Solar Physics: New Look at Old Enigma

Dr. Lakshmi Pradeep Chitta from MPS receives Early Career Researcher Prize from the European Physical Society.

The European Physical Society has awarded Dr. Lakshmi Pradeep Chitta from the Max Planck Institute for Solar System Research (MPS) with this year's Early Career Researcher Prize of the European Solar Physics Division (ESPD). The ESPD honors Chitta's new view of processes enabling the exchange of energy and mass between the visible surface of the Sun and its atmosphere. His research results could help to explain the huge temperature difference between the two regions.

Our star is surrounded by a highly dynamic layer of hot ionized gas ? and it holds a secret: How is it possible that the temperature of the solar atmosphere, called corona, is more than a million degrees, when the Sun's visible surface located much closer to the energy producing core is only 5500 degrees hot? How does the energy from the solar surface reach the corona and heat it?

While there have been theories for decades on how to answer this question, there is still no coherent explanation for the observed phenomena. In the past four years, Dr. Lakshmi Pradeep Chitta contributed a fresh approach to the discussion – with a closer look at coronal loops, enormous arc-shaped plasma flows that extend up to 100,000 kilometres into the corona.

"Coronal loops originate at the solar surface. They constitute a link between the cool surface and the hot atmosphere," says Chitta. At their footpoints, Chitta discovered regions of opposite magnetic polarity at spatial scales of 100 to 1000 kilometers: magnetically positive regions occur in close proximity to magnetically negative ones. Until now, researchers had assumed that only regions with uniform magnetic polarity produce coronal loops.

Data from the balloon-borne solar observatory Sunrise, analyzed by Chitta, now provide a more refined picture. During its second flight in 2013, the observatory peered at the magnetic fields on the solar surface for several days and was able to discern structures as small as 50 kilometres for the first time. Combined with images of the overlying corona, taken by the NASA’s space-based Solar Dynamics Observatory, Chitta was able to present a novel look at our star’s outer shell.

"This discovery requires us to rethink. Completely new processes must now be considered as candidates for coronal heating," says Prof. Dr. Sami K. Solanki, Director at MPS. Among other things, Chitta was able to show that the magnetic fluxes at the foot of the coronal loops partially cancel each other. This suggests that reconnection of the magnetic field can release large amounts of energy at the solar surface ? and thus possibly heat up the Sun’s atmosphere.

Lakshmi Pradeep Chitta studied physics at Acharya Nagarjuna University and the University of Hyderabad in India. Already in his doctoral thesis, which he prepared at the Indian Institute of Astrophysics in Bangalore and partly at the Harvard-Smithsonian Center for Astrophysics in the USA, he turned to small magnetic structures in the solar atmosphere. Since 2015 Chitta has been conducting research at the Max Planck Institute for Solar System Research, temporarily as a Marie Sk?odowska-Curie Postdoctoral Fellow (grant agreement No. 707837). 

The European Physical Society is an association of 42 national physical societies. European solar physicists are organized within the European Solar Physics Division (ESPD). The ESPD’s Early Career Researcher Prize is awarded annually to a scientist who is still at the beginning of his or her scientific career, but has already made a significant contribution to his or her field of research.  

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