J. Space Weather Space Clim.
Volume 6, 2016
|Number of page(s)||7|
|Published online||04 March 2016|
An empirical model of heliospheric cosmic ray modulation on long-term time scale
ReSoLVE Centre of Excellence, University of Oulu, 90014
2 Sodankylä Geophysical Observatory, University of Oulu, Oulu, FIN-90014, Finland
* Corresponding author: Eleanna.Asvestari@oulu.fi
Accepted: 5 February 2016
Galactic Cosmic Rays (GCRs) entering the heliosphere are subject to modulation processes due to variable solar magnetic activity. Finding a relationship between cosmic-ray variations and the heliospheric parameters is important for reconstruction of solar activity in the past. Here, we develop a semi-empirical model describing the heliospheric modulation of GCRs in terms of heliospheric parameters such as the open solar magnetic flux, the tilt angle of the heliospheric current sheet and the polarity of the large scale solar magnetic field. Our model is fitted using annual data obtained for the period 1976–2013, which includes the very weak solar minimum during 2008–2010. The model shows a good agreement with the data, and therefore, can be used for reconstructions of the modulation potential at different levels of solar activity. The model’s validity is also tested using the cosmogenic radionuclides 14C and 10Be stored in terrestrial archives. The tilt angle used to fit the parameters in our semi-empirical modulation model is reconstructed by a mathematical model described here.
Key words: Heliosphere / Cosmic ray / Current sheet / Solar activity / Cosmogenic isotopes
© E. Asvestari and I.G. Usoskin, Published by EDP Sciences 2016
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.