The Role of the Coronal Magnetic Field
The solar wind escapes primarily through
coronal holes,
which are found predominantly near the Sun's poles; in the equatorial plane the
magnetic field lines of the Sun are more likely to close on themselves,
particularly in periods of low solar activity. These closed field lines trap the
hot coronal gases, leading to enhanced X-ray emissions from these hotter regions,
but suppressing contributions to the solar wind.
The adjacent image shows an enhanced image of the solar corona. In this image
the magnetic field lines of the corona correspond approximately to the boundaries
between regions of different color
(more info). Notice that in the equatorial regions the field
lines traced by these color boundaries tend to form closed loops, indicating the
trapping of coronal gas.