Two coronal mass ejections (CME's) erupted from the surface of the Sun, placing residents of Earth on alert for a possible pair of geomagnetic storms. Electrically-charged material from our home star is headed toward collisions with the Earth.
On 9 September, a coronal mass ejection resulted in material rising from a sunspot labeled by astronomers as Active Region 2158. A second solar eruption was spotted rising from the same feature at 1:45 EDT on the following day.
The Solar Dynamics Observatory (SDO) spacecraft recorded each eruption. The vehicle was launched on a mission to study the Sun on 11 February 2010. The observatory examines the magnetic field of our home star, in an effort to understand processes in the Sun.
Solar flares are ranked by the amount of energy contained in the storm. The most powerful of these events, including the most recent pair, are classified a X-class flares. These classes are further ranked by number, with the event on 10 September classified as X 1.6. The second flare was the more powerful of the pair of events.
Material from the CME's poses no significant danger to people or satellites, but geomagnetic storms may form, caused by interactions between charged material from the CME and the magnetic field of the Earth. This could cause some disruptions to communication and guidance systems. In addition to CME's, the spacecraft also records information on the solar wind, a breeze of material constantly emanating from the Sun.
"Geomagnetic storms remain in the forecast for September 12th as a result of the coronal mass ejection... observed on the 9th. The latest... model run has the CME... arriving mid to late day on that same day. A G3 (Strong) Geomagnetic Storm Watch has been issued for September 13th due to the combined influence of these two events," officials for the Space Weather Prediction Center said.
Material from the coronal mass ejections are racing toward the Earth at a velocity of around 2.5 million miles per hour. This is faster than normal for such events in this class, although faster events are seen from time-to-time. These events mark the first time in several year that such powerful CME's have been witnessed emanating from the center of the Sun. Each of the slugs of gas will avoid direct impact, passing slightly over the planet.
A storm due for Friday 12 September would be the result of the first, smaller storm, while the following event would be brought about as a combination of both CME's.