1. Status_Penetrating_Radiation Flag Branislav Mihaljčić, A Fazakerley 1

2. Introduction The Penetrating Radiation flag is to help the user in identifying intervals when PEACE sensors (HEEA and LEEA) were affected by PR during perigee passes and Solar Energetic Proton (SEP) events. All other intervals during an orbit are treated as no radiation cases 2

3. Method Identify intervals likely to require checking for Penetrating Radiation – For Earth’s trapped radiation belts we check for intervals based on the JSOC PSE auroral oval events – For SEP events we consider intervals during which the ACE proton flux (>10 MeV) exceeds a threshold We consider: – The ratio, Fn, of LEEA-to-HEEA electron densities in the energy overlap region – This ratio should be close to 1 if the HEEA and LEEA sensors are well inter-calibrated – It may deviate from 1 if there are very high counts in HEEA, or HEEA and LEEA – It may deviate from 1 if there are significant levels of Penetrating Radiation reaching the MCPs We use the best available densities (cal. version 6.0) at the time of writing – We use MOMS_L2 data (short for moments, level 2), more specifically L1L2 and H1H2 moments when both sensors ‘see’ the same plasma, but have the same energy coverage. – The moments product CPCMOM is the original on-board moments data, computed on- board by the DPU, while MOMS_L2 is the same data, but with corrections applied on-the- ground, which change as the sensors age throughout the mission and has to be applied for each sensor according to its unique MCP alpha factor history. 3

4. Penetrating Radiation during Perigee crossing Perigee Pass (high PR case) HEEA (dEF) RAP e - (line) LEEA (dEF) RAP e - (line) n e (m -3 ) HEEA (black) LEEA (Red) counts HEEA (black) LEEA (Red) When PR is high during a Perigee pass then: LEEA>HEEA density and HEEA=LEEA counts. HEEA & LEEA density match, except during the perigee crossing when PR is present and when HEEA and LEEA counts become equal. 4

5. Penetrating Radiation during Perigee crossing Perigee Pass (low PR case) HEEA (dEF) RAP e - (line) LEEA (dEF) RAP e - (line) n e (m -3 ) HEEA (black) LEEA (Red) counts HEEA (black) LEEA (Red) 5 When PR is low during a Perigee pass then: LEEA>HEEA density and HEEA>LEEA counts. HEEA and LEEA density match, except during the perigee crossing.

6. Examples of Penetrating Radiation flag Perigee crossing case (2003-06-06) PEACE (dEF) EFW (eV) MCP (level) Fn (LEEA/HEEA) PR Flag (red) Orb. Phase (black) n e (m -3 ) HEEA (black) LEEA (Red) counts HEEA (black) LEEA (Red) 6 Blue box interval, JSOC PSE oval auroral crossing code – PSE flag test is applied inside here for Earth radiation belt penetrating radiation

7. SEP identification: ACE Proton Flux Identify intervals likely to require checking for Penetrating Radiation – For SEP events we consider intervals during which the ACE proton flux (>10 MeV) exceeds a threshold of 2.5 PFUs – Event list is available if useful to other teams 7

8. During non-SEP event FGM (nT) FGM θ FGM φ RAP (ions) CIS RAP (e - ) PEACE (#cnts/s) During an non-SEP event, PEACE is not affected in all energies and there is a difference in RAP and CIS behaviour compared to an SEP event. 8

9. During strong SEP event FGM (nT) FGM θ FGM φ RAP (ions) CIS RAP (e - ) PEACE (#cnts/s) 9 During a strong SEP event, background levels are visibly raised in all the particle instruments, though the degree of background is a function of location in the magnetosphere as well as the SEP fluxes outside the magnetosphere

10. Examples of Penetrating Radiation flag SEP event case (2003-10-29) PEACE (dEF) EFW (eV) MCP (level) Fn (LEEA/HEEA) PR Flag (red) Orb. Phase (black) n e (m -3 ) HEEA (black) LEEA (Red) counts HEEA (black) LEEA (Red) 10 During a strong SEP event, background levels are visibly raised in all the particle instruments, though the degree of background is a function of location in the magnetosphere as well as the SEP fluxes outside the magnetosphere: e.g. pre-perigee we see stronger SEP effects in this example

11. End 11