The method for predicting solar proton events

Dynamic processes in the interplanetary space have been investigated using time variations in time parameters of the cosmic-ray rigidity spectrum. Change of heliosphere electromagnetic characteristics has been found out to precede sporadic phenomena on the Sun. In particular, it is shown that sporadic phenomena are followed by generation of local polarization electric fields, decrease of the magnetic-field strength in small-scale heliospheric structures, and increase of the potential difference between the pole and the plane of the ecliptic. These features allow prediction of solar proton events in advance (from several hours to several tens of hours) with a high degree of confirmation.     

Variations in rigidity spectrum and anisotropy of cosmic rays during sporadic phenomena in the heliosphere in October–November 2003

The variations in the cosmic ray (CR) anisotropy have been studied by the method of spectrographic global survey in the period from October 1 to November 30, 2003. The data of ground-based observations of CR intensity measured by the world network of stations were used. It is shown that at some instants of the period under investigation a bidirectional anisotropy of large amplitude (tens of percent) is observed in the angular distribution of particles. This indicates, first, a carryover of looplike structures of the interplanetary magnetic field (IMF) by coronal mass ejections and, second, a high degree of regularity of the IMF in these structures. The maximum amplitude of the bidirectional anisotropy (for particles with a rigidity of 4 GV) was observed on October 29 and 31 (50% and 30%, respectively) and on November 21–24 (15%). Using the data of ground-based and satellite measurements of the CR intensity in the period under study, we have investigated variations of the rigidity spectrum of protons in the energy range from 15 MeV to tens of GeV. The analysis was carried out in the context of the model of CR modulation by regular electromagnetic fields of the heliosphere. Parameters of the model rigidity spectrum of CRs are determined for every hour of observation. Using their values we have estimated the characteristics of electromagnetic fields of the solar corona and heliosphere that were responsible for powerful sporadic phenomena from the end of October to the beginning of November and after November 20, 2003.Translated from Kosmicheskie Issledovaniya, Vol. 42, No. 6, 2004, pp. 645–652.Original Russian Text Copyright © 2004 by Dvornikov, Sdobnov, Yudina.     

Estimation of the solar proton spectrum in the GLE70 event

The GLE event on December 13, 2006 as observed by network station neutron monitor data is investigated (is considered). The GLE energetic spectrum suggested for this event is estimated taking into account the primary differential spectrum of galactic cosmic rays, coupling coefficients and integral multiplicities of concrete detectors at different latitudes and levels of observation. It is noted that the additional increase of solar protons is also manifested in the ionization chamber ASK-1 data at the Yakutsk station.     

On the possibility to check the magnetosphere’s model by CR: The strong geomagnetic storm in November 2003

We report on a study of cosmic ray cutoff rigidity variations during the strong geomagnetic storm of 18–24 November 2003. We employed the most recent Tsyganenko magnetospheric model to represent the very strong disturbed Magnetosphere. We used this magnetic field for the cosmic ray trajectory calculations to determine the geomagnetic cutoff rigidity throughout this period of severe geomagnetic disturbance. We determine the cutoff rigidity changes during this period by two methods, by trajectory calculations and by the spectrographic global survey method. The values of the change of cutoff rigidities obtained by two different methods are correlated with the D_st and interplanetary magnetic field and plasma parameters and result in correlation coefficients in the range 0.63–0.84 for the various cosmic ray stations. The result of this study indicates that the most significant contributions to the cutoff rigidity changes are due to D_st variation although the influence of solar wind density and B_z and B_y components of IMF variations is significant.