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A Very Small and Super Strong Zebra Pattern Burst at the Beginning of a Solar Flare  

Baolin Tan   Submitted: 2014-07-10 18:55

Microwave emission with spectral zebra pattern structures (ZPs) is observed frequently in solar flares and the Crab pulsar. The previous observations show that ZP is only a structure overlapped on the underlying broadband continuum with slight increments and decrements. This work reports an extremely unusual strong ZP burst occurring just at the beginning of a solar flare observed simultaneously by two radio telescopes located in China and Czech Republic and by the extreme ultraviolet (EUV) telescope on board NASA's satellite Solar Dynamics Observatory on 2013 April 11. It is a very short and super strong explosion whose intensity exceeds several times that of the underlying flaring broadband continuum emission, lasting for just 18 s. EUV images show that the flare starts from several small flare bursting points (FBPs). There is a sudden EUV flash with extra enhancement in one of these FBPs during the ZP burst. Analysis indicates that the ZP burst accompanying EUV flash is an unusual explosion revealing a strong coherent process with rapid particle acceleration, violent energy release, and fast plasma heating simultaneously in a small region with short duration just at the beginning of the flare.

Authors: Baolin Tan, Chengming Tan, Yin Zhang, Jing Huang, Hana Meszarosova, Marian Karlický, Yihua Yan
Projects: None

Publication Status: ApJ, 2014, accepted
Last Modified: 2014-07-11 14:34
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Statistics and Classification of the Microwave Zebra Patterns Associated with Solar Flares  

Baolin Tan   Submitted: 2014-07-10 18:50

The microwave zebra pattern (ZP) is the most interesting, intriguing, and complex spectral structure frequently observed in solar flares. A comprehensive statistical study will certainly help us to understand the formation mechanism, which is not exactly clear now. This work presents a comprehensive statistical analysis on a big sample with 202 ZP events collected from observations at the Chinese Solar Broadband Radio Spectrometer at Huairou and the Ondřejov; Radiospectrograph in Czech Republic at frequencies of 1.00 - 7.60 GHz during 2000 - 2013. After investigating the parameter properties of ZPs, such as the occurrence in flare phase, frequency range, polarization degree, duration, etc., we find that the variation of zebra stripe frequency separation with respect to frequency is the best indicator for a physical classification of ZPs. Microwave ZPs can be classified into 3 types: equidistant ZP, variable-distant ZP, and growing-distant ZP, possibly corresponding to mechanisms of Bernstein wave model, whistler wave model, and double plasma resonance model, respectively. This statistical classification may help us to clarify the controversies between the existing various theoretical models, and understand the physical processes in the source regions.

Authors: Baolin Tan, Chengming Tan, Yin Zhang, H. Meszarosova, M. Karlický
Projects: None

Publication Status: ApJ, 2014, 780, 129
Last Modified: 2014-07-11 14:34
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New Aspects on Particle Acceleration in Solar Flares from RHESSI Observations  

Baolin Tan   Submitted: 2008-06-19 20:22

From the observations with the Chinese Solar Broadband Radiospectrometer (SBRS/Huairou) in the frequency range of 1.10 - 2.06 GHz and 2.60 - 3.80 GHz during 2004 - 2006, we select 14 flare events which were associated with numerous fast microwave sub-second pulsating structures (period: P<0.5 s). In order to describe these sub-second pulsating structures comprehensively, we defined a set of observable parameters including emission frequency (f0), bandwidth (bw), polarization degree (r), period (P), duration(D), modulation depth (M), quality factor (Q), single pulse frequency drifting rate (Rspfd), global frequency drifting rate (Rgfd), and symmetrical factor of the pulse profile (S). Then based on a detailed analysis of the spectrograms of the fast pulsations which occurred in one of these flares (an X3.4 flare/CME event occurred on 13 Dec. 2006), we discuss the possible relations among these observable parameters and their physical implications for the dynamical processes of solar eruptive events, and applied them to interpret the nature of the pulsations in the flare/CME event. Such study of microwave periodic pulsations provide us a useful tool to probe the details of the flare kernels, and understand the physical mechanism of solar eruptive processes.

