Cloudy, with a chance of solar flares

by Konstantina Loumou

-Tickets?
-Got them.
-Passport?
-Here.
-What about the weather?
-Checked!

This could be a discussion before a trip to France nowadays… or a  trip to Mars sometime in the future.

Space weather is a branch of astrophysics that studies the Sun and the solar phenomena. Eruptions of different magnitudes are taking place in our star’s atmosphere, feeding the space among the planets with particles. They then travel in space much like a wind, tied to the Sun’s magnetic field, being driven by it and driving it along. Now imagine you’re travelling in space, paying a visit to your friends on a nearby planet. You would probably want to know where those particles are going!

Artist’s impression of the Sun’s magnetic field reconnecting with the Earth’s magnetic field after a solar flare. Credits: ESA

Even though scientists are still searching for the drivers of space weather, they do have a basic picture of what leads to it. The Sun is essentially a large magnet with a magnetic field that resembles the Earth’s. As the field rises from the interior and expands towards the interplanetary space of our solar system, it gets twisted and stretched. This process can cause two magnetic lines of opposite polarities to come in close proximity. According to electromagnetism, if we have a point source in the region of an electromagnetic field being subjected to these conditions, forces can get strong enough to cause the lines to connect, releasing energy at the same time. This energy gets absorbed by particles in interplanetary space which will travel towards the planets and everything in between.

Through this process, it is possible for a storm of space particles to enter the Earth’s atmosphere, changing its density and interacting with the atmospheric particles. This means that the refractive index of radio waves essential for communication with satellites orbiting in the ionosphere is also changing, altering the travel-time of the wave. Aeroplane navigation systems rely upon satellite navigation systems, and a delayed signal from those systems can lead to problems as the plane attempts to land. At the same time, this disturbance of the geomagnetic field can induce additional currents, which themselves can propagate through the electric grid, causing its degradation at a much faster rate than normal. The current induced in electrical transformers can have as a result catastrophic increases in their temperature, which have the potential to lead to a black-out. While this may sound like doom-mongering, it has happened before: in March 1989 Quebec was subjected to a twelve hour-long power-cut, due to a transformer overheating , and in September 2005 a solar flare lead to a complete loss of radio communication in both North and South America. According to the most recent global road map for space weather4, the estimated impact of induced current can lead to damages of $5-10 billion (£4.1-8.2 billion) every year. Insurance companies are increasingly interested in knowing the exact effect of space weather on the technology they manage so that they can adjust their claims accordingly. The same interest is also shared by governments and the military, for whom the long-term running of satellites is vital.

At the same time, a solar storm can pose a health risk for travellers. When an eruption happens, the particles that have absorbed the released energy are free to travel in very high energies. Thankfully, our planet has a magnetic field strong enough to keep an atmosphere that acts as a shield. However,  transatlantic flights tend to fly at high latitudes, thus having a smaller fraction of the atmosphere protecting them from harmful highly energetic particles . In an attempt to mitigate risks, transatlantic trips tend to change their flightpath. Things are worse for the astronauts working on the International Space Station, who have no protection apart from their uniform, and let us not forget your trip to that Martian resort. With the number of manned space missions increasing and Virgin Galactic, a space tourism company, already established, it is crucial to be aware of the occurrence time and direction of any storm which should be avoided.

So, what can we do about it? Solar physicists are developing different techniques in an attempt to forecast those events. However, although large steps have been made, the exact physics governing these events is still unknown. Moreover, the existing observational data and the simulations available don’t agree with each other. Theorists need far more precise data and a lot more information to create a model describing exactly what is happening in the Sun. Therefore, any forecasting method to date, consists of  determining a physical quantity that, according to plasma theory,  might give an indication of an imminent eruption. Its verification can only happen via statistical analysis, which leaves space for uncertainty.

Space Weather has a long way to go, but it is undoubtedly an exciting and promising field, with many more applications in the foreseeable future as humanity continues reaching for the stars.

 

References

  1. Cade, WB; Chan-Park, C. The origin of space weather. Space Weather 13:2:1542
  2. Leighton, RB; Noyes, RW; Simon GW. Velocity fields in the solar atmosphere. I. Preliminary Report. Astrophysical Journal. 135:474
  3. Stix, M. The sun: an introduction. Springer, 2002.
  4. Schrijver, CJ et al. Understanding space weather to shield society: A global road map for 2015-2025 commissioned by COSPAR and ILWS. Advances in Space Research. 55:2745

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