"I have a liking for the sun." This is the motto Louise Harra uses to headline her Twitter account. Indeed, the Northern Irish-born astrophysicist has devoted her entire research life to our central star. For three years now, the astrophysicist has been the head of the 'Physical-Meteorological Observatory Davos' (PMOD), a research institution rich in tradition for the exploration of the sun and the exact determination of solar radiation.
On the day of our conversation, it is gloomy in Davos. The sky is overcast, winter is on its way. Even though the Davos sun does not always shine, there were good reasons to build a research facility for measuring solar radiation up here, 1560 metres above sea level, in 1907. "We have significantly more sunny days than in the cities of the Mittelland. At our altitude we have clear skies, which are very important for the work of our institute," says Louise Harra. "The fact that it also snows here from time to time and that the sun disappears early behind the mountain tops are things we can live with well."
The original standard for solar radiation
The institute Louise Harra is talking about is the 'Physical-Meteorological Observatory Davos' (PMOD). Harra has headed the facility, housed in a former school building, since 2019, and around 60 scientific and technical experts work here. One of their central tasks is to measure solar radiation so precisely that this measurement can be used as the original standard. To do this, they use an observation instrument consisting of six meteorological radiation measuring instruments (cavity pyrheliometers). With this so-called 'World Standard Group', solar radiation has been measured in Davos since 1971 on behalf of the World Meteorological Organisation in order to calibrate solar measuring instruments worldwide and thus make their measurements comparable. Thanks to this mandate, the PMOD also bears the name 'World Radiation Center'/WRC.
The measurements of the PMOD/WRC are of central importance for weather research including forecasts, but also for the global solar industry. The Davos precision measurements also play an important role in maintaining quality standards in global climate monitoring programmes. These programmes are based, among other things, on long-term observations. Meanwhile, the Davos Research Institute has measurement series spanning over a hundred years.
Expert on solar flares and solar wind
In her personal research, Louise Harra focuses on the sun itself, or more precisely: on the processes that take place in the sun's atmosphere. One focus is solar flares, i.e. rapid discharges of enormous amounts of energy on the surface of the sun. A second field of research is the solar wind, the particle beam of protons and electrons emitted by the sun. Louise Harra conducts basic research. But the results also have practical significance, for example in describing space weather. This refers to weather-like phenomena that are caused in space and near the Earth by solar wind and cosmic rays and which, in the worst case, can affect flight operations or technical equipment of industrial and electricity companies on Earth. "Our forecasts for space weather today are still as rudimentary as the forecasts for Earth weather 50 years ago. Solar research is helping us to improve them," says Harra.
Today, the exploration of the sun is mainly done by spacecraft. Space probes equipped with measuring devices approach the sun as far as possible. There they record the data, which are later evaluated and interpreted on Earth. After completing her PhD at the University of Belfast, Louise Harra went to Japan and worked in a team of scientists for the satellite-based Yohkoh space telescope, which took several million X-ray images of the Sun from 1991 to 2001. In 1995, she moved to England to the University of Birmingham, from where she works for the SOHO solar and heliospheric observatory, among others. The European Space Agency (ESA) mission, launched in 1995, continues to this day. The PMOD/WRC is involved in one of SOHO's measuring instruments, which observes the variability of solar radiation. Later Harra moved to University College London. She worked there for about 20 years and was involved in various space missions during that time.
Promoting diverse research teams
"Before I came to PMOD/WRC three years ago, I was all about space," says Louise Harra with a smile. "Now I do solar research from Davos, which brings my research down to earth, if you will." In February 2020, her last business trip before the Corona pandemic took her to the launch of the Solar Orbiter space probe, which aims to find out what causes the solar wind. In addition to research, Louise Harra now has other commitments: She teaches as a professor of solar astrophysics at ETH Zurich. In addition, she is the administrative director of a PMOD/WRC. In doing so, she is also confronted with the gender issue. "I prefer to talk about 'diversity' rather than 'gender'," says the institute director, "Diversity advances research." To ensure diversity in the research teams, Harra says there is no need for positive discrimination. What is important is flexible working conditions for all employees, depending on their family situation. "With us, the best application gets a chance, regardless of gender." Today, female scientists prevail thanks to their competence, she says, referring to her last job in London. There, she says, she was the only woman in her research group in 1995, and when she left in 2019, it was an equal mix of men and women.
Author: Benedikt Vogel
Portrait #10 of Women in science in the fields of MAP (2021/22)