Visualization of the solar magnetic field using coefficients of harmonic expansion in the potential approximation

A method for visualization of the solar magnetic field is suggested and implemented. The harmonic expansion coefficients obtained in the potential approximation from magnetic-field observations at the photospheric level are used as an input. Three-dimensional equations for field lines are numerically integrated, and the results are presented in the form of projections onto the picture plane. The density of the line number is assumed to be proportional to the magnetic flux density. The lines of different topological connectedness are differently colored and show areas with open and closed configurations, thus mapping the information about the field direction and magnitude. This method is useful for research and applied studies related to investigation and forecasting of space weather.     

On the visible shape of the cold plasma jets in the solar chromosphere

Lines of equal optical thickness are calculated for cold plasma jets propagating in the simplest magnetic configuration. The paraxial approximation is used in the case of jets directed along the axis of a magnetic dipole. The results explain the apparently convergent as well as divergent shapes of the jets in a divergent magnetic configuration.     

On interplanetary electric and magnetic fields

A kinematic model of the stationary electromagnetic fields in interplanetary space with finite conductivity is considered. The electrodynamic problem is solved for a medium with uniform conductivity and radial plasma outflow from a spherical source. Simple analytical formulae are obtained for electric and magnetic fields, currents and charges in the case of a uniformly-magnetized rotating sphere.     

Radiation conditions of a mission to Jupiter and Europa

Radiation conditions in Jupiter’s environment and the plasma environment in interplanetary space during a Jupiter-Europa mission are estimated. The numerical modeling results can be used when planning the mission.     

Statistical distributions and classification of X-ray flares according to their duration on the sun

The results of the statistical analysis of the GOES data related to the length of the period, during which the X-ray emission of solar flares increases, provide reliable grounds for the objective distinction of different types, sometimes referred to in the literature as typical and nontypical for bimodal classification. The events may be also partitioned into three (“impulsive”, “typical”, and “long duration”) or more “types”. These “types” should be separated from statistical fluctuations in the case of rare events. When the number of analyzed events increases, these fluctuations are gradually smoothed and become less significant, and the distribution of flares according to the duration of their growth is, on the whole, well described by the single lognormal law.     

Geodynamic Regimes of Carbonatite Formation According to the Paleo-Reconstruction Method

Doklady Earth Sciences - Three models of geodynamic regimes of carbonatite formation are now actively being developed because of the high trace metal potential of this rock type: carbonatite melt...     

Hydrodynamic Classification of Solar Wind Flows

At the present time, there is no generally accepted classification of the solar wind flows. There are various approaches to this problem depending on the goal of the study. In our paper, we propose the binary classification of the solar wind types by the main hydrodynamic parameters (velocity, temperature, and density) based on the statistical analysis of the solar wind. The analysis of the OMNIWeb one-minute data is performed for the period from 1996 to 2017, which encompasses solar cycle 23 and current solar cycle 24. Eight types of the solar wind are distinguished: fast-hot-dense, fast-hot-rarefied, fast-cold-dense, fast-cold-rarefied, slow-hot-dense, slow-hot-rarefied, slow-cold-dense, slow-cold-rarefied. These types occur with different frequency and are the consequences of different manifestations of solar activity. Of particular interest are the solar wind flows, the parameters of which deviate from the averages most significantly.

     

Sporadic and recurrent geomagnetic disturbances in 1859–1860 according to the archived data from the Russian network of stations

Based on an analysis of the available archived data from the Russian network of geomagnetic stations, it has been indicated that the known event of August–September 1859 was the first and the greatest event in the series of the recurrent geomagnetic storms. Similar series were repeatedly observed in the next years. These series are caused by the processes on the Sun and in the heliosphere related to the superposition of the solar wind flows. The sporadic and regular components in joint activity of the complex, including active regions and coronal holes on the rotating Sun, play the role of the Bartels M regions responsible for initiation and development of geomagnetic storms. Neither coronal holes nor active regions can separately explain observations. During interpretation, active regions and coronal holes should be considered as a unified complex.     

Solar wind variation with the cycle

The cyclic evolution of the heliospheric plasma parameters is related to the time-dependent boundary conditions in the solar corona. “Minimal” coronal configurations correspond to the regular appearance of the tenuous, but hot and fast plasma streams from the large polar coronal holes. The denser, but cooler and slower solar wind is adjacent to coronal streamers. Irregular dynamic manifestations are present in the corona and the solar wind everywhere and always. They follow the solar activity cycle rather well. Because of this, the direct and indirect solar wind measurements demonstrate clear variations in space and time according to the minimal, intermediate and maximal conditions of the cycles. The average solar wind density, velocity and temperature measured at the Earth’s orbit show specific decadal variations and trends, which are of the order of the first tens per cent during the last three solar cycles. Statistical, spectral and correlation characteristics of the solar wind are reviewed with the emphasis on the cycles.