Statistical properties of super-hot solar flares

Journal Article · Mon Jan 20 04:00:00 EST 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/781/1/43· OSTI ID:22348166

Caspi, Amir ^[1]; Krucker, Säm; Lin, R. P. ^[2]

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1. Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 (United States)
2. Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)

We use Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) high-resolution imaging and spectroscopy observations from ∼6 to 100 keV to determine the statistical relationships between measured parameters (temperature, emission measure, etc.) of hot, thermal plasma in 37 intense (GOES M- and X-class) solar flares. The RHESSI data, most sensitive to the hottest flare plasmas, reveal a strong correlation between the maximum achieved temperature and the flare GOES class, such that 'super-hot' temperatures >30 MK are achieved almost exclusively by X-class events; the observed correlation differs significantly from that of GOES-derived temperatures, and from previous studies. A nearly ubiquitous association with high emission measures, electron densities, and instantaneous thermal energies suggests that super-hot plasmas are physically distinct from cooler, ∼10-20 MK GOES plasmas, and that they require substantially greater energy input during the flare. High thermal energy densities suggest that super-hot flares require strong coronal magnetic fields, exceeding ∼100 G, and that both the plasma β and volume filling factor f cannot be much less than unity in the super-hot region.

• OSTI ID: 22348166
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 781; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CORRELATIONS
ELECTRON DENSITY
EMISSION
ENERGY DENSITY
GAMMA RADIATION
HEAT EXCHANGERS
KEV RANGE
MAGNETIC FIELDS
RESOLUTION
SOLAR FLARES
SPECTROSCOPY
SUN
X RADIATION