The ESA’s some unique observations of Venus through a period of low solar wind pressure, discovering that the planet's ionosphere swells in its night side, like the tail of a Comet.
The ionosphere is a weekly electrically charged gaseous region far above the main body of the planet's Atmosphere. The form and are partially controlled by the internal magnetic field of the planet.
For the Earth, which has a strong magnetic field, the ionosphere is relatively stable under different solar wind conditions. In comparison, Venus has an internal magnetic field itself, and depends on interactions with the solar wind to shape its ionosphere. Thus much depends on the strength of the solar wind, has been controversial, but the new results from Venus Express reveal, for the first time, the effect of a solar wind pressure very low on the ionosphere of a planet with no magnetic field.
The observations were made in August 2010, when the Stereo-B spacecraft of NASA measured a drop in solar wind density of 0.1 particles per cubic centimeter, about 50 times less than what is normally seen, is maintained for about 18 hours. When Venus hit the solar wind so low, Venus Express was the planet's ionosphere swell out in the night 'downwind' of the planet, with a very similar to the ion tail flowing from a comet in similar conditions.
"This is like a Tear from the ionosphere began to form after 30-60 minutes disminuyese normal pressure of the solar wind. For two Earth days, stretched in space until at least two radii of Venus, "said Yong Wei the Max Planck Institute for Solar System Research in Germany, lead author of the new findings.
The new observations Zanjan discussion on how it affects the strength of the solar wind to the way the ionospheric plasma is transported from day to night side of Venus. Normally, this material flows along a thin channel in the ionosphere, but scientists were not sure what was going on weak solar viewing conditions. Is the flow of plasma particles increases when the channel widens due to the lower confinement pressure or decreases because less power is available to push the plasma through the channel?
"We know, finally, that the first effect outweighs the second, and significantly expands the ionosphere during conditions of low solar wind density," says Markus Fraenz, also of the Max Planck Institute, and co-author. It is also expected that a similar effect occurs around Mars, another planet with no magnetic field of our inner solar system.
"We often talk about the effects of the solar wind communication with the interplanetary atmosphere during periods of intense solar activity, but Venus Express has shown that when there is reduced activity of the solar wind, the sun can still significant pressure the environment our planetary neighbors, "says Hakan Svedhem, project scientist for Venus Express ESA.