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Radio “screams” portend severe solar storms
May 30, 2007
Courtesy ESA
and World Science staff
Updated May 31
Researchers say they have discovered that the Sun gives off “screams” of radio waves that can provide advance warning of hazardous radiation storms from the star. In this animation,
the sun launches a coronal mass ejection.
Its shock accelerates electrically charged particles. When these arrive at Earth, they are deflected by our planet's
global magnetic field, represented by the large, purple bubble. The particles
next arrive at Mars. Mars only has local magnetic fields (purple bubbles). These local fields are believed to be remnants of
a global magnetic field, which vanished billions of years
ago, and they don't deflect the particles very
well. Scientists believe such particle storms, and solar wind, may have gradually removed
much of the Martian atmosphere after Mars' global magnetic field vanished.
(Credits: ESA, NASA)
In these storms, called coronal mass ejections, the Sun spouts off great amounts of gas that can result in harm to human infrastructure, as well as to astronauts in space.
A coronal mass ejection begins when the Sun casts off around a billion tons of electrically conducting gas, or plasma, into space at millions of kilometres (miles) per hour.
The cloud is laced with magnetic fields that can smash into Earth’s magnetic field and dump energy into it, causing magnetic storms. These in turn can cause widespread blackouts by overloading power line equipment.
Some of these events also bring intense radiation storms that can disable satellites or cause cancer in unprotected astronauts. As the gas ejection blasts through space, it plows into a slower stream of plasma blown constantly from the Sun in all directions, called the solar wind.
The more sudden plasma ejection causes a shock wave in the solar wind. A strong enough shock accelerates electrically charged particles that make up the solar wind to high speeds, forming the radiation storm.
The trick is to identify which ejections “produce dangerous radiation, so we can warn astronauts and satellite operators,” said Natchimuthuk Gopalswamy of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, lead author of the study.
Gopalswamy added that his team may have found a way to do just that. Coronal mass ejections with powerful shocks, capable of causing radiation storms, “scream” in radio waves as they slam through the solar wind, according to the team. They presented the findings at the American Astronomical Society’s annual meeting May 27-31 in Honolulu.
The researchers used data from the Solar and Heliospheric Observatory (SOHO) spacecraft of the European Space Agency and NASA, as well as the latter agency’s Wind spacecraft. They studied 472 coronal mass ejections from 1996 to 2005 that were fast and covered large areas of sky. They found that those that generated a radio signal also produced radiation storms, but those without a radio signal didn’t.
Strong shocks accelerate electric ally charged subatomic particles called electrons in the solar wind, which in turn produce the radio signal, the astronomers said. 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 [the] 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.”
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Researchers say they have discovered that the Sun gives off “screams” of radio waves that can provide advance warning of hazardous radiation storms from the star. In these storms, called coronal mass ejections, the Sun spouts off great amounts of gas that can result in harm to human infrastructure, as well as to astronauts in space. A coronal mass ejections begins when the Sun launches around a billion tons of electrically conducting gas, or plasma, into space at millions of kilometres (miles) per hour. The cloud is laced with magnetic fields that can smash into Earth’s magnetic field and dump energy into it, causing magnetic storms. These in turn can cause widespread blackouts by overloading power line equipment. Some of these events also bring intense radiation storms that can disable satellites or cause cancer in unprotected astronauts. As the gas ejection blasts through space, it plows into a slower stream of plasma blown constantly from the Sun in all directions, called the solar wind. The more sudden plasma ejection causes a shock wave in the solar wind. A strong enough shock accelerates electrically charged particles that make up the solar wind to high speeds, forming the radiation storm. The trick is to identify which ejections “produce dangerous radiation, so we can warn astronauts and satellite operators,” said Natchimuthuk Gopalswamy of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, lead author of the study. Gopalswamy added that his team may have found a way to do just that. Coronal mass ejections with powerful shocks, capable of causing radiation storms, “scream” in radio waves as they slam through the solar wind, according to the team. They presented the findings at the American Astronomical Society’s annual meeting May 27-31 in Honolulu. The researchers used data from the Solar and Heliospheric Observatory (SOHO) spacecraft of the European Space Agency and NASA, as well as the the latter agency’s Wind spacecraft. They studied at 472 coronal mass ejections from 1996 to 2005 that were fast and covered large areas of sky. They found that those that generated a radio signal also produced radiation storms, but those without a radio signal didn’t. Strong shocks accelerate electrically charged subatomic particles called electrons in the solar wind, which in turn produce the radio signal, the astronomers said. 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 [the] 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.”