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Venus doesn't have a magnetic

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field. So, Venus is just this big rock with this atmosphere and the ionosphere, sitting

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in space, and the super sonic solar wind with interplanetary magnetic field

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whacks into Venus, and it can't penetrate through the 

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ionosphere. So, the interplanetary field lines sort of pile

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up ahead of Venus, like cars on freeway. This solar wind

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whacking into it essentially sort of strips off the atmosphere, and

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it literally forms this long tail, like a comet, but stretching out into space.

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Pioneer Venus Orbiter was the first spacecraft to

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really thoroughly explore that nightside region where the 

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atmosphere is all escaping away. It discovered this really

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mysterious phenomena which has yet to really be explained.

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Imagine that we are flying from pole to pole on the nightside.

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We are feeling the plasma around us, and then suddenly, the ionosphere disappears.

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And then is sort of comes back. This is what an ionospheric hole is,

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it's like a cassam in the sky, a big hole where the ionosphere is

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just absent. So, Pioneer Venus Orbit basically measured inside these

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things, and we saw that there is very little plasma, and there's all this

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magnetic field, and from that, they sort of suggested that this is essentially 

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a magnetic structure that is sitting in the nightside.

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I wanted to see if I could go looking for these things with Venus Express.

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What we saw is essentially this really exciting, strong

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great magnetic field line that we expected, and really boring

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plasma signatures. It shows us that this is a magnetic structure, right?

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This is a tube of interplanetary magnetic field, that, well

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PVO saw it coming of the ground, and now we've seen it way out in the tail.

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These things continue out to much higher altitudes that we have previously have found them at.

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And the other thing that is important is where Pioneer Venus Orbiter

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only saw them during solar maximum, when the sun is really

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disturbed and blowy and stormy.

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We've now been seeing them all throughout the solar cycle.

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There's sort of two explanations for what might be causing this.

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One possibility is that these field lines, they come in from space

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and they get sort of stuck in the ionosphere

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The ionosphere sort of flows from the dayside to the nightside. As it goes around, it sort of

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meets the plasma that is in the tail. There's sort of a pile up.

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between the two. So, that's one idea. And the other idea is that

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on the dayside, the field lines come in, and they actually sink

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through the ionosphere, go through the rocky mantle, and then get hung on the this big

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metallic core. These field lines essentially end up draping around the core and stick out

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the rock at the back. One of the main differences between

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Venus and the Earth is simply that Venus doesn't have a magnetic field.

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The way it interacts with the star is completely different.

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If you want to understand how did Venus get that way, 

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why does Venus not have any ocean, you need to understand the interaction

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between the star and the planet.

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beeping

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