Solar Section        


Reverse polarized areas during the transition of Solar Cycles

Most solar amateurs are familiar with the Sun’s 11 year cycle going from low activity through high activity back to low activity. Most of those are also familiar with the fact that the Sun reverses its polarization at solar minimum with every cycle, so that after roughly 22 years the Sun’s polarization returns again to that as it was at the beginning of the 22 years.

Active Region areas move from East to West on the hemisphere. This is left to right on most images since most images of the Sun show North up, East to the left and West to the right. So “leading” the area is to the right of the area, and “following” is on the left. When the magnetic fields in active regions break through the surface of the Sun we can see the magnetic activity, and identify the magnetic poles of the area by looking at how the particles move. (red shifted and blue shifted) This is clearly shown in the “magnetograms” of the Sun and published on the NASA’s SDO website, resulting in the white and black colorization of the full disk image. Also note that the polarization of the areas in the Northern hemisphere are opposite of those in the Southern hemisphere.

So to check for new solar cycle activity, one should not only look for low active region activity but also if new reverse polarized areas can be detected. As an example, look at figure 1. As you can see, in the full disk image, AR2738 which is at the left in the Northern hemisphere is still a Cycle 24 area and it shows the black area on the right (leading) and white on the left, and the same for the remnant of AR2737 in the right in the image. That is how the Cycle 24 areas are polarized in the Northern hemisphere. For the Southern hemisphere it is exactly the opposite.
Next look at the images in the overview (Click the link at the end of this page) which have been annotated with arrows to point out where the regions are. The magnetogram shows again the poles of the area in black and white areas. Then look at the small area in the image of the others. The one in the northern hemisphere has the white leading (to the right), but the one in the southern hemisphere has the black leading. That is just opposite of what they would look if they had Cycle 24 polarization.

Now, these are very small areas. In fact so small that at the current time, almost none of them qualify to be named as an Active Region or even a pore. When Cycle 25 becomes evident, we need to see a number of named active regions with that polarization. Another requirement is that the latitude of these regions need to fit the butterfly pattern shown at the end of the overview. This means that they should start showing up in the higher latitudes, North or South, and not near to the equator of the Sun.

So until these areas become the norm, we keep looking for evidence of reverse polarization of these small areas and will update this overview until we reach Cycle 25 or until it becomes too much work.  A last word: Come back frequently, click this link to the pdf document containing the areas, and check on the progress being made in the transition.






Figure 1

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