Thesis defence in the University of Oulu

Doctoral Candidate

Master of Science Iiro Virtanen

Faculty and research unit

University of Oulu Graduate School, Faculty of Science, Space Climate

Field of study

Physics

Date and time of the thesis defence

6.9.2019 12:00

Place of the thesis defence

Linnanmaa, auditorium L4

Topic of the dissertation

Surface flux transport simulations of the photospheric magnetic field

Opponent

Professor Kristóf Petrovay, Eötvös university, Budapest, Hungary

Custos

Professor Kalevi Mursula, University of Oulu

Simulating the evolution of the magnetic field at the surface of the Sun

I have studied the evolution of the magnetic field at the surface of the Sun by simulating the movement of magnetic flux that rises to the surface in so-called active regions. It has long been known that the direction of the magnetic field of the Sun reverses approximately every eleven years. By using simulations I show that this reversal happens in both hemispheres even if active regions are concetrated to only one of them.

I also develop a new method to reconstruct the magnetic field without direct observations of it. The method is based on determining the locations of active regions and the magnetic flux inside them from other observations, and then simulating the movement of the magnetic flux after it has emerged. This method allows one to study the evolution of the magnetic field in times before direct observations of the magnetic field were possible.

Last updated: 30.8.2019