Abstract
Differential emission measures (DEMs) during the impulsive phase of
solar flares were constructed using observations from the EUV
Variability Experiment (EVE) and the Markov-Chain Monte Carlo method.
Emission lines from ions formed over the temperature range log
Te = 5.8-7.2 allow the evolution of the DEM to be studied
over a wide temperature range at 10 s cadence. The technique was applied
to several M- and X-class flares, where impulsive phase EUV emission is
observable in the disk-integrated EVE spectra from emission lines formed
up to 3-4 MK and we use spatially unresolved EVE observations to infer
the thermal structure of the emitting region. For the nine events
studied, the DEMs exhibited a two-component distribution during the
impulsive phase, a low-temperature component with peak temperature of
1-2 MK, and a broad high-temperature component from 7 to 30 MK. A
bimodal high-temperature component is also found for several events,
with peaks at 8 and 25 MK during the impulsive phase. The origin of the
emission was verified using Atmospheric Imaging Assembly images to be
the flare ribbons and footpoints, indicating that the constructed DEMs
represent the spatially average thermal structure of the chromospheric
flare emission during the impulsive phase.
Original language | English |
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Article number | 84 |
Pages (from-to) | 1-8 |
Journal | Astrophysical Journal |
Volume | 779 |
Early online date | 26 Nov 2013 |
DOIs | |
Publication status | Published - 10 Dec 2013 |
Keywords
- Sun: activity
- Sun: chromosphere
- Sun: corona
- Sun: flares