The DUJS talked to Mary K. Hudson, Professor of Physics and instructor of popular introductory physics courses, many of which are open to both undergraduate and graduate students, to gain insight into her life as a researcher, mentor, and teacher.

What was your path to becoming a professor at Dartmouth?

I knew just from when I was a little girl that I wanted to be a physicist, though I don’t think I really knew what that meant at the time. I had seen this wonderful program when I was a child called “Our Friend the Atom” by Walt Disney. Back before PBS and Nova, Walt Disney would have a science special once a month. I got the book that went with the program and got very excited about what I had perceived as physics and an understanding of the physical world. I went on to major in physics at UCLA, and right at the time I graduated-I graduated early, in March-I had six months before starting graduate school.

I had already decided to go to graduate school in physics, but I hadn’t really decided what kind of physicist I wanted to be. I had been working with the experimental cyclotron group at UCLA as an undergraduate, which was a particle accelerator that we had on campus that people used before they went off to Europe to do their particle physics experiments. Because I graduated early, I interviewed with some California aerospace companies to find a six-month job. I went to work for The Aerospace Corporation, which does the technical management of the Air Force space program. It is a non-profit chartered-by-congress corporation, sort of like NASA for the Air Force. I was working with a research group there and I just had gotten really interested in space physics; I knew when I started graduate school that I wanted to do this. I grew up in the era of Sputnik and Apollo, so I was primed to be excited about space. I had decided to stay on at UCLA because they had a really good program in space physics and plasma physics, the study of ionized gases, which is what most of the space near earth is. I pursued my Ph.D in space physics at UCLA; I actually stayed on for two years at The Aerospace Corporation, my first two years of grad school, because they were giving me research projects, and I thought, “Well, this is pretty exciting stuff!” They were really at the cutting edge out there, so I stayed with them while I was taking classes.

In the process of working on my research project for my Ph.D, I started interacting with the experimental group at UC Berkley at the Space Sciences Laboratory. The group has now built its own satellites. Even back then the group was involved in a lot of NASA projects, so I decided that it was where I wanted to go after I got my Ph.D. I went up to Berkley for a post­doc, and I wound up staying there for 10 years. I built my own research group and I got funding from NASA, NSF, and NOAA, the National Oceanic and Atmospheric Administration. I taught a couple of classes at Berkley, and some classes at Mills College in Oakland. I knew I wanted an academic position, so when the opportunity for the position at Dartmouth came along, I applied. Professor Sonnerup over at the engineering school was on a search committee for this department. Whenever Dartmouth has a “senior hire,” they tend to have people on the search committee not just in one department but

somebody from another related department. At that time, Professor Agnar Pytte was leaving this department to become Provost of the College; he was a plasma physicist. Then, the junior plasma physicist Chris Celata decided to go to Berkley. I applied for the position here, and David Montgomery applied at the same time. We were both hired as two new people in plasma physics; my focus really is on space plasma while David has worked with both space and laboratory plasmas. We both came in 1984, and it was pretty exciting to be starting up anew area within the department focused on space physics.

Before I came here, no one was doing space physics in this department. Professor Sonnerup had been doing space physics over at the engineering school and that’s how he knew me and encouraged me to apply. It really makes a difference when someone encourages you to apply for a position. You take it more seriously. So, I came in 1984, and my husband Bill Lotko came at the same time. He is a professor at the engineering school now so we were both able to work out appointments here at Dartmouth in two separate departments. That’ s how I got to be here at Dartmouth!

What does your current research focus on?

I study the near-earth space environment and the effect of solar activity on the near-earth space environment. In particular, right now I’m focusing on the Van Allen radiation belts. I didn’t always work just in this one area. I started out working on disturbances of the equatorial ionosphere that affect communications near the equator and then I migrated to high latitude and worked on auroral processes and then lately -over the last decade or so-I’ve been working on the radiation belts and how they are affected by solar activity. They’re very dynamic, actually. Particle flux levels have been relatively quiet the last couple of years because we’ve been at solar minimum, but now we’re starting to come out of solar minimum. Sunspot numbers are increasing and solar activity is increasing. But, by 2012-2013, we’ll be at another solar maximum. I’m involved in a number of research projects that are aiming to do experiments at that time. Professor Robyn Millan, in this department, has a balloon program that’s going to launch balloons at that time. I have a meeting I’m going to tomorrow [May 26, 2010] in Minnesota that pertains to one the instruments on a pair of satellites that will be up at that time.

Can you tell me a little about the upper level physics courses you teach?

I taught Physics 13 and 14-Introductory Physics I and II- last year, and I’ll be teaching P14 next spring. This year, I taught a sequence of three courses that I do every other year. Physics 68 in the fall is the Introductory Plasma Physics course, so ionized gases in space and in the laboratory. In the winter, I taught a graduate level course that follows on to that, Kinetic Theory of Ionized Gases. Then this spring, I taught Physics 74, Introduction to Space Physics. Both the fall and the spring courses are open to undergraduates as well as graduate students, and typically I have some of both in those courses.

How, as a professor, do you inspire students?

