What is the heliopause?

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Offline chris

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What is the heliopause?
« on: 07/01/2010 04:11:37 »
What is the heliopause (presumably not the pedological equivalent of a menopause), and why is it important?

Chris
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Offline LeeE

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What is the heliopause?
« Reply #1 on: 07/01/2010 16:29:23 »
I'll quote directly from from wikipedia as it's as concise an explanation as any:

Quote
The heliopause is the theoretical boundary where the Sun's solar wind is stopped by the interstellar medium; where the solar wind's strength is no longer great enough to push back the stellar winds of the surrounding stars.

There's also considered to be a heliopause between the Earth and the Sun due to Earth's magnetosphere blocking and diverting the solar wind.
« Last Edit: 07/01/2010 16:32:38 by LeeE »
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline Meera

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What is the heliopause?
« Reply #2 on: 07/01/2010 18:34:06 »
The distance to the solar system heliopause must be enormous though, presumably?

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Offline LeeE

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What is the heliopause?
« Reply #3 on: 08/01/2010 18:00:04 »
Hmm... although that wikipedia article I linked to says that it's the point where the local stellar wind is balanced by the combined stellar winds of the surrounding stars, which implies that the heliopause is located roughly half way between stars (depending on the type of star), it is more due to it no longer being strong enough to compress the rarified hydrogen forming the interstellar medium, along with the the virtual particles popping into and out of existence in interstellar space, which finally halts it.

As such, the solar wind is halted well before it actually encounters the stellar winds from nearby stars, and so is not roughly half way between them but much closer to the local star.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline techmind

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What is the heliopause?
« Reply #4 on: 09/01/2010 10:34:41 »
We did all about this in our Solar-Terrestrial physics lectures ... but that was well over a decade ago and I don't remember the details.

I don't have it to hand, but am pretty certain the answer will be well-explained in this textbook that we used:
http://www.amazon.co.uk/Introduction-Physics-Cambridge-Atmospheric-Science/dp/0521457149/ref=sr_1_20?ie=UTF8&s=books&qid=1263033148&sr=1-20

I'm sure you can browse for the answer in a local Cambridge bookshop.
"It has been said that the primary function of schools is to impart enough facts to make children stop asking questions. Some, with whom the schools do not succeed, become scientists." - Schmidt-Nielsen "Memoirs of a curious scientist"

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Offline LeeE

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What is the heliopause?
« Reply #5 on: 10/01/2010 00:58:37 »
Big rivers maintain their coherence quite a long way into the oceans.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!