---------- Forwarded message ----------
Date: Wed, 12 Apr 2000 05:45:13 PDT
From: Bernardo Zavattini <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Aurora Borealis
A s t r o A l e r t
Sun-Earth Alert
Valid: 13-14 April (UTC days)
** Potential Category G1 Geomagnetic Storm **
A solar flare observed near the center of the Sun's visible disk at
23:42 UTC (7:42 pm EDT) on 09 April appears to have been associated with an
extremely dim halo coronal mass ejection (CME). The event is only dimly
visible in specially processed movies of the SOHO spacecraft LASCO imagery.
Movies developed by the Solar Terrestrial Dispatch (http://www.spacew.com)
that show this apparent halo CME are publically available at:
http://www.spacew.com/c2.mpg (1MB) and http://www.spacew.com/c3.mpg (2.9MB).
Concentrate on the frames between 01:30 and 06:00 UTC.
Solar radio noise observed during and after the solar flare suggested a
coronal mass ejection may have occurred, but the tell-tale signs of the
coronal mass ejection never became apparent until solar forecasters knocked
heads together in the analysis of the SOHO spacecrafts LASCO coronagraph
imagery. There is a chance that what we are seeing is something else
entirely
harmless, but the imagery is suggestive enough of a CME that forecasters now
believe a halo CME may have been associated with the M-class flare of 09
April.
If the analysis of the imagery holds true, a coronal mass ejection may
impact the Earth sometime late on 12 April or on 13 April (UTC time). We are
suggesting a preferred impact time of between 04:00 UTC and 13:00 UTC
(betwen midnight and 9 am EDT) on 13 April, although the actual impact could
deviate from this preferred interval by many hours.
The disturbance may be capable of driving periods of low to moderately
strong auroral activity over the high latitude regions. Dark-sky middle
latitude locations may be able to glimpse periods of this minor activity, if
it occurs. The disturbance might also be too weak to produce any substantial
enhancements of auroral activity.
There is no indication that this disturbance will be anywhere as large
as the storm that occurred on 06/07 April. In all likelihood, it will be
very
much inferior to that event. Nevertheless, no one can or will know for
certain how geoeffective the disturbance might be until after the
disturbance
reaches the Earth, assuming the disturbance exists.
For these reasons, we are issuing a Middle Latitude Auroral Activity
Watch for the 13-14 April time frame, with heaviest emphasis on 13 April.
This is a watch only, not a warning. In other words, it is intended to alert
observers of the potential that exists for the possible development of
auroral activity that might become visible from dark-sky middle latitude
locations.
Anyone who believes they may have spotted auroral activity are
encouraged to report their findings to:
http://www.spacew.com/www/subaurora.html
A near-real-time updated list of observations reported through this
form
page is available from: http://www.spacew.com/www/auroras.html
** End of AstroAlert **
