Study of Cosmic-Ray Modulation during the Recent Unusual Minimum and Mini Maximum of Solar Cycle 24

TL;DR

This study analyzes cosmic-ray intensity variations during the unusual solar minimum and mini maximum of Solar Cycle 24, examining how solar activity and heliospheric parameters influence cosmic-ray modulation.

Contribution

It provides a detailed analysis of cosmic-ray modulation across different solar activity phases using neutron monitor data and explores the influence of various heliospheric parameters.

Findings

Cosmic-ray intensity varies with solar activity phases.

Heliospheric parameters influence cosmic-ray modulation.

Time lag between cosmic rays and solar parameters differs across phases.

Abstract

After a prolonged and deep solar minimum at the end of Cycle 23, the current Solar Cycle 24 is one of the lowest cycles. These two periods of deep minimum and mini maximum are separated by a period of increasing solar activity. We study the cosmic-ray intensity variation in relation with the solar activity, heliospheric plasma and field parameters, including the heliospheric current sheet, during these three periods (phases) of different activity level and nature: (a) a deep minimum, (b) an increasing activity period and (c) a mini maximum. We use neutron monitor data from stations located around the globe to study the rigidity dependence on modulation during the two extremes, i.e., minimum and maximum. We also study the time lag between the cosmic-ray intensity and various solar and interplanetary parameters separately during the three activity phases. We also analyze the role of various parameters, including the current sheet tilt, in modulating the cosmic-ray intensity during the three different phases. Their relative importance and the implications of our results are also discussed.