Jacques van Oene
August 16th 05, 08:16 PM
Erica Hupp
Headquarters, Washington August 16, 2005
(Phone: 202/358-1237)
Bill Steigerwald
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-5017)
Buddy Nelson
Lockheed Martin, Palo Alto, Calif.
(Phone: 510/797-0349)
RELEASE: 05-226
NASA SCIENTISTS CLOSER TO TIMELY SPACE WEATHER FORECASTS
Scientists funded by NASA have made big strides in learning how to
forecast "all clear" periods, when severe space weather is unlikely. The
forecasts are important because radiation from particles from the sun
associated with large solar flares can be hazardous to unprotected
astronauts, airplane occupants and satellites.
"We have a much better insight into what causes the strongest, most
dangerous solar flares, and how to develop forecasts that can predict an
'all clear' for significant space weather, for longer periods," said Dr.
Karel Schrijver of the Lockheed Martin Advanced Technology Center (ATC),
Palo Alto, Calif. He is lead author of a paper about the research published
in the Astrophysical Journal.
Solar flares are violent explosions in the atmosphere of the sun caused by
the sudden release of magnetic energy. Like a rubber band twisted too
tightly, stressed magnetic fields in the sun's atmosphere (corona) can
suddenly snap to a new shape. They can release as much energy as one, 10
billion megaton nuclear bomb.
Predicting space weather is a complicated problem. Solar forecasters focus
principally on the complexity of solar magnetic field patterns to predict
solar storms. This method is not always reliable, because solar storms
require additional ingredients to occur. It has long been known large
electrical currents must be present to power flares.
Insight into the causes of the largest solar flares came in two steps.
"First, we discovered characteristic patterns of magnetic field evolution
associated with strong electrical currents in the solar atmosphere," said
ATC's Dr. Marc DeRosa, co-author of the paper. "It is these strong
electrical currents that drive solar flares."
Subsequently, the authors discovered the regions most likely to flare had
new magnetic fields merge into them that were clearly out of alignment with
the existing field. This emerging field from the solar interior appears to
induce even more current as it interacts with the existing field.
The team also found flares do not necessarily occur immediately upon the
emergence of a new magnetic field. Apparently the electrical currents must
build up over several hours before the fireworks start. Predicting exactly
when a flare will happen is like studying avalanches. They occur only after
enough snow built up. Once the threshold is reached, the avalanche can
happen anytime by processes not yet completely understood.
"We found the current-carrying regions flare two to three times more often
than the regions without large currents," Schrijver said. "Also, the average
flare magnitude is three times greater for the group of active regions with
large current systems than for the other group."
The researchers made the discovery by comparing data about magnetic fields
on the sun's surface to the sharpest extreme-ultraviolet images of the solar
corona. The magnetic maps were from the Michelson Doppler Imager (MDI)
instrument on board Solar and Heliospheric Observatory (SOHO) spacecraft.
SOHO is operated under a cooperative mission between the European Space
Agency and NASA.
The corona images were from the NASA Transition Region and Coronal Explorer
spacecraft (TRACE). The team also used computer models of a
three-dimensional solar magnetic field without electrical currents based on
SOHO images. Differences between images and models indicated the presence of
large electrical currents.
"This is a result that is more than the sum of two individual missions,"
said Dr. Dick Fisher, Director of NASA's Sun-Solar System Connection
Division. "It's not only interesting scientifically, but has broad
implications for society."
For imagery about the research on the Web, visit:
http://www.nasa.gov/vision/universe/solarsystem/clear_weather.html
For information about NASA and agency programs on the Web, visit:
http://www.nasa.gov/home/index.html
-end-
--
--------------
Jacques :-)
www.spacepatches.info
Headquarters, Washington August 16, 2005
(Phone: 202/358-1237)
Bill Steigerwald
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-5017)
Buddy Nelson
Lockheed Martin, Palo Alto, Calif.
(Phone: 510/797-0349)
RELEASE: 05-226
NASA SCIENTISTS CLOSER TO TIMELY SPACE WEATHER FORECASTS
Scientists funded by NASA have made big strides in learning how to
forecast "all clear" periods, when severe space weather is unlikely. The
forecasts are important because radiation from particles from the sun
associated with large solar flares can be hazardous to unprotected
astronauts, airplane occupants and satellites.
"We have a much better insight into what causes the strongest, most
dangerous solar flares, and how to develop forecasts that can predict an
'all clear' for significant space weather, for longer periods," said Dr.
Karel Schrijver of the Lockheed Martin Advanced Technology Center (ATC),
Palo Alto, Calif. He is lead author of a paper about the research published
in the Astrophysical Journal.
Solar flares are violent explosions in the atmosphere of the sun caused by
the sudden release of magnetic energy. Like a rubber band twisted too
tightly, stressed magnetic fields in the sun's atmosphere (corona) can
suddenly snap to a new shape. They can release as much energy as one, 10
billion megaton nuclear bomb.
Predicting space weather is a complicated problem. Solar forecasters focus
principally on the complexity of solar magnetic field patterns to predict
solar storms. This method is not always reliable, because solar storms
require additional ingredients to occur. It has long been known large
electrical currents must be present to power flares.
Insight into the causes of the largest solar flares came in two steps.
"First, we discovered characteristic patterns of magnetic field evolution
associated with strong electrical currents in the solar atmosphere," said
ATC's Dr. Marc DeRosa, co-author of the paper. "It is these strong
electrical currents that drive solar flares."
Subsequently, the authors discovered the regions most likely to flare had
new magnetic fields merge into them that were clearly out of alignment with
the existing field. This emerging field from the solar interior appears to
induce even more current as it interacts with the existing field.
The team also found flares do not necessarily occur immediately upon the
emergence of a new magnetic field. Apparently the electrical currents must
build up over several hours before the fireworks start. Predicting exactly
when a flare will happen is like studying avalanches. They occur only after
enough snow built up. Once the threshold is reached, the avalanche can
happen anytime by processes not yet completely understood.
"We found the current-carrying regions flare two to three times more often
than the regions without large currents," Schrijver said. "Also, the average
flare magnitude is three times greater for the group of active regions with
large current systems than for the other group."
The researchers made the discovery by comparing data about magnetic fields
on the sun's surface to the sharpest extreme-ultraviolet images of the solar
corona. The magnetic maps were from the Michelson Doppler Imager (MDI)
instrument on board Solar and Heliospheric Observatory (SOHO) spacecraft.
SOHO is operated under a cooperative mission between the European Space
Agency and NASA.
The corona images were from the NASA Transition Region and Coronal Explorer
spacecraft (TRACE). The team also used computer models of a
three-dimensional solar magnetic field without electrical currents based on
SOHO images. Differences between images and models indicated the presence of
large electrical currents.
"This is a result that is more than the sum of two individual missions,"
said Dr. Dick Fisher, Director of NASA's Sun-Solar System Connection
Division. "It's not only interesting scientifically, but has broad
implications for society."
For imagery about the research on the Web, visit:
http://www.nasa.gov/vision/universe/solarsystem/clear_weather.html
For information about NASA and agency programs on the Web, visit:
http://www.nasa.gov/home/index.html
-end-
--
--------------
Jacques :-)
www.spacepatches.info