Space Weather – The Meteorological Frontier

Talk about a subject that tilts heads, space weather is a rapidly growing field in science. I was first exposed to the subject in my Intro to Atmospheric Science class my freshman year at Purdue University. The professor, Dr. Ernest Agee pulled up two websites at the start of every class. The first being spaceweather.com and the other being the NCAR Real-Time Weather site. I had no clue why we were looking at space weather in that class. Weather in space? How does that work out!? Heliophysics… Sounds like a made up sci-fi term. These were thoughts that were running through my head. Little did I know how awesome the subject was! Four years later and I still look at the same space weather website nearly daily. The subject is intriguing, complex, dynamic, and is now becoming more and more economically important. Many people are turning to meteorologists for information about this subject and therefore many meteorologists are being recruited into this field which has been particularly significant for me as I start to consider career options. In this post, I plan to address a question that is commonly asked at me. What is space weather and why is it a growing field in science right now?

As defined by the Space Weather Prediction Center, space weather describes the variations in the space environment between the Sun and Earth. The study of space weather explains the multiple phenomena that can bring harm to satellite and Earth based infrastructure. Heliophysics is the branch of science that describes space weather (to make this post simple, this will be the only time I bring up the term heliophysics). It is no surprise that as we rely more and more on technology, we are relying more and more on satellite based communication and a dependable supply of electricity. GPS services, satellite based communication, astronauts and polar flight routes are just a few examples of services that can be interrupted by space weather.

Okay, so space weather refers to the phenomena that occurs between the Sun’s surface and the Earth. How does space weather work though? What are the phenomena? First off, I would like to comment on the consistency of the Sun’s energy output. This may seem elementary, but its important. The Earth is ALWAYS being bombarded with various wavelengths of radiation from the Sun. These include ultraviolet, visible and infrared radiation. Earth’s atmosphere manages to absorb and reflect much of the harmful UV radiation and much of what we experience on Earth’s surface is of visible wavelengths with a minimal amount of infrared radiation. Note figure 1 one showing the distribution of radiation we see on the surface of Earth. The Sun doesn’t go to bed at night and it doesn’t take naps in the middle of day behind cloud cover. Its ALWAYS present and thank goodness that it is! It is this radiation from the Sun that allows the existence of life on Earth.

Figure 1 // Spectrum for Solar Radiation on Earth. Note that visible wavelengths have the highest irradiance (or flux of energy per unit area).

Going off this idea that the Sun is ALWAYS spewing energy in all directions. The Sun’s outer atmosphere also releases energy in the solar wind, large amounts of radiation in solar flares and magnetic fields and plasma with coronal mass ejections (CME’s).  All 3 of these processes are the main phenomena that make up space weather.

The solar wind is a continuous out flowing of electrons and protons in the form of plasma from the Sun’s surface. There are also embedded magnetic fields with this plasma which will be very important when looking at how the solar wind will interact when it collides with Earth’s magnetic field. The solar wind varies in speed and density based on surface conditions of the Sun (look into coronal holes). The solar wind alone has the power to spark auroras and geomagnetic storms if its speed, density and magnetic field direction are working together.

Figure 2 // Shown above is the latest forecast of conditions in the solar wind, as predicted by the WSA-Enlil model from the SWPC website. I include this because it allows one to visualize how the solar wind travels from the Sun outward into space.

A solar flare is another process that powers space weather. A solar flare is a large release of radiation from the surface of the Sun and are commonly associated with CME’s which will be covered in the next section. A solar flare releases extreme amounts UV radiation and X-rays thanks to a re-connection of magnetic field lines on the Sun. Its this process that causes radio blackouts on Earth. Though it may seem like radio usage is decreasing, it is still a widely used technology by the military, air traffic controllers and various emergency response organizations.

Figure 3 // An X-class solar flare on July 6th, 2012.

Last, but certainly not least is the Coronal Mass Ejection (CME). The Sun produces an UNBELIEVABLE magnetic field from the amount of energy that is being produced from its core. On the surface (the corona), these magnetic field lines tend to get tangled and twisted with huge amounts of energy being transported by extreme convection. When this happens, potential energy builds until this large gradient is released in the form of a CME. Nature always wants to be in equilibrium, even on the Sun. With this said, CME’s contain magnetic fields and plasma and spark enhanced geomagnetic storms and auroras on Earth. Below, you will find a video showing a CME eruption on March 14th of this year.

Figure 4 // An image from SWPC that summarizes the locations of space weather processes. This image is a dramatization and is not to scale.

 

Since the Sun is constantly releasing these flares, ejections, wind and what not, why don’t we see more geomagnetic storms and auroras? Much like how the ozone layer protects us from harmful UV radiation, Earth’s magnetic field protects us from the solar wind and CME’s. Earth’s magnetic field can be simply visualized like that of a magnet. Its shape changes like that seen in Figure 4 thanks to the pressure of the solar wind. The solar wind causes a compression on the day side of Earth and stretching on the night side. Its Earth’s magnetic fields that explain why the auroras and geomagnetic storms occur most frequently at the poles! Energy released in CME’s and contained in the solar wind travel along the magnetic field lines of Earth which are directed to the poles. It is here that this energy excites oxygen and nitrogen molecules in the ionosphere. When these molecules return to their steady state, they release energy in the form of light! This creates the aurora. A geomagnetic storm is a large disturbance in the magnetic field of Earth. It is CME’s that most often cause this large disturbance. These storms cause heating in the ionosphere which can cause errors in GPS positioning information, extra drag on satellites in low orbit and geomagnetic induced currents in the power grid and pipelines. Not only this, but storms can also expose people and flights in polar regions to unhealthy amounts of radiation. If given a warning in advance, companies can take precautions to save millions and even billions of dollars in damage.

The Sun is a fusion masterpiece. We have seen all of these processes described above for thousands of years. Its only been in the last two centuries that people have begun to study and understand what is going on. Today, greater than ever, we look to understand the variations in the Earth-Sun space environment to protect life and property. It is why this field is growing so quickly. Forecasters at the Space Weather Prediction Center take analysis data from satellites and models to predict if and when a particular storm will impact Earth. If they issue a warning, this allows companies to take the necessary precautions to protect the power grid, drilling and satellite operations, and astronauts in space. They just released a new website thanks to the increasing demand from companies and even the general public. The more we rely on satellites, the more we explore into space, the more we will need to understand and predict space weather.

Science rules!

Joe Bauer

 

 

For more information on space weather, explore the SWPC website and this website.

Further reading // where I got my knowledge:

Howard, T. A., Webb, D. F., Tappin, S. J., Mizuno, D. R., & Johnston, J. C. (2006). Tracking halo coronal mass ejections from 0–1 AU and space weather forecasting using the Solar Mass Ejection Imager (SMEI). Journal of Geophysical Research: Space Physics (1978–2012), 111(A4).

Liu, Y., Thernisien, A., Luhmann, J. G., Vourlidas, A., Davies, J. A., Lin, R. P., & Bale, S. D. (2010). Reconstructing coronal mass ejections with coordinated imaging and in situ observations: Global structure, kinematics, and implications for space weather forecasting. The Astrophysical Journal, 722(2), 1762.

Lanzerotti, L. J. (2001). Space weather effects on technologies. Space Weather, 11-22.

Schwenn, R. (2006). Space weather: The solar perspective. Living Reviews in Solar Physics, 3(2), 1-72.