22 nd CAA Cross-Calibration Workshop, 18 th – 19 th November 2015, Tenerife, Spain N. Doss, A.N. Fazakerley, C. Anekallu, B. Mihaljcic, G. Watson. Presented by Natasha Doss UCL Department of Space and Climate Physics Mullard Space Science Laboratory Cluster PEACE Calibrations, cross-calibrations and support for other teams

Topics: (i)PEACE Calibration Progress (ii)Inter-spacecraft comparisons from 2007 and 2010 (iii)Support for other teams

PEACE Calibration Progress: cross-calibration with WHI density Since the last meeting... Alpha factors for Dec 2013 – Jun 2014 determined for all sensors by comparing with WHISPER densities. Alpha factors for Jul 2013 – Nov 2013 determined for all sensors using linear interpolation.

Alpha factors: Dec 2013 – Jun 2014

During Dec 2013 – Jun 2014 the observational SC was Cluster-2. SC2 on throughout the orbit except at perigee (if L<3.6). In the wind the LEEA sensor is set to look at lower energies than the other SC. SC1,3,4 powered off at perigee (if L<3.6) and for the sheath, but we try to catch magnetopause and bow-shock crossings. In the wind LEEA and HEEA set to look at higher energies (strahl). Routine commanding

Observational SC: Magnetopause:HEEA 949 – eVLEEA 4.7 – 2880 eV Magnetosheath:HEEA 949 – eVLEEA 4.7 – 2880 eV Bow shock:HEEA 949 – eVLEEA 4.7 – 2880 eV Solar wind:HEEA 949 – eVLEEA 4.7 – 2880 eV Non-observational SC: Magnetopause:HEEA 949 – eVLEEA 4.7 – 2880 eV Magnetosheath:HEEA offLEEA off Bow shock:HEEA 949 – eVLEEA 4.7 – 2880 eV Solar wind:HEEA 34 – 949 eVLEEA 34 – 949 eV Routine commanding

It has become increasingly difficult to perform calibrations due to lack of useable intervals (good sheath, good overlap between HEEA & LEEA). We now routinely perform special calibration operations during normal modes and when possible during burst modes. We put the sensors in the same energy range to maximize the overlap. We perform these in the sheath. That way we can also compare HEEA data directly with WHISPER. 7 Special Calibration Intervals

No changes to the method used and presented in previous Cross-cal meetings except: 1) we now correct the EFW SC potential on C2 and C3 prior to producing PEACE densities. 2) PEACE densities also include the correction for the broken anodes on C2 and C3 (linear interpolation). The following slides show the degradation for each LEEA sensor. The top plots show weekly averaged density ratios of PEACE (LEEA) / WHISPER (ACTIVE) in manually selected ‘good’ sheath intervals. The PEACE densities used in these comparisons were calculated using only the ground calibration geometric factor. Thus they do not include: - post launch geometric factor corrections needed to correct densities - inter-anode calibration correction factors needed to correct velocity The bottom plots show the corresponding alpha factors (extended to 25th Aug – end of the eclipse season power off). Thruster firings on: Jan 16 th (All), Jan 24 th (All), Mar 07 th (SC1,3,4), Mar 10 th (SC2), Mar 17 th (SC1), May 19 th (All), May 26 th (All), June 6 th (All) LEEA degradation Dec 2013 – Jun 2014

Cluster-1 LEEA MCP - lowered Upper line – MCP operational Lower line – MCP lowered Firings alpha (start Dec 2013) ~ alpha (end Aug 2014) ~ (Values for MCP operational) Density ratio 1 0 Alpha Factor MCP - operational

Cluster-2 LEEA MCP - lowered Upper line – MCP operational Lower line – MCP lowered Firings alpha (start Dec 2013) ~ alpha (end Aug 2014) ~ (Values for MCP operational) Density ratio 1 0 Alpha Factor MCP - operational

Cluster-3 LEEA alpha (start Dec 2013) ~ alpha (end Aug 2014) ~ Density ratio 1 0 Alpha Factor MCP - operational MCP operational Firings

