S&T AstroAlert: Today's flare and potential auroral activity forOct 29/30

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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
Sun-Earth Alert

Solar Terrestrial Dispatch
http://www.spacew.com

Images and movies of this event are available at:
http://www.spacew.com/astroalert.html

28 October 2003

* INTENSE CLASS X17 SOLAR FLARE OBSERVED!
* MIDDLE LATITUDE AURORAL ACTIVITY WARNING ISSUED
* LOW LATITUDE AURORAL ACTIVITY WATCH ISSUED

PLEASE NOTE: Our web site (all space weather web sites) are seeing
significant levels of traffic and will be slow to respond. Please
be patient.


INTENSE CLASS X17 SOLAR FLARE OBSERVED!

At 04:35 UTC on 28 October (11:35 pm EST on 27 October), Solar
Terrestrial Dispatch issued a warning of a possible imminent
X-class flare from Region 486. Commencing at 09:51 UTC (4:51 am
EST on 28 October), one of the largest solar flares this solar
cycle blew out of Region 486. Solar flares can come larger, but
not by much. Events up to approximately twice the strength of
todays flare are possible. Nevertheless, this event had bulging
muscles and has great potential for producing significant displays
of auroral activity ("Northern Lights") TONIGHT and TOMMORROW
night, with heavier preference on TONIGHT.

The solar flare reached a class X17.2 intensity at an x-ray
wavelength between 1 and 8 Angstroms. That is over 1,700 times
more powerful than your regular every-day run-of-the-mill C-class
x-ray flares and it is over 34 times more powerful than the
lowest-category major solar flare. X-rays from this flare reached
a maximum intensity at 11:10 UTC on 28 October.

X-rays were so intense that on the day-side of the Earth (over
Europe), ionospheric currents formed that caused the Earth's
magnetic field to dip a little bit in strength. Known as a
magnetic crochet, these events are detected by magnetometers and
are typically only observed during very intense solar flares.

Invisible to all instruments, this solar flare had accelerated
protons to extremely high energies and beamed them toward the
Earth. Ten minutes after x-rays had reached their maximum
intensity, the blast of energetic protons began flooding the
Earth's space environment and bombarding the Earth's protective
ionosphere. Not to worry though. Our ionosphere can easily handle
the onslaught. Protons with energies well in excess of 100 MeV
have been observed. In fact, the influx of energetic protons was
so intense that they produced secondary reactions within the
ionosphere that could be observed by neutron monitors at
ground-level in the arctic regions. These "Ground Level Events"
(or GLEs) are symptoms of an intense space radiation storm. In
fact, before this space radiation storm ends, there is a chance
radiation levels could surpass category S4 levels (on a scale
between S1 and S5). There are usually only about 3 radiation
storms per solar cycle (~11 years) that reach that intensity.

Didier Van Hellemont reported that the members of an astronomical
observatory in Belgium were testing their camera during the
morning and fortuitously caught the elusive and rare white-light
component of this flare on video! A frame of the video containing
the white-light flare is visible at:

http://www.urania.be/php-txt/dynpage...solarflare.jpg

While observing the Sun using a small reflector telescope in
Germany, Peter Kuklok is also said to have observed the
white-light component of this flare within the penumbral area of
Region 486.

We extend our congratulations to these individuals and groups! It
is an extraordinary feat to catch a white-light flare in progress!
White-light flares are only observed during the most intense solar
flares - and then only for a brief period of time.

So what can we expect from this solar flare? If we're lucky,
perhaps a really good light show TONIGHT in the heavens above.

The coronal mass ejection associated with this major flare was
directed squarely at the Earth. A near perfect halo coronal mass
ejection rapidly formed. When the velocity of this CME was
measured from images taken by the LASCO coronagraph, jaws dropped.
The velocity of the disturbance in the plane of the sky was
measured by SOHO scientists to be near 2,125 kilometers per
second. At that velocity, the disturbance could reach the Earth
within 19 hours. However, they do decelerate as they expand
outward and this deceleration increases the time it takes them to
reach the Earth.

Even accounting for this delay (which is hard to predict), there
is a good chance this disturbance could reach the Earth in the
early to mid morning UTC hours of 29 October.

