A strong geomagnetic storm that rated a G4, the second highest rating on the
NOAA space weather scales, was reported today at 5 a.m. EDT by the NOAA Space
Environment Center in Boulder, Colo. These storms are disturbances in the
geomagnetic field caused by gusts in the solar wind that blows by Earth.

Storms of this magnitude can affect power systems and satellite operations. Such
storms can also interfere with high frequency radio communications. During such
storms, the aurora has been seen as low as Illinois and Oregon.

NOAA forecasters report that this storm, caused by an increase in the solar wind
speed, combined with an associated interplanetary magnetic field opposite that
of Earth’s, struck the Earth’s magnetic field on August 17 at 9:40 a.m. EDT.
Forecasters issued early low-level warnings at that time, but it took almost 11
hours for the stronger characteristics of a G4 to develop.

A G4 geomagnetic storm can affect power systems with possible widespread voltage
control problems, and some protective systems will mistakenly trip out key
assets from the grid. Spacecraft operations may experience surface charging and
tracking problems, which may require corrections for orientation problems. Other
systems affected include satellite navigation, which may be degraded for hours,
and low-frequency radio navigation can also be disrupted.

The NOAA Space Environment Center is the nation’s official source of space
weather alerts and warnings. SEC continually monitors and forecasts Earth’s
space environment.

NOAA is dedicated to enhancing economic security and national safety through the
prediction and research of weather and climate-related events and providing
environmental stewardship of the nation’s coastal and marine resources. NOAA is
part of the U.S. Department of Commerce.

Relevant Web Sites

* NOAA Solar X-ray Imager

* NOAA Solar X-Ray Imager — Images

* NOAA Space Environment Center

* New Solar Storm Detector Sending Real-time Images Used to Warn of Sun’s
Damaging Storms; Solar X-ray Imager Onboard GOES-12 Environmental Satellite

[http://www.noaanews.noaa.gov/stories/images/sun081803-1538z.jpg (31KB)]
NOAA satellite image of the sun taken on Aug. 18, 2003, at 11:38 a.m. EDT.
Please credit "NOAA."

For latest view of the sun,