Authors: Baolin Tan
Projects: None

Publication Status: accepted by Solar Physics, DOI:10.1007/s11207-008-9235-3
Last Modified: 2008-09-23 20:59
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Subject will be restored when possible  

Baolin Tan   Submitted: 2008-06-12 20:13

From the observations with the Chinese Solar Broadband Radiospectrometer (SBRS/Huairou) in the frequency range of 1.10 - 2.06 GHz and 2.60 - 3.80 GHz during 2004 - 2006, we select 14 flare events which were associated with numerous fast microwave sub-second pulsating structures (period: P<0.5 s). In order to describe these sub-second pulsating structures comprehensively, we defined a set of observable parameters including emission frequency (f0), bandwidth (bw), polarization degree (r), period (P), duration (D), modulation depth (M), quality factor (Q), single pulse frequency drifting rate (Rspfd), global frequency drifting rate (Rgfd), and symmetrical factor of the pulse profile (S). Then based on a detailed analysis of the spectrograms of the fast pulsations which occurred in one of these flares (an X3.4 flare/CME event occurred on 13 Dec. 2006), we discuss the possible relations among these observable parameters and their physical implications for the dynamical processes of solar eruptive events, and applied them to interpret the nature of the pulsations in the flare/CME event. Such study of microwave periodic pulsations provide us a useful tool to probe the details of the flare kernels, and understand the physical mechanism of solar eruptive processes.

Authors: Baolin Tan
Projects: None

Publication Status: accepted, DOI: 10.1007/s11207-008-9235-3
Last Modified: 2008-06-13 06:53
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Subject will be restored when possible  

Baolin Tan   Submitted: 2008-06-12 20:13

From the observations with the Chinese Solar Broadband Radiospectrometer (SBRS/Huairou) in the frequency range of 1.10 - 2.06 GHz and 2.60 - 3.80 GHz during 2004 - 2006, we select 14 flare events which were associated with numerous fast microwave sub-second pulsating structures (period: P<0.5 s). In order to describe these sub-second pulsating structures comprehensively, we defined a set of observable parameters including emission frequency (f0), bandwidth (bw), polarization degree (r), period (P), duration (D), modulation depth (M), quality factor (Q), single pulse frequency drifting rate (Rspfd), global frequency drifting rate (Rgfd), and symmetrical factor of the pulse profile (S). Then based on a detailed analysis of the spectrograms of the fast pulsations which occurred in one of these flares (an X3.4 flare/CME event occurred on 13 Dec. 2006), we discuss the possible relations among these observable parameters and their physical implications for the dynamical processes of solar eruptive events, and applied them to interpret the nature of the pulsations in the flare/CME event. Such study of microwave periodic pulsations provide us a useful tool to probe the details of the flare kernels, and understand the physical mechanism of solar eruptive processes.

Authors: Baolin Tan
Projects:

Publication Status: accepted by Solar Physics, DOI: 10.1007/s11207-008-9235-3
Last Modified: 2008-09-23 20:59
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The Microwave Pulsations and the Tearing modes in the Current-Carrying Flare Loops  

Baolin Tan   Submitted: 2007-08-13 21:48

Solar microwave observations of the X3.4 Flare/CME event observed in Chinese solar broadband radiospectrometer (SBRS/Huairou) on December 13, 2006, show a series of very short period pulsations (VSP) with the period of <1.0 s in the frequency range of 2.60 - 3.80 GHz. Many pulsating events have the period of only several decade milliseconds. These pulsations are quasi-periodic, broad bandwidth, and ubiquitous during all the phases of the flare/CME event. Based on theoretical analysis of the temporal behavior of the resistive tearing mode in the electric current-carrying flare loops, we proposed that microwave pulsations are resulted from the modulation of the tearing mode oscillations in the current-carrying flare loops. Our calculations of the period of the tearing mode oscillations are in good agreement with the observations.

Authors: Baolin Tan, Yihua Yan, Chengming Tan, and Yuying Liu
Projects: None

Publication Status: accepted by the Astrophysical Journal, 2007
Last Modified: 2007-08-14 07:35
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Abstracts by Author
A Very Small and Super Strong Zebra Pattern Burst at the Beginning of a Solar Flare
Statistics and Classification of the Microwave Zebra Patterns Associated with Solar Flares
New Aspects on Particle Acceleration in Solar Flares from RHESSI Observations
Subject will be restored when possible
Subject will be restored when possible
The Microwave Pulsations and the Tearing modes in the Current-Carrying Flare Loops

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