ESA'S VENUS EXPRESS spacecraft has spotted the planet blowing back million-mile-per-hour solar winds in weather explosions similar to what happens outside Earth's magnetic shield.
"THEY'VE BEEN SEEN AT SATURN, THEY MAY HAVE BEEN SEEN AT MARS, AND NOW WE'RE SEEING THEM AT VENUS. BUT AT VENUS, SINCE THERE'S NO PROTECTIVE MAGNETIC FIELD, THE EXPLOSION HAPPENS RIGHT ABOVE THE SURFACE OF THE PLANET, says Goddard scientist Glyn Collinson and the first author on the new paper.
It also shows that HFAs there are far different than what happens near our planet, which has a strong magnetic field, they added. "AT VENUS, SINCE THERE'S NO PROTECTIVE MAGNETIC FIELD, THE EXPLOSION HAPPENS RIGHT ABOVE THE SURFACE OF THE PLANET," study lead author Glyn Collinson, of NASA's Goddard Space Flight Center in Greenbelt, Md., said in a statement, NASA.
The solar wind isn't a one-directional gust - instead it's blustery because its own magnetic fields contain discontinuities, so the gale abruptly and sharply changes directions. At times, the wind forms a puddle on top of the Venusian bow shock, the point where the supersonic solar blast slows down and diverts around the planet.
These puddles collect into pools of plasma that can expand to the size of Earth, and then explode out from the bow shock.
Scientists were tipped off that HFAs might be happening at Venus when NASA's MESSENGER SPACECRAFT spotted what amounted to a suggestive magnetic signature that hinted at HFA activity. But Messenger, which is really studying Mercury not Venus, didn't have the instruments to detect the temperature inside the signature and figure out if it was hot.
The reason the researchers are so interested in the phenomenon is because of its effects on a planet with no magnetic shield. On Earth, HFA explosions off the magnetosphere can create a downdraft that compresses the entire shield for minutes at a time, causing charged particles to tumble along magnetic lines and fall through to the atmosphere as dayside aurora at the poles.
