Here we are, at the Sun’s photosphere. What a vision!
Seeing it through special filters we witness a vast plum of plasma shooting up and arching back to the photosphere. A prominence! Several Earths could fit into the arch. Above us we see those spicules of plasma in the solar transition layer. From below they look like pointy bubbles, moving away and disappearing.
Below we see what we call granulation, millions of bright hexagonal shapes with darker edges covering the photosphere. They are monstrous columns of plasma seeping up from below, kind of like columnar lava flows on Earth.
Then we see a filament below. It looks like a big piece of thread but undulating and growing. Oh, wait, it’s coming right at us and we get slammed as it engulfs us! Now it’s above us and…it’s a prominence! Seen from above a forming prominence looks like a fiber, so they are called filaments.
Following a prominence to the photosphere, we see where it started, and it’s dark, a sunspot, and there’s another nearby where the prominence is returning. Sometimes we see prominences twist around each other, causing explosions. They are following magnetic fields that are twisting. Why are they twisting?
Sometimes the Sun seems to burp, shooting plasma out. A Coronal Mass Ejection…look out!
Below the photosphere is the convective zone, a roiling boil of plasma. The plasma temperature rises from 5700 to 2 million degrees kelvin as we continue our dive. It boils steadily but there is a disturbance. Seems magnetic fields are crisscrossing and twisting around here causing the rising plasma to do the same. Let’s keep diving.
OK, here’s the culprit, the tachocline. It’s a relatively thin layer of the Sun, resulting from differential spin between the convection zone above and radiative zone below. The tachocline is a miserable place, where all kinds of electromagnetic energy is produced leading to intense, twisting magnetic fields. How about a roller coaster, tilt-a-whirl combo? Sick yet? It is thought that the tachocline is where the Sun’s overall magnetic field is produced.
Below the tachocline we cruise through the relatively calm but increasingly dense and hot radiative zone, where plasma temperatures increase from 2 million to 7+ million degrees kelvin as we get closer to the core.
Then there is the core. Taking up about 25 percent of the Sun’s diameter it holds the key to being a star. This is where fusion takes place, hydrogen is fused together by the intense pressure from gravity and heat of 15 million degrees kelvin. Out pops helium and a bucket load of photon energy.
It takes up to 170,000 years for photons to work their way to the photosphere (324 thousand miles). Then about 8.5 minutes to reach Earth (93 million miles).
What’s in the Sky?
August 21 &22; after sunset; west-southwest: Watch a waxing crescent Moon dance with γVirginis on the 21st and bright star Spica on the 22nd.