Earlier, we showed that according to the nature of the location of sources of preflare X-ray pulsations relative to the main solar flare, events are divided into at least two types: in type I events, the sources of pulsations and the main flare are in the same active region (AR) and in type II events they are in different regions. This paper presents an analysis of a type II event in which, according to data from the Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) space observatory, X-ray sources of preflare quasi-periodic pulsations (with a period P = 1.5 ± 0.1 min), which began at ~1802 UT, were located in AR 11 884 in the Western Hemisphere, and the sources of the main flare M1.0 SOL2013-11-05T18:08 were located in AR 11 890 in the Eastern Hemisphere. The pulsations were also observed with the Gamma-Ray Burst Monitor (GBM) aboard the Fermi space observatory and the X-Ray Sensor (XRS) aboard the Geostationary Operational Environmental Satellite (GOES), excluding the possibility of their artificial origin. According to the data of the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) in the extreme ultraviolet range, it was found that the sources of pulsations were located at the base of coronal jets that flowed out at velocities of ~100–1500 km/s. The distance between AR 11 884 and AR 11 890 was ~1.4 R S . It would take ~17–250 min for the jet plasma to reach AR 11 890, which is much longer than the time interval between the onset of pulsations (jets) and the flare (~6 min). No loops connecting AR 11 884 and AR 11 890 were observed in the corona. Moreover, no connection of these regions by magnetic field lines extrapolated from the photosphere to the corona in the potential approximation was found. These arguments indicate that the jets (and associated pulsations) could not be the trigger for the flare. Thus, a vivid example of an event is presented in which there was no physical connection between preflare X-ray pulsations (and jets) and the flare that followed them. This event demonstrates the importance of spatially resolved observations in the study of pulsations on the Sun and stars.

To facilitate the study of solar flares and active regions, we have created a modeling framework, the freely distributed GX Simulator IDL package, that combines 3D magnetic and plasma structures with thermal and nonthermal models of the chromosphere, transition region, and corona. Its object-based modular architecture, which runs on Windows, Mac, and Unix/Linux platforms, offers the ability to either import 3D density and temperature distribution models, or to assign numerically defined coronal or chromospheric temperatures and densities, or their distributions, to each individual voxel. GX Simulator can apply parametric heating models involving average properties of the magnetic field lines crossing a given voxel, as well as compute and investigate the spatial and spectral properties of radio, (sub)millimeter, EUV, and X-ray emissions calculated from the model, and quantitatively compare them with observations. The package includes a fully automatic model production pipeline that, based on minimal users input, downloads the required SDO/HMI vector magnetic field data, performs potential or nonlinear force-free field extrapolations, populates the magnetic field skeleton with parameterized heated plasma coronal models that assume either steady-state or impulsive plasma heating, and generates non-LTE density and temperature distribution models of the chromosphere that are constrained by photospheric measurements. The standardized models produced by this pipeline may be further customized through specialized IDL scripts, or a set of interactive tools provided by the graphical user interface. Here, we describe the GX Simulator framework and its applications.

The goal of the work is to identify and study the dynamics of solar hot jets. Collimated, ray-like structures with temperatures above the transition-zone temperature are recorded in time series images in the extreme ultraviolet (EUV) range. Observations with a high spatiotemporal resolution reveal various morphological features of the jets, their dynamics, and relationships with other coronal structures. To determine and diagnose the parameters of hot jets, an algorithm has been developed to search automatically for jets in homogeneous time series of images. The algorithm is based on the selection of contrasting details in the images of the “running difference” (the difference in the observed intensities at adjacent times). The identified time series of contrasting details are then automatically analyzed according to a number of parameters (area, aspect ratio, length of the time series), and a decision is made to assign the event to the jet class. Upon completion of the analysis, a report is generated (a machine-readable file indicating the parameters of the assumed jets and video files with images of the intensity, the running difference, and the assumed jets). Processing is implemented in the form of a “pipeline” (data loading–fragment cutting–construction of the running difference–search for candidates–report construction) in the IDL language. The described diagnostics was applied to observations in EUV light based on data from the Solar Dynamics Observatory (SDO) AIA for the period 2011–2019. The results are presented in a catalogue (“Catalogue of hot jets in the solar corona,” http://www.spbf.sao.ru/coronal-jets-catalog ). The characteristics of the identified jets were estimated for a sample of 80 events: a duration of 1–17 min, an aspect ratio (ratio of length to width) of 4–21, and a length of 13–144 arc s. The further goal of this diagnostics is the statistical analysis of event parameters and the determination of the physical mechanisms responsible for the generation, collimation, and dynamics of plasma jets in the solar atmosphere.

