My horoscope told me to "concentrate on the leisure angle" and "take it easy; enjoy a long lunch with friends" so here's a leisurely-written science entry for you.
First off, Happy Birthday to Alec Baldwin! Talk about an epic actor.
In honor of another movie that uses science to create fiction then removes the science from it, here's an explanation of a solar flare-based armageddon.
Solar flares are...well, let's pretend like a sunspot is a zit on the face of the sun. A solar flare is the pus that shoots out when the zit is popped. The intense magnetic fields formed by the sunspot cause a violent explosion(s) of plasma from the sun, which can travel nearly the speed of light. This plasma leaves the sun in the form of a wide band of radiation, from gamma rays all the way down to long-band radio waves. When they hit the earth, they can cause all sorts of problems.
So imagine, if you will, that a massive once-in-1,000-years solar flare comes speeding towards earth. The first thing you'll notice is that your Garmin GPS has stopped working. This is because a massive burst of ionizing electrons has fried every satellite in orbit. The three astronauts in the International Space Station will also stop transmitting...for the worst reason. In fact, it's likely the energy will be sufficient to vaporize the entirety of the ISS, so anyone looking into the right part of the sky will see a tiny explosion as the ISS fragments and burns.
Then the sky will be bathed in ionization, which will look like the Northern Lights times one million. At that point, don't panic, you still have time to hug your kids.
Most of the harmful radiation from the sun will be absorbed in the earth's magnetosphere, and will superheat the atmosphere, destroying the ozone layer. However, all life on earth's surface will still be bathed in a massive dose of gamma rays. Of course, no one will immediately notice. We'll all just look up at the sky and watch the fireworks, then turn on the TV to see the news about what happened.
Unfortunately your TV won't turn on. The EMP will have fried all electronic devices on earth, and even if you did have a working TV because you happened to have had it in a Faraday cage during the solar flare, the broadcast satellites have burned up in the atmosphere, so there is nothing transmitting to your TV anyway.
Our cell phones won't work, the radio won't work, electrical transmission wires won't work, so by that evening you'll be sitting by candlelight in your dark, cold home wondering "just what the government is doing about this."
Unfortunately, the government won't be able to do anything. By the next morning, most of us will be throwing up blood as our internal organs dissolve. That massive dose of radiation we engorged yesterday will have killed the DNA in most, if not all, of our cells, so our bodies are dying off at a rapid pace. Cells that reproduce rapidly, like skin cells and the cells that line our stomachs and intestines, will be the first to go, so watch for your skin to start sloughing off like you have massive burns and you'll start leaking fluid. You'll also probably go blind, and your senses of smell and taste will disappear. Within another 24 hours, any organs that remain, like your kidneys and liver, have shut down both from an overload of work, and the fact that your body has no ability to absorb water. By 48 hours after the solar flare, you and every other living creature on Earth's surface, will be dead or nearly so.
The lucky ones, who happened to be deep underground or underwater during the event, will emerge to find the world a desolate place. All surface life is dead or dying, so food production will be difficult. It will also be hard to grow new food, as all seeds that were splashed with radiation are no longer viable. You cannot eat the dead, they are so strongly dosed with radiation that going near them will give you cancer. Your best bet is to eat fish, which were largely protected from the radiation by the water.
Of course, that's only a temporary solution, as the complete collapse of the planet's ecosystem will soon carry over into a massive dump of phosphorous and nitrogen into the world's oceans. Algae (assuming some survived the flare) will bloom like never before, de-oxygenating the world's oceans, killing all the fish.
The world really probably would never recover, or at least not for thousands of years. The massive burn up of ozone from the flare would open the world to being constantly splashed with cosmic radiation, which would consistently wipe out any DNA-based life forms that tried to leave the deep sea. Eventually, in thousands and thousands of years, the atmosphere might recover enough for earth to support life. Maybe.