ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Copernicus Publications Göttingen, Germany 10.5194/angeo-27-3677-2009 On acceleration of <1 MeV/n He ions in the corotating compression regions near 1 AU: STEREO observations Bučík R. 1 2 Mall U. 1 Korth A. 1 Mason G. M. 3 Max-Planck-Institut für Sonnensystemforschung, 37191 Katlenburg-Lindau, Germany Institute of Experimental Physics, 04001 Košice, Slovakia The Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA 30 09 2009 27 9 3677 3690 Copyright: © 2009 R. Bučík et al. 2009 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://angeo.copernicus.org/articles/27/3677/2009/angeo-27-3677-2009.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/27/3677/2009/angeo-27-3677-2009.pdf

Observations of multi-MeV corotating interaction region (CIR) ions are in general consistent with models of CIR shock acceleration and transport. The presence of suprathermal particles near 1 AU in unshocked compression regions is not adequately explained. Nonetheless, more recent works demonstrate that unshocked compression regions associated with CIRs near 1 AU could energize particles. In the energy range from ~0.1 to ~1 MeV/n we investigate CIR events observed in 2007–2008 by the STEREO A and B spacecraft. We treat the predictions of compression acceleration by comparing the observed ion intensities with the model parameters. These observations show that the ion intensity in CIR events with in-situ reverse shock is well organized by the parameters which characterize the compression region itself, like compression width, solar wind speed gradients and the total pressure. In turn, for CIR events with the absence of the shocks the model predictions are not fulfilled.

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