Modeling Particle Acceleration and Transport at CIRs

Gang Li1, Lulu Zhao2, Robert W Ebert3, Mihir Indrajit Desai4, Maher A Dayeh4, Glenn M Mason5, Yao Chen6 and Zhao Wu6, (1)University of Alabama in Huntsville, Department of Space Sciences and CSPAR, Huntsville, AL, United States, (2)University of Alabama in Huntsville, Huntsville, AL, United States, (3)University of Texas at San Antonio, Department of Physics and Astronomy, San Antonio, United States, (4)Southwest Research Institute, San Antonio, United States, (5)Johns Hopkins University Applied Physics Laboratory, Laurel, United States, (6)Shandong University at Weihai, Weihai, China
Abstract:
CIRs are a major site for particle acceleration during solar minimum. Earlier Ulysses observations have found that particles can be accelerated at both the forward and the reverse shocks that often form at a few AUs. The accelerated particles then propagate back to the Earth along Parker's field line. Theoretical calculations predicted a modulation of the spectrum at low energies, qualitatively agreed with obsevations at 1 AU. However, this picture was recently challenged by STEREO observations, where local accelerations near 1 AU were inferred in many events. In this work, we perform a detailed numerical calculation to study particle acceleration and transport in one CIR event which was observed by both ACE and STEREO spacecraft. We obtain particle currents at different heliocentric distances and different longitudes, as well as particle anisotropy. These values are compared with observations and the implication on the acceleration site and the interplanetary turbulence spectrum is discussed.
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