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Vol 64, No 2 (2024)
Articles
Criteria for Forcast of Proton Events by Real-Time Solar Observations
Abstract
The sequence of overcoming threshold values of a number of physical characteristics for proton event forecast in real time is discussed. Each characteristic adds a new physical meaning that refines the forecast. To take into account all the characteristics, the following continuous patrol observations are necessary: 1) the magnetic field of the active region (ascent of the flux) and the general magnetic field of the Sun, which can predict the onset of flare activity several days before the main events; 2) soft X-ray radiation in two channels to calculate the temperature (T) and the measure emission of plasma, which can show the preheating to T > 10 MK required to begin proton acceleration (the first minutes before the start of hard X-ray (HXR) radiation with energies >100 keV); 3) HXR radiation >100 keV or microwave radiation (>3 GHz), which indicate the intensity and duration of operation of the electron accelerator (units and tens of minutes before the arrival of protons with energies >100 MeV); 4) radio emission at plasma frequencies (< 1000 MHz), showing the development of the flare process upward into the corona and leading to a coronal mass ejection (CME) several minutes before the onset of radio bursts of types II and IV (the first tens of minutes before the appearance of a CME in the field of view of the coronagraph); 5) the direction and speed of CME propagation, which determine the conditions for the release of accelerated protons into the heliosphere. These stages of solar proton flares are illustrated by observations of proton events on August 2—9, 2011. To quantitatively predict the onset time, maximum and magnitude of the proton flux, as well as its fluence, it is necessary to create statistical regression models based on all of the listed characteristics of past solar proton events.
163-174
Evolution of Characteristics of Vertical Electric Current and Magnetic Field in Active Regions of the Sun and their Relation to Powerful Flares
Abstract
The study of evolution of magnetic field and electric currents in active regions of the Sun over a long-time interval is of interest for understanding the processes of accumulation and release of energy in them, leading to various phenomena that affect space weather. In this work, based on the photospheric vector magnetograms of the Helioseismic and Magnetic Imager instrument aboard the Solar Dynamics Observatory, an analysis was made of the evolution of a number of characteristics of the magnetic field and vertical electric current in three active regions 11158, 11675, and 12673 that produced class M and X flares, during the time from their origin in the Eastern hemisphere, during the passage through the solar disk, and until the disappearance near the Western limb with a step of 2 hours. The characteristics under consideration included: the power-law exponent of the probability density function of the absolute value of the vertical electric current density, the maximum of the absolute value of the vertical current density, the signed and unsigned total vertical currents and the unsigned total vertical and horizontal magnetic fluxes, the energy of the nonlinear force-free and potential magnetic fields, the free magnetic energy, and the number of islands with strong vertical current. Some regularities in the behaviour of the characteristics under consideration are found, in particular regarding the occurrence of solar flares. The correlation coefficients between pairs of these characteristics are calculated. Additionally, M. Aschwanden’s approach is shown to be promising for predicting the maximum X-ray class of a flare based on the calculation of the energy of the potential magnetic field in active regions. The results obtained can be used to predict powerful solar flares.
175-198
Spatial Distribution of the Eddy Diffusion Coefficient in the Plasma Sheet of Earth’s Magnetotail and its Dependence on the Interplanetary Magnetic Field and Geomagnetic Activity based on MMS Satellite Data
Abstract
The article presents the results of a statistical analysis of the distribution of the eddy diffusion coef-ficient depending on the coordinates in the plasma sheet of Earth’s magnetosphere based on data from the Magnetospheric Multiscale Mission satellite system (MMS) for the period from 2017 to 2022. The localization of satellites inside the plasma sheet was recorded from the concentration and temperature of plasma ions according to the data of the same instruments and the value of plasma parameter β. Significant anisotropy of the eddy diffusion coefficient was revealed. The dependence of the eddy diffusion coefficient on the inter-planetary magnetic field is analyzed, showing that with the southern orientation of the interplanetary magnetic field, the eddy diffusion coefficients are 1.5–2 times greater than with the northern orientation. It is also shown that under disturbed geomagnetic conditions (SML < –200 nT), the eddy diffusion coefficients are several times greater than under quiet geomagnetic conditions (SML > –50 nT).
199-207
The Substorms Impact on Processes in the Ionosphere and Plasmasphere of the Earth
Abstract
During magnetospheric substorms in the F region of the ionosphere and up to altitudes of ~1000 km, a polarization jet (PJ) is developed. Measurements of energetic ring current ions on the AMPTE/CCE satellite and driftmeter data on the DMSP satellites evidence that the formation of PJ is associated with the injection of energetic ions (10–100 keV) into the inner magnetosphere during substorms. In the region of PJ development, the characteristics of the ionospheric plasma change: the plasma density decreases, sometimes by an order of magnitude, and at the same time, the plasma temperature increases significantly. In addition, simultaneously with the westward plasma drift, upward plasma drift is usually observed. The upward ion flux from the region of PJ development of ~109 cm–2 s–1 is an order of magnitude greater than the average daytime ion flux from the ionosphere to the plasmasphere. Measurements on the MAGION-5 satellite in the plasmasphere on the same L-shells, where the polarization jet is recorded in the ionosphere, show an increase in the cold ion density. The density “humps” observed near the plasmapause are apparently formed due to plasma flows from the ionosphere accompanying the formation of the polarization jet. Thus, the consequences of substorms are observed throughout almost the entire magnetosphere.
