Saturday, July 25, 2015

Huge explosions from Magnetic Reconnections

Large flares are often associated with huge ejections of mass from the Sun, although the association is not clear. These coronal mass ejections (CMEs) are balloon-shaped bursts of solar wind rising above the solar corona, expanding as they climb. Solar plasma is heated to tens of millions of degrees, and electrons, protons, and heavy nuclei are accelerated to near the speed of light. The super-heated electrons from CMEs move along the magnetic field lines faster than the solar wind can flow.

CMEs are not small either...
Rearrangement of the magnetic field, and solar flares may result in the formation of a shock that accelerates particles ahead of the CME loop. Each CME releases up to 100 billion kg (220 billion lb) of this material, and the speed of the ejection can reach 1000 km/second (2 million mph) in some flares. Solar flares and CMEs are currently the biggest "explosions" in our solar system, roughly approaching the power in one billion hydrogen atomic bombs.

Recent scientific research has shown that the phenomenon of magnetic reconnection is closely associated with CMEs and solar flares. Magnetic reconnection is the name given, within magnetohydrodynamic theory, to the rearrangement of magnetic field lines when two oppositely directed magnetic fields are brought together. This rearrangement is accompanied with a sudden release of energy stored in the original stressed magnetic fields.

Visual representation of the factors involved in a CME inlcuding Earth's defences
On the sun, magnetic reconnection may happen on solar arcades—a series of closely occurring loops of magnetic lines of force. These lines of force quickly reconnect into a low arcade of loops, leaving a helix of magnetic field unconnected to the rest of the arcade. The sudden release of energy during this process causes the solar flare and ejects the CME. The helical magnetic field and the material that it contains may violently expand outwards forming a CME. This also explains why CMEs and solar flares typically erupt from what are known as the active regions on the sun where magnetic fields are much stronger on average.

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