Irina V. Dorman

Long-term cosmic ray/solar activity hysteresis phenomenon and properties of solar wind for the last 200 years

On the basis of cosmic ray (CR) neutron monitor data of the station Climax (University of Chicago, P.I. Prof. J. A. Simpson), as well as of solar activity (SA) data for 1953–1997 (about 4 solar cycles), the CR/SA hysteresis phenomenon is investigated. We consider the time lag between the processes in the interplanetary space responsible for CR modulation and the corresponding processes on the Sun. By these results we estimate the average dimension of the Heliosphere and CR modulation parameters, over about 4 solar cycles. The results obtained for the last 4 cycles are used for determining the long-term CR variations during 1750–1970 on the basis of solar activity data (the last 18 years are used to compare the observed and expected CR intensities).

Propagation of inclined solar neutrons: Scattering, energy decrease, attenuation, and refraction effect

We develop our simulation and analytical calculation results of solar neutron propagation in the atmosphere for different initial zenith angles, taking into account not only scattering and attenuation, but also neutron energy decrease (what leads to increase both of cross-section of interaction and scattering angles, what is especially important for small energy solar neutrons). We test the usually used suggestion that solar neutron propagation through the atmosphere of depth h at some initial zenith angle θO is the same as for vertical direction, but for depth h/cos θO. Our calculations of multi-scattering of neutrons on small angles with attenuation and energy change for different initial zenith angles, show that this suggestion is not correct. Taking into account the neutron energy change shows that with decreasing of solar neutron energy the asymmetry in solar neutron propagation and refraction effect became stronger. We show that during the propagation through the atmosphere the effective zenith angl...