Volume 519, September 2010
|Number of page(s)||7|
|Published online||09 September 2010|
Solar near-relativistic electron observations as a proof of a back-scatter region beyond 1 AU during the 2000 February 18 event
Department of Physics, University of Helsinki, 00014 Helsinki, Finland
2 Space Sciences Laboratory, University of California, Berkeley, CA 94720, USA e-mail: email@example.com
3 Applied Physics Laboratory, The Johns Hopkins University, Laurel, MD 20723, USA
4 Departament d'Astronomia i Meteorologia & Institut de Ciències del Cosmos, Universitat de Barcelona, 08028 Barcelona, Spain
Accepted: 3 May 2010
Aims. We study the near-relativistic (NR; >30 keV) electron event observed on 2000 February 18 by near-Earth spacecraft. Previous works have explained this event by assuming that the propagation of NR electrons is essentially “scatter-free” at heliocentric radial distances r < 1 AU, and that beyond 1 AU particles are “back-scattered” by magnetic field irregularities.
Methods. Our aim is to re-visit this interplanetary propagation scenario and infer the injection profile at the Sun by fitting the electron directional intensities observed by the Advanced Composition Explorer.
Results. We use a Monte Carlo transport model to explore this approach. We assume that the interplanetary magnetic field is an Archimedean spiral and that the interplanetary transport of NR electrons is characterized by a large radial mean free path ( > 0.5 AU) and anisotropic pitch-angle scattering for r <1 AU, and a small radial mean free path ( < 0.5 AU) and isotropic scattering in the back-scatter region.
Conclusions. The event cannot be explained without assuming a back-scatter region beyond 1 AU. The best fit is obtained by assuming = 3.2 AU in the inner heliosphere and a back-scatter region characterized by a small mean free path = 0.2 AU located beyond 1.2 AU.
Key words: Sun: particle emission / Sun: flares / Sun: coronal mass ejections (CMEs) / interplanetary medium
© ESO, 2010
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.