This series of images follows the progress of a coronal mass ejection (CME) associated with the powerful solar flare on Tuesday 10 April 2001. The images were made using observations from the Large Angle and Spectrometric Coronagraph (LASCO) instrument on the Solar and Heliospheric Observatory (SOHO) spacecraft. The LASCO instrument uses a coronagraph (blue disk in the middle of each image) to block direct light from the Sun so the much fainter solar atmosphere (corona) can be seen. The white circle in the middle of the coronagraph disk represents the apparent size of the Sun as viewed from SOHO's position in space.
The CME first comes into view in the left image, and appears as a white, feathery area at the bottom and sides of the LASCO coronagraph. As it expands into space, it becomes larger and fainter (middle and right images). Earth-directed CMEs like this one are called "halo" CMEs, because the expanding gas cloud appears as a halo around the Sun from our perspective.
CME eruptions, often associated with flares, are clouds of electrified, magnetic gas weighing billions of tons ejected from the Sun and hurled into space with speeds ranging from 12 to 1,250 miles per second (about 20 to 2,000 kilometers per second). The CME associated with Tuesday's flare was thrown from the Sun at the high end of this scale, estimated at 994 miles per second (1,600 kilometers per second). CMEs can be even more powerful than flares - the total energy in a good-sized CME is about 100 times greater than that of the largest flares. (Solar flares, also among the solar system's mightiest eruptions, are tremendous explosions in the atmosphere of the Sun capable of releasing as much energy as a billion megatons of TNT.)
Depending on the orientation of the magnetic fields carried by the CME cloud, Earth-directed CMEs cause magnetic storms by interacting with the Earth's magnetic field, distorting its shape and accelerating electrically charged particles (electrons and atomic nuclei) trapped within. Severe solar weather is often heralded by dramatic auroral displays (northern and southern lights), but magnetic storms are occasionally harmful, potentially disrupting satellites, radio communications, and power systems.
IMAGE CREDIT: NASA and the European Space Agency
For official space weather predictions, and an explanation of the severity scales for space storms, refer to:
For more updates on space weather, refer to: