Periodic variations of GCR related to solar rotation by ACE/CRIS, STEREO, SOHO/EPHIN and neutron monitors

Discussion timeslot (ZOOM-Meeting): 14. July 2021 - 18:00
ZOOM-Meeting URL: https://desy.zoom.us/j/96969970711
ZOOM-Meeting ID: 96969970711
ZOOM-Meeting Passcode: ICRC2021
Corresponding Session: https://icrc2021-venue.desy.de/channel/21-Short-term-modulation-SH/117
Live-Stream URL: https://icrc2021-venue.desy.de/livestream/Discussion-07/8

Abstract:
'We study the periodic variations of GCRs related to solar rotation based on neutron monitor, ACE/CRIS, STEREO and SOHO/EPHIN measurements. Now there is an opportunity to re-analyze the polarity dependence of the amplitudes of the recurrent GCR variations in 2007-2009 for negative A smaller 0 polarity and in 2017-2019 for A larger 0. We use the Fourier analysis method to study the periodicity in the GCR fluxes. Since the GCR recurrence is a consequence of solar rotation, we analyze not only GCR fluxes, but also solar and heliospheric parameters examining the relationships between the 27-day GCR variations and heliospheric, as well as, solar wind parameters. We find that the polarity dependence of the amplitudes of the 27-day variations of the GCR intensity and anisotropy for NMs data is kept for the last two solar minima: 23/24 (2007-2009) and 24/25 (2017-2019) with greater amplitudes in A larger 0 solar magnetic polarity. ACE/CRIS, SOHO/EPHIN and STEREO measurements are not governed by this principle of greater amplitudes in A larger 0 polarity. GCR recurrence caused by the solar rotation for low energy ( smaller 1GeV) cosmic rays is more sensitive to the enhanced diffusion effects, resulting in the same level of the 27-day amplitudes for positive and negative polarities. While high energy ( larger 1GeV) cosmic rays registered by NMs, are more sensitive to the large-scale drift effect leading to the 22-year Hale cycle in the 27-day GCR variation, with the larger amplitudes in the A larger 0 polarity than in the A smaller 0.'

Authors: Renata Modzelewska | Agnieszka Gil
Indico-ID: 361
Proceeding URL: https://pos.sissa.it/395/1271