Latitudinal Distribution of Photospheric Magnetic Fields of Different Magnitudes

Abstract

Photospheric magnetic fields are studied using synoptic maps from 1976 to 2003 produced at the National Solar Observatory, Kitt Peak (NSO/KP). Synoptic maps were averaged over the time interval of nearly three solar cycles (Solar Cycles 21 – 23). The change in the latitudinal distribution was considered for the following groups of magnetic field values: $B = 0 \,\mbox{--}\, 5~\mbox{G}$, $B = 5 \,\mbox{--}\, 15~\mbox{G}$, $B = 15 \,\mbox{--}\, 50~\mbox{G}$, and $B > 50~\mbox{G}$.

Magnetic fields in each of the above groups have common latitudinal distribution features, while for different field groups these features are significantly different. Each of the groups is closely related to a certain manifestation of solar activity. Strong magnetic fields are connected with two types of solar activity: active regions (magnetic fields $B>15~\mbox{G}$) that are related to sunspot zones, and polar faculae (magnetic fields $50~\mbox{G} > B > 15~\mbox{G}$) that occupy latitudes around $65^{\circ}-75^{\circ}$. Fields from 5 to 15 G occupy the polar regions and are connected with polar coronal holes (the global solar dipole). Fields of $B<5~\mbox{G}$ occupy a) the equatorial region and b) latitudes $40^{\circ}$ – $60^{\circ}$.