The Nepal earthquake and space weather

High above Earth, more than 60 km above sea level, there is a layer of our planet's atmosphere called "the ionosphere". It is where UV radiation from the sun strips electrons away from the atoms of normal air, creating a zone of charged gas that envelopes the globe. The ionosphere is very sensitive to solar storms. Turns out, it can be sensitive to earthquakes, too. NASA is reporting that the magnitude 7.8 earthquake in Nepal on April 25th created waves of energy that penetrated the ionosphere and disturbed the distribution of electrons. Note the wave pattern, circled, in the upper panel of this ionospheric electron density plot:

Basically, these are waves of electron density rippling from a point in the ionosphere above the epicenter of the quake. The waves were measured by a science-quality GPS receiver in Lhasa, Tibet. It took about 21 minutes for the waves to travel 400 miles between the epicenter and the GPS receiving station.

The bottom panel of the plot is a "dynamic spectrum." Note the hot spots outlined in black. They show that the ionosphere was ringing with periods of ~2 and ~8 minutes. Presumably, these "tones" are related to atmospheric pressure waves billowing up from the trembling Earth below.

The ionosphere is the stage upon which much of space weather plays out. Auroras, meteors, and noctilucent clouds all occur there. The "Ionosphere Natural Hazards Team" at JPL studies how Earth itself affects this stage via earthquakes, volcanoes and tsunamis. You can read their report about the Nepal earthquake here.
www.spaceweather.com