sun is continually releasing hot gases from its surface, a steady
stream of particles—mostly protons and electrons—known
. The solar wind flows out from the sun especially
strongly through coronal holes.
Ordinarily, magnetic field lines at the sun’s surface form
closed loops that keep gases contained. Coronal holes are places
where magnetic field lines don’t close back on themselves,
but instead stick straight out into space. This leaves an open channel,
out of which the solar wind can blast unobstructed.
Coronal holes make for a gusty solar wind. For example,
the solar wind usually leaves the sun at speeds of around 250 miles
(400 kilometers) per second, but solar wind leaving through the center
of a coronal hole travels much faster, up to 500
miles (800 kilometers) per second. When these solar wind particles
reach the earth—which
takes two to four days, depending on their speed—modest geomagnetic
storms can result. High-speed wind gusts can also disturb satellites
in earth orbit.
Look for current coronal holes using live data.
Coronal holes appear as dark spots
in ultraviolet pictures of the sun.