THE SOLAR CORONA AS PROBED BY COMET LOVEJOY (C/2011 W3)

Extreme-ultraviolet images of Comet Lovejoy (C/2011 W3) from the Atmospheric Imaging Assembly show striations related to the magnetic field structure in both open and closed magnetic regions. The brightness contrast implies coronal density contrasts of at least a factor of six between neighboring fl...

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Bibliographic Details
Published in:The Astrophysical journal 2014-06, Vol.788 (2), p.1-8
Main Authors: Raymond, J C, McCauley, P I, Cranmer, S R, Downs, C
Format: Article
Language:English
Subjects:
ACCELERATION
ALFVEN WAVES
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Atmospherics
BRIGHTNESS
COMETS
Coronas
DENSITY
EMISSION
EXTREME ULTRAVIOLET RADIATION
FORECASTING
IONS
MAGNETIC FIELDS
Magnetohydrodynamics
Mathematical models
PLASMA
SOLAR CORONA
SOLAR WIND
Striations
SUN
VELOCITY
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Summary:Extreme-ultraviolet images of Comet Lovejoy (C/2011 W3) from the Atmospheric Imaging Assembly show striations related to the magnetic field structure in both open and closed magnetic regions. The brightness contrast implies coronal density contrasts of at least a factor of six between neighboring flux tubes over scales of a few thousand kilometers. These density structures imply variations in the Alfven speed on a similar scale. They will drastically affect the propagation and dissipation of Alfven waves, and that should be taken into account in models of coronal heating and solar wind acceleration. In each striation, the cometary emission moves along the magnetic field and broadens with time. The speed and the rate of broadening are related to the parallel and perpendicular components of the velocities of the cometary neutrals when they become ionized. We use a magnetohydrodynamic model of the coronal magnetic field and the theory of pickup ions to compare the measurements with theoretical predictions, in particular with the energy lost to Alfven waves as the cometary ions isotropize.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/788/2/152