Webinar 10 "A Course of Solar Physics"

Talk 1 A General Introduction of the Sun PPT and VIDEO
Talk 2. Ground-based Observations of the Sun PPT and VIDEO
Talk 3 Space-borne Observations of the Sun PPT and VIDEO
Talk 4 The Solar Interior: Theory and Probes  PPT and VIDEO
Talk 5 Helioseismology: Techniques and Results  PPT and VIDEO
Talk 6 Solar Activity and Magnetic Cycles   PPT  and  VIDEO
Talk 7 Solar Explosive Phenomena: Flares PPT &  VIDEO 1 ,  VIDEO 2
Talk 8 Solar Explosive Phenomena: CMEs   PPT  and  VIDEO

This series consisted of eight talks by Prof Ashok Ambastha. The talks were made live during 06:00 – 07:00 UT on 19th, 20th, 21st, 22nd, 25th, 26th, 27th, and 28th February 2019..

About the speaker (Prof Ashok Ambastha) Professor Ashok Ambastha was born on 17 May 1954 in Jashpurnagar, India. He obtained his B.Sc. in 1972 and M.Sc. in 1974 from Pt. Ravishankar Shukla University, Raipur. He joined Physical Research Laboratory (PRL), Ahmedabad, as research scholar in 1975, and received his Ph.D. degree in 1981 from Gujarat University, under the supervision of Prof. Ram K. Varma. After his post-doctoral research at PRL on numerical experiments on plasmas in magnetic mirrors, in 1983 he joined Udaipur Solar Observatory (USO), Udaipur, a unit of PRL, Department of Space, Government of India, on a permanent scientific position. Since then, he has worked at various positions at USO, until his superannuation as senior professor in 2014.  He has worked as a member in various national and international bodies. He has guided several students for M.Sc. and Ph. D. and published over 100 research papers in reputed journal. Presently, he is an honorary scientist with USO-PRL

Brief Abstracts of these talks are given below:

1. A General Introduction of the Sun 

The Sun, our day-time star is source of all forms of energy, sustains life, drives weather and climate on the Earth. It has played major role in development of mathematics, physics and astrophysics. We discuss the Sun as a star, its place in larger astrophysical context, and its general properties derived from known laws of physics.

2. Ground-based Observations of the Sun

The Sun is our closest and the only star, where it is possible to observe various physical processes occurring in its visible surface (photosphere) at high spatial and temporal scales.  From ground-based solar instruments, however, the Sun can be observed only in the visible, and radio wavelengths, revealing a variety of features and facets of the Sun.   

3. Space-borne Observations of the Sun

The outer atmospheric layers of the Sun are much hotter and extremely rarefied, therefore, are generally `invisible' in optical wavelengths. These layers emit high energy UV, EUV and X-ray photons, which are absorbed in Earth's atmosphere; therefore, can only be observed from space.  Several new discoveries have been made from these observations. 

4. The Solar Interior: Theory and Probes

The solar interior is not directly accessible as it is hidden underneath the opaque photosphere. Therefore, information about solar interior is traditionally obtained using mathematical models. Neutrinos, produced in solar core, and photospheric solar oscillations provide new tools and direct probes of solar interior, and help in testing solar models.

5. Helioseismology: Techniques and Results

Helioseismology is based on solar photospheric oscillations, which propagate inside the Sun and carry information about the solar internal structure and dynamics. However, stringent detection precision, and continuous solar observations spanning over long time periods are required for accurate identification of individual modes. We discuss the techniques, results and new discoveries made from helioseismology in recent years.

6. Solar Activity and Magnetic Cycles

Long term solar observations reveal various manifestations of the Sun: quiet, active, dynamic and explosive. Sunspot numbers, when plotted against time, prominently exhibit activity cycle of an average 11-year period. Solar magnetographic observations show a corresponding magnetic cycle of 22-years. Observations and models shall be discussed to understand features of these cycles.

7. Solar Explosive Phenomena: Flares

Solar flares are spectacular explosive transient phenomena that occur in the outer atmospheric layers of the Sun. They are sudden, catastrophic enhancement of energy over entire electromagnetic spectrum, in time scales of a few minutes to several hours, occurring in localized regions. Flares severely affect the interplanetary space and planetary environments.

8. Solar Explosive Phenomena: CMEs 

Coronal Mass Ejections (CMEs) are large expulsions of magnetized plasma clouds propagating and sweeping across solar corona and interplanetary medium. They were first discovered from space in early 1970s. CMEs involve energies like the flares and cause significant transient effects in space and magnetic environments of planets.