From Cosmic Explosions to Terrestrial Fires?: A Reply

TL;DR

This paper critiques a previous hypothesis linking cosmic ray flux from supernovae to terrestrial fires, arguing that only the most energetic cosmic rays can reach Earth's atmosphere and influence lightning, challenging the original proposal.

Contribution

The authors provide a detailed analysis showing that most cosmic rays from supernovae are too energetic to be deflected by Earth's magnetic field, limiting their impact on lightning and fires.

Findings

Most cosmic rays from supernovae are too energetic to be deflected by Earth's magnetic field.

Only the highest energy cosmic rays can reach the troposphere and potentially influence lightning.

The proposed link between cosmic explosions and terrestrial fires is less plausible given cosmic ray energy constraints.

Abstract

Deschamps and Mottez (hereafter DM) argue that the Gauss-Matuyama terrestrial magnetic field reversal may have left a vanishing main dipole moment to the field for a time of order 10,000 years. They say this may have allowed an enhanced cosmic ray flux, boosting the effect we proposed in Melott and Thomas (2019). We point out that the bulk of the cosmic ray flux from a nearby supernova should be too energetic, up to a million times more energetic than the limits of deflection by the terrestrial magnetic field. In fact, only those highly energetic ones will directly reach the troposphere, relevant for cloud-to-ground lightning. From Cosmic Explosions to Terrestrial Fires?: A Discussion. F. Deschamps and F. Mottez. J. Geology 128, online ahead of print. (2020) From Cosmic Explosions to Terrestrial Fires?: A Reply A.L. Melott and B.C. Thomas. J. Geology 128, online ahead of print. (2020) From cosmic explosions to terrestrial fires? (A.L. Melott and B.C. Thomas) Journal of Geology, 127, 475-481 10.1086/703418 (2019) [arXiv:1903.01501]