The Sun: Space Weather Machine
As temperatures creep toward the triple digits this week, it’s probably not hard to remember that the Sun is our primary source for heat and light. Perhaps less obvious is that the Sun is also responsible for space weather, defined as the varying conditions surrounding the Earth that are due to solar wind and other energetic outbursts from the Sun’s surface. While there is no conclusive linkage between space weather and Earth’s climate, solar particles penetrating Earth’s magnetic field risk disrupting performance and reliability of space-borne and ground-based technological systems, satellites, and even possibly endangering life. One of the main objectives of space missions currently studying the Sun is to better understand extreme space weather events, how and when they occur, and how life on Earth may be affected, now and in the future.
STEREO (Solar Terrestrial Relations Observatory) has revolutionized the study of the Sun-Earth system. Consisting of two nearly identical observatories, one ahead and one behind Earth in its orbit of the Sun, STEREO traces the flow of energy and matter from the Sun to the Earth, revealing 3-dimensional structures of violent eruptions coming off the Sun’s surface. If directed toward Earth, these eruptions, called coronal mass ejections (or CMEs), can trigger severe magnetic storms when they collide with Earth’s magnetic field, disrupting satellites and power grids. CMEs are also extremely hazardous to astronauts on the International Space Station and performing Extra Vehicular Activities. Studying these violent solar storms in detail helps scientists understand their fundamental nature and origin, and the extent to which they can affect life on Earth.
Computer models of superstorms such as the one of 2012, shown above, have helped scientists better understand and predict the onset of storms that could be directed at Earth. By matching their models to past observations, solar astronomers have found that it is not only the origin of CMEs at the Sun’s surface, but also the interactions between successive CMEs farther out in interplanetary space that contribute to extreme space weather events. The Solar Dynamics Observatory (SDO) is another satellite mission taking unprecedented images of the Sun, showing its surface features, storms and flares in great detail, enabling the study of solar prominences and energetic outbursts that regularly spew into space. Orbiting the Earth at nearly 7000 miles per hour, SDO has captured the most detailed imagery of the Sun to date, revealing its surface in amazing fiery and dynamic detail. The image below shows a dark region called a coronal hole in the surface of the Sun, an area where high-speed solar wind particles stream into space.
Solar flares are sudden flashes of brightness from the Sun’s surface, linked to great releases of energy, often occurring just prior to CMEs. Such bright regions can be seen in many SDO images, including the one below, which also shows loops of superheated plasma seen extending off the surface; these loops can’t escape the magnetic filed of the Sun but rather follow the field lines back to the surface.
Solar flares strongly influence space weather near Earth, producing streams of energetic particles in the solar wind. When solar wind particles impact the Earth’s magnetic field, they can generate a geomagnetic storm which presents radiation hazards to satellites and humans on Earth and in space. To generate some of the remarkable imagery and videos for scientists and astronomy enthusiasts, SDO’s instruments capture images of the Sun at frequent intervals, showing how the surface changes rapidly. The gorgeous composite below was made from 25 separate images taken at extreme ultraviolet wavelengths, which enable viewing very high temperature solar material.You can see the Sun changing over the course of 3 years in this video. Because the distance between the SDO spacecraft and the Sun varies over time, the apparent size of the Sun subtly increases and decreases over time in the video. What does extreme space weather mean for our future? Aside from immediate power grid and satellite concerns, short-term radiation risks posed by solar flares are being considering in current planning stages for sending humans to Mars, the Moon, and even other planets. Energetic protons passing through the human body can cause serious biochemical damage, harming astronauts not only during interplanetary travel but also once they arrive at their destination. In the very far future, the Sun will become a red giant and engulf the Earth; but not to worry, as this won’t happen for another 5 billion years or so. In the meantime, scientists are studying space weather and extreme solar events that can affect life on our planet in order to be better prepared for living with our star. This information is further useful for understanding how stars affect life on planets beyond our solar system, some of which may ultimately be the future home for our species long after the Sun is gone. For more amazing solar footage, play the video compilation of SDO’s “best video imagery” from the last 5 years, below:
Want to learn more about the Sun, extreme space weather, and solar missions, and view its surface safely through solar telescopes? Join us for International SUNday (and the first day of summer!) this Sunday, June 21, for special presentations and solar viewing (weather permitting). More details on International SUNday can be found here.