Space weather researcher sees more than beauty in aurora borealis

Predicting space weather accurately is absolutely critical to our society. However, our ability to do so is terribly lacking and a far cry from meteorology. “It’s a little like if we knew perfectly well that wind from the North brings us cold weather, but we would have no idea what happens when the wind turns East or West,” says space physicist, Academy Research Fellow Lauri Holappa.

A familiar example of space weather is the aurora borealis, when charged particles from the Sun enter Earth’s magnetic field and flow toward the North and South poles. The particles react with the nitrogen and oxygen molecules in our atmosphere and create the colorful lights that we admire. Enormous coronal mass ejections (CMEs) from the Sun have the potential to create a massive magnetic storm, which could wreak havoc on our electricity infrastructure and communication systems. The time to react to such a storm is limited, as solar winds can move at speeds of 2,000 kilometers per second, which would leave a little less than 24 hours before they reach Earth.

In 1859 there was an exceptionally bright onset of auroras which could be observed far from the polar latitudes, even near the equator. While the skies put on an astonishing show for onlookers at the time, the auroras brought with them extraordinary and confounding side effects. Telegraph systems around the globe went haywire and even ceased to function. On the other hand, some stations reported being able to send messages even after unplugging the batteries from their transmitters, as if the air itself was carrying them.

During these exceptional auroras, a British astronomer named Richard Carrington observed a massive cluster of sunspots on the surface of the Sun and the first ever solar flare that was seen by a human observer. Soon the observation was linked to the off-the-chart readings of magnetometers and stunning auroras. The incident of 1859 became known as the Carrington Event and we are lucky not to have experienced a solar storm of that scale in our current era––that is, not yet.

The study and prediction of solar storms is closely linked to Lauri Holappa’s research. Holappa is conducting fundamental research in the Space Physics and Astronomy Research Unit of the University of Oulu. Holappa is not directly concerned with things like calculating the loads stressing our power grids, but rather he is interested in the effects of space weather and solar winds, because much of it is still unknown to us.

“The basic issue with this is the massive size and complexity of the system. Earth-based weather is very complicated, too, but we have a vast array of sensors and metering equipment to provide us with data. Ships measure the temperatures of the oceans, airplanes give us accurate data on the atmosphere and we have tons of ground-level instruments. By comparison, in space there are very few,” says Holappa.

A simple question belies a complicated phenomenon

Holappa’s research hinges on a very simple question. How do changes in the magnetic field of solar wind affect the precipitation of charged particles into the atmosphere? He takes to the blackboard to visualise the concept.

Earth’s magnetic field flows from the South pole to the North pole. On the day side, or the side facing the Sun, Earth’s magnetic field is squeezed against the surface of our planet, while on the night side the magnetic field opens up to form a kind of tail behind it. The magnetic field is responsible for life on Earth as it protects us from the constant bombardment of particles and radiation from the Sun. Solar wind and the accompanying interplanetary magnetic fields (IMF), however, open our magnetic field and let charged particles in.

“This is a phenomenon that we have understood well since the 1960’s. In a two-dimensional model the IMF opens Earth’s magnetic field, when these two magnetic fields are moving in opposite directions, for instance, one is moving North and the other South. The process clears a path for the particles from the solar wind to Earth’s proximity where the magnetic field carries them to the poles”, Holappa says and draws an arrow pointing down, or South, on the blackboard.

“But in reality, the IMF can point in any direction, which makes the whole phenomenon three-dimensional, and this we still struggle with theoretically”, Holappa continues, and draws the magnetic field to point in through the blackboard to the adjacent office and out of the blackboard to his office.

The properties of solar wind control the precipitation of electrons and protons into the atmosphere, which affects the way electricity flows in the ionosphere, the top section of the atmosphere. The changing flows of electricity in the ionosphere work like an induction stove in a kitchen: the flows induce current to terrestrial power lines much like an induction cooktop boils water in a kettle.

The exact way the flow of electricity in the ionosphere is linked to solar wind is a theoretical puzzle. Holappa is eager to access the data from the EISCAT3D radar when it becomes operational in the near future. Its measurements will shed light on electric currents in the scale of under 100 kilometers, which is unattainable by current methods. Holappa is lead researcher in the ICONIC project at the University of Oulu, which is poised to solve the challenges in space weather modelling.

“To understand this process would also make it easier to predict disturbances in power grids,” Holappa says.

Solar wind still carries many questions

Holappa says he was interested in space and Northern lights as much as anybody when he was young, but he never thought he’d be studying space when he grows up. In school he was interested in middle-distance running, but also physics and natural sciences. He ended up having a summer job with the space research unit, which in turn inspired him to direct his studies to astrophysics. Holappa got his doctorate in 2017 and he has been to the United States with two post-doc research positions at NASA Goddard Space Flight Center in the Washington D.C. area. He recalls giving a presentation on the impact of the direction of the solar wind’s magnetic field on particle precipitation to NASA researchers, who got very interested in Holappa’s research.

“They realised that this is an actual phenomenon and something to be studied and understood thoroughly. Turns out that things don’t go as expected. We had discovered something that inspired other researchers and that has led to a great amount of international collaboration and more research,” Holappa says.

In addition to his own research, Holappa is supervising two PhD students. Holappa is also working as an Academy Research Fellow in the MIDAS project that’s run by the Research Council of Finland and splits his time between this and the ICONIC project. The two projects are closely linked but differ in their research methods. The MIDAS project involves using high-performance computing in cooperation with NASA researchers.

There are many potential research themes in the chalk illustration Holappa outlined on the blackboard in his office, and he says he is quite content with his own research and directing his PhD students. Space weather research is progressing at a healthy clip and is catching up to meteorology all the time. The launch of small satellites, or smallsats, is becoming more affordable with commercial operators, which means that researchers don’t have to rely solely on large organisations like NASA or ESA. Advances in computing power is helping also with the so-called empty space problem, as it becomes possible to make more and more accurate models of space weather, which is something that Finland has a high level of expertise in.

But what does an astrophysicist see, when he looks up at the Northern night sky and sees aurora?

“I am checking online to see real-time data on solar wind and measurements from the Sodankylä Geophysical Observatory and try to deduce if the aurora will grow stronger or weaker. There is so much we still don’t understand about aurora borealis as they are such a complex, dynamic phenomenon. The complexity pulls me in, but of course I can simply admire a vibrant aurora as much as anyone else,” Holappa says.

Lauri Holappa's research profile: https://www.oulu.fi/en/researchers/lauri-holappa

ICONIC-project: https://www.oulu.fi/en/projects/iconic

The list of the Kvantum Institute's Emerging projects 2023-2026.

Story: Janne-Pekka Manninen
Photos: Janne-Pekka Manninen, Lauri Holappa