Preflare Heating and Mass Motion in a Solar Flare Associated with Hot Plasma Ejection: 1993 November 11 C9.7 Flare

Ohyama, M.; Shibata, Kazunari

doi:10.1093/pasj/49.2.249

Cited by 130 publications

(83 citation statements)

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“…Upward dark supra-arcade flows have not been reported in the imaging SXT or TRACE data. However, Asai et al (2004) suggest that soft X-ray emitting, so-called plasmoid ejections (e.g., Ohyama & Shibata 1997Khan et al 2002) may be the upflow counterpart of dark supra-arcade downflows. However, it is not clear why the downflows are dark while the upflows are bright.…”

Section: Discussionmentioning

confidence: 99%

Observations of simultaneous coronal loop shrinkage and expansion during the decay phase of a solar flare

Khan¹,

Fletcher²,

Nitta

2006

A&A

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We report what we believe are the first direct and unambiguous observations of simultaneous coronal magnetic flux loop shrinkage and expansion during the decay phase of a solar flare. The retracting and expanding loops were observed nearly face-on (i.e., with the loop major axis approximately orthogonal to the line of sight) in emission in imaging data from the Yohkoh Soft X-ray Telescope (SXT). The retracting loop is observed to shrink with a speed of 118 ± 66 km s −1 . The faint outward moving loop-like feature occurred ∼200 above the shrinking loop during the time of the shrinking loop. We estimate the speed of the outward moving loop was ∼129 ± 74 km s −1 . We interpret the shrinking loop and simultaneous outward moving loop as direct evidence for reconnected magnetic field lines during a flare.

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Section: Discussionmentioning

confidence: 99%

Observations of simultaneous coronal loop shrinkage and expansion during the decay phase of a solar flare

Khan¹,

Fletcher²,

Nitta

2006

A&A

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“…The time variation of the convective electric field defined by Equation (16) is also plotted at this panel. Figure 43b shows the height-time relations of an observed plasmoid as well as hard X-ray intensity (Ohyama and Shibata, 1997). When comparing these simulation and observation, we assume that the time variation of the convective electric field is closely related to the time variation of hard X-ray emissions because the electric field can accelerate particles which contribute to producing hard X-ray emissions.…”

Section: Plasmoid Ejectionmentioning

confidence: 95%

“…Time variation of the conductive electric field defined by Equation (16) is also plotted (from Magara et al, 1997). (b) Time variations of the height of an observed plasmoid as well as hard X-ray intensity (modified from Ohyama and Shibata, 1997).…”

Section: Plasmoid Ejectionmentioning

confidence: 99%

Solar Flares: Magnetohydrodynamic Processes

Shibata

Magara

2011

Living Rev. Solar Phys.

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753

647

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This paper outlines the current understanding of solar flares, mainly focused on magnetohydrodynamic (MHD) processes responsible for producing a flare. Observations show that flares are one of the most explosive phenomena in the atmosphere of the Sun, releasing a huge amount of energy up to about 10 32 erg on the timescale of hours. Flares involve the heating of plasma, mass ejection, and particle acceleration that generates high-energy particles. The key physical processes for producing a flare are: the emergence of magnetic field from the solar interior to the solar atmosphere (flux emergence), local enhancement of electric current in the corona (formation of a current sheet), and rapid dissipation of electric current (magnetic reconnection) that causes shock heating, mass ejection, and particle acceleration. The evolution toward the onset of a flare is rather quasi-static when free energy is accumulated in the form of coronal electric current (field-aligned current, more precisely), while the dissipation of coronal current proceeds rapidly, producing various dynamic events that affect lower atmospheres such as the chromosphere and photosphere. Flares manifest such rapid dissipation of coronal current, and their theoretical modeling has been developed in accordance with observations, in which numerical simulations proved to be a strong tool reproducing the time-dependent, nonlinear evolution of a flare. We review the models proposed to explain the physical mechanism of flares, giving an comprehensive explanation of the key processes mentioned above. We start with basic properties of flares, then go into the details of energy build-up, release and transport in flares where magnetic reconnection works as the central engine to produce a flare.

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“…This specific configuration was usually used to perform joint diagnostics on the basis of hard and soft X-ray images including full-Sun soft X-ray spectra recorded by the Bragg Crystal Spectrometer. In this way, soft X-ray bright loop-top kernels (Khan et al, 1995;Mariska et al, 1996;Sterling et al, 1996;Mariska & Doschek, 1997;Ohyama & Shibata, 1997) as well as flare-associated Xray plasma ejections (Ohyama & Shibata, 1997;Tomczak, 2004Tomczak, , 2005 were investigated. Mariska & McTiernan (1999) have done a comparison of hard and soft X-ray characteristics for 28 partially occulted and 17 non-occulted limb flares observed by Yohkoh between 1991 and 1996.…”

Section: Introductionmentioning

confidence: 99%

The YOHKOH survey of partially occulted flares in hard X-rays

Tomczak

2009

A&A

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Context. Modern solar X-ray imagers did not breakthrough the problem of detailed diagnostics of faint hard X-ray sources in the presence of stronger ones. This is the case of the impulsive phase of solar flares in which footpoint sources are usually stronger than loop-top ones. Aims. For this aim, flares being partially occulted by the solar limb, are the best reservoir of our knowledge about hard X-ray loop-top sources. Recently, the survey of partially occulted flares observed by the RHESSI has been published . The extensive Yohkoh database still awaits such activities. This work is an attempt to fill this gap. Methods. Among from 1286 flares in the Yohkoh Hard X-ray Telescope Flare Catalogue (Sato et al. 2006), for which the hard X-ray images had been enclosed, we identified 98 events that occurred behind the solar limb. We investigated their hard X-ray spectra and spatial structure. Results. We found that in most cases the hard X-ray spectrum of partially occulted flares consists of two components, non-thermal and thermal, which are co-spatial. The photon energy spectra of the partially occulted flares are systematically steeper than spectra of the non-occulted flares. Such a difference we explain as a consequence of intrinsically dissimilar conditions ruling in coronal parts of flares, in comparison with the footpoints which usually dominate the hard X-ray emission of disk flares. At least two reasons of the difference should be taken into consideration: (1) stronger contamination of hard X-rays with emission of thermal plasma, (2) different mechanism in which non-thermal electrons radiate their energy. For events unbiased with the thermal component the difference, ∆γ =γ LT −γ FP , is equal to 1.5. Conclusions. A schematic picture, in which thin-target mechanism is responsible for hard X-ray emission of loop-top sources and thick-target mechanism -for emission of footpoint sources, is modified by the presence of some coronal thick-target sources. At least a part of them suggests a magnetic trapping. Investigated flares do not respond the overall (global) magnetic configuration of the solar corona. For their characteristics conclusive is rather the local magnetic configuration in which they were developed.

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Preflare Heating and Mass Motion in a Solar Flare Associated with Hot Plasma Ejection: 1993 November 11 C9.7 Flare

Cited by 130 publications

References 0 publications

Observations of simultaneous coronal loop shrinkage and expansion during the decay phase of a solar flare

Observations of simultaneous coronal loop shrinkage and expansion during the decay phase of a solar flare

Solar Flares: Magnetohydrodynamic Processes

The YOHKOH survey of partially occulted flares in hard X-rays

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