Probes Watch Solar Storms Hit Earth
Scientists have long understood that satellites are at risk from bombardment by solar storms. Now, they’ve gotten a closer look at how the storms are punishing Earth’s magnetosphere, leaving satellites exposed. The movie above, and the solar flare video below, were today released by the European Space Agency, along with descriptions of two solar eruptions spotted using their four “Cluster” satellites and the two Chinese/ESA “Double Star” satellites.
Under normal solar conditions, satellites orbit within the magnetosphere — the protective magnetic bubble created by the Earth’s magnetic field. However when solar activity increases, the picture changes significantly: the magnetosphere gets compressed and particles get energized, exposing satellites to higher doses of radiation that can affect signal reception.
Scientists have found that extreme solar activity drastically compresses the magnetosphere and modifies the composition of ions in the near-Earth environment. They are now tried to find out how these changes affect orbiting satellites, including the many GPS satellites.
During two extreme solar explosions, or solar flares, on 21st January 2005 and 13th December 2006, the Cluster and Double Star satellites were favourably positioned to observe events on a large scale.
During both events, the velocity of positively charged particles in the solar wind was found to be higher than 500 miles per second, more than twice their normal speed. In addition, the density of charged particles around the Earth was recorded at five times higher than normal. The measurements taken in January 2005 also showed a drastic change in ion composition.
The second explosion in December 2006 released extremely powerful high-energy X-rays followed by a huge amount of mass from the solar atmosphere (called a coronal mass ejection). During the event, GPS signal reception on the ground was lost. These factors together caused the magnetosphere to be compressed. Data show that the “nose” of the magnetopause (the outer boundary of the magnetosphere), was shifted by nearly 30,000 miles.
About five hours after the coronal mass ejection hit Earth’s magnetosphere, the Double Star satellite observed penetrating solar energetic particles on the night side. These particles are hazardous to astronauts as well as satellites.
“With these detailed observations, we’ll be able to plug in data and better estimate what happens to the inner magnetosphere and near-Earth space during such explosions on the Sun,” said Iannis Dandouras, principal investigator of the Cluster Ion Spectrometer and lead author on a paper about the findings.
“Looking at such a large-scale physical phenomena with a single satellite is akin to predicting the impact of a tsunami with a single buoy,” added Matt Taylor, ESA’s Project Scientist for Cluster and Double Star. “With Cluster and Double Star we have monitored both sides of Earth simultaneously, and obtained valuable in-situ data.”
The results appear in the February 2009 issue of Advances in Space Research.