomagnetic conditions –E-range keV –L=6-7 –Kp=2-4 Young et al., 1982 Fit to CODIF data Maggiolo and Kistler, 2014 (1-40 keV,L=7-8)

Comparisons O+, He+ and O+/H+ ratio are all in reasonable agreement with Young et al., both in their dependence on F10.7 and Kp, and in their overall values. However, to get this agreement, an adjustment to the He+ efficiency was necessary.

Adjustments to He Efficiencies He+ is particularly difficult to calibrate in-flight, because there are almost no time periods where it contributes significantly to the density, pressure or flux. For this reason, we have just assumed that the temporal changes to the He+ absolute efficiency have followed the O+ changes. For H+ and O+, we used time periods when they dominated the pressure in the plasma sheet to adjust the absolute efficiency to achieve pressure balance. This was initially done in , and led to an initial “absolute efficiency” file that sets the baseline for the later temporal changes. Initially, the pressure balance check was done for H+, and all species were adjusted by the same factor. It was found that the H+ efficiency had decreased from pre- launch by a factor of ~2.5, and so this factor was incorporated into the ABSEFF file for all species. However, when O+ dominated time periods were identified, we found that this adjustment made the O+ pressure too high. The best initial flight O+ efficiency was actually very close to its pre-launch calibration value. Thus, the factor of 2.5 was removed from the O+ ABSEFF. However, we did NOT remove it from the He+.

Adjustments to He Efficiencies Thus, while all subsequent changes to the calibrations had the He+ efficiencies follow the O+ efficiencies, this initial step in 2003 decreased the efficiency (increasing the flux) of He+ relative to O+ by a factor of 2.5. This comparison with the Young et al., 1982, statistical dataset found that the He+ density was in fact high by a factor of 2 to 3. Comparisons with other measurements (e.g. Scatha measurements in Strangeway and Kaye, 1986) also indicated that the CODIF He+ fluxes were too high. Thus we have adjusted the He+ efficiencies to include the same change to the initial ABSEFF value as was done for O+. The efficiency has been increased by a factor of 2.5, which reduces the flux by a factor of 2.5. Thus in all steps now, the He+ changes are the same as the O+ changes. It is with this revision to the He+ that we get very good agreement with earlier measurements.

New Files We have modified the SC4 ABSEFF files to adjust the He+ efficiency. This effects the He+ fluxes for the whole mission. These files are almost ready for delivery. The He+ efficiencies for SC1 and SC3 still need to be finalized. There are a number of steps that need to be taken. These are: –Finalize the anode-dependent spillover from H+ to He+ subtraction –Redo the anode efficiencies, using the background subtraction –Compare H+ spectra between the 3 spacecraft during conjunction time periods, and compare statistical values. We have put in a proposal for NASA funding to continue the CODIF calibration effort for another year. This He+ task would be part of that effort, if it is funded.

HIA Calibrations New HIA Calibrations, by Adrian Blagau (October 2015):  HIA - HS side calibrations for November November  Comparisons with WHISPER plasma density.  For the data after 2012 the results show very stable efficiencies for the operating HIA sensor (C1, HS - side). HIA in-flight calibration article, by Blagau et al., at the G.I. special issue.

Evolution of the HIA calibration factors for the Cluster 1 HS side for , with respect to the 2011 efficiencies HIA Calibrations