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Multiple Plasmoid Ejections and Associated Hard X-ray Bursts in the 2000 November 24 Flare  

Naoto Nishizuka   Submitted: 2013-01-29 00:43

The Soft X-ray Telescope (SXT) on board Yohkoh revealed that the ejection of X-ray emitting plasmoid is sometimes observed in a solar flare. It was found that the ejected plasmoid is strongly accelerated during a peak in the hard X-ray emission of the flare. In this paper we present an examination of the GOES X 2.3 class flare that occurred at 14.51 UT on 2000 November 24. In the SXT images we found multiple plasmoid ejections with velocities in the range of 250-1500 km s-1, which showed blob-like or loop-like structures. Furthermore, we also found that each plasmoid ejection is associated with an impulsive burst of hard X-ray emission. Although some correlation between plasmoid ejection and hard X-ray emission has been discussed previously, our observation shows similar behavior for multiple plasmoid ejection such that each plasmoid ejection occurs during the strong energy release of the solar flare. As a result of temperature-emission measure analysis of such plasmoids, it was revealed that the apparent velocities and kinetic energies of the plasmoid ejections show a correlation with the peak intensities in the hard X-ray emissions.

Authors: N. Nishizuka, H. Takasaki, A. Asai, and K. Shibata
Projects: Yohkoh-SXT

Publication Status: The Astrophysical Journal, 711, 1062 (2010)
Last Modified: 2013-01-29 12:19
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The Power-Law Distribution of Flare Kernels and Fractal Current Sheets in a Solar Flare  

Naoto Nishizuka   Submitted: 2013-01-29 00:41

We report a detailed examination of the fine structure inside flare ribbons and the temporal evolution of this fine structure during the X2.5 solar flare that occurred on 2004 November 10. We examine elementary bursts of the C IV (1550A) emission lines seen as local transient brightenings inside the flare ribbons in the ultraviolet (1600A) images taken with Transition Region and Coronal Explorer, and we call them C IV kernels. This flare was also observed in Ha with the Sartorius 18 cm Refractor telescope at Kwasan observatory, Kyoto University, and in hard X-rays (HXR) with Reuven Ramaty High Energy Solar Spectroscopic Imager. Many C IV kernels, whose sizes were comparable to or less than 2'', were found to brighten successively during the evolution of the flare ribbon. The majority of them were well correlated with the Ha kernels in both space and time, while some of them were associated with the HXR emission. These kernels were thought to be caused by the precipitation of nonthermal particles at the footpoints of the reconnecting flare loops. The time profiles of the C IV kernels showed intermittent bursts, whose peak intensity, duration, and time interval were well described by power-law distribution functions. This result is interpreted as evidence for ''self-organized criticality'' in avalanching behavior in a single flare event, or for fractal current sheets in the impulsive reconnection region.

Authors: N. Nishizuka, A. Asai, H. Takasaki, H. Kurokawa, K. Shibata
Projects: TRACE

Publication Status: The Astrophysical Journal, 694, L74 (2009)
Last Modified: 2013-01-29 12:19
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Fermi Acceleration in Plasmoids interacting with Fast Shocks of Reconnection via Fractal Reconnection  

Naoto Nishizuka   Submitted: 2013-01-29 00:36

We propose the particle acceleration model coupled with multiple plasmoid ejections in a solar flare. Unsteady reconnection produces plasmoids in a current sheet and ejects them out to the fast shocks, where particles in a plasmoid are reflected upstream the shock front by magnetic mirror effect. As the plasmoid passes through the shock front, the reflection distance becomes shorter and shorter driving Fermi acceleration, until it becomes proton Larmor radius. The fractal distribution of plasmoids may also have a role in naturally explaining the power-law spectrum in nonthermal emissions.

Authors: N. Nishizuka and K. Shibata
Projects: RHESSI

Publication Status: to be published in Phys. Rev. Lett.
Last Modified: 2013-01-29 12:19
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Abstracts by Author
Multiple Plasmoid Ejections and Associated Hard X-ray Bursts in the 2000 November 24 Flare
The Power-Law Distribution of Flare Kernels and Fractal Current Sheets in a Solar Flare
Fermi Acceleration in Plasmoids interacting with Fast Shocks of Reconnection via Fractal Reconnection

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