How is Solar Wind Caused?
Venus Climate Orbiter "AKATSUKI" Elucidated Solar Wind Acceleration
December 18, 2014 (JST)
Japan Aerospace Exploration Agency (JAXA)
The University of Tokyo
Researchers at the Institute of Space and Astronautical Science (ISAS) and the University of Tokyo studied solar wind flowing a long distance from the Sun's vicinity, whose distance is about 20 times the radius of the Sun, and found that the wind drastically accelerated at around a location that is five times the radius away from the Sun. They also clarified that the acceleration of solar wind in such a faraway place was related to heating cause by an energy source of waves transmitting through solar wind.
This research result was attained thanks to an onboard instrument of the AKATSUKI, which observes Venus as it travels toward it. The achievement will provide us with a clue to solve the "corona heating issue," which has long been veiled in mystery.
The above research thesis was published in the U.S. magazine "The Astrophysical Journal" in its June 20 and December 10, 2014, issues.
A schematic diagram shows the research result summary. We found that the solar wind drastically accelerated around a location that is five times the radius away from the Sun. We also clarified that this acceleration was caused by heat created when sound waves that are generated within the solar wind are destroyed. The blue curvy lines indicate the lines of magnetic force, blue arrows are solar wind speed, and red marks are images of sound waves.