Andrew Yee[_1_]
June 7th 07, 09:18 PM
ESA News
http://www.esa.int
29 May 2007
Radio 'screams' from the Sun warn of radiation storms
ESA's SOHO has helped uncover radio screams that foretell dangerous Coronal
Mass Ejections, or CMEs, which produce radiation storms harming
infrastructure on ground, in space as well as humans in space.
Scientists made the connection by analysing observations of CMEs from
ESA/NASA's SOHO (Solar and Heliospheric Observatory) and NASA's Wind
spacecraft. The team includes researchers from Goddard, the Catholic
University of America, Washington, the Naval Research Laboratory,
Washington, and the Observatory of Paris.
A CME is a solar slam to our high-tech civilisation. It begins when the Sun
launches a thousand million tons of electrically conducting gas (plasma)
into space at millions of kilometres per hour.
A CME cloud is laced with magnetic fields and when directed our way, smashes
into Earth's magnetic field. If the magnetic fields have the correct
orientation, they dump energy into Earth's magnetic field, causing magnetic
storms. These storms can cause widespread blackouts by overloading power
line equipment with extra electric current.
Some CMEs also bring intense radiation storms that can disable satellites or
cause cancer in unprotected astronauts. As the CME blasts through space, it
plows into a slower stream of plasma blown constantly from the Sun in all
directions, called the solar wind. The CME causes a shock wave in the solar
wind. If the shock is strong enough, it accelerates electrically charged
particles that make up the solar wind to high speeds, forming the radiation
storm.
"Some CMEs produce radiation storms, and some don't, or at least the level
of radiation is significantly lower," said Dr. Natchimuthuk Gopalswamy of
NASA's Goddard Space Flight Center in Greenbelt, Maryland, lead author of
the results. "The trick is to identify the ones that can produce dangerous
radiation, so we can warn astronauts and satellite operators."
Gopalswamy and his team may have found a way to do just that. CMEs with
powerful shocks capable of causing radiation storms 'scream' in radio waves
as they slam through the solar wind, according to the team.
SOHO's Large Angle and Spectrometric Coronagraph (LASCO) can see CMEs and
the Energetic and Relativistic Nucleon and Electron experiment (ERNE)
detects their radiation. Wind has an instrument that can pick up a CME's
radio signal (The Radio and Plasma Wave experiment).
The team compared observations from both SOHO and Wind and looked at 472
CMEs between 1996 and 2005 that were fast and covered a large area of the
sky. They discovered that those CMEs which generated a radio signal also
produced radiation storms, but CMEs without a radio signal did not.
Strong CME shocks accelerate electrons in the solar wind, which in turn
produce the radio signal. The same strong shock must also accelerate atomic
nuclei in the solar wind, which produce the radiation storm, according to
the team.
"Since the radio signal moves at the speed of light while the particles lag
behind, we can use a CME's radio noise to give warning that it is generating
a radiation storm that will hit us soon," said Gopalswamy. "This will give
astronauts and satellite operators anywhere between a few tens of minutes to
a couple of hours to prepare, depending on how fast the particles are
moving."
The team also noticed that most radio-loud CMEs came from parts of the Sun
in line with Earth (areas near the solar equator), while radio-quiet CMEs
mostly came from the edges of the Sun. Since all the CMEs studied were fast
and could have produced strong shocks, detecting radio noise and radiation
from some but not others might simply be due to geometry.
CMEs near the edge of the Sun only present a small section of their shock
surface towards us as they expand through space, and therefore tend to be
radio-quiet and radiation-free from our point of view, according to the
team. However, it means that explorers on other worlds in our Solar System,
like Mars, will need a spacecraft positioned between them and the Sun to
take advantage of the radio warning.
Notes for editors:
The research, funded by NASA, is presented at the American Astronomical
Society's 210th Meeting during 27-31 May 2007 in Honolulu, Hawaii.
SOHO is a cooperative project between ESA and NASA, launched in 1995. NASA's
Wind spacecraft was launched on 1 November 1994.
