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Between 2010 and 2013, three different spacecrafts could simultaneously view the entire solar corona from different angles, revealing coronal brightpoints shown in red (from the STEREO-Behind satellite), white (Solar Dynamics Observatory), and blue (STEREO-Ahead).
Planetary scientists who study space weather—the impact of solar storms and similar phenomena on Earth’s magnetic field—would like to predict the arrival of such disturbances much sooner than is possible at present. Space weather events can cause direct, identifiable impacts on Earth, such as damage to orbiting satellites and interference with electric power grids, costing billions of dollars per year, according to a National Science Foundation estimate.
Predicting weather on Earth is aided by examining the movement of high altitude winds over the planet, known as Rossby waves. These waves, which include the jet stream, are induced by Earth’s rotation, and their speed and intensity vary depending on their latitude and whether they are propagating toward the poles or the equator. Scientists have long sought to confirm the existence of Rossby-like waves on the Sun, which could improve the forecasting of space weather events. This confirmation had been impossible because the Sun’s atmosphere was observed from only one viewpoint, Earth.
This situation changed with the relatively recent introduction of three NASA satellites. The two Solar Terrestrial Relations Observatory (STEREO) satellites, placed in Earth’s orbit—one ahead of our planet and one behind— were launched in 2006. In 2010, STEREO was joined by the Solar Dynamics Observatory (SDO), positioned between Earth and the Sun. Together, the three spacecrafts provided the first-ever instantaneous 360-degree coverage of the Sun.
The satellites allowed researchers, led by astrophysicist Scott McIntosh of the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, to observe and track coronal brightpoints as they rotated with the Sun from 2010 to 2013. The brightpoints trace bands of magnetic convection currents, analogous to Earth’s Rossby waves, below the Sun’s surface. The newly-completed analysis of these observations finally confirmed the existence of such waves on the Sun.
Unfortunately, in 2014 one of the STEREO satellites lost contact with Earth. Without its input, the observations were no longer global in coverage and were terminated. McIntosh is convinced that continuous tracing of the Sun’s magnetic waves would aid in predicting space weather on Earth. “Progress in this area,” he notes, “requires that we adopt a continuous presence in space” to monitor the Sun, as was possible for several years. No new satellite is currently planned, however, to replace the malfunctioning STEREO spacecraft. (Nature Astronomy)