AstroAlert: New X-Class Solar Flares Extend Aurora Warning

[PeterKuklok]

A s t r o A l e r t

14 September 2005

Solar Terrestrial Dispatch
www.spacew.com


NEW X-CLASS SOLAR FLARES EXTEND AURORA WARNING

Active sunspot region 10808 produced two new X-class solar x-ray flares
during the last 24 hours. The most energetic of these produced an
Earthward-directed coronal mass ejection that is expected to impact the Earth
late this afternoon or evening. The impact is expected to reignite auroral
storm conditions. If it arrives as-expected, the resulting intensification of
auroral activity may place North America in a good position for observing the
activity TONIGHT. The mid-latitude auroral activity warning has been extended
through to 16 September. The next 3 to 4 days will be critical, as this is
the time that Region 808 is "pointed" most directly toward the Earth. Coronal
mass ejections follow essentially straight trajectories to the Earth, unlike
the energetic protons that stream from strong solar events.

For spacecraft and their sensitivity to energetic protons (the radiation
environment), the most vulnerable period will be later this week when Region
808 begins to approach the western solar limb. At that time, the Earth should
be best "connected" to the magnetic field lines that emanate from Region 808
and gradually spiral outward toward the Earth in an archimedes-type spiral
pattern. Energetic protons from major solar flares often reach the Earth
fastest (and are associated with the highest energies and densities) when the
Earth is magnetically connected to the flaring region. This is because
enegetic protons are charged particles, and as such they prefer to follow the
magnetic lines of force outward from the Sun.

The updated warning statement is appended below.


MIDDLE LATITUDE AURORAL ACTIVITY WARNING
Updated: 11:45 UTC on 14 September 2005
Solar Terrestrial Dispatch
www.spacew.com


VALID BEGINNING AT: EFFECTIVE IMMEDIATELY
VALID UNTIL: 23:00 UTC (5 pm EDT) ON 16 SEPTEMBER

HIGH RISK PERIOD: 14-15 SEPTEMBER (UTC DAYS)
MODERATE RISK PERIOD: 14-16 SEPTEMBER

PREDICTED ACTIVITY INDICES: 30, 50, 30, 20 (14 - 17 SEPTEMBER)

POTENTIAL MAGNITUDE OF MIDDLE LATITUDE AURORAL ACTIVITY: MODERATE TO HIGH

POTENTIAL DURATION OF THIS ACTIVITY: MAIN BELT = 24 HOURS
MINOR BELT = 24-48 HOURS

ESTIMATED OPTIMUM OBSERVING CONDITIONS: NEAR OR AFTER LOCAL MIDNIGHT

EXPECTED LUNAR INTERFERENCE: MODERATE

OVERALL OPPORTUNITY FOR OBSERVATIONS FROM MIDDLE LATITUDES: FAIR TO 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.

SYNOPSIS...

Active region 10808 continues to produce energetic solar flare activity.
The latest X-class flare was associated with an Earthward-directed
(full-halo) coronal mass ejection that is expected to arrive at the Earth
near the end of the UTC day of 14 September (for North American observers,
this translates to the late afternoon and/or evening hours of Wednesday, 14
September). This disturbance will have the potential to produce periods of
moderate to strong auroral storm conditions. Observations should
be possible over wide-spread mid-latitude locations. We are expecting to see
the passage of a magnetic cloud with this disturbance, which could further
enhance the potential for storm conditions (preceded or succeded by quieter
conditions as the IMF rotates away from a favorable orientation).

This warning will remain valid through 23:00 UTC (5 pm EDT) on
16 September, with a good chance that it will be extended beyond the 14th.
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 **