Prof. Helen Mason OBE

The solar corona, as seen during a total eclipse of the Sun, is over 1MK. At such temperatures the plasma emits strongly in the UV and X-ray wavelength ranges, which can only be studied with solar space observatories. The heating mechanism for the solar corona is a topic of hot debate, still not fully understood. The magnetic field of the Sun is known to play a key role in transporting and releasing energy in the solar atmosphere. During solar flares, explosive releases of energy, the plasma temperature can reach 10MK or even higher. The X-ray wavelength range is ideal for studying this very hot plasma, with a range of emission lines from highly ionised ions. This talk will review some early observations of X-ray emission lines from rockets, OSO-5 and Solar Maximum Mission, including some of the key spectroscopic diagnostics which were developed. More recent work has been carried out to study X-ray emission lines from active regions and small flares with the XSM (X-ray Solar Monitor) on ISRO’s Chandraayan2 (in collaboration with colleagues at the Physical Research Laboratory, Ahmedabad). These X-ray observations are combined with data from other space observatories, such as SDO, Hinode and Solar Orbiter, to get a better knowledge of the plasma parameters for different solar features. The launch of India’s first solar space mission, ISRO’s Aditya-L1, in 2023 will provide major advances in solar physics research, enabling outstanding questions about coronal heating to be addressed.