HS Hudson | PubMed Health

PubMed2000

Implosions in Coronal Transients.

Coronal events such as flares or coronal mass ejections derive their energy from the energy stored locally in the magnetic field. This leads to the conjecture that a magnetic implosion must occur simultaneously with the energy release. The site of the implosion would show the location of preflare energy storage, and its detection should have a high priority. The Transition Region and Coronal Explorer EUV observations, for example, have sufficient resolution to show the geometry of a flare implosion by following the motions of tracers in the images.

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PubMed1999

TRACE and Yohkoh Observations of High-Temperature Plasma in a Two-Ribbon Limb Flare.

The ability of the Transition Region and Coronal Explorer (TRACE) to image solar plasma over a wide range of temperatures (Te approximately 104-107 K) at high spatial resolution (0&farcs;5 pixels) makes it a unique instrument for observing solar flares. We present TRACE and Yohkoh observations of an M2.4 two-ribbon flare that began on 1999 July 25 at about 13:08 UT. We observe impulsive footpoint brightenings that are followed by the formation of high-temperature plasma (Te greater, similar10 MK) in the corona. After an interval of about 1300 s, cooler loops (Te<2 MK) form below the hot plasma. Thus, the evolution of the event supports the qualitative aspects of the standard reconnection model of solar flares. The TRACE and Yohkoh data show that the bulk of the flare emission is at or below 10 MK. The TRACE data are also consistent with the Yohkoh observations of hotter plasma (Te approximately 15-20 MK) existing at the top of the arcade. The cooling time inferred from these observations is consistent with a hybrid cooling time based on thermal conduction and radiative cooling.

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