Voyager Enters Final Frontier Of Solar System Options

[Explorer1]

I think this time they're very sure this is the last section before true interstellar space (in terms of particles, not gravity). It was described as the 'off-ramp' to the stars in the recent teleconference. And the team will know it when they see it.
Once Voyager 2 crosses into this same area, we might even be able to guesstimate the large-scale shape of this 'highway'.

[djellison]

There will be no sharp cut off of gravity - why do you mention that?

[0101Morpheus]

What I meant is that the scientists told us there was a clear boundary between the heliosphere and the outside. First they said there was a blow shock. Now we know the Sun doesn't have one. Then they said that the boundary would be when the solar wind stopped and there would be a sharp increase in cosmic rays. And thats what we've seen. But now they say were still inside the heliosphere because of the magnetic orientation. This new "in-between" area.

The heliosphere is the edge of the suns magnetic field. I was led to think there would be a sharp boundary. Now it seems to depend of interpretation. Is the edge where the influx of cosmic rays begins, or is it when the sun's magnetic field gives way to the galactic magnetic field? Thats all.

[Explorer1]

I was replying to 0101Morpheus about whether there's a clear transition into interstellar space which the heliopause crossing will be. Yet it really depends on our definitions of solar system; the sun's gravitational influence will be felt much farther, tens of thousands of AU, while the high energy particle environment can and does change rapidly, as this recent discovery shows. The Oort cloud would be 'outside' our solar system by the latter particle definition, but clearly still gravitationally bound to the Sun.

[0101Morpheus]

Seems we got our replies mixed up.

Yes I know the sun's gravity doesn't stop. You can keep going for a light year and still be inside its hills sphere.

[TheAnt]

In the data for Voyager 2 we got a dip for the particle flux now in the first week of December then it had a small peak, to fold back down in about the same pace in the last days.
This might be similar as what we did see for V1 in August.

However this is one "stay tuned" post of mine for those interested, a heads up that also V2 might get close to the boundary but that it's not quite there yet.
Voyager 2 data page

[djellison]

V2 is clearly in a very different environment to V1. V2 has had a very gradual decline over the past year to about 50% of initial levels. V1 was almost static at a fixed level until a very sudden and rapid decline by an order of magnitude in literally a day that bounced back and forth a little then dropped for good. Fascinating.

[Explorer1]

Until New Horizons gets out there, these two are the only data points we have on what is certain to be complex large scale structures. Glad both are still functioning.

[stevesliva]

Until New Horizons gets out there, these two are the only data points we have on what is certain to be complex large scale structures. Glad both are still functioning.

No magnetometer on NH, though. Going to be a very long time until another magnetometer heads out there. (Comments about exactly how far NH will get aside.)

[TheAnt]

V2 is clearly in a very different environment to V1.

My little personal hypothesis is that it is the same environment, the graph certainly dropped like a rock for V1 - which made me pay attention that something had happened. V1 are heading in a direction nearly bulls eye on the solar apex (the direction which the sun are travelling) - so the sphere might be somewhat flattened there and the border zone itself compressed.
But that V2 are entering it at a point nearly 90 degrees from the solar apex and so the process will take a longer time.

Since my post the particle count have started to drop down again - but as said, my post were merely a heads-up I am fully aware from my own work not to build intricate theories on just a hump in a graph. =)

[TheAnt]

I have to admit bafflement for how the data have turned out. The particle count went down until early January which suggested a slower but continued decrease, after that it have been climbing up and approaches the average level. So djellison might have been right that the environment here are quite different indeed. I abandon any pet hypothesis gladly when there's a chance for something new, interesting or unexpected. =)

[brellis]

ack, I have some more innocent questions:

Are there interstellar elements still floating inside the solar system? Towards us? Has Voyager 1 and/or 2 helped determine that distinction?

[TheAnt]

ack, I have some more innocent questions:

Are there interstellar elements still floating inside the solar system? Towards us? Has Voyager 1 and/or 2 helped determine that distinction?

Oh there have been several spacecraft that have detected interstellar particles IBEX and Ulysses are two of those, the Stardust mission were to collect interstellar material, and I tend to think that also the Deep impact/EPOXI spacecraft did enter a stream of material thought to have originated outside the solar system. So there might be plenty more to find also if future spacecraft are provided with instruments to detect such.

[MarcF]

False alarm :-(
http://voyager.jpl.nasa.gov/news/voyager_update.html

[TheAnt]

You had me wonder for a bit, then I found that the NASA disclaimer seem to be referring to this item.

Though they do not say with certainty that Voyager are in interstellar space: "However, Webber notes, scientists are continuing to debate whether Voyager 1 has reached interstellar space or entered a separate, undefined region beyond the solar system."

Edit: And the headline in the piece I linked were changed to the more neutral "...entered a new region of space" a short while after my post were made.

And here's the actual paper in preprint.