5. Energetic protons. The solar flare and the intense CMEs also accelerated protons to energies of 30 million electron volts or higher. Across the Arctic, where Earth’s magnetic field affords the least protection, these particles penetrated to an altitude of 50 kilometers and deposited additional energy in the ionosphere. According to Brian C. Thomas of Washburn University, the proton shower from the 1859 superstorm reduced stratospheric ozone by 5 percent. The layer took four years to recover. The most powerful protons, with energies above one billion electron volts, reacted with the nuclei of nitrogen and oxygen atoms in the air, spawning neutrons and creating the nitrate abundance anomalies. A rain of neutrons reached the ground in what is now called a ground level event, but no human technology was available to detect this onslaught. Fortunately, it was not hazardous to health.
6. Massive electric currents. As the auroras spread from the usual high latitudes to low latitudes, the accompanying ionospheric and auroral electric currents induced intense, continent-spanning currents in the ground. These currents found their way into telegraph circuitry. The multiampere, high-voltage discharges caused near electrocutions and were reported to have burned down several telegraph stations.