Supersonic plasma jets discovered

http://www.esa.int/Our_Activities/Observing_the_Earth/Swarm/Supersonic_plasma_jets_discovered

by vermontdevil • 9 years ago

161 37 9 years ago

dahart4• 9 years ago

Something I somehow missed in school and only found out recently is that temperatures in the upper atmosphere are super high. The thermosphere is often reported as going up to ~2k degrees Celsius. (And you wouldn't even know it if you were there, due to the low density.)

I'm curious what supersonic means in this case - what is the speed of these plasma jets; what is supersonic speed in the ionosphere?

djaychela• 9 years ago

There's a nice graph on Wikipedia about this, and what I didn't realise is that the pressure doesn't have a lot of influence on the speed, it's nearly all temperature-based. I would never have looked had you not made the comment above.

https://en.wikipedia.org/wiki/Speed_of_sound#Altitude_variat...

colechristensen5• 9 years ago

For practical engineering purposes, it is only dependent on temperature, proportional to the square root of the temp.

A mediocre intuition is that the speed of sound is governed by the speed of the individual gas molecules. Higher pressure and density mean there are more molecules hitting each other more often, but the speed of any individual molecule is the same and defined by temperature only. (it's only a mediocre intuition because the statistical dynamics that relate bulk properties to individual molecule interactions are complicated)

TeMPOraL• 9 years ago

Wow, I completely forgot the ranges of different atmosphere regions since I was in secondary school.

This picture here makes me wonder:

https://upload.wikimedia.org/wikipedia/commons/8/8c/Earth%27...

Did any spacecraft manage to fly through an aurora? Wouldn't it be cool if someone did that and shoot photos from within?

ygra2• 9 years ago

Usually spacecraft are launched near the equator if possible, so aurorae aren't particularly prevalent there. Furthermore, since the atmosphere is ionized there, I'd guess spacecraft would avoid launching if it meant passing through it. Since atmospheric charges due to thunderstorms and clouds are already a concern I wouldn't expect an ionized part of the atmosphere to be any different.

dahart4• 9 years ago

Check this out https://www.nasa.gov/content/flying-through-an-aurora

Also google image search for "space shuttle aurora"... spectacular pictures!

danesparza• 9 years ago

The article points out temperatures rise "up to almost 10,000°C"

I had no idea!

colechristensen5• 9 years ago

And if you were floating in it shaded from the sun you'd freeze to death. It's something like talking about the temperature of the air in a vacuum chamber. There is _always_ air in a vacuum chamber and it'll have a temperature, and that temperature will mean different things than normal intuition gives.

unityByFreedom2• 9 years ago

T-minus 10 minutes until Musk explains there is a way to easily harness the electrical energy from these jets, and it'll only take Tesla a year to do it.

TECHGUYOC• 9 years ago

.....or it's free!

jlebrech3• 9 years ago

or he could aim his rockets so they can ride the jets

cat199• 9 years ago

Tesla probably already did it in a year - too bad his notebooks were 'lost' ...

michaelcampbell• 9 years ago

Is there a history behind this quote? Would love to hear it.

blurbleblurble• 9 years ago

I came to the comments because I'm worried about just that kind of attitude. It strikes me that messing with this kind of thing could have some major impacts on the functioning of the atmosphere and magnetosphere, so I'd want to see very careful studies done by numerous independent organizations before we even remotely considered collectively giving Elon Musk a chance at something like that.

unityByFreedom2• 9 years ago

Nahh, Musk is a scientist, if he says it, it has to be true!

... that was a joke, HN, lighten up =)

SjuulJanssen• 9 years ago

Anyone else who clicked on the link and expected airplanes?

officelineback• 9 years ago

Yeah I kind of thought that, but "discovered" gave pause to that thought, since it's not "invented."

greglindahl4• 9 years ago

I was wondering why they were announcing that they'd found an astrophysical jet, when there are a zillion of them known already. 'Jet' is an overloaded term in science.

jlebrech3• 9 years ago

so here's our space elevator, nature already created it for us.

problem it only takes us up from the 2nd floor.

lolc• 9 years ago

And to get any lift you have to disintegrate into molecules first.

jlebrech3• 9 years ago

you don't have to be in the epicenter.

eternalban• 9 years ago

So what's the best way to harvest this energy?

Supersonic plasma jets discovered

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