Solar energetic electron events measured by MESSENGER and Solar Orbiter: Peak intensity and energy spectrum radial dependences: Statistical analysis
Authors
Rodríguez García, Laura; Gómez Herrero, Raúl; Dresing, N.; Lario, David; Zouganelis, Ioannis; [et al.]Identifiers
Permanent link (URI): http://hdl.handle.net/10017/58866DOI: 10.1051/0004-6361/202244553
ISSN: 0004-6361
Publisher
The European Southern Observatory (ESO)
Date
2023-02-02Funders
Agencia Estatal de Investigación
European Commission
Bibliographic citation
Rodríguez García, L. [et al.], 2023, "Solar energetic electron events measured by MESSENGER and Solar Orbiter: Peak intensity and energy spectrum radial dependences: Statistical analysis", Astronomy & Astrophysics, vol. 670, art. no. A51, pp. 1-19.
Keywords
Sun: particle emission
Sun: coronal mass ejections (CMEs)
Sun: flares
Sun: corona
Sun: heliosphere
Project
info:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016/ESP2017-88436-R/ES/ENERGETIC PARTICLE DETECTOR EN SOLAR ORBITER: FASES D Y E/
info:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2017-2020/PID2019-104863RB-I00/ES/ENERGETIC PARTICLE DETECTOR EN SOLAR ORBITER: FASE E, CALIBRACION Y EXPLOTACION DE DATOS/
info:eu-repo/grantAgreement/EC/H2020/101004159/EU/Solar EneRgetic ParticlE aNalysis plaTform for the INner hEliosphere/SERPENTINE
Document type
info:eu-repo/semantics/article
Version
info:eu-repo/semantics/publishedVersion
Publisher's version
https://doi.org/10.1051/0004-6361/202244553Rights
Attribution 4.0 International (CC BY 4.0)
Access rights
info:eu-repo/semantics/openAccess
Abstract
Context. We present a list of 61 solar energetic electron (SEE) events measured by the MESSENGER mission and the radial depen dences of some parameters associated with these SEE events. The analysis covers the period from 2010 to 2015, when the heliocentric
distance of MESSENGER varied between 0.31 and 0.47 au. We also show the radial dependences for a shorter list of 12 SEE events
measured in February and March 2022 by spacecraft near 1 au and by Solar Orbiter at about its first close perihelion at 0.32 au.
Aims. We study the radial dependences of the electron peak intensity and the energy spectrum of the electron intensity at the time of
the SEE event peak intensity, taking advantage of multi-spacecraft measurements.
Methods. We compiled the list of SEE events measured by MESSENGER and Solar Orbiter using hourly averages to find the prompt
component of the near-relativistic (∼70–110 keV) electron peak intensities and to calculate the peak-intensity energy spectra. We also
obtained the peak intensities and energy spectra for the same events as measured by the STEREO-A, -B, ACE, or Wind spacecraft
when one of these spacecraft was in close nominal magnetic connection with MESSENGER or Solar Orbiter to derive the radial
dependences of these SEE parameters.
Results. (1) Because the background intensity level of the particle instrument on board MESSENGER is high, the SEE events mea sured by this mission are necessarily large and intense; most of them are accompanied by a shock driven by a coronal mass ejection
and are widely spread in heliolongitude. The SEE events display relativistic (∼1 MeV) electron intensity enhancements. For this SEE
sample, we found that (2) the SEE peak intensity shows a radial dependence that can be expressed as R
α
, where the median value of
the α index is αMed = −3.3±1.4 for a subsample of 28 events for which the nominal magnetic footpoints of the near 0.3 au and 1 au
spacecraft were close in heliographic longitude. (3) The mean spectral index δ of a subset of 42 events for which the energy spectrum
could be analysed is hδi = −1.9±0.3, which is harder than the value found in previous studies using data from spacecraft near 1 au.
SEE events observed by Solar Orbiter also display harder energy spectra than previous studies using data obtained near 1 au.
Conclusions. There is a wide variability in the radial dependence of the electron peak intensities, but on average and within uncer tainties, the ∝R
−3 dependence found in previous observational and modelling studies is confirmed. The electron spectral index found
in the energy range around ∼200 keV (δ200) of the backward-scattered population near 0.3 au measured by MESSENGER is harder
by a median factor of ∼20% and ∼10% when comparing to the near 1 au anti-sunward propagating beam and the backward-scattered
population, respectively.
Files in this item
Files | Size | Format |
|
---|---|---|---|
Solar_Rodriguez_Astron_Astroph ... | 2.316Mb |
|
Files | Size | Format |
|
---|---|---|---|
Solar_Rodriguez_Astron_Astroph ... | 2.316Mb |
|
Collections
- FISICA - Artículos [76]
- Horizon 2020 Framework Programme [138]
- IDESRG - Artículos [21]