Mid-term periodicities of cosmic ray intensities

Abstract

Galactic cosmic ray intensities (GCRs) observed by five neutron monitors (NMs) have been used to study cosmic ray modulations between 1971 and 2007. The influence of interplanetary magnetic polarity (IMF) states has been studied for the A < 0 and A > 0 epochs. A comparison of the spectra for both positive IMF polarities indicated different solar origins. The spectra have different power amplitudes and most peaks of different locations. In addition, the differences in the cosmic ray modulations, conditions for solar activity minima and maxima periods are probably associated with the influence of drift effects. The observed differences are related to the 22-year cycle in heliospheric modulations of cosmic rays, leading to the different shapes of CR maxima and the hysteresis effect. Accordingly, drift effects dependent on the polarity of the global solar magnetic field may play a significant role in the observed differences between maxima and minima periods. The drift mechanism is enhanced during periods of low to moderate SA, i.e., around solar cycle minima, during negative polarity periods, when A < 0.

Solar and Geomagnetic Activity Effects on Global Surface Temperatures

“…A large part of this warming is attributed to the anthropogenic effects due to the enhanced green house gases concentrations [1,2 ]. Nevertheless , there seems to be some evidence that solar variab ility can contribute at least to part of this global warming [3][4][5][6][7][8][9]. The 11-yr-solar cycle and the associated variability that it has on the electromagnetic environ ment of Earth have been largely studied in the last decades [10,11] .…”

North-south asymmetry in solar, interplanetary, and geomagnetic indices

“…Others [21,24] suggested that the geomagnetic activity is high during the passage of the sources and in turn, appears to be related to the active region (geomagnetically) on the Sun (northern or southern hemispheres).…”

“…The spectrum of large-scale fluctuations in the solar wind ion density has revealed the existence of peaks with the solar rotation period (27 days) and a broad peak near 1.3 years, and the observed variations in ion density appeared to reflect the true variations in the solar wind speed [e.g., 24,25]. The existence of the periodic 1.3-year enhancements in SWS from 1987 to 1995 have been reported [26,27].…”

“…In addition, similar periodicities in Ap (a measure of geomagnetic disturbances) have been observed. Yearly averaged variations in the interplanetary plasma (SWS, N, and T) and magnetic-field magnitude (B) over more than two solar cycles were studied in detail [8,24,25]. Some clear periodicities were evident, and some of the observations showed solar cycle dependence.…”