Coronal Mass Ejections (CMEs), or magnetic explosions of plasma from the solar corona, are truly powerful. They can trigger high-energy space storms that expand for millions of kilometers. The resulting wave endangers satellites, astronauts, and even electronic devices within the Earth‘s atmosphere. Despite this, NASA‘s Parker Solar Probe passed unscathed through a coronal mass ejection on September 5, 2022.
CMEs as Cosmic Dust Busters
Scientists have many scientific reasons to be pleased with the probe’s work. The bold and perilous journey offered a golden opportunity to closely observe a CME. In fact, Parker’s observations have helped scientists validate a two-decade-old theory. As suggested by two scientists in 2003, CMEs can push away interplanetary dust (ref.). The tiny debris comes from planets, asteroids, and comets that drift around the Sun and are then swept away by CMEs.
Interplanetary dust is small and challenging to observe, but Parker’s Wide-field Imager for Solar Probe (WISPR) camera managed to detect light reflected by the particles. The grains were still quite fine, but scientists improved the signals by subtracting the average brightness from images that WISPR had acquired during similar orbits.
CMEs blow away the dust along a path about 9.7 million kilometers from the Sun. Guillermo Stenborg, an astrophysicist at Johns Hopkins University and lead author of the paper (ref.), likened the observed effect to that of a vacuum cleaner. Just like in a freshly vacuumed room, the empty space in the interplanetary dust quickly filled with more dust.
Whether all CMEs clear away dust in this manner remains an open question. Since astronomers have observed the phenomenon only with this 2022 event, Stenborg and colleagues believe that only the most powerful CMEs may be responsible for such tidying up. Fortunately, the Sun is approaching solar maximum, and the Parker probe and other observers may have more opportunities to witness another coronal mass ejection.