208-216
Schwabe Solar Cycle in 1000–1700: Variations in the Length and Amplitude
Abstract
One of the most significant features of solar activity is its variability over a wide range of periods, with the dominance of the 11-year cycle or the Schwabe cycle. In this work, a wavelet analysis of data on solar activity in 1000–1700 was carried out, obtained using the number of auroras, taking into account the contribution of the geomagnetic field. The obtained results demonstrate the stable presence of an 11-year cycle during the entire time interval of 1000–1700 A. D. It was found that in 1000–1350 there was a systematic increase in the length of the Schwabe cycle, after which its decline was traced. At the same time, the length of the solar cycle increases during the grand minima of Oort (13 years), Wolf (14 years) and Spörer (14–15 years). It was found that the correlation between the amplitude and the length of the solar cycle was maintained throughout the entire period of time 1000–1700, but its sign changed. In addition, it was obtained that the correlation between the amplitude of the cycle and the length of the previous cycle is stronger than the correlation between the amplitude and length of the same cycle. This result is similar to that previously known for instrumental series. However, we have shown that this pattern persists over a much longer time interval, and it does not depend on the sign of the correlation. The paper also provides indications of the existence of a variation with a period of 30–40 years in solar activity in 1000–1550.
217-229
Forecast of Modulation of Cosmic Rays with Rigidity of 10 GV in the 25th Solar Activity Cycle
Abstract
Based on a forecast of solar activity parameters and the model developed by the authors for modulation of Galactic cosmic rays, we forecasted cosmic ray variations in the 25th solar activity cycle. The cosmic ray flux forecast is based on correlation with the number of sunspots (single-parameter model) or with a set of solar (mainly magnetic) parameters (multiparameter model). The forecast for the number of sunspots was taken from published data; the forecast for other solar parameters was done in the study. It is shown that variations in cosmic rays over three years of the current 25th cycle, in general, do not contradict the forecasts and indicate that the 25th solar activity cycle is expected to be slightly more active compared to the 24th.
230-239
Anomalic Quasi-Recurrent Variations of Cosmic Rays in September 2014 – February 2015
Abstract
An abnormal behavior of galactic cosmic rays in September 2014 – February 2015, manifested in a significant modulation of its flux with a period close to solar rotation, is studied. The state of the solar magnetic field, changes in the parameters of the solar wind and interplanetary magnetic field during the specified period are analyzed. The reasons for the occurrence of longitudinal asymmetry in the distribution of galactic cosmic rays in the inner heliosphere are discussed. It has been established that the period under study is divided into two parts with different physical conditions on the Sun. Conclusions have been drawn about the decisive joint influence of sporadic and recurrent events: repeatedly renewable “magnetic traps” created by successive coronal mass ejections from the same longitudinal zone and anomalously expanded polar coronal holes with an enhanced magnetic field.
240-252
Dependence of foF2 on Solar Activity Indices Based on the Data of Ionospheric Stations of the Northern and Southern Hemispheres
Abstract
An analysis of the dependence of the F2-layer critical frequency on solar activity indices that has been started earlier based on the Juliusruh station data is continued. The data of six stations in the Northern Hemisphere and five stations in the Southern Hemisphere are analyzed in this paper. The determination coefficient R2 for the foF2 dependence on solar activity in each particular situation (station, month, local time) is taken as a measure of the quality of that dependence. The conclusion that a well-pronounced diurnal variation in R2 is observed in the winter months is confirmed for four solar activity proxies: this value is maximum and changes weakly in the daytime but decreases substantially to the nighttime hours. It is found that the F30 proxy is the best solar proxy to describe the foF2 behavior in the solar cycle, whereas the sunspot number Rz is the worst. Based on a comparison of the changes in R2 with LT in the same months at stations of the Northern and Southern hemispheres, it is shown that the aforementioned well-pronounced diurnal behavior in R2 is observed only in winter and is absent in summer
253-264
Determination of the Velocity of Ionospheric Disturbances from the Dynamics of Additional U-Shaped Traces on Ionograms
Abstract
One of the approaches to solving the inverse problem of determining the parameters of ionospheric disturbances is the multiple solution of the “homing-in” problem with the subsequent comparison of the simulation results with the observed data (ionograms). However, this approach is usually associated with significant calculation time costs, which makes it impossible to process large arrays of sounding data. The method described in this paper makes it possible to quickly determine the horizontal velocity of the ionospheric disturbance by descent rate of an additional U-shaped trace moving to lower virtual heights on the vertical ionograms: in order to calculate the velocity, it is proposed to use the results of the ray tracing obtained for the reference background profiles with the disturbances superimposed on them.