Cluster-4 LEEA alpha (start Dec 2013) ~ alpha (end Aug 2014) ~ MCP - operational Density ratio 1 0 Alpha Factor MCP operational Firings

New method: 1) To calibrate the HEEA sensors we compare the HEEA densities with the corrected LEEA densities for the special calibration intervals. 2) We also compare the HEEA densities directly with the WHISPER densities. This has only become possible since we started performing these special calibration intervals. 3) We then cross compare the 2 sets of results. The following slides show the degradation for each HEEA sensor. The top left plots show the weekly averaged density ratios of PEACE-HEEA/WHISPER. The top right plots show the weekly averaged density ratios of HEEA/LEEA(v6.0). The HEEA densities used in these comparisons were calculated using only the ground calibration geometric factor. The LEEA densities use the determined v6.0 alpha factors. The bottom right plots compares the modal density ratios from PEACE HEEA / WHISPER and PEACE HEEA / PEACE LEEA. The bottom left plots show the corresponding alpha factors. HEEA degradation Dec 2013 – Jun 2014

Cluster-1 HEEA Density ratio 1 0 Alpha Factor 1 0 MCP – both operational HEEA/WHISPERHEEA/LEEA alpha (start Dec 2013) ~ alpha (end Aug 2014) ~ HEEA/WHISPER x - HEEA/LEEA

Cluster-2 HEEA Density ratio 1 0 Alpha Factor 1 0 MCP – both operational HEEA/WHISPERHEEA/LEEA alpha (start Dec 2013) ~ alpha (end Aug 2014) ~ HEEA/WHISPER x - HEEA/LEEA

Cluster-3 HEEA Density ratio 1 0 Alpha Factor MCP – both operational HEEA/WHISPERHEEA/LEEA alpha (start Dec 2013) ~ alpha (end Aug 2014) ~ HEEA/WHISPER x - HEEA/LEEA

Cluster-4 HEEA Density ratio 1 0 Alpha Factor MCP – both operational alpha (start Dec 2013) ~ alpha (end Aug 2014) ~ HEEA/WHISPERHEEA/LEEA + - HEEA/WHISPER x - HEEA/LEEA

Conclusion: Although we see a decline in the sensitivity of all sensors, this decline is much less severe than in the last few dayside seasons as we have not had any GI intervals for long periods in the magnetosheath this time around. The special calibration intervals in the sheath do not appear to have had an impact on the sensitivities. Future work: For the current dayside season we have continued to command the instruments in such a way in order to protect the MCP’s as much as possible. This results in less useable events for calibration work and so we continue to perform special calibration intervals (~1 hour) once per week.

Thank-you to the WHISPER and EFW teams and the CSDS Hungarian Data Centre for all the data they have provided to make this work possible. We look forward to receiving WHISPER data for the rest of 2014 and early 2015 so we can more accurately calibrate our data for the Pitout, Balikhin and Alexandrova GI intervals. It would also be valuable for operational reasons (current and future operations) to have the most up to date alpha factors.

Inter-spacecraft Comparisons: 2007 and 2010 These slides complement the comparison of 2002 Moments data give at the Operational Review

Calibration Status – Comparison between 4 instruments CSA PEACE Moments: In order to illustrate good quality inter-instrument and inter-sensor calibration we will compare moments of the velocity distribution; density, bulk velocity, temperature At the OR we presented Moments data that are in the CSA, for all times between 01 April – 31 May We showed good agreement between the four spacecraft on the following slides. Note that in later years (not shown, to limit the presentation length!) where inter- anode calibration has not been done, the agreement is poorer, particularly for Vz. Here we illustrate that statement. Comparison C3/C4 September 02 – October Comparison C1/C2/C3/C4 September 15 – November

Calibration Status – Comparison between 4 instruments CSA PEACE Moments: comparison during C3/C4 40km separation (2007) DensityT perp T para 22 C3 C4 C3C4 1 – 100 MK 0.06 – 1 MK cm cm -3

Calibration Status – Comparison between 4 instruments CSA PEACE Moments: comparison during C3/C4 40 km separation (2007) 23 C3 C4 C3C4 Velocity V x -400 to 400 km/s V y -500 to 400 km/s V z -500 to 400 km/s

