Clusters of Solar Radio Spikes Modulated by Quasi-Periodic Pulsations in a Confined Flare |
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Jing Huang Submitted: 2022-07-17 19:49
Spikes are typical radio bursts in solar flares, which are proposed to be the signal of energy release in the solar corona. The whole group of spikes always shows different spectral patterns in the dynamic spectrum. Here, we present a special new feature at 0.6–2 GHz in a confined flare. Each group of spikes is composed of many quasi-periodic sub-clusters, which are superposed on the broadband quasi-periodic pulsations (QPPs). The quasi-periodic cluster of spikes (QPSs) have very intense emissions, and each cluster includes tens of individual spikes. When the intensity of background pulsation is increased, the intensity, duration and bandwidth of the spike cluster are also enlarged. There are 21 groups of QPSs throughout the confined flare. The central frequency of the whole group shifts from 1.9 to 1.2 GHz, and the duration of each cluster shows a negative exponential decay pattern. We propose that nonthermal electron beams play a crucial role in emitting both pulsations and spikes. The tearing-mode oscillations of a confined flux rope produce periodic accelerated electron beams. These electron beams travel inside the closed magnetic structure to produce frequency drifting pulsations via plasma emission and scattered narrowband spikes by electron-cyclotron maser emission (ECME). The slow rise of flux rope makes the source region move upward, and thus, QPSs shift towards low frequency. We propose that the confined flux rope may provide the essential conditions for the formation of QPSs.
Authors: Huang, Jing ; Tan, Chengming ; Chen, Xingyao ; Tan, Baolin ; Yan, Yihua ; Zhang, Yin ; Ma, Suli ; Zhou, Zhichao ; Zhang, Minghui ; Wang, Wei ; Chen, Linjie
Projects: None
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Publication Status: Universe, vol. 8, issue 7, p. 348 (published)
Last Modified: 2022-07-18 09:56
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Quasi-periodic pulsations with varying period in multi-wavelength observations of an x-class flare |
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Jing Huang Submitted: 2014-08-03 20:53
This work presents an interesting phenomenon of the period variation in quasi-periodic pulsations (QPPs) observed during the impulsive phase of a coronal mass ejection-related X1.1 class flare on 2012 July 6. The period of QPPs
was changed from 21 s at soft X-rays (SXR) to 22?23 s at microwaves, to ∼24 s at extreme ultraviolet emissions
(EUV), and to 27?32 s at metric?decimetric waves. The microwave, EUV and SXR QPPs, emitted from flare loops
of different heights, were oscillating in phase. Fast kink mode oscillations were proposed to be the modulation
mechanism, which may exist in a wide region in the solar atmosphere from the chromosphere to the upper corona
or even to the interplanetary space. Changed parameters of flare loops through the solar atmosphere could result
in the varying period of QPPs at different wavelengths. The first appearing microwave QPPs and quasi-periodic
metric-decimetric type III bursts were generated by energetic electrons. This may imply that particle acceleration or magnetic reconnection were located between these two non-thermal emission sources. Thermal QPPs (in SXR and EUV emissions) occurred later than the nonthermal ones, which would suggest a some time for plasma heating or
energy dissipation in flare loops during burst processes. At the beginning of flare, a sudden collapse and expansion
of two separated flare loop structures occurred simultaneously with the multi-wavelength QPPs. An implosion in the corona, including both collapse and expansion of flare loops, could be a trigger of loop oscillations in a very large region in the solar atmosphere.
Authors: Jing Huang, Baolin Tan, Yin Zhang, Marian Karlickýy, and Hana M?esz?arosov?a
Projects: GOES X-rays ,SDO-AIA,SDO-HMI
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Publication Status: published
Last Modified: 2014-08-04 17:58
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Energetic electron propagation in the decay phase of non-thermal flare emission |
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Jing Huang Submitted: 2014-06-12 01:45
On the basis of the trap-plus-precipitation model, the peculiarities of non-thermal emission in the decay phase of
solar flares have been considered. The calculation formulas for the escape rate of trapped electrons into the loss cone in terms of time profiles of hard X-ray (HXR) and microwave (MW) emission have been obtained. It has been found that the evolution of the spectral indices of non-thermal emission depend on the regimes of the pitch angle diffusion of trapped particles into the loss cone. The properties of non-thermal electrons related to the HXR and MW emission of the solar flare on 2004 November 3 are studied with Nobeyama Radioheliograph, Nobeyama Radio Polarimeters, RHESSI, and Geostationary Operational Environmental Satellite observations. The spectral indices of non-thermal electrons related to MW and HXR emission remained constant or decreased, while the MW escape rate as distinguished from that of the HXRs increased. This may be associated with different diffusion regimes of trapped electrons into the loss cone. New arguments in favor of an important role of the superstrong diffusion for high-energy electrons in flare coronal loops have been obtained.
Authors: Jing Huang, Yihua Yan, and Yuri T. Tsap
Projects: Nobeyama Radioheliograph
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Publication Status: ApJ, Volume 787, Page 123, 2014
Last Modified: 2014-06-12 14:54
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