Magnetic Storms

Sunspots are areas on the surface of the sun where the solar magnetic field has become contorted, preventing the normal flow of heat and resulting in cooler, so darker, areas. Associated with sunspots are flares on the sun. These are explosions of unimaginable violence typically lasting a few minutes. A solar flare emits vast amounts of high-energy electromagnetic (UV and X-rays) and ionized particle radiation (protons) into the solar system.

When a solar flare is directed towards the earth, the EM radiation, travelling at the speed of light, arrives in a little over 8 minutes, coincident with the visual observation of the event. Much of the energy of this radiation is absorbed in the ionospheric D-region (around 65 km), impulsively increasing the ionization density there, and bringing about short-wave fadeouts (SWF) and heralding the onset of a magnetic storm. A small signature of this kind of event, a solar flare effect, is detected at magnetic observatories in daylight at the time of the flare.

The particle radiation from a solar flare, travelling at speeds of the order of 1000 km/sec., takes a day or two to reach the earth. When it does arrive a shock-wave is generated in the earth's magnetic field when it is suddenly compressed. This is simultaneously detected at magnetic observatories around the globe. An impulsive step in the magnetic field is observed, followed by large excursions in the magnetic field's intensity and orientation. A magnetic storm engulfs the earth for anything from a few hours to several days.

Unusually huge electric currents flow in the earth's ionosphere, compasses are diverted, radio broadcasts are received in areas far from where they are intended, Auroras are seen at latitudes much nearer the equator than usual, some say homing pigeons are lost, and GPS are affected, currents are induced in long conductors like pipelines and powerlines.

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