In what already has been a stellar career, University of Delaware physicist William H. Matthaeus has been elected to membership in the National Academy of Sciences, one of the most prestigious honors a scientist can receive. He joins a fellowship that has included the likes of Albert Einstein, Richard Feynman, Thomas Edison, Edwin Hubble and Vera Rubin.

Matthaeus is an internationally known expert on the sun’s dynamic, magnetic atmosphere — the heliosphere — including the powerful solar wind that shoots out from the sun at a million miles per hour, carrying electrically charged gas called plasma, the turbulence created by that wind, and the impact those interactions have on space weather. The geomagnetic storms created by explosive bursts of plasma from the outer edge of the sun can endanger astronauts and disrupt power grids, telecommunications and satellite systems.

In addition to his NAS membership, Matthaeus is a fellow of the American Association for the Advancement of Science, American Geophysical Union, American Physical Society, and Institute of Physics and is a winner of the James Clerk Maxwell Prize for Plasma Physics, the highest award given in that field. He has published more than 500 papers.

At UD, where Matthaeus has served on the faculty for 42 years, he was recognized with the highest faculty honor — the Francis Alison Award — in 2024. UDaily offers this Q&A to provide new insights into his work and legacy:

Q: What tilted you toward physics?

Matthaeus: When I was a kid, I engaged in all sorts of experiments. I had a number of chemistry sets (do young people today even know what they are?) and I used to build things with wires, batteries, light bulbs, switches, magnets and so on. I loved all science and always thought in terms of some device or experiment to do with it, or how to make it or take it apart and reassemble it. It was great fun. 

I cruised through biology and chemistry courses and was awarded the gold medal for top grades in both. But in senior year I took physics. It seemed too simple at first — just a collection of equations at the high school level. But not wanting to just memorize, I realized that the alternative was to understand why the math worked the way it did. Furthermore, this was the key to really getting at the underpinnings of all the electrical experiments I had always loved. I didn’t realize it, but I was starting to lean towards theory. 

Q: When did you begin to focus on space and the solar wind?

Matthaeus: In grad school at William and Mary, I attended a colloquium given there by David Montgomery, a renowned plasma theorist. I was hooked and asked to be his student. 

But then Prof. Montgomery was asked to chair a NASA committee with the goal of understanding if turbulence theory ideas could be investigated in space, and — in particular — in the solar wind. When his report was done, he forwarded it to me and proposed that I could go to Goddard Space Flight Center to implement the ideas in that report using spacecraft data. I wrote a proposal along these lines to the National Research Council that was accepted. 

After earning my Ph.D., I found myself at Goddard carrying out theoretical studies using experimental data from the two iconic Voyager spacecraft. I complemented the experimental/observational approach with computer simulations and analytical theory. I have spent much of the past 40 years pursuing studies using this multifaceted approach. 

Q: What would you say was the most exciting discovery you have been part of?

Matthaeus: Much of my work has been to understand how the solar wind is accelerated and heated. In the late 1990’s we formulated a theory of how turbulence accomplishes these major effects, which ultimately are responsible for the existence of the heliosphere as we know it. Turbulence refers to the complex dynamics of a fluid or plasma. It occurs due to nonlinear interactions and it influences flows and structures over a wide range of space and time scales. Over the last few decades this theoretical development has progressed from being a novel suggestion to a near universally accepted explanation. 

Q: Was there ever a time that you were discouraged and wondered if you should consider another direction for your life? If so, how did you overcome that?

Matthaeus: At one point in my academic career, there was a full professor who thought that I was not cut out to do physics research. This was perhaps because I was known to spend a lot of time playing basketball and my team won the university intramural championship. He said to me that in his professional judgment, I could not finish a Ph.D., and if I did, I would never be able to do research. I had to leave that program but ended up at William and Mary and that all worked out for me. I did not take his opinions seriously and just kept at it.  Once I started with research, I was firing on all cylinders. And here I am. Because of this history, I always tend to take the side of students who are stumbling or are being judged harshly on small evidence.

Q: How do you spot a promising student? And what trait(s) would you say is/are most important for a student who wants to pursue physics?

Matthaeus: I like to have students who have done well in courses and big exams. But it is even more important that when interviewing them they show enthusiasm for learning what needs to be absorbed to do research. I also prefer students who like interacting with their peers and who are not very competitive with each other. Teamwork makes the dream work!

Q: What is an example of knowledge or technology that exists now that you never would have expected when you started out?

Matthaeus: The construction and implementation of the Parker Solar Probe mission is simply mind-boggling in its technological accomplishments.

Q: What would you say to those who wonder why it’s worth the time and expense to understand what’s going on in space? 

Matthaeus: We live in the atmosphere of a magnetic star, which controls our immediate cosmic neighborhood and supplies Earth with most of its energy.  It’s pretty compelling to understand how the processes governed by the sun are operating. Knowledge of the underlying basic physical principles at work is needed to understand our environment in the cosmos.