3.41 Sspd_chapter 1_appendices_space weather research  (Page 2/3)

The photosphere has a mosaic of bright spots called granulations plus sporadically appearing darker patches called SUNSPOTS. At the granulations areas the photosphere is 1000 to 2000 km thick.

The average temperature of the photosphere is 6400 degree centigrade but at the Sun-spot it is cooler at 2,000 to 3,000 degree. Here magnetic fields are emanating which are 25,000 times stronger than earth magnetic field. Sun Spots appear and disappear. They are surrounded by clouds of bright, burning gas called faculae. Sun Spots number and sizes are indicative of Sun’s Solar Activity. Larger sizes and more numerous number is indicative of Sun’s Activity. The Sizes and number wane and wax in cycles of 11 years. This is known as 11 years cycle of Sun Activity. By studying the sun spot, the rate of rotation of Sun has been determined to be 27 days.

SOLAR CORONA- SOLAR FLARES-CORONAL MASS EJECTIONS

There is a pink fringe several thousand kilometers broad, around the solar disc. This Pink fringe is called the chromospheres. As the solar activity increases, magnificent prominences shoot out from this layer. They look like curls or bushes. These are Coronal Mass Ejections (CME). In these coronal mass ejections the sun blasts billion of tons of plasma blob material at very high speed. These prominences are sculpted by the magnetic field. The gas is ejected and re-circulated back at a high speed of 1000 km/sec. Sometimes this velocity is as high as 500,000km/sec.

Sudden explosions of Solar Atmospheres release energy equivalent to billions of Atomic Bombs within few minutes. The abrupt rearrangement of solar magnetic field , which arch upward from the surface of the sun, lead to this sudden release of energy.CME are accompanied with burst of X-Rays. Solar flares and different aspects of Space Weather involve the interplay of magnetic field and plasma.

The exact physics has been unraveled by the study of Yohkoh satellites&Ramaty High Energy Solar Spectroscopic Imager(RHESSI). Solar flares erupt from Sun Spots. At Sun Spots the solar magnetic fields is much stronger. It is the magnetostatic energy of these powerful magnetic fields which are unleashed during solar flares as thermal energy. Oppositely directed magnetic field lines come together and partially annihilate and rearrange. This is known as RECONNECT. This magnetic reconnection is responsible for the solar flare and CME. Invisible Magnetic Loops are emanating and terminating at the sun spots. These magnetic loops trap hot plasma. Initially this plasma is at several million Kelvin temperature. Hot charged particles spiral around the magnetic lines of force to and fro between the two foot points. The acceleration and deaccleration lead to synchrotron radiation in form of extreme UV and hard X-ray. In the process plasma heats up to 10 to 40 million Kelvin. As the magnetic reconnect takes place, gigantic solar flares erupt and CME occurs. As the sun spot increases , number of magnetic loops increase and hence the magnetic reconnect becomes more numerous leading gigantic solar storms.