The Sun is Not so Quiet, part 2

One of the jobs of the Solar Observatory at CSU's Space Science Center is to monitor solar activity. The animated image you see above is a series of images taken by CSU student Jodie Hood, who captured a small prominence at edge of the solar disk (the "limb") on Sept. 4. (You can download a better video in QuickTime format.)

Follow up:

Last week I wrote that the Sun is not as quiet as you think - that the Sun's current lack of activity is not really at unusual levels for a solar minimum, and it's just percolating along with the occasional sunspot pair every few weeks. I neglected to bring up another point: even when there are no visible sunspots, that doesn't mean there's no activity at the solar exterior. The recent observations of this solar prominence nicely illustrate that point.

A solar prominence, like a sunspot, is a magnetic phenomenon. As the Sun's magnetic field twists around, loops of it will pop up out of the solar photosphere. These loops in the magnetic field trap some of the extremely hot, electrically charged plasma, which flows along the loops in a beautiful display. The loops can be many times the size of Earth, and can hold billions of tons of plasma. We can see these loops most clearly at the limb of the Sun, where they stand out nicely against the dark of space. (Note that to make it stand out more, we've blocked off the bright disk of the Sun itself.) Prominences are often associated with sunspots; in this image, there may be sunspots at the base of the loop which are just out of sight behind the solar limb.

Prominences aren't just magnetic field "nets" to trap and hold plasma high above the solar photosphere, however. They're constantly in motion, as you can see from the video here. The magnetic fields are forming, twisting, changing, and interacting, and the plasma flowing along them follows suit. Sometimes, the "net" breaks - and then billions of tons of solar material can come hurtling out into the solar system. (Fortunately, Earth's magnetic field and atmosphere work together to protect us from the worst effects, although high-orbit satellites, for instance, can be damaged.)

So, during the Sun's quiet periods, there's still a fair amount of activity going on. Even when sunspots aren't clearly visible on the Sun's face, the magnetic field is still constantly changing, and the plasma constantly interacting with it. There have even been major solar events during solar minimum. All of this underscores how very dynamic the Sun really is... and how important it is to constantly monitor its activity.

Update: Click here for further comments on space-based views of prominences and solar activity.