Modeling solar near-relativistic electron events

Free access article

Issue		A&A Volume 507, Number 2, November IV 2009


Page(s)		981 - 993
Section		The Sun
DOI		http://dx.doi.org/10.1051/0004-6361/200912224
Published online		24 September 2009

A&A 507, 981-993 (2009)
DOI: 10.1051/0004-6361/200912224

Insights into solar injection and interplanetary transport conditions

N. Agueda¹, D. Lario², R. Vainio¹, B. Sanahuja^{3, 4}, E. Kilpua¹, and S. Pohjolainen⁵

¹ Department of Physics, University of Helsinki, 00014 Helsinki, Finland
e-mail: neus.agueda@helsinki.fi
² Applied Physics Laboratory, The Johns Hopkins University, Laurel, MD 20723-6099, USA
³ Departament d'Astronomia i Meteorologia, Universitat de Barcelona, 08028 Barcelona, Spain
⁴ Institut de Ciències del Cosmos, Universitat de Barcelona, 08028 Barcelona, Spain
⁵ Department of Physics and Astronomy, University of Turku, Tuorla Observatory, 21500 Piikkiö, Finland

Received 29 March 2009 / Accepted 14 August 2009

Abstract
Context. Solar near-relativistic electrons (>30 keV) are observed as discrete events in the inner heliosphere following different types of solar transient activity. Several mechanisms have been proposed for the production of these electrons. One candidate is related to solar flare activity. Other candidates include shocks driven by fast coronal mass ejections (CMEs) or processes of magnetic reconnection in the aftermath of CMEs.
Aims. We study eleven near-relativistic (NR) electron events observed by the Advanced Composition Explorer (ACE) between 1998 and 2005 with the aim of estimating the roles played by solar flares, CME-driven shocks, and processes of magnetic restructuring in the aftermath of the CMEs in the injection of NR electrons. The main goal is to infer the underlying injection profile from particle observations at 1 AU, as well as the interplanetary transport conditions.
Methods. We used Monte Carlo simulations to model the transport of particles along the interplanetary magnetic field. By taking the angular response of the LEFS60 telescope of the EPAM instrument onboard ACE into account, we were able to deconvolve the transport effects from the observed intensities, and thus infer the solar injection profile.
Results. In this set of events, we have identified two types of injection episodes: short (<15 min) and time-extended (>1 h). Short injection episodes seem to be associated with the flare processes and/or the reconnection phenomena in the aftermath of the CME, while time-extended episodes seem to be consistent with injection from CME-driven shocks.
Conclusions. We find that there is no single scenario that operates in all the events. The interplanetary propagation of NR electrons can occur both under strong scattering and under almost scatter-free propagation conditions and several injection phases (related to flares and/or CMEs) are possible.

Key words: Sun: particle emission -- Sun: flares -- Sun: coronal mass ejections (CMEs)

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.