Postcards from Science: Studying Terrestrial Gamma Ray Flashes from Ishikawa, Japan
Today’s blog post marks the beginning of a series called ‘Postcards from Science’ which features science conducted by UCSC researchers in other parts of the world. The series will explore not only the details of the research, but also why the location is ideal, and what kinds of surprises and challenges the scientists encountered. Join us as we simultaneously explore groundbreaking research and our own planet.
Studying thunderstorms might evoke images of meteorologists analyzing weather patterns, chasing storms through the plains of the United States, or perhaps even Benjamin Franklin flying a kite. However, the discovery of bursts of high energy radiation associated with thunderstorms less than 30 years ago called for many more creative and novel techniques. These bursts, called terrestrial gamma-ray flashes (TGFs), are studied by researchers at UCSC. Physics Professor David Smith leads the group, which also includes current graduate student Greg Bowers.
The microphysics of TGFs is well understood, but characteristics of the flash are not. Essentially, you have an electric field in a thunder cloud, and electrons being accelerated in that field. The acceleration of electrons is what produces the gamma rays. “It’s pretty basic physics from that regard,” says Dr. Smith. “Why they’re bright and so sudden, is something that’s still pretty wild.” There are several models, and their group aims to differentiate between the models based on observations.
To observe TGFs, Dr. Smith’s group built the Airborne Detector for Energetic Lightning Emissions (ADELE), an instrument made to fly on airplanes. When Greg joined the group in 2011, he worked on getting ADELE ready to fly, including rigorous NASA flight certification of the instrument. Unfortunately, two flights of ADELE did not result in any TGF observations. “They were amazing experiences, but they were kind of disappointing because we didn’t see a lot of science,” says Greg. Despite investing significant time and effort, one of the reasons they didn’t see any TGFs was simply because there were fewer hurricanes, and thus less thunderclouds to produce TGFs, that year. But of course physicists are problem solvers by nature, so the group sought out other ways to observe these seemingly elusive TGFs. “I felt like a way to try get more science was to do more with the instrument that we had,” says Greg. After all, it was only taking data for a few months, once per year. Researchers in Florida utilize detectors that have been operating for at least a decade, resulting in two TGF observations. However, this requires significant time and resources. Greg’s thought was, “Well, if there’s another location somewhere that has lots of lightning, we can just sit there.” His thought led their group to the next phase of the project and 8000 kilometers across the Pacific Ocean.
The key to exact location selection is to find a place where the instrument can be close to the charge center of the cloud — where we expect to see the most high energy emission. Greg notes that “For whatever weird meteorological reason, Japan gets low thunderstorms in the winter.” On the west coast of the country, near Ishikawa prefacture, there is a region where the charge center of the thunderclouds come less than half of a kilometer above the ground (compare this to Florida, where charge centers are 10 kilometers above the ground!). If they could place their detector in that part of the country during the winter, there was a good chance of observing TGFs from the ground. Using spare lab parts and recycling the instrumentation, their group built an instrument deployable on the ground: Gamma-ray Observations During Overhead Thunderstorms (GODOT). GODOT actually consists of five detectors. Three are for science and two are for measuring noise. The three science detectors are all different and allow for a large dynamic counting range. After successful testing in Mexico, GODOT was ready for data taking in Japan.
By utilizing contacts from Dr. Smith’s former student Nicole Kelley, their group found out about an ideal location to deploy GODOT: an abandoned elementary school in Japan. While in Japan, their host would be Dr. Masashi Kamogawa at Tokyo Gakugei University. His research group also studies lightning related phenomenon. Dr. Kamogawa connected them to Dr. Atsushi Matsuki at Kanazawa University who was able to secure them a spot on the roof of the abandoned school. This school, Kodomari Elementary, is in Ishikawa, and was taken over by weather research facilities instead of left to deteriorate. Dr. Smith’s group is not the first to study lightning from the roof of this school. Japanese researchers use radiation detectors from power plants to study longer duration high energy emission. As Dr. Smith says, “They’re good detectors, but they tend not to have a high speed data read out. They’re looking for a cloud of radiation wafting over you, not millisecond pulses.” They wouldn’t be able to detect TGFs like the UCSC group hopes to do.
The instrument is ready. The location is set. What can go wrong, you ask?
While the group’s research aims to answer questions relevant to all world citizens, we are in fact living in a world that makes divisions based on country. A result of this is that moving valuable goods across borders is non trivial. “The most difficult thing about this entire experience, for me, wasn’t so much anything that had to do with building the instrument or doing the calibrations, it was trying to figure out how to get it through customs,” says Greg. The customs officials would be deciding whether or not the instrument was something that you could sell upon entry into Japan. If they decided it was, they charged you a tax on it. With an instrument as valuable as GODOT, this tax wasn’t feasible to pay–even though it would be reimbursed when the instrument returned to the U.S. To get around this, they obtained a carnet, which is a document permitting temporary import and export. As Dr. Smith puts it, “It’s like a passport for goods.” The company issuing the carnet pays the tax for you, for a smaller flat fee, and deals with the reimbursement.
Greg comments that the fun didn’t stop once they obtained the carnet: “The other thing is that when you check something on the plane, they have their overage fees based on weight and size. If it’s over 100 pounds, they won’t carry it no matter how much you pay them. The instrument and everything was 115 pounds.” So Greg took out the NaI detector, which solved the problem of the weight overage. However, the detector qualified as a “clubbing object” which are banned from being carried onto a plane. After being escorted out of security by TSA and missing his flight, a worker at the airline company got Greg on a another flight and safely to Tokyo. Perseverance sure pays off in science!
Meeting up with his Japanese hosts allowed Greg a glimpse at a few cultural differences. One in particular related to the research lab. There were about a dozen undergraduates working in the lab on different projects. The lab itself had a more homey feeling than most research labs in the U.S. They would cook dinners together there, and was a very welcoming place to be. A second unexpected cultural difference was the requirement to remove shoes at the entrance of each building. Slippers were provided, instead. This Japanese tradition is now a part of the etiquette and culture, and Greg says he will be bringing warmer socks on his next visit.
After all the work to get their instrument to Japan and back, the data do look promising. In fact, Dr. Smith’s team is hoping to bring GODOT back to Japan in the near future to take more data. Their creativity and perseverance in the face of previous null results is the sort that drives fields of research forward. It is a necessary quality in scientists. Greg’s experience with customs and the challenges bringing equipment into a foreign country are a good reminder that the challenges facing scientists are not contained to a lab or to instrumentation. Conducting research away from the comforts of our home town, city or state highlights a unique intersection between science and culture. We are able to look at the world through the eyes of global citizens, not just citizens of individual countries.
Edit: An earlier version stated that Greg joined Dr. Smith’s group in 2009, but in reality it was 2011.