The time-exposed photo above shows the northern lights hugging the northern horizon on Sebago Lake, Maine as viewed on August 5, 2011. A high level of solar activity the week before, including M-class solar flares, created conditions favorable for observing aurora, which occurred two and one half days after the flares were recorded. Photographer John Stetson
It takes this long for the solar wind to travel the 93 million mi (150 million km) or so to the Earth’s upper atmosphere. North of about 60 degrees north latitude, it’s too bright at night now and all through the summer (the Sun is up more than 16 hours each day) to clearly see this phenomenon. Note that Big Dipper is at the center of the photo.