What is a Solar Flare?
Here’s a quick and easy to understand definition of what a solar flare is. Magnetic energy builds up in the solar atmosphere. Once this pent up energy reaches a certain level it can no longer be contained and is suddenly released in the phenomenon known as a solar flare. This massive release of energy can be equivalent to the explosion of millions of 100-megaton hydrogen bombs and emits radiation throughout the whole electromagnetic spectrum, from low energy radio waves, to visible light, to higher energy radiation such as x-rays and gamma-rays.
Most solar flares have been known to have three stages. The first of these stages is known as the precursor stage. During this stage the initial release of magnetic energy is triggered and soft x-rays are emitted (NASA.gov). The second stage is called the impulsive stage. Different particles, such as protons, electrons, and heavy nuclei are heated up by the released magnetic energy and are accelerated into the solar atmosphere. During this stage we see radio waves, hard x-rays, and gamma-rays being emitted (NASA.gov). The final stage is dubbed the decay stage, in which the build-up and decay of soft x-rays can be observed.
Solar flares reach out to the outermost layer of the Sun’s atmosphere, called the corona, which is made up of gasses that normally have temperatures of a few million degrees Kelvin, but during a flare these gasses can reach upward to 100 million degrees Kelvin. The number of flares that occur is directly related to the Sun’s eleven year cycle. When the cycle is near its minimum the numbers of active regions (areas where solar flares and sunspots occur) are fewer, hence less solar flares and when the cycle is near its maximum the inverse can be expected to occur, more active regions equaling more solar flares. The Sun reached its maximum in approximately 2011 (NASA.gov).
Now that some of the basics are known about solar flares, it’s time to give credit where credit is due and acknowledge the discoverers of the solar flare. As it so often happens in the realm of astronomy, this phenomenon was observed by an amateur astronomer. The day was September 1st, 1859 and Richard Carrington observed four points of light coming from the surface of the Sun, while observing sunspot clusters near the Sun’s equator (WordPress.com). After checking his equipment for malfunctions and finding none that he could see he went back to continue his recording only to find the event much diminished and near its end. His observations were then validated by an independent observer named Richard Hodgson, who also saw the flare on the same day and proved the observation wasn’t due to an equipment malfunction. These two men are credited with the discovery of the solar flare and marked the beginnings of our understanding of these solar events.