[SixClub] AstroAlert: Major Solar Flare Prompts an Auroral Activity Warning

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This  Is SKY & TELESCOPE's AstroAlert for Sun-Earth  Interactions
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A  s t r o A l e r t

14 May 2005

Solar Terrestrial  Dispatch
www.spacew.com

MAJOR SOLAR FLARE PROMPTS AN AURORA  WARNING

The Sun is known for producing energetic  spurts of activity, even during
the less active periods around the solar  sunspot minimum years. We are now a
little more than one year from reaching  the solar minimum. The frequency of
energetic solar events has diminished  over the last year, as has the number
of sunspots that pepper the face of the  Sun. But as has been the case with
most solar cycles in recorded history, the  Sun is not always quiet. It
occasionally hiccups and produces large and  complex sunspots capable of
influencing space weather at the  Earth.

We are currently experiencing one of those  'hiccups.' Several large
sunspots have appeared recently that have had the  potential to produce
energetic solar flare activity. Region 10759, now  nearing the central solar
meridian, spawned a major class M8.0 solar x-ray  flare at 16:57 UTC on 13
May. The event was associated with strong radio  bursts across the spectrum.
Such bursts have the potential to disrupt  cellular phone services when the
Sun is aligned with the direction of  cellular signal propagation (most
dominantly near sunrise and sunset when  solar elevation angles are more
in-line with cellular signal trajectories).  This event has also been blamed
for producing a weak space radiation storm,  where energetic particles
(protons) arrive from the Sun travelling at near  relativistic velocities.
Such storms have the potential to affect the health  and stability of
satellites orbiting the Earth.

Perhaps most significantly, this solar flare was associated with a
coronal  mass ejection that appears to be directed squarely at the Earth.
Sometime on  15 May (perhaps during the early to mid UTC hours of 15 May,
corresponding to  the late evening to early morning hours of 14/15 May for
North Americans),  this cloud of solar plasma will impact the Earth's
magnetosphere and energize  it. What follows will depend upon the energy of
the impact and the  orientation of the imbedded solar magnetic fields that
interact with the  Earth's magnetic field. If the imbedded magnetic fields are
oriented  appropriately, they will generate a potentially strong geomagnetic
storm and  produce auroral activity ("northern lights") that may become
visible across  extensive middle latitude regions (central United States
through perhaps  central Europe, New Zealand and southern Australia).

Given our proximity to the solar minimum and the decreasing frequency  of
auroral storm events, it may be prudent to watch the skies carefully  for
activity this weekend (particularly on Saturday and Sunday nights).  Current
information can be found at www.spacew.com or www.sec.noaa.gov. Those  who
succeed in observing activity are encouraged to report their observations  to
the Global Auroral Activity Observation Network  at:
www.spacew.com/submitsighting.html. A near-realtime accounting of  reported
sightings can be found at:  www.spacew.com/www/auroras.html.

This disturbance is  expected to last roughly 18 to 24 hours and may only
provide an opportunity  to observe auroral activity for one evening. There may
be additional  opportunities to observe activity over the coming week, as the
active sunspot  complex responsible for producing this disturbance may yet
spawn additional  major flares and Earthward-directed CME's in the days ahead.

A copy of the official Middle Latitude Auroral Activity Warning  is
appended below for your convenience.


MIDDLE LATITUDE AURORAL  ACTIVITY WARNING
Issued: 05:05 UTC on 14 May 2005
Solar Terrestrial  Dispatch
www.spacew.com


VALID BEGINNING AT: 00:00 UTC 15 MAY  2005
VALID UNTIL: 23:00 UTC (6 pm EST) ON 16 MAY

HIGH RISK PERIOD: 15  MAY (UTC DAYS)
MODERATE RISK PERIOD: 15-16 MAY

PREDICTED ACTIVITY  INDICES: 14, 70, 30, 12 (14 - 17 MAY)

POTENTIAL MAGNITUDE OF MIDDLE  LATITUDE AURORAL ACTIVITY: MODERATE TO HIGH

POTENTIAL DURATION OF THIS  ACTIVITY: MAIN BELT = 12-18 HOURS
MINOR BELT = 18-24 HOURS

ESTIMATED OPTIMUM OBSERVING CONDITIONS:  NEAR OR PRIOR TO LOCAL MIDNIGHT

EXPECTED LUNAR INTERFERENCE:  LOW

OVERALL OPPORTUNITY FOR OBSERVATIONS FROM MIDDLE LATITUDES:  GOOD

AURORAL ACTIVITY *MAY* BE OBSERVED APPROXIMATELY NORTH OF A LINE  FROM...
(THIS LINE IS VALID *ONLY* IF FAVORABLE STORM CONDITIONS  OCCUR)

OREGON TO SOUTHERN IDAHO AND NORTHERN UTAH TO WYOMING  TO NEBRASKA TO
NORTHERN MISSOURI TO SOUTHERN ILLINOIS TO  KENTUCKY TO VIRGINIA.

ACTIVITY *MAY* ALSO BE OBSERVED APPROXIMATELY NORTH  OF A LINE FROM...
(THIS LINE IS VALID *ONLY* IF FAVORABLE STORM  CONDITIONS OCCUR)

CENTRAL FRANCE TO NORTHERN SWITZERLAND TO  SOUTHERN GERMANY TO THE CZECH
REPUBLIC TO POLAND TO CENTRAL  RUSSIA.

NEW ZELAND AND SOUTHEASTERN AUSTRALIA SHOULD ALSO BE  ABLE TO SPOT PERIODS
OF ACTIVITY IF SUITABLE STORM CONDITIONS  MATERIALIZE DURING DARKNESS.

SYNOPSIS...

A  major class M8.0 solar flare on 13 May has been associated with a
coronal  mass ejection that appears to be strongly Earthward-directed. A  
major
geomagnetic and auroral storm is expected to materialize on 15 May when  the
CME impacts the Earth. Periods of moderate to strong auroral storm  conditions
could be observed with this disturbance. Many middle latitude  observations of
activity should be possible after the disturbance arrives.  Impact is expected
sometime during the early to mid UTC hours of 15 May and  the disturbance
should persist well into 16 May. For North American  observers, the first
opportunity to observe activity may come as early as the  very early morning
hours (pre-dawn) of 15 May. The next (slightly less  favorable) opportunity
will be on the evening of 15 May, although depending  on when the disturbance
arrives, storm conditions may be on the decline by  the time darkness falls
over North America. Observers are encouraged to watch  for activity. As we
approach the solar minimum, these opportunities to  observe the "northern
lights" will diminish in frequency. This disturbance  may have the potential
to produce fairly vigorous auroral storming for brief  periods of time.

This warning will remain valid  through 24:00 UTC (6 pm EDT) on
16 May. It will be updated or allowed to  expire at that time. For updated
information, visit:  http://www.spacew.com/aurora/forum.html. For real-time
plots of current  activity, visit: http://www.spacew.com/plots.html

PLEASE REPORT VALID OBSERVATIONS OF AURORAL ACTIVITY  TO:
http://www.spacew.com/submitsighting.html


**  End of  AstroAlert   **
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