On Aug. 6, Hopkins graduate student Regupathi Angappan was awarded the Future Investigators in NASA Earth and Space Science and Technology (FINESST) grant — a big grant fitting a big project like his. Angappan’s research uses the incredibly weak and “noisy” magnetic field of Mercury to help reveal the planet’s interior structure.
What drives his work is a passion for understanding why magnetic fields behave the way they do. And while his plans have changed numerous times along the way, he has no regrets about where he wound up.
In an interview with The News-Letter, Angappan explained that his research interests are broadly focused on the interiors of different planets.
“There are a few ways to study the interiors of planets,” he said. “I like to use magnetic field of planets to infer something their interiors. Up until now I’ve been working on Earth’s magnetic field to better characterize the shape.”
While his current research focuses on Earth, the FINESST grant will allow Angappan to apply his knowledge of magnetic fields to an extraterrestrial context.
“The next thing that I’m working on is looking at the structure of Mercury’s magnetic field,” he said.
The two most recent NASA missions to Mercury, MESSENGER and Mariner 10, gave scientists some insight into what Mercury’s incredibly small and weak magnetic field looks like. For the most part, however, they left scientists with even more questions.
“We have a rough idea of what the magnetic field looks like but it’s unlike any other magnetic field we’ve seen in the solar system. It’s offset... from the center of the planet,” he said.
Angappan is using computer simulations to try to gain a more accurate view of Mercury’s interior magnetic field, which is not an easy issue to tackle.
“One of the big problems with Mercury’s magnetic field is that it has a lot of external influence,” he said. “The magnetic environment around Mercury is very noisy. It’s very close to the sun, so there is a lot of very active magnetic activity in that region. It’s not easy to get an idea of what the internal magnetic field looks like.”
Angappan’s research uses a code called GAMERA developed at the Applied Physics Laboratory to perform “magnetohydrodynamic” simulations.
“We give the program some parameters and it will run the simulation and tell us what the magnetic environment is around the area,” he said. “Essentially, it’s a fancy model that gets rid of things that we don’t want and allows us to peer into the planet.”
From this data, Angappan will be able to infer things about the depth at which the field was created. While we have some idea of where that is, the range typically reported is huge.
“Just by the presence of a dynamic magnetic field, we know there has to be something flowing in the deep interior,” Angappan stated. “Each study, not just in our work, but all the studies that are being published, is just trying to get more and more evidence towards narrowing down this interior structure.”
Although the model won’t pump out chemical formulae or mineral structures, Angappan explained that it will allow him to broadly infer structural and compositional characteristics of Mercury’s interior.
Measuring Mercury’s magnetic field is notoriously difficult. With a slow rotation, and a close proximity to the sun, its field is very weak and noisy, which is why models like GAMERA are necessary.
“With Mercury because the magnetospheric currents are so strong, even when you’re within the magnetosphere you have all these externally driven currents contributing an external magnetic field of their own; that’s what we’re trying to account for,” Angappan said.
In his research, Angappan views each planet as a lab, each with a different method of creating magnetic fields. The end result, especially on Earth, is crucial for life: Earth’s magnetic field shields us from the high energy plasma which is emitted from the sun. More recently, the presence of magnetic fields has been discussed in the conversation surrounding extraterrestrial life.
“A big discussion in planetary science now is the question of habitability of other planets and exoplanets. Should we be looking for a magnetic field?” Angappan questioned. “Do planets like mercury, or of Mercury’s size — which is really small — have the capacity to shield?”
Angappan’s journey to Hopkins began in Malaysia, where he received his primary and secondary education. It was at the end of his high school career that he decided he’d like to join the medical profession. However since there was an abundance of doctors at the time, the Malaysian government reduced the number of medical scholarships available; this limited Angappan’s options.
With medicine out of the question, Angappan decided that he wanted to pursue something that he wouldn’t regret in the future, but also something that he was very interested in. Ultimately, he decided on a topic that had interested him as a kid.
“If I opened an encyclopedia, I really enjoyed the astronomy side of the encyclopedia. It was just really fascinating to me,” he recalled.
He also joked that he found physics a more suitable profession because of his disdain for memorization. According to Angappan, even the most complex equations are rooted in Newton’s second law of motion. The law states that the force (F) acting on an object is equal to the mass (m) multiplied by the acceleration (a) of the object.
“It all has to come back to an F = ma. That’s the beauty of physics and I love that. You don’t have to remember anything else. Just go from F = ma and derive everything else,” he said.
After applying to scholarship programs, Angappan received a full ride from PETRONAS — an oil and gas company — to study geophysics at the University of Washington. It was there, in an introductory geology course, that magnetic fields first captured his attention.
Angappan fondly recalled one of his professors explaining how ocean floor records revealed the poorly understood “flip-flopping” Earth’s magnetic field.
“That lecture really captured my imagination.” Angappan said.
Through that same professor, Angappan got his start in undergraduate research on paleomagnetism. Eventually, he applied to graduate schools and ended up at Hopkins.
When he’s not peering into the internal structures of planets, Angappan can be found painting and sketching, and attending weekly symphonies. Some of his work also includes trying to understand the lack of diversity in the geosciences and how to get a more diverse background of students involved.
“One of the biggest things that I always look up to is how to engage a large, diverse audience in any scenario,” Angappan stated. “We’re interested in engaging more people.”
One of Angappan’s main insights from his scientific journey is to let your interests guide you.
“Sometimes you’re sitting in a class because it’s a requirement for your major. You need to do that for your degree’s sake, but I think while doing that there’s a lot of things that you should do for yourself and your curiosity,” he said.
It is curiosity about the hidden workings of the natural world that led Angappan to prod the boundaries of math and computer simulations.
“We always say curiosity kills the cat, so maybe it’s not good for the cats,” Angappan joked, “but it seems to work great for us.”
