Archive for Convection

On the Surface of the Sun

Posted in The Universe and Stuff with tags , , , on January 30, 2020 by telescoper

There are some wonderful images and movies going around from the Daniel K Inouye Solar Telescope which has produced the highest resolution images of the solar surface ever seen.

Here’s a snapshot:

And here’s a movie:

In the above image you can see the granular structure of the Sun’s photosphere. The cells you can see are a manifestation of the large-scale convective motions that transport energy from the Sun’s inner regions to the surface. This energy is created by nuclear reactions in the solar core and it sets up convective motions in the outer layers rather like those in a pan of boiling water set up by heating from below (or perhaps the gentler motions that appearin a lava lamp).

The surface structure looks surprisingly regular but the highly turbulent magnetized plasma is responsible to an extraordinary range of activity, from sunspots, flares and prominences, to the heating of the solar corona and the generation of the solar wind.

 

Lectures and Lava Lamps

Posted in Education, Maynooth, The Universe and Stuff with tags , , , on November 7, 2018 by telescoper

Teaching at Maynooth University has resumed after the Study Break, and yesterday I gave my first lecture on Astrophysics & Cosmology after a gap of a week. I still haven’t got onto the Cosmology bit yet, but am most of the way through a set of half-a-dozen lectures or so on stellar structure and evolution.

In past incarnations I’ve deployed a lava lamp as a prop to illustrate convection, one of the ways that heat can be transported from the core of a star (where it is generated by nuclear fusion) to its surface (whence it is radiated). The simple demonstration of how a temperature gradient can lead to convective motion always proved popular with students. In fact, more-or-less the only complimentary comments I ever got about my lectures on this topic were about how nice the lava lamp was.

Anyway, no longer having access to the official Cardiff University School of Physics & Astronomy Lava Lamp, I thought I’d just show a video chosen from the many available on youtube. They seem quite popular, perhaps because they are rather restful:

Unfortunately, however, the fates had it in for me yesterday. The Powers That Be decided to update the version of Windows on all the PCs in all the teaching rooms on campus during the study break. When I tried to show the video the computer crashed and would not restart. I had to run back to the office to get my laptop, which I eventually got to work, but I had lost so much time that I skipped the video. Hopefully I’ll get to show it properly at some point in the future.