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Venus doesn't have a magnetic
field. So, Venus is just this big rock with this atmosphere and the ionosphere, sitting
in space, and the super sonic solar wind with interplanetary magnetic field
whacks into Venus, and it can't penetrate through the
ionosphere. So, the interplanetary field lines sort of pile
up ahead of Venus, like cars on freeway. This solar wind
whacking into it essentially sort of strips off the atmosphere, and
it literally forms this long tail, like a comet, but stretching out into space.
Pioneer Venus Orbiter was the first spacecraft to
really thoroughly explore that nightside region where the
atmosphere is all escaping away. It discovered this really
mysterious phenomena which has yet to really be explained.
Imagine that we are flying from pole to pole on the nightside.
We are feeling the plasma around us, and then suddenly, the ionosphere disappears.
And then is sort of comes back. This is what an ionospheric hole is,
it's like a cassam in the sky, a big hole where the ionosphere is
just absent. So, Pioneer Venus Orbit basically measured inside these
things, and we saw that there is very little plasma, and there's all this
magnetic field, and from that, they sort of suggested that this is essentially
a magnetic structure that is sitting in the nightside.
I wanted to see if I could go looking for these things with Venus Express.
What we saw is essentially this really exciting, strong
great magnetic field line that we expected, and really boring
plasma signatures. It shows us that this is a magnetic structure, right?
This is a tube of interplanetary magnetic field, that, well
PVO saw it coming of the ground, and now we've seen it way out in the tail.
These things continue out to much higher altitudes that we have previously have found them at.
And the other thing that is important is where Pioneer Venus Orbiter
only saw them during solar maximum, when the sun is really
disturbed and blowy and stormy.
We've now been seeing them all throughout the solar cycle.
There's sort of two explanations for what might be causing this.
One possibility is that these field lines, they come in from space
and they get sort of stuck in the ionosphere
The ionosphere sort of flows from the dayside to the nightside. As it goes around, it sort of
meets the plasma that is in the tail. There's sort of a pile up.
between the two. So, that's one idea. And the other idea is that
on the dayside, the field lines come in, and they actually sink
through the ionosphere, go through the rocky mantle, and then get hung on the this big
metallic core. These field lines essentially end up draping around the core and stick out
the rock at the back. One of the main differences between
Venus and the Earth is simply that Venus doesn't have a magnetic field.
The way it interacts with the star is completely different.
If you want to understand how did Venus get that way,
why does Venus not have any ocean, you need to understand the interaction
between the star and the planet.
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