Intense Solar Flare Prompts Warnings

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Na kratko:

A rare X10 solar flare has erupted from the Sun. If it persists, it
could significantly affect radio communications and power grids
around the globe.

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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

07 September 2005

Solar Terrestrial Dispatch
www.spacew.com


INTENSE SOLAR FLARE PROMPTS WARNINGS

A very strong class X17.1 solar flare exploded on the Sun at
17:40 UTC
(1:40 pm EDT). This is a significant event. Very few solar flares
ever reach
the X-class rating, and far fewer ever exceed an X10 level. Only a
few solar
flares each solar cycle (a 10-year period) exceed an X10 rating. An
X17 solar
flare is 17 times more intense in x-rays than a class X1.0 (which is,
by
itself, a very energetic event). This particular event was strong
enough to
saturate one of the x-ray sensors on the GOES spacecraft and very
nearly
saturated both sensors. This intense solar flare was visible in white-
light
by observers at Holloman solar observatory in New Mexico.

This event was associated with intense radio emissions and a
strong
high-velocity coronal mass ejection that was ejected well to the
southeast of
the Earth. Despite the poor location of this event, there is a chance
the
extreme western flanking edge of the associated shock wave may reach
the
Earth sometime on 9 September. Prior to that time, energetic protons
from the
solar flare may begin reaching the Earth and result in an increase in
the
radiation environment in the near-Earth space environment. Although no
significant geomagnetic or auroral storming is expected this time,
additional
possible major solar flares from this region during the next two
weeks could
easily provide the impetus for very strong space weather storms.

The sunspot complex responsible for this event is an
old "friend," by
the name of Region 10798, which was responsible for producing periods
of
severe geomagnetic storming last month. It's longevity is impressive,
as most
sunspot groups do not survive this long. As it came into view, NOAA
assigned
a new number to this region. It will hereafter be known as Region
10808 (nick
named Region 808).

The fact that this region has produced such a powerful flare
suggests
that it contains a complex magnetic topology. It is just now coming
into view
around the eastern limb of the Sun and is still too close to the limb
to
discern any significant detail. We expect additional major flares and
possibly additional significant major flares of X10 or greater
intensities,
during the next week.

Region 808 will gradually rotate across the solar disk during
the next
two weeks. During that time, if it retains its volatility, it may
produce
some serious effects at the Earth. The health of spacecraft may be
compromised if additional extreme events are observed. Power grids
may suffer
from induced currents caused by intense geomagnetic storms. Radio
communications may suffer from strong scintillation and absorption.
And large
regions of the Earth may be able to spot periods of auroral activity
("northern lights"). Region 808 will be best positioned to inflict
strong
impacts on the Earth in approximately another 4 to 5 days, with
maximal
effects possible from roughly 11 September through 18 September.
Spacecraft
will remain vulnerable to potential strong space radiation storms
through to
about 23 September.

It is perhaps produnt to note that these strong solar flares
pose no
known significant health threat to humans on the Earth. There is a
greater
threat to human health for astronauts on the International Space
Station, but
even they are relatively well protected in the heavily shielded
regions of
the space station. The combined effects of the Earth's magnetic field
and the
ionosphere protect human activities on Earth. However, some sensitive
industries on the ground can be adversely effected, including
electrical
power generation facilities, ionospheric radio communications,
satellite
communications, cellular phone networks, sensitive fabrication
industries,
and others. During the next two weeks, these industries may see an
increase
in anomalous incidents that may be attributed to space weather
effects.
** End of AstroAlert **
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