Rings of very old trees help Montana State physicist quantify strength of historic cosmic storms

Montanans have been dazzled in recent months by colorful displays of the aurora, or northern lights, which occur when plasma and energetic particles ejected by the sun slam into Earth’s atmosphere and clash with the planet’s magnetic field.

As spectacular as those light shows have been, Montana State University solar physicist Rachael Filwett says the solar energetic particle, or SEP, events that caused them were insignificant compared to others that have bombarded our planet in the distant past. Those events carried radiation levels dangerous enough to kill astronauts in space, wipe out satel...