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Theoretical model suggests that the sunís next phase of activity will be mild!

- Prof. Arnab Rai Choudhuri, Physics

  A new theoretical calculation suggests that the next active phase of our sun will be rather mild. A recent paper presenting this calculation has been selected as "Editors' suggestion" in Physical Review Letters - one of the world's top honours for a physics paper.

  Once every 11 years, our sun enters into a tizzy of activity for a while (about 3-4 years), marked by increased number of sunspots and gigantic explosions called solar flares Ė often hurling huge chunks of hot plasma into the interplanetary space, along with charged particles accelerated to nearly the speed of light. These disturbances can pose serious threats to man-made satellites orbiting the earth, can disrupt various electronic communication channels and can even trip electrical power grids. The sunís next active phase is scheduled around 2010-2011 Ė called cycle 24 in scientific jargon. Whether this next cycle will be strong or weak is being hotly debated.

  The reason behind the sunís cycles is the sunís magnetic field, which is produced by a hydromagnetic dynamo process underneath the sunís surface and is cyclic in nature. The fundamental theoretical paper establishing the dynamo process was written by Parker [1] about half a century ago. However, only within the last few years, theoretical models of the sunís dynamo have become sophisticated enough to explain many aspects of the sunís cycle. As recently as one year ago, Dikpati and Gilman [2] made the first attempt of using a theoretical dynamo model to predict the strength of the upcoming cycle 24. They concluded that this cycle is going to be the strongest in 50 years. Now Choudhuri, Chatterjee and Jiang [3] point out that some assumptions in the Dikpati-Gilman model are unjustified. On using what they regard as more reasonable assumptions, their model (based on the earlier work of Nandy and Choudhuri [4]) of the sunís dynamo predicts that the cycle 24 will be about the weakest in a century.

  We now have to wait for about 4-5 years to find out which prediction will come closer to truth.

  1. Parker, E.N. 1955, Astrophysical Journal 122, 293.
  2. Dikpati, M., and Gilman, P.A. 2006, Astophysical Journal 649, 498.
  3. Choudhuri, A.R., Chatterjee, P., and Jiang, J. 2007, Physical Review Letters 98, 131103.
  4. Nandy, D., and Choudhuri, A.R. 2002, Science 296, 1671.