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Title: HIGH-RESOLUTION IMAGING OF SOLAR FLARE RIBBONS AND ITS IMPLICATION ON THE THICK-TARGET BEAM MODEL

Abstract

We report on high-resolution optical and hard X-ray observations of solar flare ribbons seen during the GOES X6.5 class white-light flare of 2006 December 6. The data consist of imaging observations at 430 nm (the Fraunhofer G band) taken by the Hinode Solar Optical Telescope with the hard X-rays observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager. The two sets of data show closely similar ribbon structures, strongly suggesting that the flare emissions in white light and in hard X-rays have physically linked emission mechanisms. While the source structure along the ribbons is resolved at both wavelengths (length {approx} 30''), only the G-band observations resolve the width of the ribbon, with values between {approx}0.''5 and {approx}1.''8. The unresolved hard X-ray observations reveal an even narrower ribbon in hard X-rays (the main footpoint has a width perpendicular to the ribbon of <1.''1 compared to the G-band width of {approx}1.''8) suggesting that the hard X-ray emission comes from the sharp leading edge of the G-band ribbon. Applying the thick-target beam model, the derived energy deposition rate is >5 x 10{sup 12} erg s{sup -1} cm{sup -2} provided by an electron flux of 1 x 10{sup 20} electrons s{sup -1} cm{supmore » -2} above 18 keV. This requires that the beam density of electrons above 18 keV be at least 1 x 10{sup 10} cm{sup -3}. Even if field lines converge toward the chromospheric footpoints, the required beam in the corona has too high a density to be described as a dilute tail population on top of a Maxwellian core. We discuss this issue and others associated with this extreme event, which poses serious questions to the standard thick target beam interpretation of solar flares.« less

Authors:
; ;  [1]; ; ;  [2]; ;  [3]
  1. Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450 (United States)
  2. Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)
  3. Institute of 4D Technologies, School of Engineering, University of Applied Sciences Northwestern Switzerland, 5210 Windisch (Switzerland)
Publication Date:
OSTI Identifier:
21587455
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 739; Journal Issue: 2; Other Information: DOI: 10.1088/0004-637X/739/2/96; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; EMISSION; HARD X RADIATION; SOLAR FLARES; ELECTROMAGNETIC RADIATION; IONIZING RADIATIONS; RADIATIONS; SOLAR ACTIVITY; STELLAR ACTIVITY; STELLAR FLARES; X RADIATION

Citation Formats

Krucker, Saem, Hudson, H. S., Lin, R. P., Jeffrey, N. L. S., Battaglia, M., Kontar, E. P., Benz, A. O., and Csillaghy, A., E-mail: krucker@ssl.berkeley.edu. HIGH-RESOLUTION IMAGING OF SOLAR FLARE RIBBONS AND ITS IMPLICATION ON THE THICK-TARGET BEAM MODEL. United States: N. p., 2011. Web. doi:10.1088/0004-637X/739/2/96; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Krucker, Saem, Hudson, H. S., Lin, R. P., Jeffrey, N. L. S., Battaglia, M., Kontar, E. P., Benz, A. O., & Csillaghy, A., E-mail: krucker@ssl.berkeley.edu. HIGH-RESOLUTION IMAGING OF SOLAR FLARE RIBBONS AND ITS IMPLICATION ON THE THICK-TARGET BEAM MODEL. United States. doi:10.1088/0004-637X/739/2/96; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Krucker, Saem, Hudson, H. S., Lin, R. P., Jeffrey, N. L. S., Battaglia, M., Kontar, E. P., Benz, A. O., and Csillaghy, A., E-mail: krucker@ssl.berkeley.edu. Sat . "HIGH-RESOLUTION IMAGING OF SOLAR FLARE RIBBONS AND ITS IMPLICATION ON THE THICK-TARGET BEAM MODEL". United States. doi:10.1088/0004-637X/739/2/96; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
@article{osti_21587455,
title = {HIGH-RESOLUTION IMAGING OF SOLAR FLARE RIBBONS AND ITS IMPLICATION ON THE THICK-TARGET BEAM MODEL},
author = {Krucker, Saem and Hudson, H. S. and Lin, R. P. and Jeffrey, N. L. S. and Battaglia, M. and Kontar, E. P. and Benz, A. O. and Csillaghy, A., E-mail: krucker@ssl.berkeley.edu},
abstractNote = {We report on high-resolution optical and hard X-ray observations of solar flare ribbons seen during the GOES X6.5 class white-light flare of 2006 December 6. The data consist of imaging observations at 430 nm (the Fraunhofer G band) taken by the Hinode Solar Optical Telescope with the hard X-rays observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager. The two sets of data show closely similar ribbon structures, strongly suggesting that the flare emissions in white light and in hard X-rays have physically linked emission mechanisms. While the source structure along the ribbons is resolved at both wavelengths (length {approx} 30''), only the G-band observations resolve the width of the ribbon, with values between {approx}0.''5 and {approx}1.''8. The unresolved hard X-ray observations reveal an even narrower ribbon in hard X-rays (the main footpoint has a width perpendicular to the ribbon of <1.''1 compared to the G-band width of {approx}1.''8) suggesting that the hard X-ray emission comes from the sharp leading edge of the G-band ribbon. Applying the thick-target beam model, the derived energy deposition rate is >5 x 10{sup 12} erg s{sup -1} cm{sup -2} provided by an electron flux of 1 x 10{sup 20} electrons s{sup -1} cm{sup -2} above 18 keV. This requires that the beam density of electrons above 18 keV be at least 1 x 10{sup 10} cm{sup -3}. Even if field lines converge toward the chromospheric footpoints, the required beam in the corona has too high a density to be described as a dilute tail population on top of a Maxwellian core. We discuss this issue and others associated with this extreme event, which poses serious questions to the standard thick target beam interpretation of solar flares.},
doi = {10.1088/0004-637X/739/2/96; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)},
journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 739,
place = {United States},
year = {2011},
month = {10}
}