Coronal Holes and Background Magnetic Fields on the Sun

Abstract Size, lifetime and rotational rate of coronal holes (CH) and their connection with background magnetic field (BMF) structures were studied on the base of Solar Geophysical Data (1977-1987). Mean sizes of CH are (1-3) × 1011cm, changing with solar cycle and latitude. Mean life time is 5 rotations. Only small part of CH has rigid rotation. Most of them show differential rotation. CH appear in structures of BMF with the sign of polar magnetic field of corresponding hemisphere about 5-10 rotations after polar field reversal. Rotation rates of CH and BMF near the solar equator are almost the same. Rotational rate of BMF falls with latitude faster than the CH rate. Rotation differential of CH changes with solar cycle, BMF has no such connection. These results speak about different nature of BMF and CH, and the different depth of their sources. The source of CH is located deeper than that of the background magnetic field.