Coronal electron temperature inferred from the strahl electrons in the inner heliosphere: parker solar probe and helios observations
File(s)Bercic_al_2020.pdf (5.1 MB)
Accepted version
Author(s)
Type
Journal Article
Abstract
The shape of the electron velocity distribution function plays an important role in the dynamics of the solar wind acceleration. Electrons are normally modeled with three components, the core, the halo, and the strahl. We investigate how well the fast strahl electrons in the inner heliosphere preserve the information about the coronal electron temperature at their origin. We analyzed the data obtained by two missions, Helios, spanning the distances between 65 and 215 R S, and Parker Solar Probe (PSP), reaching down to 35 R S during its first two orbits around the Sun. The electron strahl was characterized with two parameters: pitch-angle width (PAW) and the strahl parallel temperature (T s∥). PSP observations confirm the already reported dependence of strahl PAW on core parallel plasma beta (${\beta }_{\mathrm{ec}\parallel }$). Most of the strahl measured by PSP appear narrow with PAW reaching down to 30°. The portion of the strahl velocity distribution function aligned with the magnetic field is for the measured energy range well described by a Maxwellian distribution function. T s∥ was found to be anticorrelated with the solar wind velocity and independent of radial distance. These observations imply that T s∥ carries the information about the coronal electron temperature. The obtained values are in agreement with coronal temperatures measured using spectroscopy, and the inferred solar wind source regions during the first orbit of PSP agree with the predictions using a PFSS model.
Date Issued
2020-04-01
Date Acceptance
2020-02-28
Citation
The Astrophysical Journal: an international review of astronomy and astronomical physics, 2020, 892 (2), pp.1-14
ISSN
0004-637X
Publisher
American Astronomical Society
Start Page
1
End Page
14
Journal / Book Title
The Astrophysical Journal: an international review of astronomy and astronomical physics
Volume
892
Issue
2
Copyright Statement
© 2020. The American Astronomical Society. All rights reserved. This is an author-created, un-copyedited version of an article accepted for publication in The Astrophysical Journal. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The definitive publisher authenticated version is available online at https://doi.org/10.3847/1538-4357/ab7b7a.
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000523445200001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
Solar wind
Solar physics
Space plasmas
Space vehicle instruments
Astronomy data analysis
Solar corona
Solar atmosphere
RADIAL EVOLUTION
HEAT-FLUX
WIND
VELOCITY
MODEL
DISTRIBUTIONS
PROTONS
ENERGY
SLOW
HALO
Publication Status
Published
Article Number
ARTN 88
Date Publish Online
2020-04-01