Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Flare Ribbon Energetics in the Early Phase of an SDO Flare   The sites of chromospheric excitation during solar flares are marked by
extended extreme ultraviolet ribbons and hard X-ray footpoints. The standard
interpretation is that these are the result of heating and bremsstrahlung
emission from non-thermal electrons precipitating from the corona. We examine
this picture using multi-wavelength observations of the early phase of an
M-class flare SOL2010-08-07T18:24. We aim to determine the properties of the
heated plasma in the flare ribbons, and to understand the partition of the
power input into radiative and conductive losses. Using GOES, SDO/EVE, SDO/AIA
and RHESSI we measure the temperature, emission measure and differential
emission measure of the flare ribbons, and deduce approximate density values.
The non-thermal emission measure, and the collisional thick target energy input
to the ribbons are obtained from RHESSI using standard methods. We deduce the
existence of a substantial amount of plasma at 10 MK in the flare ribbons,
during the pre-impulsive and early-impulsive phase of the flare. The average
column emission measure of this hot component is a few times 10^28/cm^5, and we
can calculate that its predicted conductive losses dominate its measured
radiative losses. If the power input to the hot ribbon plasma is due to
collisional energy deposition by an electron beam from the corona then a
low-energy cutoff of around 5 keV is necessary to balance the conductive
losses, implying a very large electron energy content. Independent of the
standard collisional thick-target electron beam interpretation, the observed
non-thermal X-rays can be provided if one electron in 10^3 - 10^4 in the 10 MK
(1 keV) ribbon plasma has an energy above 10 keV. We speculate that this could
arise if a non-thermal tail is generated in the ribbon plasma which is being
heated by other means, for example by waves or turbulence.

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The categories of this paper are: math-ph
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The categories of this paper are: hep-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: stat
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The categories of this paper are: chem-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: cond-mat
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The categories of this paper are: adap-org
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The categories of this paper are: eess
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The categories of this paper are: q-fin
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The categories of this paper are: q-alg
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The categories of this paper are: alg-geom
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: chao-dyn