Astronomers are hearing screams from the sun. When the sun is active, a Coronal Mass Ejection (CME) can be launched off the surface of the sun and head toward Earth. This mass of plasma races outward at millions of miles an hour. CMEs aimed toward Earth can impact our atmosphere, with a number of consequences.
CMEs cause aurora, or the southern and northern lights, when they spill their energy into our atmosphere and excite particles in Earth's magnetic field. They can also cause power disruptions and blackouts. Besides causing geomagnetic storms, CMEs can cause radiation storms, which are dangerous for astronauts and damaging to spacecraft. These storms can administer high doses of radiation to astronauts living and working in space and disable communications satellites and other space-borne equipment.
When a CME rushes away from the sun, it plows into the solar wind, a lighter and slower stream of plasma constantly blowing from our nearest star. As the CME smashes into the solar wind, it causes a shock wave. A large enough shock wave will accelerate the electrically charged particles in the solar wind and give birth to the radiation storm.
Because not all CMEs create a shock wave large enough to trigger radiation storms, scientists have been looking for a signal to tell them which ones will or won't. Dr. Natchimuthuk Gopalswamy of NASA's Goddard Space Flight Center and his team have identified "screams" in radio waves caused by the CMEs impacting the solar wind. They discovered the storms that screamed, or were "radio loud," produced radiation storms, while CMEs without a radio signal failed to generate that kind of storm.
"We can use a CME's radio noise to give warning that it is generating a radiation storm that will hit us soon," Gopalswamy said. "This will give astronauts and satellite operators anywhere between a few tens of minutes to a couple hours to prepare, depending on how fast the particles are moving."
The team made their discovery by poring over nine years of observations made by the SOHO and Wind spacecraft. The SOHO instrument sees CMEs and their radiation, while Wind detects the CME's radio signal.
They discovered that the scream-producing CMEs came off of the equatorial areas of the sun that were most in line with Earth, while the quiet CMEs came from the edges of the sun. This observation seems to indicate that we will only get radiation storms from the CMEs that are directly in line with Earth. However, as astronauts venture beyond Earth to Mars or elsewhere, they will need a device to signal screams and radiation storms that might be headed their way.
