The 83rd AICS Cafe
Date and Time: Thu. Jan. 21, 2016, 14:00-15:30
Place: Workshop room (6th floor) at AICS
Rescheduled from January 7
(This session will start at 14:00 on Thursday !)
Title: Numerical challenge to sunspot 11-year cycle
Speaker: Hideyuki Hotta (Assistant Professor, Chiba University; invited by Particle Simulator Research Team)
Presentation Language: Japanese
Presentation Material: Japanese
The sun is a magnetized star. We can frequently observe sunspot, i.e., strong magnetic region, on the solar surface. The magnetic field is thought to be generated in the solar interior by dynamo action of turbulent ionized plasma. The number of sunspot has a long-standing big mystery, i.e., 11-year cycle. We have not understood what makes this beautiful cycle. The key is the turbulent thermal convection in the solar convection zone. The turbulence, however, is nonlinear and complicated, and investigations by numerical calculation have important roles. Since we had problems on using large supercomputers and increasing resolution, we newly adopt a method so called, the Reduced Speed of Sound Technique (RSST) which can solve our previous problems. Using this method we have significantly improved our understanding of turbulent flow and magnetic field in the solar interior. In the talk, one example, the small-scale effect for constructing the large-scale magnetic field is shown.
Hideyuki Hotta invented a method which can efficiently use large computers even for the solar convection zone with changing an equation of the problem, while he was still a graduate student at the department of Earth and Planetary Science, The University of Tokyo. Then he reproduce the near surface shear layer which was a long standing problem in the solar physics using the K computer for the first time. After he got PhD at March 2014, he stayed High Altitude Observatory, USA as a JSPS fellow. He studied generation mechanisms of magnetic field in the solar interior and revealed that there is significantly stronger magnetic field than previously expected. From July 2015, he has moved to Chiba university as a tenure track assistant professor and continues studying the solar interior with using large computers.