STD: ANOTHER EARTH-DIRECTED CME IS POISED TO STRIKE ON 19 AP

[Mark]

Hallo,
das kam vorhin per Mail:

A s t r o A l e r t

Sun-Earth Alert

Solar Terrestrial Dispatch

http://www.spacew.com

17 April 2002

Details at: http://www.spacew.com/astroalert.html

ANOTHER EARTH-DIRECTED CME IS POISED TO STRIKE ON 19 APRIL

A major geomagnetic storm was observed on 17 April following the early
arrival of an Earthward directed coronal mass ejection (CME) that was
launched from the Sun on 15 April. The disturbance has produced periods of
strong auroral activity that has been visible across many middle latitude
regions. The present disturbed activity is expected to gradually subside over the
next 12 hours prior to the arrival of the next incoming solar disturbance.

Active sunspot region 9906 (the subject of recent AstroAlerts) spawned a
long-duration solar flare earlier on 17 April that was associated with
another Earthward-directed coronal mass ejection. Forecasters expect this
disturbance to arrive sometime during the UTC day of 19 April. Determining a
precise arrival time for this event has been complicated by the fact that
there were two coincident mass ejections in the same quadrant of the Sun but
with differing trajectories (although from Earth they appeared to have nearly
the same trajectory - an illusory effect caused by the timing and geometry of
the events).

For those less familiar with UTC time, the impact of this disturbance
could occur anytime between roughly the early evening hours of 18 April over
North America (EDT) to the late afternoon hours of 19 April (EDT). The moon
will begin to become a factor in the evening for optimally observing activity
until it sets.

The arrival of this disturbance is expected to herald a return of minor
to major geomagnetic and auroral storm conditions. Observations of auroral
activity ("northern lights") will be possible after the disturbance impacts.
In addition, there is a chance this disturbance may produce slightly stronger
levels of activity than the disturbance we are currently wading through.

The key to successfully observing auroral activity is knowing when to
look. For regularly updated information, refer to the aurora discussion forum
available at: http://www.spacew.com/aurora/forum.html . Current forecast
information (updated several times a day during disturbed periods) is also
available at the bottom of that page.

The middle latitude auroral activity watch was upgraded to a warning
earlier today following the arrival of the current disturbance. The warning
will be extended through to the latter part of the UTC day of 20 April to
cover the anticipated arrival (and effects) of the next coronal mass
ejection.

** End of the AstroAlert Bulletin **