Geophysics using Hubble Space Telescope

We exploit Hubble Space Telescope (HST) as a cosmic ray detector to probe Earth's external magnetic field through analysis of the cosmic ray flux on HST instruments. We propose to analyze 100 000+ dark images obtained during 26 years of HST operation to calculate the flux of cosmic rays at an altitude of ~500 km above the surface and estimate variations in the external magnetic field, thereby complementing geophysical observatory measurements. Our analysis will combine HST results with measurements of solar activity, cosmic ray flux on Earth's surface, and geomagnetic data to tease out external field variations. The addition of 26 years of HST data, including 10 years of measurements predating geomagnetic satellites, will provide invaluable, high-resolution observations of the geomagnetic field