Cosmic noise absorption signature of particle precipitation during interplanetary coronal mass ejection sheaths and ejecta

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Kilpua , E , Juusola , L , Grandin , M , Kero , A , Dubyagin , S , Partamies , N , Osmane , A , George , H , Kalliokoski , M , Raita , T , Asikainen , T & Palmroth , M 2020 , ' Cosmic noise absorption signature of particle precipitation during interplanetary coronal mass ejection sheaths and ejecta ' , Annales Geophysicae , vol. 38 , no. 2 , pp. 557-574 . https://doi.org/10.5194/angeo-38-557-2020

Title: Cosmic noise absorption signature of particle precipitation during interplanetary coronal mass ejection sheaths and ejecta
Author: Kilpua, Emilia; Juusola, Liisa; Grandin, Maxime; Kero, Antti; Dubyagin, Stepan; Partamies, Noora; Osmane, Adnane; George, Harriet; Kalliokoski, Milla; Raita, Tero; Asikainen, Timo; Palmroth, Minna
Other contributor: University of Helsinki, Department of Physics
University of Helsinki, Particle Physics and Astrophysics
University of Helsinki, Department of Physics
University of Helsinki, Particle Physics and Astrophysics
University of Helsinki, Space Physics Research Group
University of Helsinki, Department of Physics


Date: 2020-04-21
Language: eng
Number of pages: 18
Belongs to series: Annales Geophysicae
ISSN: 0992-7689
DOI: https://doi.org/10.5194/angeo-38-557-2020
URI: http://hdl.handle.net/10138/314881
Abstract: We study here energetic-electron (E > 30 keV) precipitation using cosmic noise absorption (CNA) during the sheath and ejecta structures of 61 interplanetary coronal mass ejections (ICMEs) observed in the near-Earth solar wind between 1997 and 2012. The data come from the Finnish riometer (relative ionospheric opacity meter) chain from stations extending from auroral (IVA, 65.2 degrees N geomagnetic latitude; MLAT) to subauroral (JYV, 59.0 degrees N MLAT) latitudes. We find that sheaths and ejecta lead frequently to enhanced CNA (> 0.5 dB) both at auroral and subauroral latitudes, although the CNA magnitudes stay relatively low (medians around 1 dB). Due to their longer duration, ejecta typically lead to more sustained enhanced CNA periods (on average 6-7 h), but the sheaths and ejecta were found to be equally effective in inducing enhanced CNA when relative-occurrence frequency and CNA magnitude were considered. Only at the lowest-MLAT station, JYV, ejecta were more effective in causing enhanced CNA. Some clear trends of magnetic local time (MLT) and differences between the ejecta and sheaths were found. The occurrence frequency and magnitude of CNA activity was lowest close to midnight, while it peaked for the sheaths in the morning and afternoon/evening sectors and for the ejecta in the morning and noon sectors. These differences may reflect differences in typical MLT distributions of wave modes that precipitate substorm-injected and trapped radiation belt electrons during the sheaths and ejecta. Our study also emphasizes the importance of substorms and magnetospheric ultra-low-frequency (ULF) waves for enhanced CNA.
Subject: ENERGETIC ELECTRON-PRECIPITATION
AURORAL RADIO ABSORPTION
HIGH-SPEED STREAMS
SOLAR-WIND
MAGNETIC-FIELD
RADIATION BELT
PLASMASPHERIC HISS
GEOMAGNETIC STORM
DYNAMIC PRESSURE
WAVE ACTIVITY
115 Astronomy, Space science
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