SUCCESSIVE MERGING OF PLASMOIDS AND FRAGMENTATION IN A FLARE CURRENT SHEET AND THEIR X-RAY AND RADIO SIGNATURES

Journal Article · Wed Jun 01 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/733/2/107· OSTI ID:21576726

Karlicky, Marian; Barta, Miroslav ^[1]

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1. Astronomical Institute of the Academy of Sciences of the Czech Republic, CZ-25165 Ondrejov (Czech Republic)

Based on our recent MHD simulations, a conception of the successive merging of plasmoids and fragmentation in the current sheet in the standard flare model is presented. Then, using a 2.5-dimensional electromagnetic particle-in-cell model with free boundary conditions, these processes are modeled on the kinetic level of plasma description. We recognize the plasmoids that mutually interacted and finally merged into one large plasmoid. Between interacting plasmoids, additional plasmoids and current sheets on smaller spatial scales were formed, congruent with the fragmentation found in MHD simulations. During interactions (merging-coalescences) between the plasmoids, the electrons were very efficiently accelerated and heated. We find that after a series of such merging processes, the electrons in some regions reached the energies necessary for emission in the hard X-ray range. Considering these energetic electrons and assuming a plasma density of 10{sup 9}-10{sup 10} cm{sup -3} and a source volume equal to the 2007 December 31 flare, we compute the X-ray spectra as produced by the bremsstrahlung emission process. Comparing these spectra with observations, we think that these processes can explain the observed above-the-loop-top hard X-ray sources. Furthermore, we show that the process of fragmentation between two merging plasmoids can generate narrow-band dm-spikes. Formulae for schematic fractal reconnection structures are derived.

• OSTI ID: 21576726
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 733; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BOUNDARY CONDITIONS
BREMSSTRAHLUNG
ELECTROMAGNETIC RADIATION
ELECTRONS
ELEMENTARY PARTICLES
EMISSION
FERMIONS
FLUID MECHANICS
FRAGMENTATION
HYDRODYNAMICS
LEPTONS
MAGNETOHYDRODYNAMICS
MECHANICS
PLASMOIDS
RADIATIONS
SIMULATION
SOLAR ACTIVITY
SOLAR FLARES
SPECTRA
STELLAR ACTIVITY
STELLAR FLARES
TAIL ELECTRONS
X-RAY SPECTRA