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Dartmouth engineering professor awarded Humboldt Prize for space physics research

Posted 06/01/01

Bengt Sonnerup, the Sydney E. Junkins Professor Emeritus at Dartmouth College's Thayer School of Engineering, has been awarded the prestigious Alexander von Humboldt Prize by the Federal Republic of Germany. The prize honors scholars living outside of Germany whose academic qualifications have earned an international reputation. The award recognizes Sonnerup's ongoing space physics research on the magnetopause, a narrow layer in space sandwiched between the earth's magnetic field and the sun's plasma emissions or solar wind.

His research aims to better understand how mass, momentum and energy from the solar wind move through the magnetopause.

"My work contributes to an important piece of the space weather puzzle," said Sonnerup. "By understanding processes in the magnetopause region, we might someday be able to better predict and prepare for the effects of space weather."

The goal of studies like this is to enable scientists to predict how severe space weather, caused by explosive mass ejections from the sun, make themselves felt near earth. There are important implications for the hundreds of orbiting communications and other satellites, like those supporting the global positioning system (GPS).

These satellites may be damaged by intense particle radiation or unexpected changes in the magnetic field during storms. Radiation is also a hazard for astronauts and for flight crews on high-flying aircraft. Disruption of radio communications and radar systems, as well as power grid surges and outages, may result from space storms. The brilliant displays of northern lights, seen in northern New England, also occur during space storms. The solar wind is a mixture of ions, mainly protons, and electrons in equal numbers. This gas is extremely thin, but it moves at high speed and has the momentum to compress and strongly distort the earth's magnetic field.

Gathering data from the magnetopause is tricky, however. It moves quickly, and it can take on unusual shapes.

The magnetopause bends and wiggles in response to changes in the solar wind, and it may swing past a research spacecraft at speeds in excess of 100 kilometers per second in response to sudden gusts or lulls in the solar wind. Such rapid motion can make detailed observations difficult.

Additionally, the magnetopause does not simply wrap around the earth like an orange peel; it is shaped like a comet, with the head facing the sun and a long tail, caused by drag against the solar wind, on the opposite side. The earth, with its magnetic field in the path of this fast moving plasma flow, creates this configuration. As research satellites briefly pass in and out of the magnetopause, they gather data on the electromagnetic field and plasma behavior.

The Humboldt prize will allow Sonnerup to spend nine months in Munich working with German colleagues to interpret new raw data from a recently-launched cluster of four satellites, all making measurements at the same time, but at slightly different points in the magnetopause.

"These unbelievably sophisticated spacecraft are gathering vital information," said Sonnerup. "While I'm in Germany, my colleagues at the Max Planck Institute for Extraterrestrial Physics and I will concentrate on analyzing the data and help the research leap forward. With data from four spacecraft flying in close formation, we will be able to distinguish between spatial and temporal variations to get better insight into the structure and dynamics of the magnetopause region. The spacecraft are making measurements in the high-latitude regions of the magnetopause about which little is known at present."

Over the past few years, Sonnerup and his students have developed advanced analysis techniques for the data gathered at the magnetopause. In 1999, they learned that the magnetopause is not uniform; it appears to have a structure that looks more like a bumpy snake or a pearl necklace. These bumps, called arrays of magnetic flux ropes or magnetic islands, may facilitate mass and energy flow into the magnetosphere.

"After we analyze the data from the four spacecraft, we'll have a much better understanding of these flux ropes and the role they play," he said.

The Alexander von Humboldt Foundation, named after the 19th century German explorer and natural philosopher, is a non-profit organization established by the Federal Republic of Germany for the promotion of international research cooperation. It enables highly qualified scholars not resident in Germany to spend extended periods researching in Germany and promotes the ensuing academic contacts and collaborations. The award is intended as a tribute to the lifelong academic and research accomplishments of award winners. The Foundation's first post-war president was Nobel Prize-winning physicist Werner Heisenberg, and the long list of past Humboldt awardees now includes more than 30 Nobel Prize winners in Chemistry, Physics and Medicine.


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