Dynamics of Microwave Sources Associated with the Neutral Line and the Magnetic-Field Parameters of Sunspots as a Factor in Predicting Large Flares

Abramov-Maximov, V. E.; Borovik, V. N.; Opeikina, L. V.; Tlatov, A. G.

doi:10.1007/s11207-014-0605-8

Cited by 15 publications

(8 citation statements)

References 41 publications

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“…According to Sych, Uralov, and Korzhavin (1993), Uralov et al (2000), Uralov, Rudenko, andRudenko (2006a, 2006b), as long as NLSs exist, small flares occur in the AR. However, these sources are also associated with strong X-class (GOES) flares -X1.0 or higher (Abramov-Maximov et al, 2014). According to one of the proposed mechanisms, a preflare current sheet is formed above the NLS, which can trigger a strong flare (Uralov et al, 2000;Uralov, Rudenko, andRudenko, 2006a, 2006b).…”

Section: Peculiar Sources or Nlssmentioning

confidence: 99%

Intersunspot Microwave Sources

et al. 2014

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We studied a number of solar active regions using two-dimensional spatially resolved microwave observations. Data from the Nobeyama Radioheliograph and the Siberian Solar Radio Telescope together with observations by the Michelson Doppler Imager (MDI) onboard the Solar and Heliospheric Observatory (SOHO) have allowed us to identify longlived intersunspot sources (ISSs) in most of the investigated active regions. Their centers are often located above the line-of-sight magnetic field inversion line that separates the leading and following polarities of a full active region (first type of ISS) or above the inversion line that separates magnetic polarities inside of a complex of sunspots (second type of ISS). ISSs of the first type are extended and, in general, they are sources of bremsstrahlung emission. ISSs of the second type are compact and are, most likely, sources of gyroresonance or gyrosynchrotron emission. We propose a qualitative model involving three types of magnetic connectivity to explain how long-lasting ISSs may be generated.

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Section: Peculiar Sources or Nlssmentioning

confidence: 99%

Intersunspot Microwave Sources

et al. 2014

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“…The NLS have typical brightness temperatures of a few MK (up to ∼ 10 MK). The spectral observations reveal a sharp spectrum with the peak at ∼ 5 − 7 GHz and a steep decrease at higher frequencies (Akhmedov et al, 1986;Alissandrakis et al, 1993;Bogod, Kaltman, and Yasnov, 2012;Abramov-Maximov et al, 2015); nevertheless, the brightness temperature can reach ∼ 1 − 2 MK at the frequencies of ∼ 17−34 GHz as well (Uralov et al, 2000(Uralov et al, , 2008Uralov, Rudenko, and Rudenko, 2006;Bakunina et al, 2015). Such spectra cannot be explained by the freefree emission mechanism; they are consistent with the thermal gyroresonance emission in a very hot plasma (and strong magnetic field) or with the nonthermal gyrosynchrotron emission.…”

Section: Neutral-line Associated Sourcesmentioning

confidence: 94%

Synthetic Radio Views of Simulated Solar Flux Ropes

2016

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In this paper, we produce synthetic radio views on simulated flux ropes in the solar corona, where finite-beta magnetohydrodynamic (MHD) simulations serve to mimic the flux rope formation stages, as well as their stable endstates. These endstates represent twisted flux ropes where balancing Lorentz forces, gravity and pressure gradients determine the full thermodynamic variation throughout the flux rope. The obtained models are needed to quantify radiative transfer in radio bands, and allow us to contrast weak to strong magnetic field conditions. Field strengths of up to 100 G in the flux rope yield the radio views dominated by optically thin free-free emission. The forming flux rope shows clear morphological changes in its emission structure as it deforms from an arcade to a flux rope, both on disk and at the limb. For an active region filament channel with a field strength of up to 680 G in the flux rope, gyroresonance emission (from the third-fourth gyrolayers) can be detected and even dominates over free-free emission at the frequencies of up to 7 GHz. Finally, we also show synthetic views on a simulated filament embedded within a (weak-field) flux rope, resulting from an energetically consistent MHD simulation. For this filament, synthetic views at the limb show clear similarities with actual observations, and the transition from optically thick (below 10 GHz) to optically thin emission can be reproduced. On the disk, its dimension and temperature conditions are as yet not realistic enough to yield the observed radio brightness depressions.

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“…Работа продолжает цикл работ авторов по выявлению признаков подготовки больших вспышек по микроволновому излучению и магнитографическим характеристикам активных областей (АО) Солнца [1][2][3]9]. Подробная история проблемы и обзор современной литературы по данной теме приведены в [1], обзор последних работ авторов дан в [9].…”

Section: Doi: 1031725/0552-5829-2018-15-18unclassified

“…Аналогичный характер изменения расстояния между областями максимальных магнитных полей противоположных полярностей обнаружен и другими авторами [5] и может быть объяснен моделью магнитного жгута, зажатого между двумя сближающимися магнитными центрами (пятнами), согласно которой сначала сближение пятен обеспечивает накопление свободной магнитной энергии в жгуте, а затем, при расхождении пятен, в нем начинается вспышечное энерговыделение [6,7]. Выявленные свойства микроволнового излучения (резкое возрастание интенсивности, увеличение наклона спектра, уменьшение степени поляризации на 3 см) позволяют предположить, что 4 сентября в АО развился NLSисточник [1], который может рассматриваться как предвестник больших вспышек.…”

Section: рисunclassified

Evolution of Solar Active Region 12673 by Ratan-600 and Sdo Data

Abramov-Maximov¹,

Observatory²,

Borovik³

et al. 2018

Proceedings of the 22nd All-Russia Conference on Solar and Solar-Terrestrial Physics

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Context: We continue our previous researches of solar active regions (ARs) where strong flares occurred to reveal features indicate that a strong flare is about to take place. Aims: The aim of this paper is to study AR NOAA 12673 on pre-flare phase in the beginning of September 2017. We focus on the behavior of microwave emission and magnetic field structure before the first M-class flare on September 4. Methods: We studied microwave emission and magnetic-field characteristics of AR as based on RATAN-600 and SDO/HMI data. For comparison we considered a well-developed AR NOAA 12674, in which there were only a few weak flares of the C-class. Results: As in the previously investigated cases, we registered a sharp increase of the magnetic field gradient with its decrease directly before the flare and a significant increase of microwave emission before the first M-class flare in NOAA 12673. In NOAA 12674 it was not detected significant changes in the gradient of the magnetic field and microwave radiation. The distance between regions of opposite magnetic polarity decrease initially. Then it begins to increase. On the phase of its increasing the flares occurred. The increase of microwave emission may be interpreted as a result of development of neutral line associated source.

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Dynamics of Microwave Sources Associated with the Neutral Line and the Magnetic-Field Parameters of Sunspots as a Factor in Predicting Large Flares

Cited by 15 publications

References 41 publications

Intersunspot Microwave Sources

Intersunspot Microwave Sources

Synthetic Radio Views of Simulated Solar Flux Ropes

Evolution of Solar Active Region 12673 by Ratan-600 and Sdo Data

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