John Carlos Baez on Nostr: The realm where ions vibrate in the Sun's magnetic fields is a strange one, and the ...

The realm where ions vibrate in the Sun's magnetic fields is a strange one, and the more we study it, the more complex it seems to get.

Parker's original model of the solar wind was spherically symmetric, so he imagined the solar wind shooting straight out of the Sun in all direction. In this model, the Alfvén surface is the sphere where the wind becomes faster the Alfvén waves. There are some nice simple formulas for all this.

But in fact the Sun's surface is roiling and dynamic, with sunspots making solar flares, and all sorts of bizarre structures made of ions and magnetic fields, like "coronal streamers" and "pseudostreamers" and "spicules"... aargh, too complicated for me to understand. This is an entire branch of science!

So in fact, the Alfvén surface is frothy and randomly changing. The Parker Solar Probe will help us learn how it works - along with many other things.

Finally, here's something mindblowing. There's a red dwarf star 41 light years away from us, called TRAPPIST-1, which may have six planets *beneath* its Alfvén surface! This means the planets can affect the motion of gases in the star!

For more, check out this:

https://en.wikipedia.org/wiki/Alfvén_wave

and this open-access article:

https://link.springer.com/article/10.1007/s11207-023-02218-2

"Combined with recent perihelia of Parker Solar Probe, these studies seem to indicate that the Alfvén surface spends most of its time at heliocentric distances between about 10 and 20 solar radii. It is becoming apparent that this region of the heliosphere is sufficiently turbulent that there often exist multiple (stochastic and time-dependent) crossings of the Alfvén surface along any radial ray."