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卷 64, 编号 1 (2024)
Articles
Coronal dimming parameters and their variations in the 24th solar cycle
摘要
We analyzed coronal dimming parameters and their relation to coronal mass ejections to determine the location of possible ejections sources on the solar disk in the 24th solar cycle. We used Solar Demon database that contains flares and dimmings parameters obtained from SDO/AIA image. Coronal mass ejections from the CACTus database were associated with 16% of all the dimmings for the period 2010–2018. On average, dimmings associated with coronal mass ejections are events with large absolute parameter values. Correlation coefficient between dimming position angle and associated coronal mass ejection position angle is 0.96. Correlation coefficients between the coronal mass ejection speed and dimming parameters are close to 0.5 for dimmings in the central region of the solar disk. Obtained results can be used to model coronal mass ejections propagation and to define the probability of their arrival in near-Earth space.
3-12
Influence of the geometrical shape of a prominence and the structure of the coronal magnetic field on the probability of eruption, flare and coronal mass ejection development
摘要
The equilibrium conditions of the magnetic flux rope containing the prominence depend on the properties of the surrounding magnetic field in the corona and the geometry of the flux rope itself. The eruption of a prominence is usually associated with a loss of stability in the external magnetic field upon reaching a height above which the decay index of the field exceeds the critical value for the development of eruptive instability. For flux ropes with an axis in the form of a straight line or a circle, the critical value of the decay index of the field lies in the range of 1.0—1.5. Based on extrapolation of the magnetic field into the corona from field measurements in the photosphere, it would be possible to predict the probability of eruption of a particular prominence. However, taking into account the fact that the ends of the magnetic flux rope are rooted in the photosphere and remain fixed due to being frozen into the photospheric plasma significantly affects the critical value of the index and complicates the forecast problem. If the magnetic flux rope retains the shape a segment of a torus in the process of evolution, then the critical value of the decay index for its apex depends on what part of the torus it constitutes, being minimal for approximately half of the torus and having a value significantly less than unity. How the eruption of the flux rope will develop after the loss of equilibrium also depends on what part of the complete torus it constitutes at the moment of the onset of the eruption. Shorter flux ropes accelerate very vigorously, but only for a short time, generating stronger electric induction fields that initiate flare processes. However, the final speed that a short flux rope can achieve during acceleration is less than that of longer flux ropes that accelerate less intensely but for a longer time. The induction effects of the latter are less pronounced, so that they are capable of producing only weak flare-like manifestations. Thus, the eruption of a short prominence, which has gained a relatively low speed, can be stopped at a certain height in the corona without generating a coronal mass ejection. But such a “failed eruption” contributes to the development of flare phenomena. On the contrary, eruptions of longer prominences more often lead to the formation of coronal mass ejections and weak flare manifestations.
13-22
Simulation of spectral observations of an eruptive prominence
摘要
The paper presents the results of an analysis of observations of an eruptive prominence on the MFS and HSFA2 spectrographs of the Ondřejov Observatory (Astronomical Institute, Czech Republic) in the lines of hydrogen, helium and calcium. After processing the spectra, the integral radiation fluxes in the lines were determined and a theoretical calculation of the physical parameters of the plasma was carried out using a model in the absence of local thermodynamic equilibrium. A comparison of the observed and calculated values showed that the observed radiation fluxes in the lines can be explained in a model of stationary gas radiation taking into account the opacity in the spectral lines. To calculate theoretical fluxes, in some cases it was necessary to introduce radiation from several layers with different temperatures and heights. The calculated radiation fluxes agree with the observed ones with an accuracy of 10%. As a result of the simulation, the main parameters of the prominence plasma were obtained: temperature, concentration, etc. The values of radiation fluxes in the spectral lines indicate the inhomogeneity of the emitting gas, and there may be regions next to each other whose temperatures differ by an order of magnitude.
23-28
Main time characteristics of cosmic ray variations and related parameters in magnetic clouds
摘要
The behavior of the main parameters of the interplanetary medium, cosmic rays, and geomagnetic activity during the passage of magnetic clouds past the Earth (465 events over the period from 1967 to 2021) has been studied. Time distributions of these parameters inside magnetic clouds are considered. It is shown that the maximum values of the solar wind velocity, interplanetary magnetic field strength, and geomagnetic activity indices are more often recorded at the beginning of the magnetic cloud, while the minimum values of the temperature index, cosmic ray density and equatorial component of anisotropy can be observed in any part of the structure under study.
