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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
21 January 2005
Solar Terrestrial Dispatch
www.spacew.com
STRONG X-CLASS SOLAR FLARE, RADIATION STORM AND AURORA WARNING
A lot has happened in the last 24 to 36 hours. A strong class X7.1
solar x-ray flare was observed on 20 January that resulted in the
strongest high-energy space radiation storm since 1989 (last solar
cycle). Energetic protons at greater than 100 MeV seldom increase in
density above 1 particle flux units (pfu). However, during this major
solar flare, energetic protons at greater than 100 MeV increased in
density to over 650 pfu. There is evidence that protons at greater
than 500 MeV (relativistic energies) bombarded the Earth for several
hours after the event. This was the "hardest" proton event since the
powerful events of 1989. Energetic proton populations were so intense
that neutron densities at ground level over the high latitude regions
suddenly increased by more than 50% above background levels, resulting
in one of the strongest Ground Level Events of this solar cycle.
Energetic protons from this flare travelled the distance from the Sun
to the Earth at almost the same time that it took light from the Sun
to reach the Earth. This is remarkable given the mass of protons and
the energy required to accelerate them to very near the speed of
light.
The arrival of these energetic protons at the Earth can result in
degradation in the efficiency of solar arrays in orbit to convert
sunlight to electricity. As a result, many spacecraft may have
observed permanent losses of electrical generation power following
this event. The protons also intensely ionized the Earth's high and
polar latitude ionospheres, resulting in the complete loss of high
frequency radio communications across the high and polar latitudes
regions.
A strong coronal mass ejection was associated with this solar flare,
with at least a portion of the ejected mass appearing to have an
Earthward-directed component. The impact of this disturbance (which is
possible anytime over the next 24 to 36 hours) could result in periods
of moderate to strong auroral activity across many dark-sky middle and
low latitude regions. A middle latitude auroral activity warning has
been issued together with a low-latitude auroral activity watch (see
below).
Region 10720, which has been solely responsible for all of this
activity, will be departing the visible side of the Sun and rotating
behind the western limb over the next few days. As a result, the
influence of this powerful active region will diminish
substantially. Whether it survives its transit of the far side of the
Sun and reappears two weeks later on the eastern side of the Sun is an
unknown question. The region has been undergoing fairly substantial
decay over the last few days. Thus, most forecasters believe it will
probably diminish in size and complexity as it passes around the far
side of the Sun.
Observers interested in seeing the "northern lights" are strongly
encouraged to watch the skies tonight and tomorrow night.
The low latitude aurora watch is essentially the same as the middle
latitude aurora warning (the same boundary lines apply). Thus, only
the mid-latitude aurora warning is appended below, with the
understanding that a low-latitude watch also exists. Visit
www.spacew.com
for regular updates and details.
MIDDLE LATITUDE AURORAL ACTIVITY WARNING
Upgraded: 20:10 UTC on 21 January 2005
Solar Terrestrial Dispatch
www.spacew.com
VALID BEGINNING AT: EFFECTIVE IMMEDIATELY
VALID UNTIL: 23:00 UTC (6 pm EST) ON 23 JANUARY
HIGH RISK PERIOD: 21-22 JANUARY (UTC DAYS)
MODERATE RISK PERIOD: 21-23 JANUARY
PREDICTED ACTIVITY INDICES: 70, 40, 20, 12 (21 - 24 JANUARY)
POTENTIAL MAGNITUDE OF MIDDLE LATITUDE AURORAL ACTIVITY: MODERATE TO
HIGH
POTENTIAL DURATION OF THIS ACTIVITY: MAIN BELT = 12-18 HOURS
MINOR BELT = 18-36 HOURS
ESTIMATED OPTIMUM OBSERVING CONDITIONS: NEAR OR AFTER LOCAL MIDNIGHT
EXPECTED LUNAR INTERFERENCE: MODERATE
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)
EXTREME NORTHERN CALIFORNIA TO NORTHERN NEVADA TO UTAH TO COLORADO
TO SOUTHERN KANSAS AND NORTHERN OKLAHOMA TO ARKANSAS TO TENNESSEE TO
SOUTH CAROLINA.
ACTIVITY *MAY* ALSO BE OBSERVED APPROXIMATELY NORTH OF A LINE FROM...
(THIS LINE IS VALID *ONLY* IF FAVORABLE STORM CONDITIONS OCCUR)
NORTHERN SPAIN AND PORTUGAL TO SOUTHERN FRANCE TO ITALY TO ROMANIA
TO UKRAINE TO SOUTHERN RUSSIA.
SYNOPSIS...
The arrival of a fairly strong interplanetary coronal mass
ejection (ICME) disturbance has prompted the upgrade of the
mid-latitude aurora watch to a mid-latitude aurora warning. Periods of
moderate to strong auroral storming could be oberved over the next 12
to 36 hours that should become visible over widespread mid-latitude
regions. There is also a slight chance some activity may become
visible into the low latitudes. A low latitude aurora watch is being
issued as well.
This warning will remain valid through 23:00 UTC (6 pm EST) on 23
January. It will be updated or allowed to expire at that time. For
updated information, visit:
www.spacew.com/aurora/forum.html
. For real-time plots of
current activity, visit:
www.spacew.com/plots.html
PLEASE REPORT VALID OBSERVATIONS OF AURORAL ACTIVITY TO:
www.spacew.com/submitsighting.html
** End of AstroAlert **
  