Update: Severe solar storm due Saturday

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SPACE WEATHER BULLETIN #00- 10 2000 July 14 at 10:14 a.m. MDT (2000 July 14 1614 UT)


A large, complex sunspot group has produced one of the largest solar flares and associated radiation storms seen in recent years. The flare peaked at 4:24 a.m. MDT (1024 UTC) on July 14 and resulted in a radio blackout that reached R3 (strong) levels and a solar radiation storm that reached S3 (strong) levels. The solar radiation storm, which continues at the time of this advisory, is the largest observed since October, 1989. Images from NASA's SOHO/LASCO spacecraft showed that a large, fast-moving coronal mass ejection (CME) followed the flare and is headed Earthward. NOAA space weather forecasters predict that the CME will impact the Earth's magnetic field on Saturday afternoon and will cause a geomagnetic storm that is expected to reach category G3 (strong) to G4 (severe) levels. The radiation and geomagnetic storms are expected to produce adverse effects on spacecraft operations, power systems, high-frequency radio communications, and low-frequency navigation signals. In addition, the geomagnetic storm is expected to produce aurora displays that will be visible over much of the U.S.

The sunspot group responsible for this event will be visible from Earth until it crosses the Sun's west limb on July 21 and more space weather storms are possible until that time.


-- Martin Thompson (mthom1927@aol.com), July 14, 2000


Thanks Martin. Protect your equipment, folks, and get ready.



BOULDER, Colorado, July 14 (UPI) -- A violent eruption observed on the sun Friday will likely engulf the Earth in a severe solar storm on Saturday, scientists say. A large coronal mass ejection has sent a giant swath of electrically charged particles hurtling toward Earth, and astronomers say it will likely reach our planet on Saturday afternoon -- possibly disrupting power grids, communications networks, and satellites.

"It may be the biggest event of this solar cycle," said Bill Murtagh of the Space Environment Center (SEC) in Boulder, Colorado. "It's certainly the biggest event we've had in ten years."

Solar activity rises and falls over an 11-year cycle. The last "solar maximum" occurred in 1989, and we are now in the middle of another peak.

While coronal mass ejections can occur at any time, the most intense events are seen at solar maximum. When this solar material reaches the Earth's magnetic field, known as the magnetosphere, it triggers solar storms (also called geomagnetic storms) as well as displays of auroras -- the "northern lights."

The SEC recently introduced a scale for measuring the intensity of solar storms, from G1 (the least intense) to G5 (extreme).

"The storm we're expecting tomorrow will be in the G4 to G5 category, so we're looking for severe to extreme conditions," Murtagh said.

In March, 1989, at the peak of the last solar cycle, a solar storm knocked out the main power grid for the province of Quebec, plunging millions of people into darkness. Murtagh says "we can't rule out" a repeat of a large-scale blackout as a result of the current solar storm.

Over the last few years, however, astronomers have made great strides in predicting solar activity-giving a "heads up" for solar storms as well as auroras.

Spacecraft such as SOHO (for Solar and Heliospheric Observatory) constantly monitor the sun, while the ACE satellite (for Advanced Composition Explorer), located between the Earth and the sun, detects any Earth-bound particles about 45 minutes before they reach our planet. That's enough of a warning for power companies to reduce the load on vulnerable circuits, or, alternatively, to add power to the system.

"I think that's the good news of this solar cycle," said John Kappenman of Metatech Corp. in Duluth, Minn. "Technologies now exist to very accurately predict when these storms are going to occur, how severe they're going to be, and how much impact they're going to have."

Kappenman cautions, though, that our power grids may be more vulnerable today that they were during the last solar maximum. Power companies now routinely transfer thousands of megawatts of electricity from one region to another along high-voltage lines. Such systems are especially vulnerable during solar storms, he says.

"The collapse or failure of one grid can lead to a cascading chain, or a domino effect, rolling into neighboring systems," Kappenman said. "We were very lucky back in March of 1989 that worse things did not happen."

While solar storms pose a very real threat to electrical systems, they can also trigger dramatic and often beautiful displays of aurora. Auroras are normally seen from high latitudes, such as the Canadian Arctic. During severe solar weather, however, such displays can be seen from much farther south. This weekend, auroras "will certainly be visible from mid-latitude states," Murtagh said. "If it's of the extreme variety, we could hear reports of aurora in southern states, even Florida."

-- Lee Maloney (leemaloney@hotmail.com), July 15, 2000.

The wave of solar particles - known as a
solar proton event - is already four times
more intense than any other event detected
since the launches of SOHO in 1995 and ACE
in 1997. At mid-afternoon (UT) on July 14th,
the storm of particles from the Sun was still


-- spider (spider0@usa.net), July 15, 2000.

Extreme Sun Storm Lights Up the Sky

By Lee Siegel Science Writer posted: 12:57 pm ET 16 July 2000 Biggest Solar Storm in Nine Years Strikes Earth

Solar Weather Forecast for July 12-18, 2000

Breakthrough On Predicting Solar Storms

Solar Eruption Hits Planet Earth

Earth was blasted over the weekend by one of the most extreme magnetic storms of the current 11-year solar cycle and by the worst solar radiation storm since 1991. The storms caused problems for satellites, triggered voltage fluctuations in some electric power systems, blacked out radio communications for commercial fishing boats and made the Northern Lights visible at mid-latitudes, including Europe and as far south as St. Louis in the United States.

Both storms resulted from a major solar flare that erupted Friday July 14 from an active sunspot region. Within 20 minutes, the flare started blasting space around Earth with an intense barrage of protons known as a solar radiation storm. The flare also triggered a mass ejection of electrified gas from the sun's outer atmosphere, hurling the material toward Earth. It hit at 10:40 a.m. EDT (14:40 GMT) Saturday, triggering a geomagnetic storm that reached category G5 or extreme levels over high and mid-latitudes later in the day.

Both storms abated Sunday July 16 as the orientation of the interplanetary magnetic field between the sun and Earth changed to "protect us from further magnetic storming," said Craig Sechrest, a forecaster at the National Oceanic and Atmospheric Administration (NOAA) Space Environment Center in Boulder, Colo.

During the storms, solar wind speeds at times reached 1,000 kilometers per second, which is equal to 3.6 million kilometers per hour or 2.24 million mph - roughly twice the normal speed of the solar wind.

Many measurements during the storms were "the highest numbers we've ever seen," Sechrest said.

http://www.space.com/scienceastronomy/solarsystem/solar_storm_aftermat h_000716.html

-- Martin Thompson (mthom1927@aol.com), July 16, 2000.

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