The halo CME observed with UVCS/SOHO on April 29, 1998
Ester Antonucci
Abstract
On April 29, 1998 the Ultraviolet Coronagraph Spectrometer (UVCS) onboard
SOHO has observed a halo coronal mass ejection in the HI Lyman alpha
line (1216 A). The coronal mass ejection material crossed the coronagraph
field of view, centered at position angle 144 degrees, counterclockwise
from the North pole, (54S at the East limb) in
the time interval between 20.45 UT on April 29 and 04.22 UT on April
30, 1998. In this interval the instantaneous field of
view moved from 1.7 to 3.6 solar radii. The Lyman alpha line profiles emitted
by the coronal mass ejection plasma are complex and extremely variable
along the instantaneous field of view. Doppler shifts are observed
that indicate that the material velocity has a component in the direction
of the observer of the order of 400 km/sec.
Authors: E. Antonucci and C. Benna
Organization: Osservatorio Astronomico di Torino
Telephone: 39 011 8101913
Fax:
39 011 8101930
e-mail: antonucci@to.astro.it
Address: Via Osservatorio 20
Pino Torinese 10025
Italy