For more information:
Bill Steigerwald
Email: William.A.Steigerwald @ nasa.gov
Bernhard Fleck
Email: bfleck @ esa.nascom.nasa.gov
[NOTE: Images and weblinks supporting this release are available at
http://www.esa.int/esaSC/SEMOPF9RR1F_index_1.html ]
http://www.esa.int
29 May 2007
Radio 'screams' from the Sun warn of radiation storms
ESA's SOHO has helped uncover radio screams that foretell dangerous Coronal
Mass Ejections, or CMEs, which produce radiation storms harming
infrastructure on ground, in space as well as humans in space.
Scientists made the connection by analysing observations of CMEs from
ESA/NASA's SOHO (Solar and Heliospheric Observatory) and NASA's Wind
spacecraft. The team includes researchers from Goddard, the Catholic
University of America, Washington, the Naval Research Laboratory,
Washington, and the Observatory of Paris.
A CME is a solar slam to our high-tech civilisation. It begins when the Sun
launches a thousand million tons of electrically conducting gas (plasma)
into space at millions of kilometres per hour.
A CME cloud is laced with magnetic fields and when directed our way, smashes
into Earth's magnetic field. If the magnetic fields have the correct
orientation, they dump energy into Earth's magnetic field, causing magnetic
storms. These storms can cause widespread blackouts by overloading power
line equipment with extra electric current.
Some CMEs also bring intense radiation storms that can disable satellites or
cause cancer in unprotected astronauts. As the CME blasts through space, it
plows into a slower stream of plasma blown constantly from the Sun in all
directions, called the solar wind. The CME causes a shock wave in the solar
wind. If the shock is strong enough, it accelerates electrically charged
particles that make up the solar wind to high speeds, forming the radiation
storm.
"Some CMEs produce radiation storms, and some don't, or at least the level
of radiation is significantly lower," said Dr. Natchimuthuk Gopalswamy of
NASA's Goddard Space Flight Center in Greenbelt, Maryland, lead author of
the results. "The trick is to identify the ones that can produce dangerous
radiation, so we can warn astronauts and satellite operators."
Gopalswamy and his team may have found a way to do just that. CMEs with
powerful shocks capable of causing radiation storms 'scream' in radio waves
as they slam through the solar wind, according to the team.
SOHO's Large Angle and Spectrometric Coronagraph (LASCO) can see CMEs and
the Energetic and Relativistic Nucleon and Electron experiment (ERNE)
detects their radiation. Wind has an instrument that can pick up a CME's
radio signal (The Radio and Plasma Wave experiment).
The team compared observations from both SOHO and Wind and looked at 472
CMEs between 1996 and 2005 that were fast and covered a large area of the
sky. They discovered that those CMEs which generated a radio signal also
produced radiation storms, but CMEs without a radio signal did not.
Strong CME shocks accelerate electrons in the solar wind, which in turn
produce the radio signal. The same strong shock must also accelerate atomic
nuclei in the solar wind, which produce the radiation storm, according to
the team.
"Since the radio signal moves at the speed of light while the particles lag
behind, we can use a CME's radio noise to give warning that it is generating
a radiation storm that will hit us soon," said Gopalswamy. "This will give
astronauts and satellite operators anywhere between a few tens of minutes to
a couple of hours to prepare, depending on how fast the particles are
moving."
The team also noticed that most radio-loud CMEs came from parts of the Sun
in line with Earth (areas near the solar equator), while radio-quiet CMEs
mostly came from the edges of the Sun. Since all the CMEs studied were fast
and could have produced strong shocks, detecting radio noise and radiation
from some but not others might simply be due to geometry.
CMEs near the edge of the Sun only present a small section of their shock
surface towards us as they expand through space, and therefore tend to be
radio-quiet and radiation-free from our point of view, according to the
team. However, it means that explorers on other worlds in our Solar System,
like Mars, will need a spacecraft positioned between them and the Sun to
take advantage of the radio warning.
Notes for editors:
The research, funded by NASA, is presented at the American Astronomical
Society's 210th Meeting during 27-31 May 2007 in Honolulu, Hawaii.
SOHO is a cooperative project between ESA and NASA, launched in 1995. NASA's
Wind spacecraft was launched on 1 November 1994.
For more information:
Bill Steigerwald
Email: William.A.Steigerwald @ nasa.gov
Bernhard Fleck
Email: bfleck @ esa.nascom.nasa.gov
[NOTE: Images and weblinks supporting this release are available at
http://www.esa.int/esaSC/SEMOPF9RR1F_index_1.html ]