University of Oulu

Leon Kocharov et al 2018 ApJL 862 L20

Spatial organization of seven extreme solar energetic particle events

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Author: Kocharov, Leon1; Pohjolainen, Silja2; Reiner, Mike J.3,4;
Organizations: 1Sodankylä Geophysical Observatory, University of Oulu, P.O.B. 3000, Oulu FI-90014, Finland
2Tuorla Observatory, University of Turku, Piikkiö FI-21500, Finland
3The Catholic University of America, Washington, DC, USA
4NASA/Goddard Space Flight Center, Greenbelt, MD, USA
5Space Climate Research Unit, University of Oulu, Oulu FI-90014, Finland
6Space Weather Research Laboratory, New Jersey Institute of Technology, Newark, NJ 07102-1982, USA
7Big Bear Solar Observatory, New Jersey Institute of Technology, Big Bear City, CA 92314, USA
8Space Research Laboratory, University of Turku, Turku FI-20014, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 0.3 MB)
Persistent link: http://urn.fi/urn:nbn:fi-fe2018082133842
Language: English
Published: IOP Publishing, 2018
Publish Date: 2018-08-21
Description:

Abstract

Emission of relativistic protons and helium responsible for extreme solar particle events (ground level enhancements (GLEs)) is often structured. We investigate its organization depending on the eruption stage characterized by the heliocentric height of associated coronal mass ejections (CMEs). Seven GLEs are considered: events on 1997 November 6, 1998 May 2, 2000 July 14, 2001 December 26, 2003 November 2, 2006 December 13, and 2012 May 17, which are half of the SOlar and Heliospheric Observatory (SOHO )-era GLEs, excluding very weak events. Count-rate profiles of the GLEs plotted as a function of the CME height reveal two types (or two components) of the high-energy particle emission. The first component rises in a step-like manner during the CME transit from 2 R to 3 R , when the CME exits from predominantly closed coronal magnetic structures, irrespective of the CME speed (type H). This component is of coronal origin. The second component of the GLE-producing particles starts to rise when CME is at about 4 R , achieves its maximum at 6–10 R , and declines shortly after that (type J). The type J particle injection into the interplanetary space coincides with the decametric–hectometric radio burst complex that includes enhanced emission of type II and concurrent low-frequency type III bursts, indicative of the CME interaction with a streamer-like structure at a few solar radii from the Sun. Those could be delayed particles from the flare region. A possible additional contribution of the CME-bow-shock acceleration in unstructured solar wind is not large in the two considered types of events.

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Series: Astrophysical journal letters
ISSN: 2041-8205
ISSN-E: 2041-8213
ISSN-L: 2041-8205
Volume: 862
Issue: 2
Article number: L20
DOI: 10.3847/2041-8213/aad18d
OADOI: https://oadoi.org/10.3847/2041-8213/aad18d
Type of Publication: A1 Journal article – refereed
Field of Science: 115 Astronomy and space science
Subjects:
Funding: This research was supported by the Academy of Finland through projects 304435 (CRIPA-X), 260596, and 267186.
Academy of Finland Grant Number: 304435
260596
Detailed Information: 304435 (Academy of Finland Funding decision)
260596 (Academy of Finland Funding decision)
Copyright information: © 2018. The American Astronomical Society. All rights reserved. Published in this repository with the kind permission of the publisher.