The Kristian Birkeland Medal 2021

Professor Shibata

Prof. Shibata is a world-renowned solar physicist. He has published more than 300 papers in refereed journals. That have been cited more than 20,000 times. Professor Shibata has contributed a lot to international collaborations not only during the duty cycle of the Yohkoh and Hinode solar space missions, but also in training students and postdocs from various countries, such as China, France, India, Saudi Arab, UK, etc.

Solar flares and coronal mass ejections (CMEs) are the major drivers of the space weather, which might sometimes lead to hazardous consequences on Earth. Prof. Shibata made significant contributions in the research of jets, solar flares and CMEs. Many of his papers are the pioneering works in the related field. Prof. Shibata discovered X-ray jets in the solar corona and X- ray plasmoid ejections from solar flares with various evidence of reconnection and successfully developed the magnetic reconnection model of coronal X-ray jets. Prof.

Shibata proposed a unified reconnection model of solar flares and jets which is now considered as the standard reconnection model of solar flares and jets. He also proposed the concept of the plasmoid-induced- reconnection and fractal reconnection and the emerging flux triggering mechanism of solar flares and CMEs. More recently, using data taken by Kepler space telescope, Prof. Shibata and his co- workers discovered many superflares on Sun-like stars, which have slow rotation similar to our Sun. This discovery raised big surprise because this was against previous belief that superflares would not occur on slowly rotating Sun-like stars, and hence on the Sun.

Prof. Shibata later showed theoretically that huge magnetic flux necessary for producing superflares with energy ~1034 erg (100 times more energetic than the largest solar flares in recent 30 years) can be amplified by the differential rotation in the solar interior within 8 years, so that such superflares (1034 erg) may occur on the present Sun. These studies posed strong impact on the solar and geophysical community, from various viewpoints such as space weather study, habitability on exoplanets, and stellar magnetic activity research. 
 In addition to these scientific accomplishments, probably his most important contribution to the community is education. It is obvious that his influence was extremely remarkable in recent 30 years in the international solar and geophysical communities.