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The A-X of Solar Flares – Observations in the EUV and Soft X-rays

Prof Helen Mason, University of Cambridge, UK

The Sun has given us quite a few X class flares recently and even some beautiful displays of the aurora in the UK. During solar flares, explosive releases of energy, the plasma temperature can reach as high as 10MK or even more. Large flares are often accompanied by filament eruptions and Coronal Mass Ejections, CMEs, and high energy particles, which can often reach the Earth’s environment. The EUV and soft X-ray wavelength ranges are ideally suited for studying this very hot plasma, with a lot of emission lines from highly ionised ions.

Some early observations of solar flares in the EUV and soft X-rays were made with the Solar Maximum Mission, then with SoHO, and more recently with Hinode and the Solar Dynamics Observatory. Spectroscopic diagnostics enable us to determine the plasma properties – peak temperature, emission measure, electron number density and elemental abundances. Recent work on small flares has also been carried out using the XSM (X-ray Solar Monitor) on Chandraayan2 in collaboration with colleagues at ISRO’s Physical Research Laboratory, Ahmedebad, India.

This talk will review observations of solar flares from small, compact flares (A-B class) to large, complex X-class flare, and what we have learnt about them.


Prof Helen Mason OBE

Helen Mason is an Emeritus Professor in Solar Physics at the University of Cambridge. Until her retirement in 2017, she was head of the Atomic Astrophysics Group at DAMTP. Her field of expertise is the ultraviolet and X-ray spectrum of the Sun. She has worked on many joint UK, NASA, ESA, Japanese and ISRO (Indian Space Research Organisation) space projects including the Solar Maximum Mission, SoHO (Solar and Heliospheric Observatory), Hinode, SDO (Solar Dynamics Observatory) and XSM, Chandraayan-2’s Solar X-ray Monitor.

Helen has always been keen to convey her passion for solar physics to the public and to students. She has given many public lectures and worked closely with schools. She has participated in several radio and TV programmes, for example BBC4’s ‘Seven Ages of Starlight’ and BBC R4’s ‘In Our Time – Solar Wind’ (2020). Helen has most recently been leading the project SunSpaceArt.org, funded by STFC, which brings scientists and artists together to run STEAM (STEM + Arts) workshops in schools.

In 2014, Helen was awarded an OBE (Order of the British Empire) for her services to Higher Education and to Women in Science, Engineering and Technology.  In 2018, she was awarded the Royal Astronomical Society’s Annie Maunder Medal for Outreach.

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