29-38
Forbush decreases and geomagnetic disturbances: 2. Comparison of solar cycles 23–24 and events with sudden and gradual onset
摘要
Statistical relationships between the values of geomagnetic indices and the characteristics of cosmic rays and interplanetary disturbances are studied for Forbush decreases with sudden and gradual onset associated with different types of solar sources: a) coronal mass ejections from active regions accompanied by solar flares; b) filament eruptions outside active regions; c) high-speed streams from coronal holes; d) several sources. Using statistical methods, the dependence of geomagnetic indices on cosmic ray and solar wind parameters for Forbush decreases in solar cycles 23 and 24 is also compared. The results obtained showed: a) interplanetary disturbances associated with coronal mass ejections from active regions cause mainly magnetic storms with a sudden onset; b) interplanetary disturbances associated with high-speed streams from coronal holes cause mainly storms with a gradual onset; c) interplanetary disturbances associated with filament eruptions outside active regions cause equally probable storms with a sudden and gradual onset. For sporadic Forbush decreases the values of cosmic ray and geomagnetic activity parameters are, on average, higher for events with a sudden onset; for recurrent Forbush decreases, the nature of the event onset does not affect the value of these parameters. For all types of solar sources the parameters of the disturbed solar wind are, on average, higher in events with a sudden onset. The geoefficiency of interplanetary disturbances is much higher in the 23rd cycle for events associated with ejections from active regions; for other types of disturbances, the difference between the cycles is weak.
39-54
Spectra and anisotropy of cosmic rays during gle64
摘要
Ground-based observations of cosmic rays by the spectrographic global survey method were used to study the ground-level enhancement in cosmic ray intensity on August 24, 2002. Spectra of variations of primary cosmic rays and their anisotropy were obtained. Based on measurements from the GOES spacecraft and global network of cosmic ray stations, the differential rigidity spectra of accelerated particles in the vicinity of the Sun were calculated. The maximum rigidity to which solar particles were accelerated was estimated.
55-59
Use of q-statistics for study of pulsating aurora
摘要
The non-extensive statistical mechanics method of Tsallis (or q-statistics) is first applied to study pulsating auroras, which are regularly observed in the auroral ionosphere during geomagnetic disturbances. For systems with long-range interactions, such as ionized gas or plasma, whose dynamics are primarily determined by long-range electromagnetic forces, one can expect that non-additive and non-extensive thermostatistical principles may characterize their macroscopic behavior. This paper shows that pulsating polar auroras exhibit non-extensive properties and can be described, in part, by q-statistics. It is also demonstrated that the non-extensive parameter q correlates well with the flatness coefficient and scaling index, indicating the applicability of this approach to auroral emissions. Thus, q-statistics can be used to analyze phenomena in the high-latitude region of the Earth.
60-73
Scenario for the formation of vortexlike structures in a presubstorm arc, taking into account changes in the arc height during its evolution
摘要
Activity in a prebreakup auroral arc in the form of vortexlike structures, the appearance/disappearance of which is preceded by an increase/decrease in the brightness of the arc, was studied in the context of a magnetospheric substorm, large-scale ionospheric convection, the situation in the interplanetary medium, and triangulation measurements of the arc height. The structures are observed in the premidnight hours and represent a superposition of two auroral forms: a large-scale bend in the arc that outlines the polar boundary of the diffuse auroras and smaller luminous tongues of luminosity (mini-torches) elongated along the convection on the western slope of the bends. The structures as a whole move against convection, towards substorm activity to the east of the observation area. We attribute the appearance of structures to the propagation of a disturbance deep into the magnetosphere, generated as a result of interaction of the magnetopause with a solar wind inhomogeneity, on the front of which Bz turns southward. The results of triangulation measurements show that the increase in brightness in the prebreakup arc shortly before the appearance of vortexlike structures is accompanied by a decrease in the height of the lower edge of the arc, which we explain by the appearance of a parallel electric field above the arc, which accelerates the precipitating electrons. The role of such a field in the formation of the torchlike structures is discussed in the framework of the interchange instability of the pole boundary of diffuse auroras.
74-92
Dependence of annual asymmetry in NmF2 on local time
摘要
Based on the global empirical model of the F2 layer critical frequency median (Satellite and Digisonde Data Model of the F2 layer, SDMF2), an analysis was made of the properties of diurnal variations in the annual asymmetry in the concentration of the F2 layer maximum NmF2 at different values of the solar activity index F. The AI index, which characterizes the relative difference in NmF2 averaged over all longitudes and latitudes between January and July at a given local time, was used as a parameter of this asymmetry. It was found that the diurnal variations of the AI index are dominated by a semidiurnal mode with maxima in the daytime and at night. The daytime maximum of the AI index is almost independent of the level of solar activity. The nighttime AI maximum decreases with increasing solar activity. For low solar activity, the daytime and nighttime AI maxima almost coincide in amplitude when AI = 16—17%. The difference in the solar radio flux between January and July due to the ellipticity of the Earth’s orbit relative to the Sun makes a significant contribution to the AI index at all hours of the day. On average, it is 3—4% and can reach 5% with low solar activity at night. The difference in the AI index for low and high activity according to the IRI model (with URSI and, especially, CCIR coefficients) is overestimated relative to the SDMF2 model at almost all hours of the day, apparently due to the limited number of experimental data when obtaining the CCIR and URSI coefficients especially over the oceans
93-100
Long-term temperature trend in the mesopause region according to observations of hydroxyl airglow in Zvenigorod
摘要
An analysis of the long-term change of the average annual OH* temperature, the values of which were obtained from nighttime spectral observations of the hydroxyl emission bands at the Zvenigorod scientific station (56° N, 37° E) from 1957 to 2022, is presented. This series of OH* temperatures, reflecting the thermal state of the mesopause region, is the longest among all known observations. On its basis, estimates of the linear trend and response of temperature to changes in solar activity was made both in general over the entire set of data and for different time intervals. In the first case, the trend was −0.23 ± 0.04 K/yr. In the second case, the analysis showed strong cooling (−0.53 ± 0.34 K/yr) until the 1970s and its slowdown to −0.14 ± 0.03 K/yr thereafter. A comparison of the results of the analysis with other measurements and model calculations shows that the latter have lower trend values. It is assumed that the reasons for the temperature trend, in addition to the growth of greenhouse gases, the main of which is CO2, may be long-term changes in the dynamics of the upper atmosphere.
