Dr. Sang-Yun Lee (He/Him)

Space Physicist
Geospace Physics Laboratory (673)

What inspired you to pursue a career in space sciences?

When I was in middle school, I had the chance to read The Elegant Universe, despite not being fond of reading. The book was written to make complex physics concepts easy to understand, and it allowed me to grasp, at least partially, ideas like the theory of relativity, quantum mechanics, and string theory—all without any equations. This sparked my enthusiasm for astronomy and physics, leading me to choose them as my first and second majors at university. Initially, my goal was to pursue a PhD in astronomy. However, after taking a course in space science and space weather, I found the subject more practical and engaging. This shift in interest ultimately led me to earn a PhD in space science.

I visited Iceland in October 2024 for a conference. During my visit, a solar flare erupted, triggering the second-largest geomagnetic storm (Dst < -300) in 2024. Although I couldn't see the aurora during the main phase of the storm due to cloudy weather, I was fortunate to witness an intense auroral display the following day. Iceland's breathtaking natural landscapes made the experience even more unforgettable, and I felt incredibly lucky to see the aurora amidst such stunning scenery.
Credit: Sang-Yun Lee

How did you end up working at NASA Goddard?

I had the opportunity to meet my current supervisor, Dr. AA, at a conference where she was advertising postdoctoral openings. Although I was interested, I hesitated to apply because the research focus was on the exosphere, which was different from my previous work. For nearly ten years, my research had been centered on plasma physics, particularly kinetic plasma simulations and radiation belt dynamics. At that moment, I took the time to reflect on what I truly wanted to pursue in my research. I realized that my passion lies in physics as a whole, not just plasma physics. I also recognized that my research could still be applied to plasma physics in meaningful ways. Now, I am very happy to be working here and thoroughly enjoy my current research.

Tell us about the research projects you are currently working on.

I am currently developing a dynamic model of Earth's exosphere called MATE (Model for Analyzing Terrestrial Exosphere). The exosphere lies above the thermosphere, typically at altitudes exceeding 500 km. At these heights, the neutral particle density is so low that collisions between neutrals can be neglected. Exospheric neutrals, particularly atomic hydrogen, play a significant role in the magnetosphere through charge exchange interactions with plasma ions.

However, existing exosphere models and observational data are quite limited. To address this gap, we are developing a dynamic exosphere model. In the future, we plan to integrate our model with other magnetospheric models to advance studies on energetic neutral atoms (ENA), soft X-ray imaging, and atmospheric loss.

What is one of your favorite moments in your career so far?

Of course, the best moment was when I received an offer from NASA. Working at NASA is a dream for many researchers in the fields of space science, astronomy, and aerospace. On top of that, I absolutely love the Goddard Space Flight Center in Maryland. The location strikes a perfect balance — it's neither an overly crowded city nor an isolated area. Additionally, there is a strong community of researchers in my field at GSFC, providing ample opportunities for collaboration and learning.

I enjoy hiking and often explore trails around the DC-Maryland-Virginia area with a local hiking group. It's a great way to stay active, connect with nature, and meet like-minded people. I'm especially happy to live close to Shenandoah National Park, which offers some of the most beautiful trails and scenic views on the East Coast. The landscapes around Shenandoah, along with other nearby trails, remind me of my hometown in Korea, which makes the experience even more special. Hiking also gives me the chance to unwind from work, clear my mind, and recharge for the week ahead.
Credit: Member of local hiking group

What is an interesting problem or hurdle that you've overcome in your work?

During undergraduate studies, we typically focus on theoretical concepts. We learn numerous equations, but rarely solve them in depth—they are often left as governing equations. For instance, in an electrodynamics class, we study the Poisson equation, which relates electric potential to charge density distribution. However, that's usually where it ends.

It wasn't until I began working in computational modeling that I had the opportunity to solve such equations on a discrete grid system. Solving the Poisson equation in multiple dimensions requires advanced techniques, especially for beginners. It took me several months to successfully solve it for the first time. Additionally, I began solving other partial differential equations and obtaining time-varying solutions, which I could visualize as images or animations.

This transition — from abstract equations to tangible, visual results — was a pivotal moment for me. It marked the beginning of my research journey in computational modeling.

If you were to expand your current research focus, what new topics would you explore?

My current research focuses on the exosphere and its impact on the plasma environment within Earth's magnetosphere. However, during my PhD, my work centered on plasma kinetics using Particle-In-Cell (PIC) simulations. I am passionate about both areas of research and am particularly interested in exploring topics that bridge the two — specifically, kinetic phenomena related to exospheric dynamics.

I sometimes go camping with friends, and I really enjoy the whole experience of being outdoors. One of my favorite parts is having a BBQ, grilling good food, and sharing a few beers while chatting around the campfire. It's a great way to relax, connect with friends, and enjoy nature.
Credit: Member of local hiking group

Tell us about a unique or interesting component of your work-life balance.

While most people work from morning to evening, I prefer working from the afternoon into the night. I find it easier to concentrate during the quieter evening hours. However, I still prefer working in the office rather than at home. As a result, when I leave the office, the parking lot is nearly empty, and there's little to no traffic, which saves me time on my commute.