For North Americans, this translates to a time of arrival sometime
around 3 am Eastern Standard Time or near midnight on the west
coast TONIGHT. If the disturbance does not arrive until later,
North America's best chance to see auroral activity will come
tommorrow night (Wednesday night, 29 October).

PLEASE REMEMBER that there is also a chance this disturbance might
produce very little Northern Lights activity. Whether it does or
doesn't depends on the internal magnetic field configuration of
the disturbance. If it produces storming, it will probably produce
STRONG storming. Otherwise, it might not much.

Be patient, watch conditions, and/or stay informed. If you are
under cloudy skies and have never seen aurora before, this might
be an event worth consdering taking a drive for.

A MIDDLE LATITUDE AURORAL ACTIVITY WARNING and a LOW LATITUDE
AURORAL ACTIVITY WATCH have been issued for the UTC day of 29 and
30 October, but with heaviest emphasis on 29 October. The middle
latitude warning is appended below. The low latitude watch is
identical except that the "Overall opportunity" for observing
auroral activity from the low latitudes is considered "Fair to
Poor" (which is remarkably good!).

Good luck to everyone!

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MIDDLE LATITUDE AURORAL ACTIVITY WARNING

WARNING ISSUED: 20:00 UTC, 28 OCTOBER 2003

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VALID BEGINNING AT: 00:00 UTC 29 OCTOBER 2003 VALID UNTIL: 23:00
UTC (7 pm EDT) ON 30 OCTOBER

HIGH RISK PERIOD: 29 OCTOBER (UTC DAYS) MODERATE RISK PERIOD: 28 -
30 OCTOBER

PREDICTED ACTIVITY INDICES: 20, 70, 40, 20 (28 OCTOBER - 31
OCTOBER)

POTENTIAL MAGNITUDE OF MIDDLE LATITUDE AURORAL ACTIVITY: HIGH

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

ESTIMATED OPTIMUM OBSERVING CONDITIONS: NEAR LOCAL MIDNIGHT

EXPECTED LUNAR INTERFERENCE: NIL TO 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)

CENTRAL CALIFORNIA TO NEVADA TO SOUTHERN UTAH TO NORTHERN NEW MEXICO
TO NORTHERN TEXAS TO OKLAHOMA TO ARKANSAS TO NORTHERN MISSISSIPPI TO
NORTHERN ALABAMA TO NORTHERN GEORGIA TO SOUTH CAROLINA.

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

SOUTHERN FRANCE TO NORTHERN ITALY TO AUSTRIA TO HUNGARY TO UKRAINE
TO CENTRAL AND SOUTHERN RUSSIA.

NEW ZEALAND AND SOUTHERN REGIONS OF AUSTRALIA MAY ALSO OBSERVE
PERIODS OF POTENTIALLY STRONG ACTIVITY.

SYNOPSIS...

FIRST, a large caveat: A strong auroral storm may happen, or it
may not. Whether it does or does not depends on conditions inside
the disturbance and how it couples with the Earth's magnetic
field. If conditions are favorable, very strong storm activity may
be possible. If conditions are not favorable, there may be no
visible auroral activity in sight. The POTENTIAL for observing
activity with this disturbance is about as high as you can ask.
Nevertheless, if the configuration of the disturbance is not
favorable for coupling with the Earth, nothing will happen.

This is without question, one of the most significant space
weather disturbances of the current 11-year solar cycle. It was
associated with a historic class X17.2 solar x-ray flare on 28
October and a high velocity coronal mass ejection that is directed
squarely at the Earth. The potential exists for a significant
space weather storm should this disturbance contain favorable
characteristics.

A middle latitude auroral activity WARNING means that conditions
are expected to become favorable for observing auroral activity
over widespread middle latitude regions. A LOW LATITUDE auroral
activity WATCH is also being issued for this event.

The disturbance is expected to impact sometime in the early to mid
UTC hours of 29 October. For North American observers, this means
activity could occur TONIGHT - LATE TONIGHT and for most regions
sometime AFTER MIDNIGHT (perhaps in the hours around or after 3 am
EST).

This warning will remain valid through 23:00 UTC (7 pm EDT) on
30 October. It will then be updated, downgraded to a watch or
allowed to expire altogether. 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 the AstroAlert Bulletin **