FYI verisimilitude, I uploaded a Helioviewer movie that I made of a couple of sunspots to show you what I mean about sunspot umbras and their polarity. I overlaid a HMI continuum image so you can (barely) see the two umbras of the two sunspots, along with a magnetogram image so that you can see the black/white color overlay from that image, and a 131 AIA image in blue which shows the coronal loop activity in the region of the sunspots:http://www.etwebsite.com/sdo/2011_10_13 ... Mag-hq.mp4
As you can see in the composite image, the sunspot umbra on the left has the opposite magnetic field polarity from the one on the right, and the coronal loop bundles are flowing from one umbra to the other. The direction of the flow of electrical current through the coronal loops dictates the polarity alignments in the umbra regions, and the umbra regions are areas of massive coronal loop activity due to charge separation in those regions.
IMO the coronal loops are actually originating from a deeper, more rigid layer of the solar atmosphere. By "rigid", I mean it's probably a solid surface IMO, but it could simply be a layer of more dense plasma. Whatever it's made of, it rotates evenly, unlike structures in the photosphere which to come and go in about 10-minute intervals and which rotate unevenly. That whole "rigid" layer rotates evenly in running difference iron ion wavelengths like this RD 131A image:http://www.etwebsite.com/sdo/2011_10_13 ... 131-hq.mp4
IMO the "rigid surface" is charged differently in different locations and the coronal loops originate at the surface of that rigid layer. Only the largest coronal loops come up and through the surface of the photosphere, and they leave their magnetic field signatures on the surface of the photosphere. As I mentioned, if you overlay 1600A and magnetogram images, you'll notice that the "hot spots" (brighter regions) in 1600A are correlated to the strong magnetic field signatures in magnetogram images. Those hot spots in 1600A also correlate to the larger coronal loop layouts. It's the heat of the coronal loop that leaves hot spots on the 1600A and 1700A images, and the current flowing through those loops also generates the magnetic field signatures in magnetogram images. If you overlay a 1600A, magnetogram and 131A for some period of time, you can observe those correlations quite easily and without exception.
The mainstream has the false impression that the footprints of coronal loops can only be seen in the "transition region" between the chromosphere and the corona, whereas in reality the footprints of coronal loops are visible below the surface of the photosphere. They are located under the photosphere IMO, at least in face on images.
Limb images however tend to give the (false) impression that there's a "transition region" above the photosphere, but that's actually an optical illusion that is caused by the absorption of those wavelength's along the limb where the light has to penetrate much more atmospheric plasma. In "face on" images however, the coronal loop footprints are originating below the surface of the photosphere, on the "rigid' layer beneath the photosphere.
In this composite 171A Trace (in blue) and Yohkoh x-ray (in yellow) image, you can see that the blue areas of the coronal loops descend much further into the solar atmosphere than the x-ray emitting 'tops" of the coronal loops which are located in the corona and are only visible in the corona. The x-rays from the loops are absorbed in the chromosphere and photosphere, but the 171A wavelengths are not as easily absorbed and are visible under the surface of the photosphere.
In virtually every respect Birkeland's terella experiment is identical to what we observe in the solar atmosphere, including the heating of the corona by the current flow through the corona.https://www.youtube.com/watch?v=m58-CfVrsN4
When Birkeland introduced an electromagnetic field inside the solar terella he was able to create coronal loops which essentially followed the magnetic field lines of the internal field. By using a 'rough' surface he noticed that the coronal loops would tend to concentrate at the tops of the bumps on the terella. The same is true in solar activity. The footprints of the coronal loops are fixed to "rigid" surface points and they tend to concentrate on the "bumps"of the rigid surface.
Sunspots have no set polarity or charge, negative/positive/N/S alignments because it's the flow of current inside coronal loops that dictate those N/S alignments, and the charge separation is actually occurring on the rigid surface below the photosphere.
As "weird" as these ideas might sound to you, they all jive perfectly with every SDO image, and every other satellite image of the sun.
Coronal loops are simply current carrying plasma threads, aka "magnetic ropes" which originate on the rigid surface and return back to the rigid surface below the photophere. The larger loops traverse the surface of the photosphere and leave their heat and magnetic field signatures on the surface of the photosphere as we see in magnetogram and 1600A images. The smaller loops never rise high enough into the atmosphere to cross the surface of the photosphere which is why we only observe strong N/S field alignments in magnetogram images near the largest loops, and not over the whole surface.
Birkeland knew more about solar physics 100 years ago than mainstream astronomers know to this day. He would have *easily* been able to explain how SDO images work, whereas the mainstream still struggles to explain them. In fact they still can't seem to explain the heat source of the corona, which is completely *obvious* to anyone who embraces Birkeland's solar model.
Virtually all these same layouts and explanations would apply to an anode Juergen's model too, but the solar wind direction and content tends to favor a rigid cathode surface rather than an anode surface IMO.