Rotational and magnetic corrections to the g-mode frequencies in a one-dimensional MHD model

The central magnetic field and rotation of the solar radiative zone are responsible for corrections to the g-mode frequencies. Magnetogravitational spectra are calculated analytically in a simple one-dimensional MHD model that goes beyond the WKB approximation and avoid any cusp resonances that trap the wave within the radiative zone in the presence of a weak magnetic background. The calculations are compared with spacecraft observations of the 1% frequency shifts for candidate g-modes found in the SOHO GOLF experiment. The magnetic correction is the main contribution for a strong magnetic field satisfying the approximation used. It is shown that a constant magnetic field of 700 kG in the radiative zone provides the required frequency shift for the n = ?10 g-mode. The rotational correction, which is due to the Coriolis force in the one-dimensional model used, is much less than a percent (α_Ω ≤ 0.003).     

Analyzing the Solar Proton Event of 22 October 1989, Using the Method of Spectrographic Global Survey

Using ground-level observations of cosmic-ray (CR) intensities from a worldwide network of stations during the ground-level enhancement (GLE) of 22–23 October 1989, variations of the particle distribution function in all phases of the event were investigated.It is shown that time intensity profiles of 2–4 GV rigidity particles differ greatly from those of higher-energy particles. After the high-energy particle intensity attains a maximum, there is an abrupt decrease in intensity below the background level, followed by the phase of slow recovery to background values. The angular distribution of high-energy particles across the celestial sphere shows, along with an increased intensity, also regions with decreased relative background intensity.To explain the detected phenomenon, it is concluded that it is necessary to consider the solar CR propagation process in the heliosphere not in terms of the movement of particles in the external electromagnetic field but with proper account of the self-consistency of fields with the particle distribution function.     

Modelling ice conditions in the easternmost Gulf of Finland in the Baltic Sea

To model ice conditions in the eastern Gulf of Finland, a high-resolution three-dimensional hydrodynamic model is coupled with the advanced sea-ice model HELMI (Haapala et al., 2005). To test the model in extreme situations, the ice pattern in the eastern Gulf of Finland was simulated for a mild ice winter (2007–2008) and for a moderate one (2003–2004). The reference runs were performed on the assumption that the ice in the model domain is fast ice if the sea depth is less than 10 m. Using this assumption, the ice thickness averaged over the Neva Bay (the easternmost part of the Gulf of Finland) is overestimated by the model for almost the entire wintertime in the mild winter and during the ice formation and melting periods in the moderate winter, as compared with the thickness reported in ice charts.     

Reflection of the solar wind parameters in the CR geomagnetic cutoff rigidity before a strong magnetic storm in November 2003

The time variations in the CR geomagnetic cutoff rigidity and their relation to the interplanetary parameters and the Dst index during a strong magnetic storm of November 18–24, 2003, have been analyzed. The Tsyganenko (Ts03) model of a strongly disturbed magnetosphere [Tsyganenko, 2002a, 2002b; Tsyganenko et al., 2003] have been used to calculate effective geomagnetic thresholds with the help of the method for tracing CR particle trajectories in the magnetospheric magnetic field. The geomagnetic thresholds have been calculated using the method of global spectrographic survey (GSS), based on the data from the global network of CR stations, and the results have been compared with the effective geomagnetic cutoff rigidities. The daily anisotropy of effective geomagnetic thresholds during the Dst variation minimum have been estimated. The relation of the theoretical and experimental geomagnetic thresholds, obtained using the GSS method, to the interplanetary parameters and Dst variation is analyzed. The Dst variations, IMF B _z , and solar wind density are most clearly defined in the geomagnetic thresholds during this storm. The correlation between B _y and experimental geomagnetic thresholds is higher than such a correlation between this parameter and theoretical thresholds by a factor 2–3, which suggests that a real dawn-dusk asymmetry during this storm was stronger than such an asymmetry represented by the Ts03 model.     

Solar proton event in December 2006

The variations in the rigidity spectrum and anisotropy of cosmic rays in December 2006 have been studied based on the surface measurements of the cosmic ray intensity at the global network of stations, using the method of global spectrographic survey. It has been indicated that the highest degree of anisotropy (to ～50%) with the maximal intensity of particles with a rigidity of 4 GV in the direction from the Sun (an asymptotic direction of about ?25° and 160°) was observed at 0400 UT on December 13. The parameters of the cosmic ray rigidity spectrum, which reflect the electromagnetic characteristics of the heliospheric fields during the studied period, have been determined when the surface and satellite measurements of protons in the energy range from several megaelectronvolts to several tens of gigaelectronvolts were jointly analyzed. The observed anisotropy and variations in cosmic rays in a wide energy range have been explained based on an analysis of the results.     

Correction of data from the neutron monitor worldwide network

The method for correcting data from individual neutron monitors at the worldwide network of cosmic ray stations, characterized by the instrument drift and sporadic variations, has been proposed. The correction is performed using the method of spectrographic global survey. The proposed method makes it possible to correct data from the global network of stations immediately during processing and can be used in studies of cosmic-ray intensity long-term variations and in the real-time operation mode.     

Variations in the geomagnetic cutoff rigidity of cosmic rays at individual points of the Asian region during the extreme events of 2003

The variations in the geomagnetic cutoff rigidity in Irkutsk, Alma-Ata, and Beijing in October–November 2003 were calculated using ground-based measurements of cosmic ray intensity from the worldwide network of stations and GOES spacecraft. The calculated variations in geomagnetic cutoff rigidity are presented together with D _st variations of the geomagnetic field. The obtained results are compared to calculations performed using the Tsyganenko model of the magnetosphere.