“The head of all flower heads is one flower; the sunflower in the sky, that gives the others vivid color stemming from the inside.”
Curtis Tyrone Jones
Most people reading this already know what a Coronal Mass Ejection isn't. It isn't what occurs when someone with Coronavirus loses their lunch in a big way. So what is a CME? I'm glad you asked!
A CME is a solar flare on steroids! I'm clearly not an astrophysicist (I don't even play one on TV), so we will try to keep it simple. The main difference between a garden variety solar flare and a CME is their spatial scale. A solar flare is a local event in which solar plasma rises well above the sun's surface but doesn't escape the star's gravity. It falls back. A coronal mass ejection leaves the surface of the sun with enough force and velocity for some of its mass to escape the sun's gravity well. Unsurprisingly, most of our star's CME's are not aimed directly at Earth. This is a good thing.
When it does reach the earth's atmosphere, the impact can range from (lower end) an increase in "Northern lights" to (upper end) some electromagnetic phenomena that are hard to conceive. A good example in recorded history of an upper end CME would be the Carrington event of 1859, which reportedly melted telegraph wires (telegraph was the height of electronics in those days), made telegraph poles burst into flames and caused telegraph keys to operate autonomously.
The Carrington event begs the question, "What would happen if such an electromagnetic event were to happen today or in the near future?" Good question. Our advanced electronics are more vulnerable to such events and our society is very dependent on its advanced electronics. Many experts are concerned that an event much smaller than the famed Carrington event could cause enough damage to severely cripple our current electronic infrastructure. This is even more likely if the CME comes in multiple waves which is what some think happened in 1859. The earth's electromagnetic shield (the same electromagnetic field which makes a compass work) serves to provide protection from such events. This field is weakened considerably by strong solar flares and/or CME's. A perfect solar storm scenario might involve either two or more large CME's directed at planet earth or multiple solar flares (weakening earth's shield) followed by even a medium sized CME. Like a combination in a prizefight, the first blows weaken the defenses and the knockout punch comes after.
We know that the sun has cycles of activity. The easiest to observe (because of its short duration) is the eleven year cycle, which is based on the reliable flipping of the star's magnetic poles during the same time period. A CME is most likely to occur during the most active part of this cycle, known as solar maximum. There are other, longer, cycles and it is beyond the scope of this discussion to cover those in depth. As our tools to observe the sun (and other stars, as well) improve, so does our knowledge. In any case, our planet earth exists within the greater atmosphere of its star. Our way of life depends on the sun, and any change in the sun's disposition can have a huge impact on our existence.