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Title: STEREO DIRECT IMAGING OF A CORONAL MASS EJECTION-DRIVEN SHOCK TO 0.5 AU

Abstract

Fast coronal mass ejections (CMEs) generate standing or bow shocks as they propagate through the corona and solar wind. Although CME shocks have previously been detected indirectly via their emission at radio frequencies, direct imaging has remained elusive due to their low contrast at optical wavelengths. Here we report the first images of a CME-driven shock as it propagates through interplanetary space from 8 R{sub sun} to 120 R{sub sun} (0.5 AU), using observations from the STEREO Heliospheric Imager. The CME was measured to have a velocity of {approx}1000 km s{sup -1} and a Mach number of 4.1 {+-} 1.2, while the shock front standoff distance ({Delta}) was found to increase linearly to {approx}20 R{sub sun} at 0.5 AU. The normalized standoff distance ({Delta}/D{sub O} ) showed reasonable agreement with semi-empirical relations, where D{sub O} is the CME radius. However, when normalized using the radius of curvature, {Delta}/R{sub O} did not agree well with theory, implying that R{sub O} was underestimated by a factor of {approx}3-8. This is most likely due to the difficulty in estimating the larger radius of curvature along the CME axis from the observations, which provide only a cross-sectional view of the CME.

Authors:
;  [1]
  1. School of Physics, Trinity College Dublin, Dublin 2 (Ireland)
Publication Date:
OSTI Identifier:
21562535
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal Letters
Additional Journal Information:
Journal Volume: 736; Journal Issue: 1; Other Information: DOI: 10.1088/2041-8205/736/1/L5; Journal ID: ISSN 2041-8205
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; EMISSION; IMAGES; INTERPLANETARY SPACE; MASS; SHOCK WAVES; SOLAR CORONA; SOLAR WIND; ATMOSPHERES; SOLAR ACTIVITY; SOLAR ATMOSPHERE; SPACE; STELLAR ACTIVITY; STELLAR ATMOSPHERES; STELLAR CORONAE; STELLAR WINDS

Citation Formats

Maloney, Shane A., and Gallagher, Peter T. STEREO DIRECT IMAGING OF A CORONAL MASS EJECTION-DRIVEN SHOCK TO 0.5 AU. United States: N. p., 2011. Web. doi:10.1088/2041-8205/736/1/L5.
Maloney, Shane A., & Gallagher, Peter T. STEREO DIRECT IMAGING OF A CORONAL MASS EJECTION-DRIVEN SHOCK TO 0.5 AU. United States. doi:10.1088/2041-8205/736/1/L5.
Maloney, Shane A., and Gallagher, Peter T. Wed . "STEREO DIRECT IMAGING OF A CORONAL MASS EJECTION-DRIVEN SHOCK TO 0.5 AU". United States. doi:10.1088/2041-8205/736/1/L5.
@article{osti_21562535,
title = {STEREO DIRECT IMAGING OF A CORONAL MASS EJECTION-DRIVEN SHOCK TO 0.5 AU},
author = {Maloney, Shane A. and Gallagher, Peter T.},
abstractNote = {Fast coronal mass ejections (CMEs) generate standing or bow shocks as they propagate through the corona and solar wind. Although CME shocks have previously been detected indirectly via their emission at radio frequencies, direct imaging has remained elusive due to their low contrast at optical wavelengths. Here we report the first images of a CME-driven shock as it propagates through interplanetary space from 8 R{sub sun} to 120 R{sub sun} (0.5 AU), using observations from the STEREO Heliospheric Imager. The CME was measured to have a velocity of {approx}1000 km s{sup -1} and a Mach number of 4.1 {+-} 1.2, while the shock front standoff distance ({Delta}) was found to increase linearly to {approx}20 R{sub sun} at 0.5 AU. The normalized standoff distance ({Delta}/D{sub O} ) showed reasonable agreement with semi-empirical relations, where D{sub O} is the CME radius. However, when normalized using the radius of curvature, {Delta}/R{sub O} did not agree well with theory, implying that R{sub O} was underestimated by a factor of {approx}3-8. This is most likely due to the difficulty in estimating the larger radius of curvature along the CME axis from the observations, which provide only a cross-sectional view of the CME.},
doi = {10.1088/2041-8205/736/1/L5},
journal = {Astrophysical Journal Letters},
issn = {2041-8205},
number = 1,
volume = 736,
place = {United States},
year = {2011},
month = {7}
}