| 2008-06-09 11:31:15 |
Radio signals from the Sun warn of radiation storms
A coronal mass ejection (CME) is a solar challenge to our more and more space-technology dependant civilization.
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 the Earth's magnetic field, causing magnetic storms. These storms can disable electronics and computers onboard of satellites and space stations, because widespread blackouts by overloading power line equipment with extra electric current, harm space based navigation and telecommunication.
Some CMEs also bring intense radiation storms that can put out of action 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."
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. 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 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 radio signal is also very important for the Space Weather service based on the particle detector data now under developing at CRD. The radio signal can be used as an independent measurement of the interplanetary disturbance to be used with particle detector data for the forecasting of the expected danger of upcoming radiation and geomagnetic storms.
On September 1 Professor Hartmut Gemmeke from research center Karlsruhe gave a seminar at CRD proposing to install there new type of antennas to detect radio-bursts from solar flares and CMEs. Seminar followed by assembling the antenna that Hartmut had brought from Germany. Karen Arakelyan, David Pokhsraryan and Gagik Hovsepyan from CRD staff not only installed the hardware, but also registered first spectra of radio frequency intensities in the Yerevan region. These first results will be followed by spectra measurements at Nor Amberd and Aragats research stations. After collecting initial data the location and configuration of new antenna network will be decided for solar physics and space weather research. Fruitful collaboration with German physicists is underway!
Figure 1 Prof Gemmeke: This antenna will detect bursts of radio waves from solar flares and CMES!
