The mid-level Solar flares happened on the surface of the sun. It occurred on March 7, 2015. How the event occurred was the sun emitted a mid-level solar flare peaking at 5:22 pm. NASA's Solar Dynamics Observatory, which they watch the sun constantly, and caught an image of the event.
How this could affect the Earth is since Solar Flares are large outbursts of electromagnetic radiation. This radiation cannot pass through through the Earth's atmosphere, so it wouldn't physically affect humans on the ground but, if there is enough intense radiation it can disturb the atmosphere layer where GPS and communications travel.
Some related topics that are similar to this are SDO captured mid - level solar flares. It happened on March 10, 2015. It's almost the same date as my other topic as well. They both got captured by NASA's solar dynamics observatory and they also captured picture of them.
"Solar Event News Archives 2010-2015." NASA. Ed. Rob Garner. NASA, 21 Apr. 2015. Web. 16 Feb. 2017.
"Captures Images Of Mid-Level Solar Flares." NASA. Ed. Brian Dunbar. NASA, 17 Mar. 2015. Web. 16 Feb. 2017.