solar waves in the Sun's atmosphere

There are basically two kinds of waves in the solar atmosphere.

There are transverse wave, which wiggle along the magnetic field lines.

We call these Alfven waves, after the Swedish astronomer, Hannes Alfven, who first described them.

They travel very fast (1,000,000 m/s). Imagine going from Edinburgh to London in less than one second!

Hannes Alfven, 1908-1995

Hannes Alfven was born in Sweden in 1908. As a child he was interested in astronomy. He also had a radio receiver and used to pick up radio transmissions from far away, even from Scotland. His work was sometimes controversial and it took a while before his ideas were accepted by other scientists.

He studied astronomy, cosmic rays and aurorae. Eventually his scientific achievements were recognised when he won the Nobel Prize for physics in 1970. He was a quiet man and enjoyed travelling to exotic places.

The Sun produces a lot of noise - its insides are always rumbling away. Some of these sound waves come to the surface and are the second kind of wave found in the Sun. They are called acoustic waves and are longitudinal waves. Rehka talked about acoustic waves inside and on the surface of the Sun in her section ‘Dive beneath the solar surface’. In this section we are only going to talk about waves in the solar atmosphere, rather than inside or on the surface of the Sun.

Some acoustic waves are guided along the magnetic field lines in the solar atmosphere. We call these magneto-acoustic waves. These waves can travel at the same speed as normal sound waves, or they can travel much, much faster, even faster than Alfven waves

How could waves heat the solar corona?

As the waves move through the solar atmosphere, energy can be transferred from the wave to the solar plasma, which then heats up. This is what we think could help heat the corona to such high temperatures and so we have been looking for evidence of waves. We think we’ve found some. Here is one example from a TRACE movie.