Meet the AAS Keynote Speakers: Prof. Kristopher Klein

In this series of posts, we sit down with a few of the keynote speakers of the 244th AAS meeting to learn more about them and their research. You can see a full schedule of their talks here, and read our other interviews here!

You’re probably very familiar with three of the states of matter – solid, liquid, and gas – and have never directly interacted with the fourth state of matter: plasma. Yet, plasma is the most common state of matter in the universe! It’s found throughout space, between galaxies, in the interstellar medium, and it’s what stars are made of. Prof. Kristopher Klein studies the behaviour of plasma that’s been ejected by our Sun into the Solar System (called the solar wind) to help build an understanding of plasma behaviour that can be applied throughout the universe.

Prof. Kristopher Klein

As a PhD student at the University of Iowa, Prof. Klein used numerical simulations to better understand the behaviour of plasma in the solar wind. From there, he went on to be a postdoctoral researcher at the University of New Hampshire, and then the University of Michigan. During this time, he worked on the instrument suite aboard the Parker Solar Probe. In 2018, he began as a professor at the University of Arizona in the Lunar and Planetary Laboratory. At AAS 244, he will be receiving the Karen Harvey Prize, which is “in recognition for a significant contribution to the study of the Sun early in a person’s professional career” and deliver a plenary lecture on his work.

When enough atoms have become ionised, matter transitions from being a gas to being a plasma. Like gases and liquids, plasma is a fluid, but the charged particles that make up a plasma simultaneously create and respond to electromagnetic fields resulting in unique and complex behaviour. The Sun is made of plasma, and at the surface of the Sun, the “gravity alone can’t actually constrain it, which causes the solar wind to blow outwards…basically filling the entirety of the solar system”, making the solar system a “natural plasma laboratory,” says Prof. Klein.

Due to their low density, solar plasmas are called weakly collisional, which means that electrons and ions are not frequently colliding with each other. In a gas, these collisions are what brings the gas into equilibrium, but in a weakly collisional system “your ions and your electrons are not going to be the same temperature,” explains Prof. Klein. The different temperatures give rise to a plethora of plasma phenomena that we do not fully understand yet. These same effects that we can observe around the Sun occur in all kinds of astrophysical environments. “We can make those assessments locally here in the heliosphere, and then use that information to better understand the visible universe around us,” he says.

To better understand the heliosphere, “you really want to understand the multi-scale, turbulent process” by leveraging data taken by instruments at different separations. Prof. Klein is the deputy Principal Investigator for HelioSwarm – an ambitious new NASA mission which aims to do just that. The mission will consist of nine individual spacecraft arranged in a way that will allow scientists to study plasma phenomena on a range of physical scales, from tens of kilometres to thousands of kilometres, and “the actual orbit will process between the pristine solar wind as well as measuring parts of the the [Earth’s] magnetosphere,” describes Prof. Klein.

Over his career, Prof. Klein has worked in a range of fields within heliophysics. During his PhD, he focused on numerical simulations which he could compare to “spacecraft data that other people had made.” But, over time, he “became really interested in actually designing what is the next kind of measurement that we need to make and then helping to build that infrastructure for the next grad students and postdocs.” Having worked in these different areas, Prof. Klein advises students to stay “open to other scientific avenues to explore.”

To hear more about our heliosphere and the plasmas that fill it, tune into Prof. Kristopher Klein’s Plenary Lecture at 4:40 pm CT on Wednesday, June 12th at #AAS242! 

Astrobite edited by Jessie Thwaites

Featured image credit: AAS 

About Nathalie Korhonen Cuestas

Nathalie Korhonen Cuestas is a first year PhD student at Northwestern University, where her research focuses on the chemical evolution of galaxies.

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