POLAR SPACECRAFT CAPTURES SOLAR STORM LIGHTSHOW
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AURORA DANCES OVER MUCH OF THE UNITED STATES, BUT DAYLIGHT OBSCURES THE VIEW
The space weather storm that began last Friday (July 14) produced the most extensive auroral storm over North America since the great storm of March 1989. Unfortunately, the "Northern lights" show was obscured by summer daylight and the full Moon.
At 14:38 Universal Time (10:38 a.m. Eastern Daylight Time) on July 15, the Visible Imaging System (VIS) on NASA's Polar spacecraft observed a brightening of the aurora caused by the pressure from the magnetic cloud that left the Sun on July 14. The aurora reached the peak of its activity at 00:30 UT (8:30 pm EDT on Saturday), covering the eastern two-thirds of the continental United States down to the southeastern states. Unfortunately for observers in North America, the Sun had not yet set. However, observers in Great Britain and much of continental Europe viewed spectacular aurora that night. The aurora began to break up at 01:30 UT (9:30 p.m. Eastern) and moved back into Canada before the end of twilight.
According to Dr. Nicola Fox of Johns Hopkins Applied Physics Laboratory and Dr. John Sigwarth of the Polar VIS team at the University of Iowa, Saturday's auroral storm reached lower latitudes and covered more of the Americas than any storm since 1989, the height of the last solar cycle.
On Saturday, the National Oceanic and Atmospheric Administration reported that a G9 magnetic storm -- the most severe on the scale -- was in progress for about nine hours, from noon to 9 p.m. Eastern.
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15 July 2000
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SUN STORM PRODUCES BRILLIANT AURORA OVER NORTHERN EUROPE, MAY LEAD TO
LIGHTSHOWS OVER NORTHERN U.S. AND CANADA TONIGHT
Stirred up by a blast of radiation from the Sun, the space around Earth lit up with bright auroras and magnetic storms on July 13. Researchers from NASA's Goddard Space Flight Center in Greenbelt, Maryland - and their colleagues at science institutions around the world - are still tracking and studying the impact of solar activity on Earth's magnetic field, or magnetosphere.
The atmospheric fireworks display that started in Europe on July 13 was Earth's response to an eruption of energy and electrically charged gas (plasma) from the Sun that left the Sun two-and-a-half days ago. Effects are expected to last at least through June 15, and scientists have reason to believe that the Sun may yet produce more flares and coronal mass ejections (CMEs) from the region that burst on July 9, 10, and 11. A space weather storm of comparable size in April 2000 caused some electric power system problems in the Northeastern United States and Scandinavia, and may have contributed to the failure of a Brazilian satellite.
On July 11, scientists working with the Solar and Heliospheric Observatory (SOHO) detected an Earth-directed "halo" type CME erupting from the Sun at 13:27 Universal Time (9:27 Eastern Daylight Time). The CME left the Sun at a speed of 1040 km/s (2.3 million miles per hour), and was accompanied by a potent "X-class" solar flare - the most intense category of flare. In the days leading up to July 11, the Sun ejected at least four CMEs and several flares on July 9-10.
Near Earth, a fleet of NASA spacecraft has been monitoring the solar wind and the response of Earth's magnetic field and atmosphere. The CME plowed through the interplanetary medium -- the tenuous solar atmosphere between the planets -- forming a shock wave like those produced by a speedboat blasting through the water. That CME shock wave was detected this morning by the Advanced Composition Explorer (ACE) spacecraft at 9:00 UT, and reached the Earth about 40 minutes later.
NASA's ACE, Polar, IMAGE, and Wind satellites continue to monitor the solar storm as it passes Earth. The shock wave and associated CME are disturbing Earth's magnetic field, distorting its shape like a jellyfish buffeted by a strong current. This interaction energizes the electrically charged particles naturally trapped in Earth's magnetosphere, causing the eerie auroral displays. The Polar spacecraft provides a large scale, global view of this activity from its unique orbit over Earth's poles.
A popular misconception holds that auroras and space weather are caused when particles from the Sun plunge directly into Earth's atmosphere near the magnetic poles. But in fact, the Sun supplies the energy -- not the particles -- to drive space weather activity around Earth. Rather than a direct trip from the solar atmosphere to Earth's poles, storms from the Sun make a link between the Sun and Earth's magnetic field, stirring up the plasma already trapped in the space around Earth. (Scientists announced this finding last month. For more background, see http://www-istp.gsfc.nasa.gov/istp/news/0005
)
Forecasters at the Space Environment Center of the National Oceanic and Atmospheric Administration (NOAA) have already detected a "strong" G3 geomagnetic storm. According to NOAA's space weather prediction scales, G3 storms can cause voltage problems and false alarms in electric power systems, increased electrical charging and atmospheric drag on spacecraft, and radio blackouts in certain high- and low-frequency radio signals. Auroras may be seen as low as 50 degrees latitude.
To view the same data and images that NASA scientists are using to follow the storm, go to http://www-istp.gsfc.nasa.gov/sun/
13 July 2000
