Improved Energy Resolution Measurements of Electron Precipitation Observed During an IPDP‐Type EMIC Event.
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| Title: | Improved Energy Resolution Measurements of Electron Precipitation Observed During an IPDP‐Type EMIC Event. |
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| Authors: | Clilverd, M. A.1 (AUTHOR) macl@bas.ac.uk, Rodger, C. J.2 (AUTHOR), Hendry, A. T.1,2 (AUTHOR), Lozinski, A. R.1,3 (AUTHOR), Sauvaud, J.‐A.4 (AUTHOR), Lessard, M. R.5 (AUTHOR), Raita, T.6 (AUTHOR) |
| Source: | Journal of Geophysical Research. Space Physics. Jul2024, Vol. 129 Issue 7, p1-12. 12p. |
| Subject Terms: | Electrons, Low temperature plasmas, Electron density, Interval analysis, Electromagnetic interactions, Electron energy loss spectroscopy |
| Abstract: | High energy resolution DEMETER satellite observations from the Instrument for the Detection of Particle (IDP) are analyzed during an electromagnetic ion cyclotron (EMIC)‐induced electron precipitation event. Analysis of an Interval Pulsation with Diminishing Periods (IPDP)‐type EMIC wave event, using combined satellite observations to correct for incident proton contamination, detected an energy precipitation spectrum ranging from ∼150 keV to ∼1.5 MeV. While inconsistent with many theoretical predictions of >1 MeV EMIC‐induced electron precipitation, the finding is consistent with an increasing number of experimentally observed events detected using lower resolution integral channel measurements on the POES, FIREBIRD, and ELFIN satellites. Revised and improved DEMETER differential energy fluxes, after correction for incident proton contamination shows that they agree to within 40% in peak flux magnitude, and 85 keV (within 40%) for the energy at which the peak occurred as calculated from POES integral channel electron precipitation measurements. This work shows that a subset of EMIC waves found close to the plasmapause, that is, IPDP‐type rising tone events, can produce electron precipitation with peak energies substantially below 1 MeV. The rising tone features of IPDP EMIC waves, along with the association with the high cold plasma density regime, and the rapidly varying electron density gradients of the plasmapause may be an important factor in the generation of such low energy precipitation, co‐incident with a high energy tail. Our work highlights the importance of undertaking proton contamination correction when using the high‐resolution DEMETER particle measurements to investigate EMIC‐driven electron precipitation. Plain Language Summary: Energetic electrons are lost rapidly from the outer radiation belt. Several processes are thought to drive the electron losses. One process is through interactions with electromagnetic ion cyclotron (EMIC) waves. Theoretical studies suggest that electrons primarily with energy >1 MeV are lost through this process, however, previous experimental satellite observations indicate that precipitation bursts with much lower electron energies are more common. One issue is that the previous satellite observations were made with poor energy resolution and are challenging to interpret due to coincident proton precipitation, which contaminate the electron measurements. Here we use observations from the DEMETER satellite which we have corrected for proton contamination. The measurements, made with higher energy resolution than before, confirm that indeed, low energy electron precipitation can happen when EMIC waves drive electron losses. The study finds that this lower energy characteristic is likely to be driven by a small subset of rising tone EMIC waves, known as Interval Pulsation with Diminishing Periods (IPDP), typically confined to the magnetic local time evening sector. Key Points: An electromagnetic ion cyclotron wave event (an interval of pulsations with diminishing period, IPDP) was studied from Low Earth OrbitCo‐incident satellite observations detected IPDP‐induced energetic electron precipitation, starting at 150 keV, peaking at 215 keVHigh‐resolution measurements from the DEMETER satellite show enhanced fluxes from 215 keV to 1.5 MeV exhibiting a "hard" power‐law spectrum [ABSTRACT FROM AUTHOR] |
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| Database: | GreenFILE |
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