As previously written, the photosphere is considered to be the “surface” of the Sun, followed by the chromosphere, and then the corona, the outermost part of the Sun’s visible atmosphere. The chromosphere is about 2000 kilometers above the photosphere and is a very thin layer compared to the Sun’s diameter of 1.4 million kilometers.
Plasmas in the chromosphere are low density, less than a millionth of Earth’s atmosphere, so it is not normally visible, because the underlying photosphere is so bright that its light is obscured. Temperatures in the chromosphere range from a high of 6000 Celsius near the photosphere to a low of 4000 Celsius in its middle regions. An ongoing mystery about the Sun is why temperatures increase to 20,000 Celsius at the top of the chromosphere.
Among heliophysicists, however, the most puzzling aspect is why the corona can be as much as two million Celsius! The hottest region of the Sun begins at 4000 kilometers, extending over a million kilometers from its surface, without any significant temperature drop. No one knows why this happens. One possible explanation is so-called “magnetic reconnection”. Since the problems with magnetic reconnection theory are detailed many times in previous Picture of the Day articles, they will not be explained here.
A recent press release states that coronal heating is due to events called nanoflares. Although they would heat and cool quickly, extremely hot plasma would accumulate into an overall method for increasing the coronal temperature. The research team admits that they have not solved the coronal heating problem, and that this is simply a first step in identifying whatever process is taking place.
The Sun is a positively charged electrode in a circuit, while the negatively charged electrode is located far beyond the planetary orbits. The “virtual cathode” is known as the heliopause. The electric solar model predicts that sunspots, flares, coronal holes, and all other solar activity comes from fluctuations in galactic electricity.
Electric charge flows out of the Sun, and is commonly called the solar wind. That outward current is balanced by electric charge flowing in, so changes in temperature most likely indicate magnetic field polarity and the strength of its electric field. Since the Sun is connected to the rest of the galaxy by Birkeland currents, it is most likely demonstrating fluctuations in electric charge arriving from the Milky Way’s generator.
Electric Universe advocate Wal Thornhill wrote:
“Sunspots are dark instead of bright, which is prima facie evidence that heat is not trying to escape from within. And the Sun’s corona is millions of degrees hotter than the photosphere. These simple observations point to the energy source of the Sun being external. Add to this the dominant influence of magnetic fields on the Sun’s external behavior and we arrive at the necessity for an electrical energy supply.”
In the electric model of the Sun, its electric field is strongest in the coronal holes, since protons are accelerated away. Outside of coronal holes, where the electric field is weak, protons move more aimlessly, resulting in more collisions. That random movement equates to temperature. Therefore, the solar wind is fastest where the corona appears coolest and is slowest where it appears hottest.