CR-SA hysteresis phenomenon on the basis of NM data, 3. results for even solar cycles 20 and 22

Details CR-SA hysteresis phenomenon on the basis of NM data, 3. results for even solar cycles 20 and 22 CR-SA hysteresis phenomenon on the basis of NM data, 3. results for even solar cycles 20 and 22

Aug 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001icrc....9.3804d&link_type=abstract

Proceedings of the 27th International Cosmic Ray Conference. 07-15 August, 2001. Hamburg, Germany. Under the auspices of the Int

Physics

Scientific paper

We found that the maximum of correlation coefficient between cosmic ray (CR) intensity and solar activity (SA) variations is occurred for even cycles 20 and 22 for about two-three times in the shorter time than for odd cycles 19 and 21. We came to conclusion that this difference is caused by CR drift effects: during even cycle drifts produced the small increasing of CR global modulation (additional to the caused by convection-diffusion mechanism) in the period from minimum to maximum of SA, and after the maximum of SA up to the minimumabout the same decreasing of CR modulation. This gives sufficient decreasing of observed time-lag between CR and SA in even solar cycles. We analyzed monthly and 11 months smoothed data of (CR) intensity observed by neutron monitors with different cut-off rigidities for even solar cycles 20 and 22. We use a special model described the connection between solar activity (characterized by monthly sunspot numbers) and CR convection-diffusion global modulation with taking into account time-lag of processes in the Heliosphere relative to the active processes on the Sun (Dorman et al., 1999). For taking into account drifts we use models described in literature (e.g. Burger and Potgieter, 1999). We approximate the expected drift modulation dependence from tilt angle (what changed the sign in periods of solar polar magnetic field reversal near maximums of solar activity) by parabola with 0-points at tilt angles 15 and 90 degrees. We suppose that final drift modulation is described by production of two functions: the first is the described above parabola approximated theoretical results of drifts calculations, and the second function can be present by two parallel lines +1 and 1 (in dependence of sign of solar polar magnetic field) connected linear during reversal periods. In the first we correct observed long-term CR modulation on drifts with different amplitudes from 0 (no drifts), then 0.15%, 0.25%,& up to 4%. For each expected amplitude of drifts we determine the correlation coefficient between expected CR variations and observed by neutron monitors with different cut-off rigidities for different times of solar wind transportation from the Sun to the boundary of the modulation region from 1 to 60 average months (it corresponds approximately to dimension of modulation region from about 6 to 360 AU). We compare observed results for even solar cycles 20 and 22. REFERENCES Burger, R. A., and M. S. Potgieter, Proc. 26 ICRC, 7, 13 (1999). Dorman, L.I.,et al., Proc. 26 ICRC, 7, 194 (1999).

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