Особенности короткопериодических колебаний микроволнового излучения активной области Солнца перед вспышкой.
Radiation of microwave sources above sunspots at a frequency of 17 GHz gives information on parameters
of solar plasma in the regions of magnetic field B ~ 200 G in the transition region between chromosphere
and corona. Short period (with periods in several minutes) oscillations of microwave emission of solar active
regions (ARs) reflect wave processes in the magnetic flux tubes of the sunspots. We present an analysis of short
period oscillations of microwave emission of AR NOAA 12242 before two flares on December 17, 2014. The
analysis is based on solar radio images, obtained using the Nobeyama Radio Heliograph. The radio maps of
the whole solar disk were synthesized in non-standard mode with a cadence of 10s and 10s averaging. The
spatial resolution of the radio maps is about 10ʹ–15ʺ. We found that about 40–50 min before the M1.5 flare
(01:00 UT) the power of about ten-minute oscillations is increased. At the same day the power of ten-minute
oscillations increased about 60 min before the M8.7 flare (04:42 UT). The observed effect is similar to the
previously detected independently by two authors effect for 3-minute oscillations, namely, for 15–20 min
before radio burst there was increase of the power of 3-minute oscillations. The effect can be interpreted as
a relationship between MHD waves, propagating along the magnetic flux tube of sunspot, and beginning of
Radio-observations allow us to reveal the long-lived (2–5 days) intersunspot sources (ISS), whose centers are often located above the neutral line of the magnetic field separating leading and following parts of a whole active region (the first type of ISS (ISS-I)) or above the neutral line separating magnetic polarities into complex sunspots (the second type of ISS (ISS-II)). ISS-I and ISS-II demonstrate gyrocyclotron or gyrosynchrotron spectra, more dynamic pre-flare behavior than ISS-III with bremsstrahlung in the quiet active regions. The qualitative model of “three magnetic fluxes” explaining the origin of accelerated particles in ISS and their long-lasting existence and spectral features is proposed.
The radiation of microwave sources above sunspots at a frequency of 17 GHz gives information about the parameters of solar plasma in the regions where the magnetic-field strength is B ∼ 2000 G in the transition region between the chromosphere and corona. Short-period oscillations (with a period of severalminutes) of microwave emission from solar active regions (ARs) reflect wave processes in magnetic flux tubes of sunspots. Short-period oscillations of microwave emission from AR NOAA 12242 before two flares on December 17, 2014 are analyzed. This analysis is based on solar radio images obtained by means of the Nobeyama Radio Heliograph with a 10"−15" two-dimensional spatial resolution. The radio maps of the whole solar disk were synthesized in a nonstandard mode with a cadence of 10 s and an averaging time of 10 s. An increase in the power of about ten-minute oscillations of microwave radiation approximately 40 to 50 min before the M1.5 flare (01 : 00 UT) is found. On the same day, an increase in the power of ten-minute oscillations is observed about 60 min before the M8.7 flare (04 : 42 UT). This effect is similar to the effect found earlier by two groups of authors independently for three-minute oscillations—namely, they observed a sharp increase in three-minute oscillations 15 to 20 min before the radio burst accompanying the flare. The effect in question may be interpreted as an relationship ofMHD waves propagating along the magnetic flux tube of a sunspot and the onset of the solar flare.
Results: The first M-class flare occurred on September 4, 2017 at 05:36-06:05 UT. We found that 100-minute oscillations were observed on September 4 during a few hours before M1.2 flare. At the same time, there were no noticeable oscillations on September 3. The observed effect is similar to the previously detected effect for 3-minute and 10-minute oscillations, namely, before radio burst there was increase of the power of oscillations. The effect can be interpreted as a relationship between MHD waves propagating along the magnetic flux tube of sunspot and beginning of the flares.
Methods: We used the Nobeyama Radioheliograph (NoRH) daily observations. The radio maps of the whole solar disk were synthesized in non-standard mode with a cadence of ten seconds and ten seconds averaging. We computed the time series of maximum brightness temperature and total flux over selected field-of-view (FOV) and used spectral wavelet analysis of the time series.
Context: We continue research the oscillation parameters in solar active regions (ARs) in connection with their flare activity.
Aims: The aim of this paper is to study oscillations of microwave emission of AR NOAA 12673 before first M-class flare in September 2017.
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 radio heliograph 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.
In this paper, we describe the spatial structure and time characteristics of the microwave emission of active region AR 12673 during the rapid changes in the magnetic flux on September 4, 2017 using Nobeyama Radioheliograph observations. It is shown that the microwave emission of the active region exhibits extremely dynamic behavior of its spatial brightness distribution as well as a very non-stationary, impulsive, emission from the specific position where М1.2 class flare happens later. It is shown from comparison of microwave and EUV maps that the strong non-stationary microwave flare happens at the position where a system of intersecting compact EUV loops appears.
Under this study we considered active region 09415 of the 23-rd cycle of solar activity which was observed with the 2D spatial resolution at three frequencies: 17 and 34 GHz with the Nobeyama Radioheliograph (NoRH) and 17 GHz with the Solar Siberian Radiotelescope (SSRT). We detected rapid development of a compact microwave source above the neutral line of the magnetic field of leading sunspot (NLS-source) few hours before the X-class flare. The position of this source is associated with the place of the maximum of magnetic field gradient at the photosphere.
The dynamics of a two-component Davydov-Scott (DS) soliton with a small mismatch of the initial location or velocity of the high-frequency (HF) component was investigated within the framework of the Zakharov-type system of two coupled equations for the HF and low-frequency (LF) fields. In this system, the HF field is described by the linear Schrödinger equation with the potential generated by the LF component varying in time and space. The LF component in this system is described by the Korteweg-de Vries equation with a term of quadratic influence of the HF field on the LF field. The frequency of the DS soliton`s component oscillation was found analytically using the balance equation. The perturbed DS soliton was shown to be stable. The analytical results were confirmed by numerical simulations.
Radiation conditions are described for various space regions, radiation-induced effects in spacecraft materials and equipment components are considered and information on theoretical, computational, and experimental methods for studying radiation effects are presented. The peculiarities of radiation effects on nanostructures and some problems related to modeling and radiation testing of such structures are considered.