Heating Events Observed in the Quiet Corona |
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Arnold Benz Submitted: 1999-11-04 13:01
The emission measure of the quiet corona, defined by the plasma hotter than one
million degrees, has been observed by EIT on SoHO to fluctuate in a alrge
majority of the 1900km x 1900km pixels during the observing time of 42 minutes.
In the average, the larger the emission measure in a pixel, the more it
fluctuates. Increases in emission measure constitute a major energy input into
the corona, suggesting that the lower corona is not just heated, but continuous-
continuously replenished by chromospheric material heated to coronal temperatur-
temperatures. We test the hypothesis that the coronal heat input may be largely
by chromospheric evaporation.
ESA Special Publication, in press
Authors: Arnold O. Benz and Säm Krucker
Projects: Soho-EIT
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Publication Status: To appear in: Magnetic Fields and Solar Processes}, 9th European Meeting on Solar Physics, Florence, Italy, 12 - 18 September 19
Last Modified: 2005-11-17 01:40
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Are Heating Events in the Quiet Solar Corona Small Flares? - Multiwavelength Observations of Individual Events |
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Arnold Benz Submitted: 1999-11-04 13:00
Temporary enhancements of the coronal emission measure in a quiet region have
been shown to constitute a significant energy input. Here some relatively large
events are studied for simultaneous brightenings in transition region lines and
in radio emission. Associated emissions are discussed and tested for characteri-
characteristics known from full-sized impulsive flares in active regions.
Heating events and flares are found to have many properties in common, including
(i) associated polarized radio emission, which usually precedes the emission
measure peak (Neupert effect) and sometimes has a non-thermal spectrum, and (ii)
associated and often preceding peaks in O V and He I emission. On the other
hand, heating events also differ from impulsive flares: (i) In half of the
cases, their radio emission at centimeter waves shows a spectrum consistent with
thermal radiation, (ii) the ratio of the gyro-synchrotron emission to the
estimated thermal soft X-ray emission is smaller than in flares, and (iii) the
associated emission in the O V transition region line shows red shifts and blue
shifts, indicating upflows in the rise phase and downflows in the decay phase,
respectively. Nevertheless, the differences seem to be mainly quantitative, and
the analyzed heating events with thermal energies around 1026 erg may in
principle be considered as microflares or large nanoflares, thus small versions
of regular flares.
Authors: Säm Krucker and Arnold O. Benz
Projects: Soho-EIT
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Publication Status: Solar Physics,191, 341 - 385 (2000)
Last Modified: 2005-11-17 01:41
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