The radial width of a coronal mass ejection between 0.1 and 0.4 AU estimated from the heliospheric imager on STEREO

Savani, N., Rouillard, A.P., Davies, J.A., Owens, M. J. ORCID: https://orcid.org/0000-0003-2061-2453, Forsyth, R.J., Davis, C. J. ORCID: https://orcid.org/0000-0001-6411-5649 and Harrison, R.A. (2009) The radial width of a coronal mass ejection between 0.1 and 0.4 AU estimated from the heliospheric imager on STEREO. Annales Geophysicae, 27 (11). pp. 4349-4358. ISSN 0992-7689 doi: 10.5194/angeo-27-4349-2009

Abstract/Summary

On 15-17 February 2008, a CME with an approximately circular cross section was tracked through successive images obtained by the Heliospheric Imager (HI) instrument onboard the STEREO-A spacecraft. Reasoning that an idealised flux rope is cylindrical in shape with a circular cross-section, best fit circles are used to determine the radial width of the CME. As part of the process the radial velocity and longitude of propagation are determined by fits to elongation-time maps as 252±5 km/s and 70±5° respectively. With the longitude known, the radial size is calculated from the images, taking projection effects into account. The radial width of the CME, S (AU), obeys a power law with heliocentric distance, R, as the CME travels between 0.1 and 0.4 AU, such that S=0.26 R0.6±0.1. The exponent value obtained is compared to published studies based on statistical surveys of in situ spacecraft observations of ICMEs between 0.3 and 1.0 AU, and general agreement is found. This paper demonstrates the new opportunities provided by HI to track the radial width of CMEs through the previously unobservable zone between the LASCO field of view and Helios in situ measurements.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/5812
Item Type	Article
Refereed	Yes
Divisions	No Reading authors. Back catalogue items
Uncontrolled Keywords	Interplanetary physics; Solar wind plasma; Solar physics, astrophysics, and astronomy; Flares and mass ejections
Publisher	Copernicus Publications
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