Superflares a Threat?

The cosmos poses many threats to Earth and to life on Earth. These include asteroid impacts, nearby supernova explosions, and gamma ray bursts, all of which could destroy all life on Earth very quickly. Climate change is by far the greatest immediate risk to life on Earth (nuclear weapons are as well), but when it comes to natural events outside of Earth that pose a risk, solar flares from the Sun rank right up there. The Sun emits blasts of energy all the time. Most of those blasts of energy are not directed at Earth, but when they are, they are often diminished and don't pose a great risk. Earth's magnetic field does a great job deflecting most of the potential harm from high energy solar particles.

Very large solar flares with larger energy can "break through" the Earth's magnetic fields with particles reaching Earth's surface. Some particles break through all the time and interact with Earth's atmosphere and produce the colorful lights we see as the aurorae, especially at the higher northern and southern latitudes. This is not a problem, yet, as the numbers are too low to cause much of a problem on the surface.

Astronomers have recently discovered that stars can occasionally produce superflares on longer time scales with a tremendous amount of energy.

Rare 'superflares' could one day threaten Earth

These superflares are more intense than the large solar flares we've seen the Sun spit out in present times. The danger is the effect these high energy particles have on our electrical grids on Earth, potentially causing widespread outages that could potentially last years! That's a problem! Our electrical grids are not updated to where they need to be to protect from these larger flares. 

And before you think this is a super rare event that will not happen in our lifetime, think again. The Carrington Event was a large blast of solar energy in 1859. Back then, this wasn't a problem as we were not dependent on electricity, but that same blast today would have been a huge problem, resulting in the deaths of thousands if not potentially millions of people across the globe. Here's a great article on the potential effects of a large solar flare.

What Damage Could Be Caused by a Massive Solar Storm?

Rare doesn't mean "will never happen". Rare events happen all the time. Winning the lottery is rare, but someone wins it all the time. We need to be prepared for rare events so the damage is limited when the rare event occurs. Right now, we, as a society, are not prepared to deal with the damage from a large solar flare.