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Storms from the sun: coronal mass ejections in three
dimensions
Sarah Gibson (DAMTP)
Coronal mass ejections (CMEs) are spectacular solar transient
events, expelling about 1015 grams of coronal material,
resulting in a large-scale reconfiguration of the coronal
magnetic field, and, if they hit the Earth, causing potentially
damaging geomagnetic storms. Coronagraphs such as those on board
the
SOHO satellite have yielded hundreds of observations of CMEs
seen at the solar edge, or limb, in white light, and some of
these events have been connected to transient events seen by
imagers of on-disk extreme ultraviolet (EUV) and X-ray emission.
The on-disk manifestations of CMEs are particularly interesting,
because they can provide a direct warning of Earth-directed CMEs.
However, both limb and on-disk observations are projections of
the three-dimensional CME, and provide only partial information
about the nature of the CME.
We will use a physical model of CMEs (Gibson and Low,
Astrophysical Journal, 493, 460, 1998), as an example of a fully
three-dimensional magnetic field structure in magnetohydrodynamic
(MHD) force balance with an emerging CME. We will show
the dynamic evolution of the magnetic field and its associated
mass eruption, seen projected at the limb and on the disk
from several viewing angles. The range of CME ``observations''
thus produced can be compared to existing CME structures observed
with white-light coronagraphs and full disk EUV and X-ray coronal
images. Moreover, they can be used to prepare for 3-d analysis
of CMEs as observed by spacecrafts at multiple viewing angles.
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