Sun is the most important celestial objects to the planet earth as it is the main source of energy to it. Sun is an average star, classified under spectral category as a G2 star having a surface temperature of 5780 degree Kelvin. Being close to the earth, sun produces a resolvable disk of great detail, which is not possible for other stars. Solar flares and coronal mass ejections are the enigmatic energetic phenomena that occur in the solar atmosphere and regularly bombard the earth’s environment in addition to the solar wind. These storms and CMEs are closely connected with the magnetically active regions that are observed all through the atmospheric levels of the sun. However, predicting them is not that much easy. Most of the studies concluded that the magnetic twist that takes place even in small active regions is found to be responsible for the triggering mechanisms of these energetic events. Though these phenomena are observed to be taking place in the outer atmosphere of the sun, their foot points are directly connected to the inner atmospheres of the sun, or even below since the magnetic field is getting generated in the interior level of the sun. When we look at this angle, we may realize the importance of ground based observations for a better understanding of these phenomena. It has been time and again observed that in most of the energetic phenomena of the sun, the magnetically active region sunspots that are observed in the surface of the sun play a vital role in the triggering mechanisms of these energetic events. The latest sunspot cycle number 24 did not have sunspots for more than 800 days before the first spot appeared. The sunspot related activity likes solar flares are not found to be strong in the present solar cycle. Therefore, it will be interesting to find out whether the next solar cycle will also behave similar to the present one or this cycle is an unusual one. It gives us a thinking to identify whether some of these energetic phenomena follow the solar cycle or irrelevant to it in addition to studying these energetic event triggering mechanisms. A branch of study ‘space weather’ had emerged in the recent past which connects the sun earth relations. This paper details about the solar activity and associated energetic phenomena that occur in the atmosphere of the sun and their influence on the earth.
Dr. K. Sundara Raman
Indian Institute of Astrophysics, Kodaikanal – 624 103, 1/22, Agraharam, Keela KalKandar Kottai, Tiruchirapalli-620011, Tamil Nadu, India.
Vierw Book:- http://bp.bookpi.org/index.php/bpi/catalog/book/193