A1 Refereed original research article in a scientific journal
The Large Longitudinal Spread of Solar Energetic Particles During the 17 January 2010 Solar Event
Authors: Dresing N, Gomez-Herrero R, Klassen A, Heber B, Kartavykh Y, Droge W
Publisher: SPRINGER
Publication year: 2012
Journal: Solar Physics
Journal name in source: SOLAR PHYSICS
Journal acronym: SOL PHYS
Volume: 281
Issue: 1
First page : 281
Last page: 300
Number of pages: 20
ISSN: 0038-0938
DOI: https://doi.org/10.1007/s11207-012-0049-y
Abstract
We investigate multi-spacecraft observations of the 17 January 2010 solar energetic particle event. Energetic electrons and protons have been observed over a remarkable large longitudinal range at the two STEREO spacecraft and SOHO, suggesting a longitudinal spread of nearly 360 degrees at 1 AU. The flaring active region, which was on the backside of the Sun as seen from Earth, was separated by more than 100 degrees in longitude from the magnetic footpoints of each of the three spacecraft. The event is characterized by strongly delayed energetic particle onsets with respect to the flare and only small or no anisotropies in the intensity measurements at all three locations. The presence of a coronal shock is evidenced by the observation of a type II radio burst from the Earth and STEREO-B. In order to describe the observations in terms of particle transport in the interplanetary medium, including perpendicular diffusion, a 1D model describing the propagation along a magnetic field line (model 1) (Droge, Astrophys. J. 589, 1027 -aEuro parts per thousand 1039, 2003) and the 3D propagation model (model 2) by Droge et al. (Astrophys. J. 709, 912 -aEuro parts per thousand 919, 2010) including perpendicular diffusion in the interplanetary medium have been applied. While both models are capable of reproducing the observations, model 1 requires injection functions at the Sun of several hours. Model 2, which includes lateral transport in the solar wind, reveals high values for the ratio of perpendicular to parallel diffusion. Because we do not find evidence for unusual long injection functions at the Sun, we favor a scenario with strong perpendicular transport in the interplanetary medium as an explanation for the observations.
We investigate multi-spacecraft observations of the 17 January 2010 solar energetic particle event. Energetic electrons and protons have been observed over a remarkable large longitudinal range at the two STEREO spacecraft and SOHO, suggesting a longitudinal spread of nearly 360 degrees at 1 AU. The flaring active region, which was on the backside of the Sun as seen from Earth, was separated by more than 100 degrees in longitude from the magnetic footpoints of each of the three spacecraft. The event is characterized by strongly delayed energetic particle onsets with respect to the flare and only small or no anisotropies in the intensity measurements at all three locations. The presence of a coronal shock is evidenced by the observation of a type II radio burst from the Earth and STEREO-B. In order to describe the observations in terms of particle transport in the interplanetary medium, including perpendicular diffusion, a 1D model describing the propagation along a magnetic field line (model 1) (Droge, Astrophys. J. 589, 1027 -aEuro parts per thousand 1039, 2003) and the 3D propagation model (model 2) by Droge et al. (Astrophys. J. 709, 912 -aEuro parts per thousand 919, 2010) including perpendicular diffusion in the interplanetary medium have been applied. While both models are capable of reproducing the observations, model 1 requires injection functions at the Sun of several hours. Model 2, which includes lateral transport in the solar wind, reveals high values for the ratio of perpendicular to parallel diffusion. Because we do not find evidence for unusual long injection functions at the Sun, we favor a scenario with strong perpendicular transport in the interplanetary medium as an explanation for the observations.
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