While outer space might seem like a static, empty place, that is not true because of the sun’s dynamic nature, which gives rise to many phenomena. Their interaction with the earth’s atmosphere gives rise to what is known as space weather. The term “space weather” deals with conditions caused by charged particles ejected from the solar atmosphere.
The study of space weather generally comes under the domain of heliophysics since the sun is responsible for all space weather phenomena. Space weather has many effects on the earth and therefore, learning more about it is essential.
Solar activity results in the ejection of energetic charged particles such as protons, electrons and alpha particles out towards the solar system. These particles have the ability to interfere with the rest of the solar system. Not much is known about the exact mechanism of how space weather arises but it is clear that it has something to do with the solar magnetic field. The solar magnetic field behaves in a complicated manner, giving rise to space weather phenomena.
The study of space weather is a broad field. It deals with how the sun works and the specific conditions that give rise to space weather as well as its impact on the rest of the solar system.
The following is an overview of how space weather arises and how it affects the solar system.
INFLUENCE OF MAGNETIC FIELD ON SOLAR ACTIVITY
The solar magnetic field is not uniform in the outer regions. It tends to fluctuate due to its interaction with plasma, which has some interesting effects.
When penetrating through the outer layers, magnetic field lines tend to “bundle up” in certain regions leading to the formation of sunspots. Sunspots appear as darkened regions on the sun’s surface, also called the photosphere. Sunspots are often associated with solar features such as prominences or flares.
Prominences are filament-like structures made from plasma that extend from the photosphere to the outer solar atmosphere or corona. These filaments are associated with regions of strong magnetic fields. Fluctuations in the magnetic field may cause them to break and erupt, giving rise to Coronal Mass Ejections (CMEs).
Solar Flares are emissions of thermal and electromagnetic radiation resulting from a release in magnetic energy due to fluctuations in the solar magnetic field.
The specifics of the formation of Solar Prominences and Flares are currently being researched. The solar magnetic field is a very complex system and a lot more work has to be done before it can be fully understood.
SOLAR WIND AND CORONAL MASS EJECTIONS
Solar wind refers to the continuous stream of gas and plasma ejected from the solar atmosphere. Although its intensity increases as the sun approaches the solar maximum, solar wind is present almost perpetually.
CMEs or Coronal Mass Ejections are eruptions of bubbles of gas and plasma arising from the corona when magnetic fields in the region close, often due to a prominence. The solar corona consists of ionized particles and is therefore held in place by the magnetic field. When prominences break, it causes the associated magnetic fields to release their hold on the solar corona, thus resulting in CMEs.
Matter released from both of these events interact with the magnetic fields and atmospheres of all bodies in the solar system, making both solar winds and CMEs are crucial components of space weather.
Solar winds and CMEs accelerate particles to speeds of anywhere between 200-800 kilometers per second (Strong et al. 2017). They can travel up to a distance of 100 A.U. (or 100 times the distance between the earth and the sun), therefore significantly affecting the entire solar system.
On earth, we are protected from high-energy ionizing radiation emitted from space weather due to the earth’s magnetic field. It deflects a large number of particles carried by space weather phenomena. The majority of particles are trapped in a doughnut-shaped region known as the Van Allen radiation belt around the earth as they follow the path of the magnetic field.
EFFECTS OF SPACE WEATHER
The most appreciated effect of space weather is the formation of auroras. Auroras are formed as a result of particles from solar winds or CMEs entering the Earth’s atmosphere and ionizing gaseous molecules, causing them to emit light. They are very well known as a popular sky show in the polar regions.
Auroras are also formed on every other planet in the solar system except for Venus, Mercury, and Mars.
Since the traveling particles are electrically charged, they tend to interfere with satellites such as those for the Global Positioning System (GPS).
In the case of powerful CMEs or solar winds, the particles may interact strongly with the Earth’s magnetic field. As a result, its strength decreases, and space weather phenomena can interact with the Earth directly. Events like these are known as Geomagnetic Storms and can interfere with power grids on the Earth, potentially causing blackouts. A particularly famous example is the Carrington Event of 1859, which turned out to be the first sighting of a solar flare. The Carrington Event saw malfunctioning telegraph systems all over the globe. The impact of a large number of ionizing particles resulted in auroras forming at very low latitudes. If such an event were to occur today, the impact would be massive due to the sheer amount of technology in use.
Space weather impacts life on earth in numerous ways. Since modern society is so heavily dependent on technology, being prepared for the impact of space weather is of the utmost importance. Learning about space weather allows us to understand stars like our sun and how the evolution of celestial bodies such as planets occurred. It may even give us an idea of the conditions required to allow the formation of life. Therefore, the study of space weather could provide us with answers to some of the most fundamental questions in the field of astronomy.
However, a large part of the reasons behind space weather and the solar activity influencing it remains unexplained. The sun behaves in a very complex manner. The exact mechanism of how it causes space weather phenomena is a growing subject of research in the field of heliophysics.
- Strong, Keith, Julia Saba, and Therese Kucera. “Understanding Space Weather: The Sun as a Variable Star.” Bulletin of the American Meteorological Society. American Meteorological Society, September 1, 2012. https://journals.ametsoc.org/bams/article/93/9/1327/60177/Understanding-Space-Weather-The-Sun-as-a-Variable.
- Strong, Keith T., Joan T. Schmelz, Julia L. R. Saba, and Therese A. Kucera. “Understanding Space Weather: Part II: The Violent Sun.” Bulletin of the American Meteorological Society. American Meteorological Society, November 1, 2017. https://journals.ametsoc.org/bams/article/98/11/2387/216011/Understanding-Space-Weather-Part-II-The-Violent.
- Strong, Keith, Nicholeen Viall, Joan Schmelz, and Julia Saba. “Understanding Space Weather: Part III: The Sun\’s Domain.” Bulletin of the American Meteorological Society. American Meteorological Society, December 1, 2017. https://journals.ametsoc.org/bams/article/98/12/2593/69977/Understanding-Space-Weather-Part-III-The-Sun-s.
- Klein, Christopher. “A Perfect Solar Superstorm: The 1859 Carrington Event.” History.com. A&E Television Networks, March 14, 2012. https://www.history.com/news/a-perfect-solar-superstorm-the-1859-carrington-event.
- “Space Weather.” NASA. NASA. Accessed October 1, 2020. https://science.nasa.gov/heliophysics/space-weather.
- Garner, Rob. “Solar Storm and Space Weather – Frequently Asked Questions.” NASA. NASA, March 19, 2015. https://www.nasa.gov/mission_pages/sunearth/spaceweather/index.html.
- “Van Allen Radiation Belt.” Encyclopædia Britannica. Encyclopædia Britannica, inc., October 11, 2018. https://www.britannica.com/science/Van-Allen-radiation-belt.