Väisänen, P., Usoskin, I., & Mursula, K. ( 2019). Long‐term and solar cycle variation of galactic cosmic rays: Evidence for variable heliospheric turbulence. Journal of Geophysical Research: Space Physics, 124, 804– 811. https://doi.org/10.1029/2018JA026135
Long‐term and solar cycle variation of galactic cosmic rays : evidence for variable heliospheric turbulence
|Author:||Väisänen, Pauli1; Usoskin, Ilya1,2; Mursula, Kalevi1|
1ReSoLVE Centre of Excellence, Space Climate Research Unit, University of Oulu, Oulu, Finland
2Sodankylä Geophysical Observatory, University of Oulu, Oulu, Finland
|Online Access:||PDF Full Text (PDF, 1.1 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe2019040511226
American Geophysical Union,
|Publish Date:|| 2019-04-05
The Sun modulates the flux of galactic cosmic rays (GCR) reaching the Earth’s orbit. GCR flux has been measured by ground‐based neutron monitors (NMs) for several decades, which provides an interesting long‐term monitor of solar activity and the heliospheric magnetic field. Here we study the long‐term evolution of the power spectrum of GCR over the last six solar cycles, using the power law slope in the frequency range 5.56·10⁻⁶ to 2.14·10⁻⁶ Hz (between 50 and 130 hr). We use data from 31 neutron monitors during 1953–2016. We show that the power law slopes vary within the solar cycle, with a Kolmogorov‐type slope observed at solar minimum and a random‐walk‐type slope observed at solar maximum. This implies that the different conditions in the different phases of the solar cycle affect the scaling properties of heliospheric turbulence and, thereby, cosmic ray variability.
Journal of geophysical research. Space physics
|Pages:||804 - 811|
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
115 Astronomy and space science
We acknowledge the financial support by the Academy of Finland to the ReSoLVE Centre of Excellence (project 307411). Pauli Väisänen acknowledges the personal research grant from the Finnish Cultural Foundation.
|Academy of Finland Grant Number:||
307411 (Academy of Finland Funding decision)
An edited version of this paper was published by AGU. Copyright 2019 American Geophysical Union.