The Dominance of perpendicular diffusion in modulating galactic cosmic rays in corotating interaction regions: observations of two last solar minima
Abstract
Corotating interaction regions (CIRs) are known to be the cause of recurrent galactic cosmic ray variations. There are two major physical processes that are thought to cause this modulation: the inhibition of diffusive transport near stream interfaces (SI) and the drift along the heliospheric current sheet. We have identified 96 CIRs from the two past solar minima of 2007-2008 and 2017-2018 and analyze the turbulent properties of the solar wind before and after each event. Superposed epoch analysis was performed on the turbulent energy and the spectral bend-over length and cosmic-ray diffusion coefficients were inferred based on this data. Our results for both periods show that the total turbulent energy is enhanced at the SI, while the bend-over length is larger in the fast wind than in the slow wind. The parallel diffusion coefficient has a dip at the SI and the perpendicular diffusion coefficient is increased in the fast wind. We report strong anti-correlation between the perpendicular diffusive mean free path and cosmic-ray proton count rates near SIs which implies that the perpendicular diffusion is most likely the dominant factor in modulating the galactic cosmic rays by the CIRs.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMSH41A..02G
- Keywords:
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- 7513 Coronal mass ejections;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY;
- 7514 Energetic particles;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY;
- 7536 Solar activity cycle;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY;
- 7974 Solar effects;
- SPACE WEATHER