Vol 59, No 7 (2019)

The distributions of temperature and density in the sunspot atmosphere are crucial for an understanding of the process of energy transfer from the photosphere upward to the corona in strong magnetic fields. The joint analysis of millimeter observations at ALMA (Atacama Large Millimeter/Submillimeter Array) and observations performed in the microwave range (centimeter wavelengths) with the RATAN-600 radio telescope of the Russian Academy of Sciences provides new data on the temperature distribution and physical processes at different altitudes above a spot. The NOAA 12470 active region was observed and mapped at 1.3 and 3 mm (ALMA) and 2–10 cm (RATAN-600) in December 2015. These observations are analyzed, and the results are compared to models of sunspot atmospheres. The fundamental problems arising in the study of atmospheres of active regions in the millimeter and centimeter ranges are determined, and the importance of the 3–18 mm range in the physics of the generation and transfer of energy for corona heating is demonstrated.

A comparative analysis of sunspot sizes in sunspot groups was performed. For this analysis, we used the database of characteristics of individual sunspots and pores according to observations at the Kislovodsk Mountain Astronomical Station (KMAS) and the photoheliographic data from the Debrecen Heliographical Observatory, Hungary (DPD). We found agreement in the full area index for sunspot groups. However, in the DPD data for 1974–2018, the number of groups is ~50% higher than that for the KMAS data. The difference is that there are a large number of groups in the DPD data with an area of 1 mdp or less. We also found a significant difference in the properties of spots and pores of different types within the group. A significant difference in the distribution pattern of the sunspot area, which is the largest in the group S_max and other spots S_nomax, was detected. There are two local maxima, \({\text{S}}_{{{\text{spt}}}}^{1}\) ~ 8–10 mdp and \({\text{S}}_{{{\text{spt}}}}^{2}\) ~ 130–180 mdp, in the area distribution of the largest sunspot S_max in the group. The first maximum is associated with the existence of pores and transition spots in which the penumbra is at the formation stage. The second maximum S_max in the distribution is associated with the existence of regular spots. For the remaining spots S_nomax in the group, the area distribution function monotonically decreases with increasing area.

Developing ideas of the paper Zaitsev and Stepanov (2018) with regards to activation of a current-carrying filament with an increase in electric current, in which the Ampère force is opposed by gravity and medium viscosity, we take into account the influence of an external magnetic field. It is shown that, depending on mutual directions of the external magnetic field and electric current in the flux rope, the additional Ampère force can lead to the deceleration or to additional eruption of the flux rope. A phase diagram describing the peculiarities of flux rope dynamics has been constructed. The maximum height and velocity of the flare loop are determined for the event on March 30, 2001.

We present a study of quasi-periodic pulsations in the microwave emission from solar active region (AR) NOAA 12673, which produced the strongest flares of the 24th solar activity cycle. The data from daily observations of the Sun at the Nobeyama Radioheliograph at a frequency of 17 GHz were used. The microwave emission of the AR was analyzed for September 3–4, 2017, i.e., before the first M-class flare, which occurred on September 4. Long-period pulsations in the microwave emission with periods of approximately 100 min appeared at least 7 h before the first M-class flare, which was followed by strong flare activity in NOAA 12673. The effect is similar to the previously discovered preflare oscillatory phenomena with different periods manifested in different ranges.

Features of the development of activity cycles in the solar-type stars and fast-rotating cool dwarfs have been considered for 65 stars observed in some decades. Cycles with duration of 7–18 years compared to the solar cycle were found for about 50% of the studied stars. In cooler dwarfs with rotation periods of less than 5 days, cyclic changes in brightness occur on longer scales, up to 80 years. Activity of the highest level is produced on K dwarfs; their main cycles are long and have the highest amplitudes. Both old and young solar-type stars show a similar tendency in increasing the cycle length with a slower rotation. No evidence for a relation between the rotation period and duration of cycles was found for cool dwarfs with P_rot < 5 days.

We present a model for the propagation of coronal mass ejections (CMEs) based on the interaction of CMEs with the solar wind through aerodynamic drag. The parameters of the solar wind are calculated based on observational data of the STOP magnetograph. The CME parameters, namely, the velocity vector and the estimated density at the initial stage of propagation, can be determined from the data of patrol telescopes. In the model, we consider a CME in the form of a cloud, represented by a set of points, and we track the trajectory of the motion of each point in the heliosphere. The simulation data can be used to estimate the geoefficiency of coronal mass ejections.

Based on observations in the Hα and extreme ultraviolet lines, as well as in the radio and X-ray wavelengths, we study the eruptive events of September 22 and 24, 2011, that occurred in the active region (AR) NOAA 11302. It has been found that a complex magnetic configuration has formed as a result of appearance of new bipolar sunspots near the tail sunspots. From the comparison of two long flares, it follows that they were related to high-energy coronal mass ejections (CMEs), whose eruption mechanisms differed significantly at the level of the chromosphere and the lower corona. In the case of September 22, repeated eruptions of prominences before the CME took place, while on September 24, recurrent jets were observed before and after the CME. In both cases, a CME merging could take place, after which the precipitating substance led to the development of long flares in the soft X-ray range and the formation of a post-eruptive arcade, which was clearly visible in the extreme ultraviolet lines.

