Topband: AstroAlert: Middle Latitude Auroral Activity Watch - 14-16 Sept

[Cary Oler]

	This service is usually quite accurate and does not
give false alarms.  We may want to watch for unusual
Topband conditions when the Aurora hits!

				73,  Bill  W4ZV

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                             A s t r o  A l e r t
                                Sun-Earth Alert

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

                               13 September 2004


MIDDLE LATITUDE AURORAL ACTIVITY WATCH - 14-16 September

      An active sunspot complex produced a near-major solar flare on 12
September that is suspected to have produced one and possibly two closely
spaced Earthward-directed coronal mass ejections (CMEs). Available data from
the SOHO spacecraft has been sparse and does not yet allow a coherent
analysis of the events. What data is available seems to contain the signature
of at least one full-halo (Earthward-directed) event.

      The inferred velocity of the mass ejection(s) have been primarily
determined from solar radio observations of the inner-coronal shock
velocities, which have averaged near 850 kilometers per second. Assuming a
radial trajectory that is centered somewhat east of the Earth, the shock
front from the leading CME should arrive at the Earth in the late UTC hours
of 14 September or the early UTC hours of 15 September (for North America,
this corresponds to the early evenings hours of 14 September to the early
morning hours of 15 September Eastern Daylight Savings Time). The second CME
(if one exists) will be imbedded within the flow of the leading CME and may
further enhance the potential for producing auroral activity.

      The impact of this disturbance has the potential to produce periods of
moderately strong auroral activity across fairly widespread middle latitude
regions. Thus, a middle latitude auroral activity watch has been issued. The
contents of the watch are included below.

MIDDLE LATITUDE AURORAL ACTIVITY WATCH
Issued: 07:20 UTC, 13 September 2004
Solar Terrestrial Dispatch
www.spacew.com


VALID BEGINNING AT: 15:00 UTC (11 am EDT) 14 SEPTEMBER
VALID UNTIL: 23:00 UTC (7 pm EDT) ON 16 SEPTEMBER

PREDICTED IMPACT TIME OF DISTURBANCE: 01:00 UTC 15 SEPT (9 pm EDT 14 Sept)

HIGH RISK PERIOD: 15 SEPTEMBER
MODERATE RISK PERIOD: 14 - 16 SEPTEMBER

PREDICTED ACTIVITY INDICES: 10, 20, 35, 17 (13 - 16 SEPTEMBER)

POTENTIAL MAGNITUDE OF MIDDLE LATITUDE AURORAL ACTIVITY: MODERATE

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: NONE

OVERALL OPPORTUNITY FOR OBSERVATIONS FROM MIDDLE LATITUDES: FAIR TO GOOD

AURORAL ACTIVITY *MAY* BE OBSERVED APPROXIMATELY NORTH OF A LINE FROM...

      NORTHERN OREGON TO SOUTHERN IDAHO TO WYOMING TO SOUTH DAKOTA TO ILLINOIS
      TO OHIO TO NORTHERN VIRGINIA TO MARYLAND.

ACTIVITY *MAY* ALSO BE OBSERVED APPROXIMATELY NORTH OF A LINE FROM...

      ENGLAND TO NORTHERN BELGIUM TO NORTHERN GERMANY TO NORTHERN POLAND TO
      NORTHERN BELARUS TO NORTH-CENTRAL RUSSIA.

ACTIVITY *MAY* ALSO BE OBSERVED APPROXIMATELY SOUTH OF A LINE FROM...

      NEW ZEALAND TO EXTREME SOUTHERN AUSTRALIA.


SYNOPSIS...

      The arrival of a coronal mass ejection will increase levels of
geomagnetic and auroral activity toward storm levels late on 14 or early on
15 September (UTC time). The potential exists for periods of moderately
strong auroral activity to become visible over fairly widespread middle
latitude regions.

      This watch will remain valid through 23:00 UTC (7 pm EDT) on
16 September. It will then be allowed to expire. 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 or
www.sec.noaa.gov.

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


** End of Astroalert **
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