It didn't baffle them. They just observed it and the press reported on this unique property.
The perfectly round shape is a result of the strong gravitational force acting as a point source. The more complex exterior effects are all plasma related, but the shape implies nothing more than gravity is doing it's job, I believe.
What should baffle them is the fact that the sun has inflow events and highly irratic circuits that imply it does burn itself out over its lifetime but instead gains some of its fuel from 'solar inflow events' periodically. As I outlined here in this post on jref a while back:
[QUOTE=Zeuzzz;3744347]This is what I'm not so sure of personally. In theory there should be this definitive region, but from where I see it the solar wind is a plasma and should not diffuse out into a definitive spherical morphology, as it should retain its filamentary structure as the currents in the wind interact with the the surrounding plasma currents in the ISM. From what I've seen there are many theories about the heliopause, but no sort of proof, and no detection of a definitive shock wave. Wiki says;
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.
And one of the hypothesis that it lists is;
"An alternative definition is that the heliopause is the magnetopause between the solar system's magnetosphere and the galaxy's plasma currents." Which implies to me that the boundary is not as set in stone as the theory implies, local EM forces and interactions between the filaments should pervade this region, with the direction and pressure of the wind varying drastically depending on the local pressure, ionization, composition of the dust particles, EM forces, and plasma instabilities in question.
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I prefer Alfvens current disruption method, partly because the reconnection rate is always arbitrarily set, positive ions are likely to be unmagnetized in the central part of the plasma sheet (indicating that the frozen-in-field concept is not valid there), the Bu approach does not include all current driven process's as Amperes law is associated with a non zero curl, and other reasons, mainly that I find the interaction of two lines that are arbitrarily put in by us somewhat meaningless.
Pickup ions at the edges of the solar system were a fairly well established effect? Its essentially a similar process to the CIV effect, but does not require as high a charge flow to be involved between the two objects in question.
Interstellar Pick-Up Ions
Physical origin of pickup currents
Voyager observations of the magnetic field, interstellar pickup ions and solar wind in the distant heliosphere
And a very similar pickup ion process on spacecraft has shown evidence of a cross current instability prodcued by the pickup ion process;
http://ieeexplore.ieee.org/Xplore/login ... pdf?temp=x which is another EM force that may shape the structure of the solar wind to something other than a clear defined spherical shock.
I guess my main problem is that current theories only include the possibility of outward going particles, and exclude the possibility of incoming particles to the solar system, which would effect the overall structure. We know that Solar inflow events are now a well documented phenomenon (
ref), of superhot "gas" (ie, plasma) flowing into the sun, against the predominant direction of the solar wind, and these events are in an area where the ram pressure and density of the solar of the wind is very considerable, if these events can flow against this outward flow right next to the sun, it seems much more likely to be occuring on a larger scale at larger radii where the pressure is less (as density and ram pressure drop off with r as r[sup]-2[/sup]). Its also known that the electrons in the solar wind tend to mill around with no preffered direction, their average velocity will be outwards with the ions in the solar wind, as they will couple with the vast majority of the protons in the solar wind due to electrostatic attraction, making any set area of the solar 'wind'
overall largely neutral. However, recent discoveries of
electron depletion in the solar wind due to “backstreaming electrons” flowing into the Sun from the surrounding medium were not expected, which have been found to be roughly symmetric about a 90° pitch angle relative to the heliospheric magnetic field. And SOHO has found
""jet streams" or "rivers" of hot, electrically charged gas called plasma flowing beneath the surface of the Sun." (
ref), much faster than would be expected from standard convection, implying electrcial activity could be shaping these fast inflows.
