|From Images 108|
From a NASA press release:
"With the Moon as the most prominent object in the night sky and a major source of an invisible pull that creates ocean tides, many ancient cultures thought it could also affect our health or state of mind– the word “lunacy” has its origin in this belief. Now, a powerful combination of spacecraft and computer simulations is revealing that the moon does indeed have a far-reaching, invisible influence– not on us, but on the Sun, or more specifically, the solar wind.
The solar wind is a thin stream of electrically conducting gas called plasma that’s constantly blown off the surface of the Sun in all directions at around a million miles per hour. When a particularly fast, dense or turbulent solar wind strikes Earth’s magnetic field, it can generate magnetic and radiation storms that are capable of disrupting satellites, power grids, and communication systems. The magnetic “bubble” surrounding Earth also pushes back on the solar wind, creating a bow shock tens of thousands of miles across over the day side of Earth where the solar wind slams into the magnetic field and abruptly slows from supersonic to subsonic speed.
Unlike Earth, the Moon is not surrounded by a global magnetic field. “It was thought that the solar wind crashes into the lunar surface without any warning or ‘push back’ on the solar wind,” says Dr. Andrew Poppe of the University of California, Berkeley. Recently, however, an international fleet of lunar-orbiting spacecraft has detected signs of the Moon’s presence “upstream” in the solar wind. “We’ve seen electron beams and ion fountains over the Moon’s day side,” says Dr. Jasper Halekas, also of the University of California, Berkeley."