Polar magnetic field geometry in the solar cycle and the relationship between spherical harmonics

• Published in: Proceedings of the International Astronomical Union 2004-06, Vol.2004 (IAUS223), p.101-102
• Main Authors: Filippov, B. P., Platov, Yu. V., Klepikov, D. V.
• Format: Article
• Language: English
• Subjects: Contributed Papers; Geometry; Harmonic analysis; Solar cycle; Solar physics
• ISSN: 1743-9213; 1743-9221
• DOI: 10.1017/S1743921304005241

Geometry of the polar magnetic field is changing during the activity cycle. Tangents to polar ray structures are usually crossed near some point below the surface. This point can be named as a “magnetic focus”. The distance $q$ between the focus and the center of the solar disk changes from the maximum value about 0.7 $R_\odot$ at solar minimum activity to the minimum value about 0.5 $R_\odot$ at solar maximum. This behavior has not been understood till now. Really, all tangents to field lines near the pole of the axially symmetric potential magnetic field described by zonal spherical harmonics cross at the same point. However, the greater is the number of a harmonic, the closer to the surface is the crossing point. As far as at activity maximum high harmonics dominate, the behavior of the focuses seems to be in contradiction with the results of the harmonic analysis. We have found that the focus depth changes could be explained by complicated relationship between the harmonics of “new” and “old” cycle near the instant of the polar magnetic field reversal.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html