I like to think I get students excited about my research. Yesterday was particularly fun for me in the P74 class; it was my last regular lecture of the term. I gave the students a long

version of a talk that I’m giving tomorrow [May 26, 2010] at the University of Minnesota, describing the dynamics of the radiation belts. I think I can be particularly inspiring when I’m talking about my own research, although I try to give them the broader picture of things. I’ve also engaged undergraduate students in research. I have a Presidential Scholar working for me and have had students work during off terms for me. Right now I have two graduate students that I’m the principal supervisor for.

Schematic of the Van Allen radiation belts.

Schematic of the Van Allen radiation belts.

Can you describe the role of a faculty member on an undergraduate’s research experience?

Well, it depends on the project. My work is computational and compares results with data taken by satellites. I tend to have to encourage students to develop their computer skills. I encourage them to take a course like ENGS 20, for example, which is a good course at the engineering school-Introduction to Scientific Computing (from the point of view of engineering). Other people in the department who are doing experimental work have students actually involved in hardware building and designing. I was on a thesis committee yesterday; senior Umair Siddiqui worked with Professor Kristina Lynch, who has a large plasma tank in the building (Wilder). He designed an electron and ion gun that can inject a beam of particles into a preexisting ionized gas, which simulates what happens in the aurora when auroral electrons hit the atmosphere and the ionosphere. They are going much faster than the average particles in the atmosphere and ionosphere. They’re trying to simulate that in the laboratory, and they use it to calibrate instruments that are flown on rockets in Alaska and Norway and so on. He built and designed this amazing, amazing device.

How broad of careers do physics majors pursue?

We usually have 12 to 22 physics majors I would say, usually in the high teens. About a third of them go directly to graduate school. Umair is going to the University of Wisconsin, we have one senior going to Berkley, another going to CalTech, and that’s pretty typical. Then, others in the group are going to Penn, YaleÉ good places. A third of them will take a year off and work, think about going to graduate school, and try to get a better grip on what it is they want to do long term. Probably a third of them go to a professional school: law school, medical school, and so on. That’s kind of a broad cut through what our students do. Of those who work for a year, some go to graduate school in physics and some go to graduate school in other areas.

What are some of the big recent discoveries in physics?

Oh wow, that’s a harder one to answer! I’m very familiar with the discoveries in my own field. In physics in general, there are going to be some amazing discoveries. Every time you build a new instrument, every time you put new instruments on satellites, you discover new things. New instruments are like opening up a new piece of the electromagnetic spectrum that had not been seen before. The same is true for particle physics; there are going to be some amazing discoveries with the Large Hadron Collider that’s just started in Switzerland. But in space physics-for example, with the earth, we have had a lot of spacecraft around the earth over the past 40 years, but where we’re making advances is with higher and higher resolution measurements and better spatial resolutions.

Most of the early measurements were made just with single spacecraft where you don’t get any space -time resolution because you just have one point measurement. Now, recently, there have been spacecraft including the THEMIS spacecraft that the Berkeley group built and flew in the last few years. There are five spacecraft that are designed to study relaxation oscillations, called substorms, of the magnetosphere, the region of space occupied by the earth’s magnetic field. The basic internal mechanisms of the magnetosphere where these relaxation oscillations

are triggered were not well-known, because we only had single point measurements before the THEMIS satellites. A lot of progress has been made with that particular program.

Of course I was excited by the measurements two solar cycles ago of how dynamic the earth’s radiation belts are that were made with a combined NASA-Air Force satellite called CRRES. In recent years, it has been two solar cycles -20-some years-since we’ve had satellites in that particular orbit. We tend not to fly satellites through the radiation belts that we want to survive very long because it’s a very hazardous place for electronics and so forth. We have not had satellites exploring that region now since 1990-9 1, and that is the region we are going to explore again in two years with the Radiation Belt Storm Probe satellites that I’m involved with. I think we’re going to learn a lot because there is a pair of satellites rather than just a single one, and so we’ll get more information from the pair where we can study spatial gradients and separate out something that is just a boundary in space from something that is changing in time. I can’t really speak for condensed matter-a whole other area of physics that people in the department are engaged in-but I’m pretty excited about the measurements that are going to be made in the next couple of years in the area I work in.

What do you enjoy doing outside of academic work?

I really enjoy hiking. My older daughter, an ’06, went to Nepal two years ago and did the Annapurna Circuit. She talked my husband and me into going to Ladakh, the Indian Himalayas. We went trekking in Ladakh last August and went over 3 passes between 15.5 and 16.5 thousand feet. It was just an amazing experience; it’s not just the mountains and the altitude and so on, but just seeing a completely different part of the world like Ladakh. We also got some appreciation of the tensions of Northern India, because this particular region is surrounded by Pakistan, the Xinjiang province in China, and Tibet on the three sides. It’s a spectacularly beautiful region. In the wintertime, I like backcountry skiing and winter hiking.

Do you ever plan to or want to travel to outer space?

No, I think I will not be going along for the ride–that is a little too high altitude for me at this point, but I do think that your generation will. Commercial access to space is coming along, and people of your generation will go to space just like I went to India last year. The more adventurous people will be doing that in their lifetimes. I envy you!