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Galactic Cosmic Rays Modulation in the Vicinity of Corotating Interaction Regions: Observations During the Last Two Solar Minima

Ghanbari, Keyvan and Florinski, Vladimir and Guo, Xiaocheng and Hu, Qiang and Leske, Richard (2019) Galactic Cosmic Rays Modulation in the Vicinity of Corotating Interaction Regions: Observations During the Last Two Solar Minima. Astrophysical Journal, 882 (1). Art. No. 54. ISSN 1538-4357. doi:10.3847/1538-4357/ab31a5.

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Corotating interaction regions (CIRs) are responsible for short-term recurrent cosmic-ray modulation, prominent near solar minima. Using the OMNI data sets for two periods of low solar activity near the beginning and end of solar cycle 24, superposed epoch analysis was performed on the solar wind plasma features for 53 and 43 events during periods 2007–2008 and 2017–2018, respectively. Turbulent properties of the solar wind were studied using the variance method for each CIR. Power spectra have been constructed for overlapped subintervals in the vicinity of stream interfaces (SIs). Using measured correlation lengths and turbulent energies, parallel and perpendicular diffusion mean free paths for cosmic-ray ions have been inferred based on two distinct theoretical formulations. For the two periods with opposite solar polarities, our results show that unlike solar wind speed, magnetic field strength, flow pressure, and proton density are relatively higher during the latest period. Increased turbulent energy and reduced parallel transport coefficients of energetic particles at the SIs are observed. The diffusion coefficients follow the same trends during both periods. The perpendicular diffusion starts increasing nearly a day before SIs and is higher in the fast wind. Superposed epoch analysis is performed on the >120 MeV proton count rate obtained from the CRIS instrument on board the ACE spacecraft for the same events. The recorded proton rates have peaks half a day before a SI and reach their minimum more than a day after a SI and have a high anticorrelation with the perpendicular diffusion coefficient.

Item Type:Article
Related URLs:
URLURL TypeDescription
Florinski, Vladimir0000-0001-5485-2872
Guo, Xiaocheng0000-0003-0541-0597
Hu, Qiang0000-0002-7570-2301
Leske, Richard0000-0002-0156-2414
Additional Information:© 2019. The American Astronomical Society. Received 2019 June 16; revised 2019 July 10; accepted 2019 July 10; published 2019 September 2. This research was supported by NASA grant NNX17AB85G. The authors appreciate being granted access to the OMNI data obtained through the GSFC/SPDF OMNIWeb interface at (
Group:Space Radiation Laboratory
Funding AgencyGrant Number
Subject Keywords:Galactic cosmic rays ; solar wind; corotating streams ; interplanetary turbulence
Issue or Number:1
Classification Code:Galactic cosmic rays (567); Solar wind (1534); Corotating streams (314); Interplanetary turbulence (830)
Record Number:CaltechAUTHORS:20190903-130240306
Persistent URL:
Official Citation:Keyvan Ghanbari et al 2019 ApJ 882 54
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:98390
Deposited By: George Porter
Deposited On:04 Sep 2019 14:59
Last Modified:16 Nov 2021 17:38

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