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A Supernova at 50 pc: Effects on the Earth's Atmosphere and Biota
A L Melott1, B C Thomas2, M Kachelrieß3
1Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045, USA.
The Astrophysical Journal
|July 24, 2018
Summary
Supernovae closer to Earth significantly increase cosmic rays (CRs) and radiation, impacting the atmosphere and life. These effects, including increased ionization and muon radiation, last for thousands of years.
Area of Science:
- Astrophysics
- Cosmic Ray Physics
- Earth Science
Background:
- Recent 60Fe data suggest supernovae occurred closer to Earth (∼50 pc) than previously estimated.
- Two supernova events are proposed: one 1.7-2.7 million years ago, and another 6.5-8.7 million years ago.
Purpose of the Study:
- To investigate the atmospheric and biological effects of nearby supernovae.
- To model the impact of cosmic rays (CRs) on Earth under different magnetic field conditions.
Main Methods:
- Simulations of cosmic ray propagation through Earth's atmosphere.
- Analysis of ionization and muon radiation under varying magnetic field strengths and orientations.
Main Results:
- A few hundred-fold increase in TeV-PeV CRs and tropospheric ionization in a weak, disordered magnetic field.
- Muon radiation load increased by approximately 150 times, returning to baseline within 10 kyr.
- In ordered magnetic fields, CR flux increases varied significantly, from below current levels to 10^4-fold increases.
Conclusions:
- Nearby supernovae have substantial, extended effects on Earth's atmosphere and biota.
- The estimated 'lethal distance' for supernovae requires re-evaluation.
- Further research is needed to fully understand these cosmic influences.
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