“We have conducted extensive measurements associated with a specific geomagnetic storm over the Arctic in 2014, and here we have found that electrons in large quantities were almost vacuumed out from areas that extend over 500 to 1000 kilometres. It happens just south of an area with strong increases in electron density, called patches,” said Professor Per Høeg from DTU Space. The new research has been carried out by the National Space Research Institute at the Technical University of Denmark (DTU Space) and collaborating international partners from NASA’s Jet Propulsion Laboratory (JPL) and the University of New Brunswick (UNB).
A surprising mechanism at play
The research indicates that there is a surprising and previously unknown mechanism at play in the geomagnetic storms. Solar activity usually tends to increase the rate of ionization in the atmosphere and thus the density of free electrons in the ionosphere or to move electrons to the polar caps. The research show that the opposite, a depletion of electrons, can take place. “It is a surprising discovery; one we had not expected. But now we can see it happening in other data sets from Canada, which indirectly support our new observations,” said Per Høeg. The new research also provides a host of other insights that increases the understanding of how such geomagnetic storms affect the Earth’s atmosphere and could possibly lead to improved radio communication and navigation throughout the Arctic. The results of the research have been published in the American Geophysical Union’s scientific journal Radio Science and featured on its cover.
The discovery is an important piece of the puzzle in understanding geomagnetic storms and their impact on the Earth’s ionosphere. Major geomagnetic storms can put astronauts on the International Space Station and those on future interplanetary space missions in danger, damage satellites, cause failing radio communications, and harm electricity grids and pipelines and so have extensive and costly consequences for society. Studying and understanding geomagnetic storms are hence fundamental for global public and financial safety.
Magnetic fields from Sun and Earth connect
The known phenomenon of adding electrons to the ionosphere also occurs at high latitudes. It happens because the sun’s magnetic field, carried along with the stream of particles following a solar eruption, interferes with the Earth’s own magnetic field, fundamentally connecting with it. Particles, including electrons, in the solar outburst can penetrate the ionosphere, following the Earth’s magnetic field lines, which converge at the poles. The explanation for this phenomenon lies presumably in the processes taking place in the Earth’s magnetic field in the direction away from the sun. Massive changes take place in the magnetic field composition in the area between the solar wind – the stream of energetic particles flowing from the sun – and the Earth’s magnetic field and this triggers powerful energy transfers. “The forerunner of the phenomenon is a violent eruption on the sun’s surface, called a coronal mass ejection, or CME, where the sun bubbles up, and slings ‘hot’ magnetized plasma in the form of very energetic ions and electrons in the direction of Earth,” said Per Høeg. The geomagnetic storm in the ionosphere over the Arctic in February 2014 was measured via satellites and from terrestrial stations. Among other sensors the GPS network GNET in Greenland provided a wealth of data.
Critical factors in satellite navigation
The research goes beyond the discovery of electrons being sucked out of the ionosphere during solar storms. “There are two aspects of the research. First, it can be used for practical purposes;, also there is a theoretical part, which is about fundamentally better understanding these phenomena,” said Tibor Durgonics who is a Ph.D. student at DTU Space and the main author of the new article in Radio Science. “Our work can help to make navigation safer during geomagnetic storms in the Arctic. Through the new research, we have identified some critical factors affecting the quality of satellite navigation, and looked at the likelihood of when these factors may occur. On a more theoretical level, we found out, that these kind of storms can remove electrons from the ionosphere, which is the opposite of what one would expect intuitively.” When the magnetic field in solar eruptions impacts the Earth’s magnetic field in the ionosphere, their force fields get merged and, through a series of complex physical processes, ultimately cause unstable areas in the ionosphere called patches. These patches extend over large areas of 500 to 1000 km near the pole and also give rise to strong northern lights displays.