265-271
Features of Radio Emission Propagation in the Ionosphere under Conditions of Threshold Nonlinearity
Abstract
The well-known problem of nonlinear “wave – ionosphere” interaction under conditions of threshold nonlinearity is considered. It is believed that nonlinear effects arise only for high-power radiation, when the wave amplitude exceeds a certain threshold value. The possibility of the existence of concentrated wave fields under these conditions is shown. It is revealed that a certain ratio of nonlinearity parameters leads to an increase in the radio emission intensity, since the interaction of individual solitons can lead to their merging into a higher-power solitary wave. The presence of threshold nonlinearity can lead to the formation of an ordered structure of solitary waves.
272-276
Evaluation of the Influence of the Dispersion and Diffraction Properties of the Ionosphere on the Bandwidth of the Trans-Ionospheric Channel
Abstract
Theoretical substantiation and development of a hardware and software complex for estimating the band of dispersion distortion and the coherence band of fading in a satellite (trans-ionospheric) radio channel based on the results of GPS monitoring of the ionosphere. The basis for solving this problem is the development of a structural-physical model of the radio channel, which allows simultaneously taking into account the phase dispersion and its diffraction in small-scale inhomogeneities of the ionosphere. Analytical dependences of the band of dispersion distortions and coherence of frequency-selective fading on the average value and small-scale fluctuations of the total electron content of the ionosphere are obtained. It is shown that under conditions of ionospheric disturbances, the coherence band of fading can be much smaller than the dispersion band. In accordance with the obtained dependencies, a structure for constructing a hardware and software complex for estimating the dispersion and coherence bands of a satellite radio channel based on the improvement of the GPS-monitoring method of the total electronic content of the ionosphere with small-scale inhomogeneities has been developed
277-293
Pitch-Angle Diffusion of Radiation Belt Electrons and Precipitating Particle Fluxes: Dependence on VLF Wavefield Parameters
Abstract
The dependence of the pitch-angle diffusion efficiency of energetic electrons in the Earth’s magnetosphere on the distribution of the whistler wave field along the geomagnetic flux tube is quantitatively studied for parameters corresponding to the location of the Sura and HAARP HF heating facilities. The expansion of the precipitation energy range with the increase of the region of geomagnetic latitudes occupied by the waves is shown. Using the calculated pitch-angle diffusion coefficient for a given spectrum of waves and their distribution along the flux tube, the ratio of the fluxes of precipitating and trapped particles at low altitude is determined. It is shown that at typical wave intensities corresponding to chorus VLF waves and plasmaspheric hiss, the fluxes of precipitating and trapped electrons can be comparable to each other. At the same time, for the wave amplitudes observed as a result of the action of heating facilities, the flux of precipitating electrons is negligible.
294-302
Identification of Possible Short-Term Ionospheric Earthquake Precursors for Seismic Events with Intermediate Hypocentrals Depths by Measuring the Standard Parameters of the Mid-Latitude Es Layer
Abstract
Changes in deviations from the background values of the parameters of the sporadic E ionosphere (Es) are studied: the effective (virtual) height h’Es and limiting reflection frequency (foEs). Basically, the analysis was carried based on hourly measurement data from several Japanese ground stations for vertical sounding of the ionosphere in order to identify possible short-term ionospheric earthquake precursors with intermediate (from 60 to 300 km) hypocentral depths. All known events (12 earthquakes, from 1969 to 2022) are considered for which the necessary ionospheric data in the Japan region and magnitudes (M) ranging from 6.5 to 7.6 are available. From coincidence of the maxima in changes in the considered Es characteristics on the same day at pairs of stations separated by hundreds of kilometers, the time of appearance of possible ionospheric earthquake precursors was recorded. According to the ionospheric data available during the preparation period for the studied earthquakes, a tendency has been identified according to which the time the moment of the main influence is anticipated depends on the magnitude of the impending earthquake. Similarities and differences in the responses of the ionosphere to the preparation of surface (crustal) earthquakes and earthquakes with an intermediate hypocentral depth are revealed. Another tendency is also revealed: earlier appearance of the identified earthquake precursors with increasing hypocentral depth for earthquakes with an intermediate hypocentral depth at the same distances from the epicenter to the observation point.
303-311
Seismogenic Quasi-Stationary Electric Fields and Currents from Large-Scale Sources on the Earth’s Surface: Comparison of Model Representations
Abstract
A comparative analysis of various model representations of seismogenic quasi-stationary electric fields/currents from large-scale sources on the Earth’s surface was carried out. It has been established that previously proposed analytical models of seismogenic quasi-stationary sources of electric field/current with field/current amplitudes continuously decreasing to zero at infinity are consistent with extreme values of electric field/current experimentally observed in epicentral zones before earthquakes. It is also shown that sharply spatially limited models of seismogenic sources of quasi-stationary electric fields/currents in the epicentral zones of future earthquakes on the Earth’s surface lead to their values being an order of magnitude or more greater than those actually observed.
312-320