Good morning, Geeks. Please take your seats.
Today we’ll discuss the science behind solar flares and the distinction between a flare and coronal mass ejections. By now you’ve all seen the images and video from Tuesday’s M2.5 flare and CME. What you may not have gotten is a look at what solar flares actually are and how they’re produced. So that’s what we’ll work through this week.
What’s up, Sun?
In order to appreciate the massive plumes of energy flying from the sun’s surface, you first have to have a basic understanding of what’s going on inside.
In the beginning, there was a nebula (or molecular cloud or interstellar gas cloud) composed primarily of hydrogen and helium. The cloud collapsed and during this process, sectioned into smaller portions which pulled themselves together to form stars. Our sun’s particular area was massive enough to reach 10 million Kelvin, initiating the production of deuterium–nuclear fusion.
Finally–after much spinning and heating and nuclear fusion and the birth of eight planets (sorry, Pluto)–following the stars’ aging process, stellar maturity, our sun is now 4.6 billion years old and a class G2 star, just like Alpha Centauri A.
Like any rotating body composed of multiple materials, the sun has layers of varying composition and temperature. From the interior outward, the sun comprises a core, radiative zone, and convective zone. The sun’s atmosphere is composed of the chromosphere, photosphere and corona (again, from the inside out).
There’s a “dynamo” joke in here somewhere.
According to the Solar Dynamo Theory (the generally accepted but still slightly flawed idea of what’s going on in there), the fun stuff starts in the convective zone, where–through convection–plasma is boiling around while the sun spins. This rotating plasma is a really good electrical conductor, which means it can build up an electromagnetic field from magnetism already present in the materials. Remember the nebula we discussed? Interstellar gas clouds have magnetic properties; the theory works if we assume that part of that magnetic field was still present when the cloud coalesced during the initial phases of star production.
The magnetic field of the sun and the majority of other stars is most concentrated at the equator. Bands of magnetic “flux ropes” wrap around the sun’s middle, causing areas of high magnetic activity, the source of all solar weather: solar wind, sunspots, solar flares and coronal mass ejections.
We need to talk about your flare.
There’s a misconception that needs to be cleared up before we go any further. A solar flare is the sudden release of energy from the sun; a coronal mass ejection (CME) is a burst of plasma from the sun. These events are sometimes interconnected, though the understanding of their relationship is not well established, but it’s important to know the difference.
A solar flare is defined as a sudden, rapid, and intense variation in brightness that occurs when magnetic energy built up in the solar atmosphere is suddenly released. All three layers of the atmosphere are affected when plasma is heated and electrons, protons, and heavier ions are accelerated nearly to the speed of light. Solar flares produce radiation at all wavelengths, from radio waves to gamma rays.
Coronal mass ejections are massive burst of solar wind, other light isotope plasma, and magnetic fields rising above the corona or being released into space. The ejected material is plasma consisting primarily of electrons and protons; sometimes, the CME can contain small quantities of helium, oxygen, and iron.
Tuesday’s widely-discussed solar event was the combination of a medium-sized solar flare and a really massive CME. It was the largest solar explosion ever witnessed, but the flare itself was fairly unremarkable. The surprise (and awesome video) comes from the CME, a feature which astrophysicist Phillip Chamberlin, of NASA’s Solar Dynamics Observatory (SDO), says, “We’ve never seen a CME this enormous.”
Here’s the footage again in the most theatrical version available.
- “How the Sun Works” on HowStuffWorks
- Stellar Evolution
- PopSci‘s gallery, “What A Giant Solar Eruption Would Do To Earth“
- Scientific American‘s article on the vulnerability of the power grid
OK, so that was the first of the “thinky topics” posts. Yea? Nay? Weigh in, Geeks.