Solar Physics

, Volume 269, Issue 2, pp 451-454

First online:

Hysteresis of Cosmic Rays with Respect to Sunspot Numbers During the Recent Sunspot Minimum

  • R. P. KaneAffiliated withInstituto Nacional de Pesquisas Espaciais – INPE Email author 

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Cosmic ray neutron monitors show intensity changes (counts) anti-correlated with sunspot number R z, but with a lag of a few months. The lag is ∼ 3 months for even cycles and ∼ 9 – 15 months for odd cycles. Thus, for the recently started even Cycle 24, a lag of ∼ 3 months was expected. However, for Cycle 24, whereas R z had a minimum value (zero) in August 2009, cosmic ray intensity decreased only after March 2010, with a lag of seven months with respect to R z. Thus, Cycle 24 did not conform to the known pattern of even cycles (lag of ∼ 3 months). It may be noted that the minimum at the juncture of Cycle 23-24 was abnormally long, tens of months instead of few months as in earlier cycles. Also, in this solar minimum, the cosmic ray intensity was much higher than in previous cycles.


Cosmic rays Hysteresis Cycle 24