Interferes with navigation and communication systems
Knowledge of geomagnetic storms is important as communications via satellites and terrestrial radio channels can be impacted. The storms can disrupt the signals from GPS and other satellites and can cause widespread electricity outages, as for example happened in Sweden in 2003 and Canada in 1989. “It is becoming increasingly important to be able to manage the impact of geomagnetic storms in that more and more of our infrastructure relies on radio signals for communications and navigation. Therefore, we are working to be able to describe and predict the geophysical changes at high latitudes, more accurately, so that among other things they can be taken into account in the design and operation of future communications systems,” explains Per Høeg.
Per Høeg hopes that the work at DTU Space in addition to ensuring better understanding of the phenomenon can help in the development and operation of communications and navigation systems, and account for the conditions during geomagnetic storms so that aircraft and shipping can operate efficiently and safely in the area. “We are seeing great interest in this field. Our latest results in particular have attracted attention from U.S. and Canadian research institutions,” he said.
Experts’ perspective: Predicting space weather is becoming increasingly important in a high-tech society.
It is becoming increasingly important to be able to describe and predict the effects of space weather caused by eruptions on the sun’s surface. The solar outbursts trigger large variations in the ionospheric electron density and changes in the Earth’s magnetic field and can cause significant problems for communication and navigation equipment.This heightened interest has led a team of internationally recognized researchers and partners in connection with DTU Space to release a new scientific article on a major geomagnetic storm that hit Greenland in 2014. According to co-author of the article Dr. Attila Komjathy from the NASA Jet Propulsion Laboratory (JPL) at the California Institute of Technology, a series of installations on Earth is affected by space weather: “The polar ionosphere is prone to space weather effects potentially impacting numerous terrestrial applications. A perturbed ionosphere can interfere with communications with aircraft flying over the North Pole. Airline regulations state that loss of communication may require that aircraft must land during such outages, or be re-routed. Another critical application during disturbed space weather conditions includes NASA’s Deep Space Network using direct communication with spacecraft that are affected by the ionosphere. The more accurately we can measure the distortions caused by the ionosphere the better accuracy for deep space navigation is achieved.”
Professor Richard Langley at the University of New Brunswick in Canada, another co-author, explains that studies of the Arctic ionosphere are important because the dynamic processes in this region differ from those at southern latitudes:
“Studies of the Arctic ionosphere are particularly important for a full understanding of the interaction between the Sun’s radiation (both energetic charged particles and electromagnetic radiation) and the Earth’s atmosphere and magnetic field. Various dynamical processes take place in the polar and auroral regions of the ionosphere, which are quite different from those at more southerly latitudes as described in the paper. A better understanding of the dynamics of the Arctic ionosphere, especially during and after geomagnetic storms, may lead to better forecasting of the effects on satellite navigation, satellite communications, and terrestrial high-frequency communications in the Arctic. Navigation and communications in the Arctic is becoming more important than ever before with the recent trend of decreasing sea ice creating greater opportunities for shipping in the Arctic Ocean. The establishment of additional ports and search and rescue facilities by some Arctic nations will also benefit from better predictions of the availability of communications systems during periods of ionospheric disturbance.”
On a more theoretical level, Professor Hans Pecseli at the University of Oslo has commented that that in recent years it has been acknowledged that the turbulent phenomena that take place near Earth associated with solar outbursts, must be approached in a new way to increase understanding of them:
“Transport in neutral gases and fluids is in most cases described in terms of diffusion processes, also in cases where matter is in a strongly turbulent state. The transport properties of plasmas are often similar to those found in neutral flows, but in recent years it has been realized that transport can also be due to burst- like phenomena mediated by large scale quasi- coherent structures. These conditions are often found for strongly inhomogeneous magnetized plasmas, as for instance found in the Earth's near ionosphere. Large-scale polar patches can also be understood in these terms. These novel features of dynamic plasma conditions as studied in the paper are best treated by a combination of analytical, experimental and numerical methods.”
http://www.space.dtu.dk/english
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