Friday, 16 February 2018

The Sunspot Delusion

Lies, Damned Lies and Statistical Mechanics - 4

The Story So Far:

The three previous blogs explained how the Sun came to be a hydrogen shell with a fusion zone supporting it by thermal pressure from below while the weight of the coronal constituents bears down on it from above. Also how the photosphere and lower corona, squeezed by gravitational pressure, have their temperatures (i.e. kinetic energies) kept low by the Pauli Exclusion Principle. The solar spectrum is then manufactured by the progress of Compton collisions through the photosphere and corona. This left us with puzzles about the nature of sunspots and the presence of elements heavier than hydrogen in the corona, bar those in the protostellar cloud that arrived late on the scene.

The delusion is that sunspots are said to be dark because “they are colder material than the super bright solar surface”. However, if that was the case, there would be a point above the surface where the sunspot outflows reached the same temperature as the photosphere and this would be visible. It seems more likely that sunspots are hotter than the photosphere. Also, why is there all that electromagnetic activity? And why do pairs of sunspots often form?

Magma Plumes on Earth

In some senses, the interior of the Earth is a structural analogue of the Sun’s interior. Think of the Hydrogen shell mimicking Earth’s crust and the internal plasma matching the Earth’s magma (molten rock, or lava beneath the crust). Then there is helioseismology. While Earth’s seismic shocks are transmitted through magma, they originate in the crust. So where do the Sun’s shocks originate?

You may be familiar with the volcanic hotspots on Earth, which arise where plumes of magma burst through the Earth’s crust, often with dramatic effect, building new islands in the Pacific or creating enormous volcanic structures like the Yellowstone caldera.

Plasma Plumes

Deep in the solar interior, much violent fusion is going on, which probably rises and falls in its intensity, occasionally building so much pressure that it bursts upwards, in the form of a plume, and breaks through the photosphere. It is also possible that stray asteroids puncture the Sun’s surface, allowing some of the plasma to escape. (Is it just a co-incidence that the solar cycle corresponds with Jupiter’s orbital period? Jupiter’s gravitational field acts as a magnet to re-focus the more eccentric small orbiting bodies)

Ions, travelling, are, in effect, electric currents. The positive ions work like a reverse direction current. So since antiparallel currents repel each other, whilst parallel currents attract each other, the two streams of positive and negative ions tend to separate streams that can become twin plumes, then each plume follows its own path along a radius out to the photosphere. Hence twin sunspots are observed. Once at the surface, the plasma from below merges with that from above, but at the point of outflow, the opposing magnetic fields, generated by the plumes create substantial magnetic fields that use the other plasma as conduits.

One might wonder why the hydrogen shell below the photosphere doesn’t disintegrate, but volcanoes on Earth don’t have this effect on Earth’s crust.

Heavy Elements in the Corona

These plasma plumes may be bringing helium and other elements from the solar centre to the corona, accounting for some of the non-hydrogen lines in the solar spectrum.

This is part 4 of my solution to the Solar temperature and heat transfer problem and completes the set.

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