Sam Van Kooten – Solar physicist at SwRI

I’m a research scientist at Southwest Research Institute in Boulder, Colorado. I recently finished my PhD with Steven Cranmer at the University of Colorado, Boulder, where I studied the motion of magnetic bright points on the solar photosphere as drivers of coronal heating via Alfvén waves. In the past, I’ve worked on thermophysical modeling of Martian sand dunes and on refining estimates of collisional timescales of asteroids.

Here’s what I’ve recently worked on, described for a…

Solar Physicist: I’m studying photospheric bright points, the bases of flux tubes that rise to the corona. Following the motion of these bright points reveals how the flux tubes are being shaken by convective churning, and this shaking is believed to excite waves in the flux tubes which carry energy to the corona. These bright points have been unresolved blobs until now, but DKIST will start to resolve them. I’m using simulated observations of DKIST-like resolution and cadence from MHD simulations to prepare and validate analysis techniques for resolved bright-point motion that can overcome the problems of traditional centroid-tracking applied to resolved motion while also taking advantage of the additional information available in resolved images—specifically, the evolution of the shape and size of bright points, which should excite wave modes beyond those driven by bulk, centroid motion.

Normal Person: The surface of the Sun is about 10,000°F (6000°C), but there’s a sort of atmosphere around the Sun, called the corona, which is a million degrees. One of the big questions in solar physics is how the corona can be heated to a million degrees by the relatively-cool solar surface—it’s like boiling a pot of water without turning on the stove. One possible explanation involes what we call flux tubes, which are tubes of gas held together magnetically. These tubes are all over on the Sun. They have one end inside the Sun’s upper layers and the other end is up inside the corona. The bottoms of these tubes get shaken by the churning, boiling motion of the Sun’s surface. This makes the whole tube above the surface shake back and forth, which means waves are traveling up the tubes. When these waves get up into the corona, they shake around the gas, heating it up. This is where we think the corona’s temperature comes from, magnetic waves injecting heat directly into the corona. It’s like boiling water with a microwave oven instead of a stove top—the water’s boiled by microwaves injecting heat directly into the water, instead of by putting the water in contact with a hot stovetop. My research, then, is looking at just how the bases of those tubes are shaken around. I’m using computer simulations of the Sun, because I can look more closely and in more detail than can be done with telescopes. I’m preparing analysis techniques to study the motion of these tube bases as will be seen by DKIST, an upcoming solar telescope that will produce clearer images of the solar surface than have ever been made before.

Five-Year-Old: The Sun is like a big ball of fire in space, and it’s super hot. But there’s a little bit of air in between the Sun and space, and it’s super mega ultra hot! We want to know why the Sun makes that air super mega ultra hot instead of just making it super hot like itself. We think it’s because the Sun works kind of like a microwave when it heats up that air, but we’re not quite sure yet. We’re working on it! I’m using special computer tools to look really closely at the surface of the Sun to see how this all works.