This moment is brought to you by the sun. That hot, trembling ball of plasma, which you probably mentioned at least once today in your mandatory small-talk about the weather, is certainly the cause of both humanity and the weather.
The star we call ours is located about 27 light years from the center of the Milky Way Galaxy, in what we humans call the Local Fluff, inside the Local Bubble. It is a ball of plasma, and not a ball of gas, the difference being that in plasma electrons are decoupled from nuclei, whereas in a gas, they stick together to form atoms. The energy required to keep the nuclei and electrons apart comes from the same source as the sun’s light: nuclear reactions.
The main type of nuclear reactions that occur in our sun are described by the proton-proton chain, where hydrogen nuclei (which are protons) are converted to helium nuclei. Other particles are also produced in this chain of reactions, like positrons, neutrinos, and gamma rays. Gamma rays are very high-energy photons, or particles of light. These gamma rays are ultimately the source of the visible light we see when we look at … anything. Between their creation in the center of the sun and their escape from the sun’s surface, the gamma rays interact many, many times with the particles inside the sun and break up into many lower energy photons. This takes several thousand years. Then it takes another eight minutes for the same photons to reach the earth.
Much like the earth, the sun has a magnetic field dipole. This is because the sun is not just a giant ball of plasma, it is a rotating giant ball of plasma. Since plasma is made of charged particles, as the sun rotates, the charged particles form a current, which then creates a magnetic field. And all that plasma, rotating so fast that the sun spins around it’s axis about every 28 days, creates a magnetic field much weaker than a fridge magnet. But that’s only the overall dipole. There are local magnetic fields at the surface of the sun that can reach thousands of time these strengths. These magnetic fields form a loop, half in the sun, half outside. Where the loop intersects the solar surface, two darker spots are formed, which we call sun spots.
Every eleven years, the sun goes through a cycle of minimum to maximum “solar activity.” This has been happening for a long time. Humans have been recording it for so long, in fact, that this year we’re having our 24th recorded solar cycle maximum. The maximum corresponds to a maximum in the number of sunspots observed on the surface of the sun. Consequently, we see more solar flares, which are huge ejections of solar material associated with sunspots. Also during the solar cycle maximum, the dipole magnetic field of the sun flips. Its south pole ends up being where its north pole used to be in the previous cycle. Another feature of a solar maximum is an increase in irradiance, or light energy coming from the sun. This includes an increase in UV light reaching the earth, which means we might be seeing higher UV indexes this summer.
If you want to learn more about the solar maximum, there is plenty of news coverage about it this year, and some beautiful images of solar flares can easily be found on the internet. More importantly, now that you know around twenty new things about the sun, imagine how much better (or worse) your small-talk is going to be.
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