THE HEIGHT OF A WHITE-LIGHT FLARE AND ITS HARD X-RAY SOURCES

Journal Article · Tue Jul 10 04:00:00 EDT 2012 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/753/2/L26· OSTI ID:22047693

Martinez Oliveros, Juan-Carlos; Hudson, Hugh S; Hurford, Gordon J; Krucker, Saem; Lin, R P ^[1]; Lindsey, Charles ^[2]; Couvidat, Sebastien; Schou, Jesper ^[3]; Thompson, W T ^[4]

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1. Space Sciences Laboratory, UC Berkeley, Berkeley, CA 94720 (United States)
2. North West Research Associates, CORA Division, Boulder, CO (United States)
3. W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA (United States)
4. Adnet Systems, Inc., NASA Goddard Space Flight Center, code 671, Greenbelt, MD (United States)

We describe observations of a white-light (WL) flare (SOL2011-02-24T07:35:00, M3.5) close to the limb of the Sun, from which we obtain estimates of the heights of the optical continuum sources and those of the associated hard X-ray (HXR) sources. For this purpose, we use HXR images from the Reuven Ramaty High Energy Spectroscopic Imager and optical images at 6173 A from the Solar Dynamics Observatory. We find that the centroids of the impulsive-phase emissions in WL and HXRs (30-80 keV) match closely in central distance (angular displacement from Sun center), within uncertainties of order 0.''2. This directly implies a common source height for these radiations, strengthening the connection between visible flare continuum formation and the accelerated electrons. We also estimate the absolute heights of these emissions as vertical distances from Sun center. Such a direct estimation has not been done previously, to our knowledge. Using a simultaneous 195 Angstrom-Sign image from the Solar-Terrestrial RElations Observatory spacecraft to identify the heliographic coordinates of the flare footpoints, we determine mean heights above the photosphere (as normally defined; {tau} = 1 at 5000 A) of 305 {+-} 170 km and 195 {+-} 70 km, respectively, for the centroids of the HXR and WL footpoint sources of the flare. These heights are unexpectedly low in the atmosphere, and are consistent with the expected locations of {tau} = 1 for the 6173 Angstrom-Sign and the {approx}40 keV photons observed, respectively.

• OSTI ID: 22047693
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 2 Vol. 753; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTROPHYSICS
DISTANCE
ELECTRONS
HARD X RADIATION
IMAGES
KEV RANGE
PHOTONS
PHOTOSPHERE
SOLAR FLARES
SUN
VISIBLE RADIATION