STD - MidLat Warning downgraded to WATCH

[Peter Kuklok]

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MIDDLE LATITUDE AURORAL ACTIVITY WATCH

WARNING DOWNGRADED TO A WATCH: 07:30 UTC, 25 OCTOBER 2003

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VALID BEGINNING AT: EFFECTIVE IMMEDIATELY
VALID UNTIL: 23:00 UTC (7 pm EDT) ON 27 OCTOBER

HIGH RISK PERIOD: 26 OCTOBER (UTC DAYS)
MODERATE RISK PERIOD: 25 - 26 OCTOBER

PREDICTED ACTIVITY INDICES: 25, 40, 20, 20 (25 OCTOBER - 28 OCTOBER)

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...

OREGON TO SOUTHERN IDAHO TO WYOMING TO NORTHERN NEBRASKA TO IOWA TO

NORTHERN ILLINOIS TO NORTHERN INDIANA TO OHIO TO PENNSYLVANIA TO NEW

JERSEY.

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

EXTREME NORTHERN FRANCE TO BELGIUM TO CENTRAL GERMANY TO NORTHERN POLAND

TO LITHUANIA TO LATVIA TO NORTH-CENTRAL RUSSIA.

NEW ZEALAND AND EXTREME SOUTHERN (PARTICULARLY SOUTHEASTERN) REGIONS OF

AUSTRALIA MAY ALSO OBSERVE PERIODS OF ACTIVITY.

SYNOPSIS...

Auroral activity on 24 October was disappointingly dismal for many
observers. The Earth passed through a region of the coronal mass ejection
that contained almost exclusively northward-directed interplanetary magnetic
fields (IMF Bz values were almost always positive in value). Northward
directed fields close off the "valves" and prevent solar wind energy from
entering the Earth's magnetosphere. As a result, auroral activity became
exceptionally quiet despite a raging disturbance outside of the domain of the
Earth's magnetic field. This is not uncommon for solar disturbances, but is
generally not as common to such a dominating degree. There are usually some
periods of southward-directed (negative Bz) IMF fields that help introduce
new substorm activity. But such was not the case with this widely and
INCORRECTLY publicized event. The news media hyped this disturbance up far
greater than it deserved. Most media outlets also made outrageously incorrect
claims, mixing up facts concerning a historic event in 1859 with current
far weaker activity.

The next possible interval of disturbed conditions is expected within
the next 24 hours when effects of coronal mass ejection activity from sunspot
Region 486 should impact the Earth. The predicted time of arrival of this
next disturbance is during the latter half of 25 October or the earlier part
of 26 October (UTC time). This translates to the afternoon or evening hours
of Saturday, 25 October for North America. Preferred time of impact is
estimated (very roughly) near 02:00 UTC on 26 October, which is 10 pm EDT on
Saturday, 25 October for North American observers.

Although this next disturbance is not expected to be particularly
intense, it certainly has the potential to be more geoeffective than the 24
October event (which was strongly NON-geoeffective). The timing also favors
observers in North America and Europe. This anticipated disturbance will be
an obliquely impacting (glancing blow) disturbance and will therefore be far
less intense than had the disturbance been firmly directed at the Earth.

This watch will remain valid through 23:00 UTC (7 pm EDT) on
27 October. It will then be updated or 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

PLEASE REPORT OBSERVATIONS OF AURORAL ACTIVITY TO:

http://www.spacew.com/submitsighting.html

** End of Watch **