This paper presents observational series of the spectral solar corona obtained with the Small Lyot Coronagraph deployed in 1948 at the Mountain Astronomical Station of the Central Astronomical Observatory, Russian Academy of Sciences (MAS CAO RAS), near the city of Kislovodsk; this is the only observatory in the world that maintains such large databases (1952–2019) of coronal intensity in the lines λ = 5303 Å (Fe XIV) and λ = 6374 Å (Fe X). Correlation and regression analysis of data from six solar activity cycles has revealed the homogeneity and stability of continuous series of intensities of the green and red corona.

Specific features of the behavior of streams of relativistic magnetospheric electrons at energies higher than 2 MeV on geostationary orbits during different types of interplanetary disturbances are studied. More than 30 years (1986–2019) of observations of these particles onboard the GOES satellites is analyzed. It is shown that plasma coronal ejections and high-speed streams from coronal holes differently influence the behavior of high-energy electrons. High-speed streams from coronal holes are more effective In formation of electron flux rises than solar plasma ejections.

The results of the study of quasi-periodic hard X-ray pulsations in solar flares with respect to the spatial localization of emission sources based on data from the RHESSI spacecraft are presented. Three events (SOL 2002-04-21T01:15, SOL 2003-10-24T02:44, and SOL 2013-05-13T15:52), the hard X-ray of which exhibited quasi-periodic pulsations in local sources, are considered. All of the studied events are characterized by differences in the properties of quasi-periodic pulsations in the different sources. The local sources of each of the flares (SOL 2002-04-21T01:15 and SOL 2003-10-24T02:44) are characterized primarily by identical properties of quasi-periodic pulsations of the hard X-rays from different energy channels. The typical values of the periods of the found quasi-periodic pulsations are 20–70 s. In the local sources of the event SOL 2013-05-13T15:52, the pulsations with nonidentical characteristics are dominant at different hard X-ray energies. The values of the periods of found quasi-periodic pulsations are 10–30 s.

Long-term variations of the magnetic field of solitary solar pores with periods in the range of 4–12 h are detected with the Helioseismic and Magnetic Imager (HMI) of the Solar Dynamics Observatory (SDO). These long-term oscillations of the pores obviously reflect the movements of these structures as whole magnetic formations around their equilibrium position. In this article, long-period oscillations of the solar pore are studied based on the SDO data for the first time. The results are interpreted with the solution obtained earlier for eigen oscillations of the system with time-varying stiffness.

A study of glacial−interglacial periods shows that, once ice sheets reach a critical maximal mass, the glaciation period changes to an interglacial one; the latter gives way to the following glaciation period, during which the ice sheet mass becomes minimal. The last interglacial period, the Holocene, has been going on for more than 10 ka; this raises the question of the timing of the end of the Holocene and the beginning of the upcoming glaciation. The retrieval of detailed information on the mechanisms of climate change is connected with the study of ice sheets in Greenland and Antarctica, oceanic sediments, and continuous terrestrial proxy data. Long-term continuous data on the variability of land ice in Greenland and Antarctica provide valuable information on the climate variability pattern in the time intervals of the transition from glacial conditions to interglacial ones and vice versa. The data on temperature anomalies in Greenland and Antarctica are compared and analyzed here. The paper mainly focuses on the temperature variability pattern for the time interval of the transition from the last glacial maximum to the present moment (i.e., the temperature and trends in its changes are reconstructed).

The hypothesis put forward by Svensmark and Friis-Christensen (1997), Svensmark (2007), Svensmark et al. (2017), and Stozhkov et al. (2017) assumes while completely ignoring the influence of quasi-200-year variation in TSI by ~0.4% (Shapiro et al., 2011; Egorova et al., 2018) that the increased penetrating by the galactic cosmic ray flux of the lower layers of the Earth’s atmosphere during the Grand Solar Minimum causes only an increase in cloud formation and the TSI reflected back into space. However, without calculating the changes in the global average annual energy balance between the Earth and space (Е₀), the authors of the hypothesis argue that this effect will lead to a long-term negative average of the Earth’s annual energy budget and to climate cooling up to a Little Ice Age. The hypothesis also completely ignores all subsequent changes in atmospheric physical processes associated with increasing cloud coverage: the increased reflection and absorption of thermal radiation from the Earth’s surface and of solar radiation reflected from the Earth’s surface, the narrowing of atmospheric transparency windows, and the enhanced greenhouse effect. These processes compensate for the cooling. Our assessment shows that the changes in the global average annual energy balance between the Earth and space before and after a 2% increase in cloud coverage in the lower atmosphere have a difference of almost zero: E₁ – E₀ ≈ 0. The potential increase in cloud coverage causes virtually no variations in the global average annual energy balance between the Earth and space and has no effect on climate change (cooling).

The index of integral solar activity F10.7 is one of the main input parameters of existing ionospheric models, including the model used at early-warning radar stations to compensate for coordinate information errors; the use of external sources of F10.7 seems to be impossible. A method is presented for highly reliable estimate of the solar X-ray flux values at a wavelength of 10.7 cm based only on the capabilities of the station itself.