101-112
Response of the lower and upper ionosphere after the eruption of Shiveluch volcano on april 10, 2023
摘要
The disturbances in the lower ionosphere and in the region of the maximum of the ionospheric F2 layer during the Shiveluch volcanic eruption in April 2023 are analyzed based on data from ground-based magnetometers and GPS radio sounding of the ionosphere. The magnetic stations were located at distances of 455 km (Paratunka) and 752 km (Magadan) from the volcano. The variations in the magnetic field and total electron content of the ionosphere were studied as characteristics of the ionospheric response to this event. An analysis of the measurements showed that the impact on the ionosphere is carried out by seismic Rayleigh waves and atmospheric acoustic-gravity waves generated by volcanic explosions. The energy of several explosions was estimated from the amplitude of the ionospheric signal in the total electron content.
113-121
Study of the delayed pumping effect in the underground laboratory by the method of correlation analysis of radon and aeroion concentrations
摘要
Measurements and correlation analysis of radon and aeroion concentrations in the underground laboratory were carried out. For pairs of variables “pressure — radon” and “pressure — ions”, a delayed pumping effect was found, similar to that previously observed for neutrons and gamma quanta. A simple phenomenological model explaining the results is presented. In this model, the reason for the delay is the gradual accumulation of radon in the room with a decrease in atmospheric pressure. The balance of the radon accumulation rate, the time of its radioactive decay and the characteristic time of pressure variations leads to an effective delay of 2 days between atmospheric pressure variations and radon concentration. Correlation analysis for the variables “pressure — ions” indicates that ions formed in the pores of the soil are already present in the air carrying radon to the laboratory. These ions make up approximately 21% of the total number of ions in the laboratory.
122-132
Developing space-time model of the main geomagnetic field based on satellite data for the epoch 2015–2020
摘要
Based on measurements of SWARM satellites, a model of the main geomagnetic field for the 2020 epoch and a model of annual field changes until 2025 were built. These models were included in the international model of the main geomagnetic field IGRF-13. The method of data selection and model calculation is described.
133-140
Experiment on long-term forecasting of geomagnetic activity based on nonlocal correlations
摘要
The experiment was performed on the use of advanced macroscopic nonlocal correlations to forecast slow random fluctuations of the Dst index of geomagnetic activity. The global maximum correlation of Dst with the signal of the electrode detector reaches 0.97, which is sufficient for the forecast, and its time shift corresponds to the advance of the detector signal relative to Dst by 329 days. The large magnitude of the time shift is due to the slow diffusion mechanism of entanglement swapping between the detector and the source. At the same time, the position of the global maximum of the correlation function coincides with the position of the global minimum of the entropy independence function, which confirms its undistorted by possible nonlinearity of the relationship and determines the optimal lead time of the forecast. Long series of test forecasts Dst have been calculated using data from a nonlocal correlation detector with a fixed lead time using three methods: current regression, current impulse transient response and current neural network. The accuracy of the forecasts is sufficient for all practical purposes.
141-148
Depth to the bottom of lithospheric magnetic sources beneath north-eastern Eurasia: lithospheric thermal regime and relation to seismicity
摘要
For north-eastern Eurasia (60—70° N, 90—180° E), the bottom depth of the lithospheric magnetoactive layer is estimated using the centroid method based on two-dimensional spectral analysis of the lithospheric magnetic field. The lithospheric magnetic field within the study region is described by the EMAG2v3 global model. The obtained results show that maximum values (> 50 km) of the depth to the bottom of lithospheric magnetic sources are observed almost everywhere under the Siberian platform north of 65° N. Minimum depth values (<30 km) are traced under the Koryak-Kamchatka fold belt and the Okhotsk-Chukotka volcanogenic belt. Under the Verkhoyansk-Kolyma fold belt, different maximums (up to 40 km) and minimums (up to 30 km) of the bottom depth are seen. Assuming that magnetite is a main magnetic mineral in the continental lithosphere, our distribution of the bottom depth evidences for the eastward lithospheric heating — from the Siberian platform to the Koryak-Kamchatka fold belt. The revealed tendency is confirmed by independent geophysical data. Comparison of the obtained results with a distribution of epicenters of regional earthquakes (M ≥ 4.0, 1962—2020) shows that most sources of strong earthquakes (M ≥ 6.0), registered during the instrumental period of observation, are confined to zones in which a sharp change in the depth to the bottom of lithospheric magnetic sources occurs.
149-160