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Voyager 2 Detects Peculiar Solar System Edge
ClickOnThis writes "CNN reports that Voyager 2 has detected evidence of the magnetic edge of the solar system (aka the heliopause) at 76 AU (1 AU = 93 million miles), much closer to the Sun than the location of 85 AU found by Voyager 1. From the article: 'This implies that the heliosphere, a spherical bubble of charged low-energy particles created by our Sun's solar wind, is irregularly shaped, bulging in the northern hemisphere and pressed inward in the south. [...] The researchers think that the heliosphere's asymmetry might be due to a weak interstellar magnetic field pressing inward on the southern hemisphere.'"
I believe from the Voyager I expedition that Voyager I detected and eventually cross the heliosphere where it was detected a year later. So the idea that the size stayed steady during the time then quickly switched sizes as Voyager II approached is unlikly... Unless the excape of Voyager I has upset the Gods... Then we are all doomed!
no, we've been taking data over many years along two different parabolic trajectories, that's a HUGE difference from sampling at two little data points. And we'll keep taking data along these curves; expansion or contraction and other variations could possibly be detected
North and south also refer to magnetic poles. North is generally assumed to be the positive pole, and south the negative, though when poles flip, as happens on earth (every one million years I think), and the sun (every 11 years or so, sometimes refered to as a period of solar maxima), common usage north and south probably won't switch. Wikipedia has a bit more info.
There's also galactic north and south, which are imaginary axes perpendicular to the the plane of the galaxy. Again, wikipedia has more info.
I'd hazard that what this article refers to as north is probably some assumed "solar north" roughly parallel to Earth's north.
...from a far less clueless source.
Here is an illustration of the phenomenon.
-mcgrew
I forgot whose talk I heard yesterday (they changed the speaking order; session was SH22A) but basically: V1 passed the termination shock (NOT the heliopause; summary is wrong) at the end of 2004; this was the big announcement at last spring AGU meeting. Before that, they were seeing foreshock signatures (plasma and magnetic). V2 is now seeing those signatures, but seeing them a fair bit closer in than V1 was observing them. So, V2 has not passed the heliopause, nor even the termination shock, but appears to be nearing the TS closer to the Sun than V1 did. This is a surprising/interesting result, but not huge overturning of theory or anything. Learning the structure of the outer regions of the Solar System is the whole point of these exercises (and the upcoming IBEX mission).