A moderate geomagnetic storm kicked up in Earth's skies Friday morning (April 20), bringing green and rare electric-blue auroras that stretched as far south as Indiana. The space-weather news site Spaceweather.com reported that an "interplanetary shock wave" hit Earth's magnetic field at about 3:50 a.m. EDT (2350 on April 19 GMT), quadrupling the intensity of the flow of particles streaming from the sun toward Earth, called the solar wind.