Anita Mohan has been pursuing research in solar physics for over 12 years and recently joined as a lecturer in Applied Physics, Banaras Hindu University.

B N Dwivedi does research in solar physics and teaches physics in Banaras Hindu University. He is involved in almost all the major solar space experiments, including Skylab, Yohkoh, SOHO and TRACE. He has received the ‘Gold Pin Award’ of the Max Planck Institut, Lindau,
Germany.

In the concluding part of our article we discuss problems of coronal heating and coronal holes and solar winds.

The Transition Region and Coronal Explorer (TRACE) satellite, operated by the Stanford-Lockheed Institute for Space Research, went into a polar orbit around Earth in 1998 and has extremely impressive imaging capabilities. The spatial resolution is of the order of 1 arcsecond (725 km), and there are wavelength bands covering the Fe IX, Fe XII, and Fe XV lines which EIT observes as well as the Ly-alpha line at 121.6 nm. Its ultraviolet telescope has obtained images containing tremendous amount of small and varying features – for instance, active region loops are revealed to be only a few hundred kilometers wide, almost thread-like compared to their huge lengths. Their constant flickering and jouncing hint at the corona's heating mechanism. There is a clear relation of these loops and the larger arches of the general corona to the magnetic field measured in the photospheric layer. The crucial role of this magnetic field has only been realized in the past decade. The fields dictate the transport of energy between the surface of the Sun and the corona. The loops, arches and holes appear to trace out the Sun’s magnetic field (see Figure 2).

Read full article (1.52 Mb)

Address for Correspondence
B N Dwivedi and A Mohan
Department of Applied Physics
Banaras Hindu University
Varanasi 221005, India
Email: bholadwivedi@yahoo.com