Calibration Status – Comparison between 4 instruments CSA PEACE Moments: comparison during ~5,000 km separation (2010) Density 24 C1 C2 C3C cm cm -3

Calibration Status – Comparison between 4 instruments CSA PEACE Moments: comparison during ~5,000 km separation (2010) Velocity 25 C1 C4 C2 C3 C1 C4 V x to 400 km/s V y -500 to 400 km/s V z -500 to 400 km/s

Calibration Status – Comparison between 4 instruments CSA PEACE Moments: comparison during ~5,000 km separation (2010) Temperature (T perp ) 26 C1 C2 C3C4 1 – 100 MK 0.06 – 1 MK

Calibration Status – Comparison between 4 instruments CSA PEACE Moments: comparison during ~5,000 km separation (2010) Temperature (T para ) 27 C1 C2 C3C4 1 – 100 MK 0.06 – 1 MK

Support for other teams (i)WHISPER We supplied carefully made partial moments for low and high energy populations to support WHI team studies of inner magnetosphere waves (a topic they raised at the previous Cross-Calibration meeting: Bernstein mode non-alignments). The main challenge was to minimise error for the < 100 eV moments, by removing internal and spacecraft photoelectron signatures with the minimum loss of plasma electron signal. In this case, SPINPAD moments are the most suitable, because 3DR data includes the internal photoelectron signal which can’t simply be removed (in existing software) without losing real signal at low energies.

Jun : 04:54-04:58 WHI Interest C2

Cluster-2, Jun : 04:54-04:58 3DR N e /cm -3 T para /eV T perp /eV Corrected CAA pot (added 3V) + 1V Reject data below corrected pot +1V Reject data below corrected pot + 1V, + 1 bin 3DR energy res. is worse than SPINPAD 12 sec snapshot!

Cluster-2, Jun : 04:54-04:58 0° 90° 180° Reject below “corrected pot +1V” SPINPAD Ionospheric photoelectrons Reject below “corrected pot +1V”

Cluster-2, Jun : 04:54-04:58 SPINPAD N e /cm -3 T para /eV T perp /eV Reject data bins < “corr. pot +1V” +1 bin SPINPAD moments assume gyrotropy

Looks like best correction Cluster-2, Jun : 04:54-04:58 SPINPAD N e /cm -3 T para /eV T perp /eV SPINPAD moments assume gyrotropy Reject data bins < “corr. pot +1V” +2 bin Hint of asymmetric spacecraft electron cloud; this may be the sun-side?

DatespacecraftN cold (/cc) Tpar_cold (eV) Tper_cold (eV) N hot (/cc) Tpar_hot (eV) Tper_hot (eV) C11 – 46 – 124 – – – – C41.5 – 4.55 – 104 – – – – C31 – 53 – 83 – 90.1 – – – C11 – 36 – 105 – – – – C41 – – 103 – – – – C30.4 – 54 – – – – C22 – 35 – 83.5 – – – – 3200 Support for other teams (i)WHISPER

Support for other teams (ii)ASPOC We supplied improved moments for a large number of magnetotail intervals (~150) that Maria has been using in her study of how to reconstruct spacecraft potential when ASPOC is active. We recalculated the moments by discarding counts below ~ 30 eV which we consider to be instrumental rather than true low energy plasma.

Moments Correction The study for Maria showed a need to improve the PEACE moments in the magnetotail, by eliminating the internal photo-electron signature. Note that the low energy signature can appear to come and go in SPINPAD (or PITCH_SPIN) 2D pitch angle data but in reality it is always present which can be seen in 3D data

Moments Correction The study for Maria showed a need to improve the PEACE moments in the magnetotail, by eliminating the internal photo-electron signature. The plot (left) shows a calculation of the partial moment due to that background signature. This appears to be consistent, but a function of V sc

Moments Correction In principle the partial moments from this steady background can be removed to correct the moments (credit MMS FPI team who are trying this) For PEACE we would need to take care about the minimum measured energy and the spacecraft potential, in order to develop a correction that can be applied to ALL moments data. But this could be a useful approach.

THE END