https://dx.doi.org/10.1088/0004-637X/777/2/167">
 

Title

ESTABLISHING A STEREOSCOPIC TECHNIQUE FOR DETERMINING THE KINEMATIC PROPERTIES OF SOLAR WIND TRANSIENTS BASED ON A GENERALIZED SELF-SIMILARLY EXPANDING CIRCULAR GEOMETRY

Abstract

The twin-spacecraft STEREO mission has enabled simultaneous white-light imaging of the solar corona and inner heliosphere from multiple vantage points. This has led to the development of numerous stereoscopic techniques to investigate the three-dimensional structure and kinematics of solar wind transients such as coronal mass ejections (CMEs). Two such methods—triangulation and the tangent to a sphere—can be used to determine time profiles of the propagation direction and radial distance (and thereby radial speed) of a solar wind transient as it travels through the inner heliosphere, based on its time-elongation profile viewed by two observers. These techniques are founded on the assumption that the transient can be characterized as a point source (fixed ϕ, FP, approximation) or a circle attached to Sun-center (harmonic mean, HM, approximation), respectively. These geometries constitute extreme descriptions of solar wind transients, in terms of their cross-sectional extent. Here, we present the stereoscopic expressions necessary to derive propagation direction and radial distance/speed profiles of such transients based on the more generalized self-similar expansion (SSE) geometry, for which the FP and HM geometries form the limiting cases; our implementation of these equations is termed the stereoscopic SSE method. We apply the technique to two Earth-directed CMEs from different phases of the STEREO mission, the well-studied event of 2008 December and a more recent event from 2012 March. The latter CME was fast, with an initial speed exceeding 2000 km s−1, and highly geoeffective, in stark contrast to the slow and ineffectual 2008 December CME.

Publication Date

10-24-2013

Journal Title

The Astrophysical Journal

Publisher

IOP

Digital Object Identifier (DOI)

https://dx.doi.org/10.1088/0004-637X/777/2/167

Document Type

Article

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