Article by Savindu Weerathunga, 3rd Year Undergraduate, Faculty of Science, University of Colombo
Unbeknownst to us humans, another vast network of weather phenomena exists beyond the limits of the Earth’s atmosphere but regardless has had a major impact on the Earth’s systems and, especially, the lives of humans and will continue to do so for millions of years to come. The not-so-empty, space of our solar system enclosed within the heliosphere encompassing complex space weather processes influences Earth and the remainder of the planetary bodies, forming an intertwined destiny. But for now, let us just focus on our blue planet.
The Sun
At the center of this network is, none other than, the Sun. For 4.5 billion years, this 1.4 million km yellow dwarf star has shaped our solar system into what it is today, and all the space weather phenomena are due to its activity. The sun is mainly composed of hydrogen and helium and can be compartmentalized into different regions. From the center to the outermost layer, they are, the Solar core, Radiative zone, Convection zone, Photosphere, Chromosphere, Transition zone, and Corona.
The Sun is the very embodiment of a nuclear fusion reactor. The energy that is produced at the core through nuclear fusion is radiated outwards through the radiation and convection zones to the photosphere. The photosphere is what is observed as the surface of the sun since it is responsible for the light emitted that we see with our eyes. Although in actuality it is the first layer of the sun’s atmosphere. The source of features like sunspots and coronal holes and the pursuing phenomena mainly solar winds, solar flares, and Coronal Mass Ejections (CMEs) is the solar atmosphere which includes the chromosphere, and corona in addition to the photosphere.
Solar winds are a continuous source of solar particles or plasma (charged particles like electrons and ionized atoms ) that carry the sun’s magnetic field with them. This basically extends the solar atmosphere to completely engulf the solar system with all its components forming the heliosphere. Due to the sun’s rotation, the magnetized solar winds take the form of a spiral known as the Parker spiral.
The solar cycle takes place every 11 years during which the magnetic polarity of the geographic poles of the sun changes. This results in violent activity within the sun’s atmosphere that creates numerous sunspots and varying events of solar flares and CMEs. The activity reaches a peak referred to as the solar maximum from a period of low activity (the solar minimum) when the sun’s atmosphere is relatively calm and quiet. As the activity of the sun changes throughout the cycle, the energy released from the sun and its interactions with the surrounding interplanetary environment within the heliosphere changes.
Space Weather and Earth
The Earth has its own magnetic field that protects the earth’s surface from space radiation that is composed mainly of solar radiation and cosmic rays. In the absence of a magnetosphere, solar winds bombarding the planet’s surface will render it inhabitable. The magnetic field wards off these solar winds which circumvent the earth, but certain charged particles are trapped within the magnetic field that reaches the poles by a process called magnetic reconnection and incident on the earth’s atmosphere, giving rise to the magnificent display of lights that one will ever encounter at the poles, called the aurora.
This energy captured and stored within the fields is also capable of creating a form of weather condition known as a Substorm, where the energy is released over a period of several minutes every 3 hours creating intense auroral displays (brighter than average aurora), causing harmful radiation leaks from the upper atmosphere and disrupt communications.
Solar flares are massive explosive events that occur at the solar surface and have an equivalent energy release of a billion hydrogen bombs. Similarly, CMEs are single events during which a large mass of plasma is released from the sun’s surface as a result of contortions that take place within the magnetic fields of the sun. Solar Energetic Particles (SEPs) are accelerated together with these ejections. At the height of its activity during the solar cycle, high-speed solar winds, solar flares, and CMEs are capable of causing a category of weather known as Solar Storms. Substorms are different to solar storms as they persist over a larger period of time while the latter result from a single major event that persist for a short period of time although its effects can last longer.
Solar storms are of 2 types, Geomagnetic and Solar Radiation Storms. Geomagnetic storms are caused by disruptions that occur to the Earth’s magnetic field as a result of the enormous amount of solar matter and energy released from such events. Solar radiation storms are caused by fast moving solar particles. Solar radiation storms mostly affect deep space missions. Geomagnetic storms affect both the space and terrestrial environments where mass disruptions can occur in relation to orbital satellites, space telescopes, and power grids and cause billions in economic loss. The solar flare that disrupted the hydro-electric power plant in Quebec, Canada back in 1989 is one such example. Solar storms and the accompanied SEPs pose even a greater threat to astronauts based in the ISS and other manned missions.
Forecasting Space Weather
It is vital for our survival to understand the mechanisms and processes behind space weather. In order to do so, it is important to observe and understand the behavior of the sun. This will allow us to predict space weather events with better accuracy. Terrestrial observatories as well as space-based observatories are employed for this purpose.
Two main bodies, NOAA’s Space Weather Prediction Center and the World Data Center for the Sunspot Index and Long-term Solar Observations, are involved in closely analyzing the solar cycle and predicting events such as earth directed solar flares and CMEs. The Heliophysics Systems Observatory (HSO) is collectively referred to the network of the space probes and observatories that are responsible for closely observing the sun’s activity. These include the Parker Solar Probe, Solar and Heliospheric Observatory (SOHO), Solar Terrestrial Relations Observatory (STEREO) that is composed of 2 components, the ESA Solar Orbiter, and many other spacecrafts with their gazes fixed on the sun.
References:
- In Depth | Sun –. (n.d.). NASA Solar System Exploration. https://solarsystem.nasa.gov/solar-system/sun/in-depth/
- NASA. (n.d.-a). Heliophysics Overview. https://www.nasa.gov/mission_pages/sunearth/overview/index.html
- NASA. (n.d.-b). The Heliopedia. https://www.nasa.gov/mission_pages/sunearth/the-heliopedia/
- The Solar Wind Across Our Solar System. (n.d.). NASA Solar System Exploration. https://solarsystem.nasa.gov/resources/2288/the-solar-wind-across-our-solar-system/
- The Solar Wind Across Our Solar System. (n.d.). NASA Solar System Exploration. https://solarsystem.nasa.gov/resources/2288/the-solar-wind-across-our-solar-system/
Image Courtesies:
- Featured image: https://shorturl.at/wOU39
- Figure 1: https://go.nasa.gov/41ltiwU
- Figure 2: https://go.nasa.gov/3m0yBlp
- Figure 3: https://bit.ly/3khITNz
- Figure 4: https://go.nasa.gov/3SozjES
- Figure 5: https://bit.ly/3IRydyE
- Figure 6: https://go.nasa.gov/3kmBmge
- Figure 7: https://go.nasa.gov/3Ett9hd
- Figure 8: https://bit.ly/3Z09DRr
- Figure 9: https://go.nasa.gov/3m1xlhH
- Figure 10: https://go.nasa.gov/41qkXrT
