Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Effects of Thomson-scattering geometry on white-light imaging of an interplanetary shock
T2 - synthetic observations from forward magnetohydrodynamic modelling
AU - Xiong, Ming
AU - Davies, J. A.
AU - Bisi, M. M.
AU - Owens, M. J.
AU - Fallows, R. A.
AU - Dorrian, G. D.
PY - 2013/7
Y1 - 2013/7
N2 - Stereoscopic white-light imaging of a large portion of the inner heliosphere has been used to track interplanetary coronal mass ejections. At large elongations from the Sun, the white-light brightness depends on both the local electron density and the efficiency of the Thomson-scattering process. To quantify the effects of the Thomson-scattering geometry, we study an interplanetary shock using forward magnetohydrodynamic simulation and synthetic white-light imaging. Identifiable as an inclined streak of enhanced brightness in a time-elongation map, the travelling shock can be readily imaged by an observer located within a wide range of longitudes in the ecliptic. Different parts of the shock front contribute to the imaged brightness pattern viewed by observers at different longitudes. Moreover, even for an observer located at a fixed longitude, a different part of the shock front will contribute to the imaged brightness at any given time. The observed brightness within each imaging pixel results from a weighted integral along its corresponding ray-path. It is possible to infer the longitudinal location of the shock from the brightness pattern in an optical sky map, based on the east-west asymmetry in its brightness and degree of polarisation. Therefore, measurement of the interplanetary polarised brightness could significantly reduce the ambiguity in performing three-dimensional reconstruction of local electron density from white-light imaging.
AB - Stereoscopic white-light imaging of a large portion of the inner heliosphere has been used to track interplanetary coronal mass ejections. At large elongations from the Sun, the white-light brightness depends on both the local electron density and the efficiency of the Thomson-scattering process. To quantify the effects of the Thomson-scattering geometry, we study an interplanetary shock using forward magnetohydrodynamic simulation and synthetic white-light imaging. Identifiable as an inclined streak of enhanced brightness in a time-elongation map, the travelling shock can be readily imaged by an observer located within a wide range of longitudes in the ecliptic. Different parts of the shock front contribute to the imaged brightness pattern viewed by observers at different longitudes. Moreover, even for an observer located at a fixed longitude, a different part of the shock front will contribute to the imaged brightness at any given time. The observed brightness within each imaging pixel results from a weighted integral along its corresponding ray-path. It is possible to infer the longitudinal location of the shock from the brightness pattern in an optical sky map, based on the east-west asymmetry in its brightness and degree of polarisation. Therefore, measurement of the interplanetary polarised brightness could significantly reduce the ambiguity in performing three-dimensional reconstruction of local electron density from white-light imaging.
KW - White-light imaging
KW - Thomson scattering
KW - Polarisation brightness
KW - Interplanetary shock
KW - CORONAL MASS EJECTIONS
KW - REMOTE-SENSING OBSERVATIONS
KW - MAGNETIC CLOUD
KW - SOLAR-WIND
KW - GEOMAGNETIC-ACTIVITY
KW - HELIOSPHERIC IMAGER
KW - STEREO MISSION
KW - ALFVEN WAVES
KW - 1 AU
KW - SCINTILLATION
U2 - 10.1007/s11207-012-0047-0
DO - 10.1007/s11207-012-0047-0
M3 - Journal article
VL - 285
SP - 369
EP - 389
JO - Solar Physics
JF - Solar Physics
SN - 0038-0938
IS - 1
ER -