Backstreaming Electrons Associated With Solar Electron Bursts
Although you dont get much mention of particles in the solar wind travelling the opposite direction than usual, there are many separate occurences of this happening which have been attributed to various theories, which does lend credence to Alfvens heliospheric current circuit model for stars. Especially since electron depletion and backstreaming has been observed to be related to the heliospheric current sheet, and the heliospheric current sheet has been known to generate dark currents (filaments) for a good few years now
"we study the typical structure, configuration, and dynamics of the interplanetary dis- turbance generated by the interaction of disappearing solar filaments with the heliospheric current sheet (HCS) and a flare using the most geoefficient (Ap = 56 nT, Dst = –166 nT) solar-activity event in 1997 as an example." (
K. G. Ivanov and E. P. Romashets, 1998)
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Thanks for the response. My line of thinking is that if the magnetosphere of the solar system is anything like the magnetosphere of planets we now know that a vital component of magnetospheres are the Birkeland current systems that they support. All planets have very high current inputs at their poles, essentially what causes the auroras, and these currents have very recently been found to directly connect the poles of Earth to the sun, transferring over 650,000 Amps. In 2007, the Themis satellite
"found evidence of magnetic ropes connecting Earth's upper atmosphere directly to the sun [in which] a burst of electrical current within the solar wind will hit the bow shock and—Bang! We get an explosion" (
ref,
ref A few interesting models that try to build a full Birkeland current circuit for planets magnetospheres based on the charge transfer and EM forces between them have been proposed previously, but I dont think that any conclusive models have been put forward as of yet (though, I may be wrong on this)
http://www.agu.org/pubs/crossref/1998/97JA02880.shtml
Heres a few more publications which consider this circuit based approach (Alfvens type of approach) to Birkeland current formations in magnetospheres;
Mercury's Birkeland current system
Birkeland current system key parameters derived from Iridium observations
Auroral structures at Jupiter and Earth
Alfvén wave coupling in the auroral current circuit
What Supports Parallel Electric Fields in Birkeland Current Regions?
Transition current systems in the Earth’s and Saturn’s magnetospheres
I believe that the full birkeland current circuit of magnetospheres is still an open question, but the incoming current input into the poles of planets seems to be consistant with all local magnetospheres, and so should imply that a similar effect occurs on the sun. Radio waves, ultra violet radiation and polar jets are all known to emanate from the suns poles, and what causes coronal holes is also considered a bit of a mystery. And the observation of bright points on the suns poles and the consequent activity certainly implies this.
http://www.mssl.ucl.ac.uk/~db2/Culhane_PASJ07.pdf
Which is nearly exactly what has been observed on Jupiter, this same type of bright spot directly on the pole;
http://photojournal.jpl.nasa.gov/animation/PIA03452
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http://photojournal.jpl.nasa.gov/browse/PIA03452.gif[/qimg]
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http://img260.imageshack.us/img260/9418 ... medfo1.jpg[/qimg]
So could the sun contain similar Birkeland current formations thoughout the solar system in its magnetosphere? Just like the currents we know enter the planets from their various magnetospheric current systems. I think its likely, we only just discovered the currents right here on Earth, its going to be a lot harder to assertain the current system of the sun where the background radiation makes it harder to see whats going on than on planets. And the currents seemingly only become energetic enough to become visible in the corona, right next to the sun, they are more diffuse further out and so are very hard to detect, often reffered to as 'dark currents' as they emit no known detectable radiation [like the ones connecting the Earth to the sun which are very hard to see]. If this does turn out correct, it has implications for the nuclear fusion model of stars and their lifetimes, as the source of the suns energy may be from an external source, from particles in the local galactic environment, not burning up exclusively internal energy it already possesses. This is probably why the idea was dismissed initially, and due to Alfvens other controversial ideas too...
The question that remains is what is the definitive solar circuit? Is the current reversable in this system, does it work both ways? Can properties of this varying current input explain the suns 22 year cycle? (see this:
Does the solar wind affect the solar cycle?) Or the reversal of polarity? I think that many of the outstanding questions of solar physics could be answered by applying the effects of the heliospheric current circuit to current models.[/QUOTE]