The paper discusses the diagnostics of plasma jets in the solar corona with the use of data from modern space- and ground-based telescopes observing the Sun in the extreme ultraviolet (EUV) and micro- wave bands. We examine observational parameters of EUV and radio emission in events associated with plasma jets, depending on the mechanism of formation, initiation conditions, and evolution of the jets. The opportunities provided by the study of plasma jets, which relies on simultaneous observations in different bands, are highlighted. For a number of jets, we have measured their primary parameters; and in this paper we present preliminary results of statistical processing of the data obtained. Microwave observations of several specific events, made by ground-based instruments RATAN-600, SRH, and Nobeyama Radioheliograph, are considered in detail. The diagnostic capabilities of these instruments for studying coronal jets are shown. To analyze the three-dimensional structure of the coronal magnetic field, we have used SDO/HMI data, which allowed for the reconstruction of the field in the lower corona. The information gained is compared with the results of diagnostics of the magnetic field at the base of the corona according to RATAN-600 data. The purpose of the methods developed is to determine the physical mechanisms responsible for the generation, collimation, and dynamics of plasma jets in the solar atmosphere.

The question why the solar corona is much hotter than the visible solar surface still puzzles solar researchers. Most theories of the coronal heating involve a tight coupling between the coronal magnetic field and the associated thermal structure. This coupling is based on two facts: (i) the magnetic field is the main source of the energy in the corona and (ii) the heat transfer preferentially happens along the magnetic field, while is suppressed across it. However, most of the information about the coronal heating is derived from the analysis of extreme ultraviolet or soft X-ray emissions, which are not explicitly sensitive to the magnetic field. This paper employs another electromagnetic channel—the sunspot-associated microwave gyroresonant emission, which is explicitly sensitive to both the magnetic field and thermal plasma. We use nonlinear force-free field reconstructions of the magnetic skeleton dressed with a thermal structure as prescribed by a field-aligned hydrodynamics to constrain the coronal heating model. We demonstrate that the microwave gyroresonant emission is extraordinarily sensitive to details of the coronal heating. We infer heating model parameters consistent with observations.

We present a catalogue of solar coronal plasma jets with a temperature above 0.5 MK, which includes primary information about the events, parameters of the diagnosed jets, as well as related eruptive phenomena. The catalogue (https://solar.sao.ru/coronal-jets-catalog/) contains data obtained using the spaceborne EUV high-precision telescope SDO/AIA and ground-based radio telescopes and spectrometers, including RATAN-600, SRH and NoRH. For a number of events data on the reconstructed magnetic field is also presented. The purpose of the catalogue is to provide summary information on coronal jets for further statistical analysis, determination of characteristic parameters of jets, and for in-depth study of the individual events by all interested researchers.

Abstract—We present a method of determination of numbers of gyroresonance layers most effectively radiating in the transition region of the active solar atmosphere. It is based on determination of frequency in the spectrum of an extraordinary wave of an active region, at which the gradient of this spectrum abruptly rises. Observations of 29 active regions carried out at the RATAN-600 radio telescope have been analyzed. The magnetic field in the transition region was determined from the frequency of bending point in the spectrum of antenna temperatures in an extraordinary mode under condition of emission in the third harmonic of the gyrofrequency. The relation between the photospheric magnetic field strength and the magnetic field strength in the transition region (1.52–2.28) is substantially greater than previously obtained, namely, the field isdecreasedonlyby10–20% in the transition region. The heights in the transition region were determined from the reconstructed magnetic field in the nonlinear force-free approximation, and are in the range of 1.00–3.57 Mm.

The strongest magnetic fields on the Sun are routinely detected at dark sunspots. The magnitude of the field is typically about 3000 G, with only a few exceptions that reported the magnetic field in excess of 5000 G. Given that the magnetic field decreases with height in the solar atmosphere, no coronal magnetic field above ∼2000 G has ever been reported. Here, we present imaging microwave observations of anomalously strong magnetic field of about 4000 G at the base of the corona in solar active region NOAA 12673 on 2017 September 6. Combining the photospheric vector measurements of the magnetic field and the coronal probing, we created and validated a nonlinear force-free field coronal model, with which we quantify the record-breaking coronal magnetic field at various coronal heights.

Models of the upper transition region of sunspots have been derived based on the observed radio spectrum between 3 and 18 GHz from Radio Astronomical Telescope of the Academy of Sciences 600 (RATAN-600) observations. Our objective is to match the spectrum to show that, within the limits of the one-dimensional observations and modeling, we have obtained a reasonable description of the upper transition-region structure of sunspots. We have developed a diagnostic method, based on iterative correction of the temperature–height profile in the transition region and lower corona, and applied it to three selected active regions with unipolar gyroresonance sources. Good agreement is achieved between observed and modeled microwave spectra using one-dimensional, time-independent models in hydrostatic equilibrium characterized by a given temperature as a function of height. We found that above sunspots the upper height of a transition region is located at 2 – 2.3 Mm, and the temperature of the low corona is about 1.5 – 2.5 MK.