Author: Msc. Marcia Guedes
Coronal holes are regions of the solar corona where the magnetic field extends into the space in lines “open”, where particles escape leading to the solar wind. Once trapped in the closed magnetic field lines, the particles are heated producing high brightness regions observed in the solar images. Once the particles escape from the sun, they cease to be heated so reducing the brightness observed on the crown and causing a dark region in the corona as shown in Figure 1.
Coronal holes were first observed in 1973. A coronal hole remain observable for a long time, though its shape is variable during the period of observation. Coronal holes located at the poles can remain visible for five or more years. When directed to the Earth, there is a flow of high-speed particles, which is widely used in the study of space weather.
On 29/01/2015 was observed coronal hole with considerable area on the solar disk, as shown in Figure 1.
Figure 1. Vast coronal hole observed at the Sun’s south pole