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Researchers follow Hannes Alfvén's path of discovery

50th anniversary of KTH professor's Nobel Prize

King Gustaf VI Adolf of Sweden presents the Nobel Prize in Physics to Hannes Alfvén in 1970.
King Gustaf VI Adolf of Sweden presents the Nobel Prize in Physics to Hannes Alfvén in 1970. Photo: Nobel Prize Museum
Published Oct 06, 2020

On the 50th anniversary of Hannes Alfvén’s Nobel Physics Prize, researchers reflect on the KTH scientist’s contributions to our understanding of space, and the paths of discovery they continue to forge.

He’s revered as one of the founders of the field of plasma physics, yet Hannes Alfvén had to earn his 1970 Nobel Prize the hard way. At the height of the Second World War, the late KTH physicist published a brief paper in the letters section of Nature which would change the course of space physics, but not before years of dismissal and resistance from his peers.

“Alfvén was working out what is happening with sun spots,” says Andris Vaivads, professor of space physics at KTH. “And he found that there is a form of electromagnetic wave that moves through plasma, including the solar winds, which he called magnetohydrodynamic (MHD) waves.”

Göran Marklund , left, and Anris Vaivads pose for photo outside their research labs.
Göran Marklund, Professor Emeritus of plasma physics at KTH, left, and Andris Vaivads, Professor of space physics.

Alfvén’s extensive contributions to plasma physics are the basis for work that continues to this day at the KTH Space and Plasma Physics Division, where Vaivads and others are currently involved in space missions to the Sun, Mercury, Jupiter and near Earth space.

Widely held belief about electromagnetic waves

As late as the late 1940s, electromagnetic waves were widely believed to penetrate only a short distance in a conductor. The better the conductor, the less these waves could propagate.

Years after publishing his discovery, Alfvén delivered a lecture at the University of Chicago where Enrico Fermi was working on cosmic rays, and he presented his idea that these low frequency oscillations could propagate in a perfect conductor, such as the ionized gas of a star, or our own Sun.

A closeup look at instruments used by Alfvén for measuring electromagnetic waves in the lab.
A closeup look at instruments used by Alfvén for measuring electromagnetic waves in the lab.

According to accounts of the event, the audience was skeptical. Could these MHD waves exist? Fermi replied, “Of course”, giving the audience the validation Alfvén’s theory had been denied.

Now known as Alfvén waves, the phenomenon has provided generations of scientists a breadcrumb trail through key areas of space study, including Earth’s aurora, planetary magnetospheres, solar wind and radiation belts, among other subjects.

“The universe is more than 99.9 percent plasma, a kind of charged gas, so space is not a void … there are structures throughout the space plasma regions and within there are these waves,” Vaivads says.

New understanding of aurorae

The most familiar example of their effect is the Northern Lights, which Alfvén studied and described in groundbreaking papers that provided a path forward for generations of physicists, including his own student, Göran Marklund, who today is Professor Emeritus of plasma physics at KTH.

A closeup view of the Nobel Physics citation presented in 1970.
Alfvén's Nobel Physics citation is on display in the Division of Plasma Physics.

Even though Alfvén’s laboratory simulations and measurements proved to be accurate, “Alfvén argued strongly for measuring electric fields in space,” Marklund says. “He suggested that static electric fields are responsible for creating aurorae. This was in 1958, before there were any space missions or satellites to measure the particles.”

Unsupported by space observations, the idea would remain unproven until 1960. Later, in the 1990s, researchers at KTH were able to detect surprising activity in auroral electric fields thanks to the higher resolution measurements taken with satellites such as Viking, Freja and Cluster.

Working with space mission observations

Drawing on data from a series of space missions spanning some 40 years, Marklund is one of several space plasma physics researchers who carry on the work at the Alfvén Laboratory, helping to shed new light on how Earth' magnetosphere interacts with solar flares or ejections, and the dynamics of aurorae formation.

The Parker Solar Probe is one of the latest platforms the KTH scientists are working with, examining measurements the spacecraft collects on its path closer to the Sun. “One of the big surprises is this huge amount of high amplitude Alfvénic waves coming from the sun,” Vaivads says. “They’re probably heating up the solar atmosphere, or corona, which drives space weather,” he says.

Marklund and Vaivads inspect a measuring unit that will be launched to Mercury.
Marklund and Vaivads inspect a free-flying unit that collected measurements of electric field and plasma properties after being ejected from the SPIDER-2 rocket in the spring. Led by Associate Professor Nickolay Ivchenko, the rocket mission was launched to take measurements in a part of the ionosphere that cannot be explored by satellites.

One of the big questions they hope to answer is, why and how is this happening?

Today with higher and higher resolution measurements from missions run by Sweden’s own space program as well as ESA and NASA, Marklund, Vaivads and their colleagues enjoy an advantage Alfvén lacked in the pre-space age. Though even years after his Nobel award, the legendary theorist still tussled with his critics.

Explore plasma physics education and research at KTH

image of Earth's magnetosphere and the four MMS mission spacecraft in space.

The legacy of Hannes Alfvén continues at the Division of Plasma Physics at KTH. Explore our first and second cycle studies and doctoral education, as well as the research that continues to reveal the mysteries of the universe.

“I remember that when I was about to publish my first paper,” Marklund recalls asking his then-supervisor in the early 1980s. “I said, ‘Will you be on my paper as co-author?’ And he replied. ‘Oh no. You’d have no chance of being published if I’m on the paper.’

“He suggested that I submit the paper in Nature, where it got published”.

“Alfvén broke new ground and provoked many scientists over his career – he essentially declared war on some of his opponents,” Marklund says.

Story and photos:
David Callahan

Existence of Electromagnetic-Hydrodynamic Waves . Nature (1942) doi: 10.1038/150405d0

The Heritage of Hannes Alfvén , Physics and Chemistry of the Earth (1997) doi: 10.1016/S0079-1946(97)00182-1

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Last changed: Oct 06, 2020