Gamma ray bursts are the most energetic phenomena in the universe, the product of explosions in far-away galaxies that release vast amounts of energy as gamma rays that race through our solar system. The potential harm of gamma ray bursts drives an important question for scientists: How do rays interact with Earth’s atmosphere?
Here Nina et al. use statistical analyses to look at the behavior of the ionosphere during gamma ray burst events. When gamma rays hit the atmosphere, they ionize the air, which increases the electron density and the ion density. This density increase affects the structure of the ionosphere and how radio waves travel through it, so ionospheric perturbations can be detected by measuring the strength of radio signals bounced into the atmosphere and back. The researchers looked at a sample of 54 gamma ray burst events detected by the telescopes aboard NASA’s Swift satellite to distinguish the relationship between these events and the low perturbations they identified as periods of radio wave strength.
Scientists measured perturbation time and location with very low frequency/low-frequency (VLF/LF) radio signals emitted from Germany, the United Kingdom, Italy, Iceland, Australia, and the United States and picked up by a receiver in Serbia. The researchers found that VLF/LF radio signals were a reliable method of gamma ray burst detection. They were able to detect ionospheric reactions immediately after the start of a gamma ray burst or with a time delay—as much as 60–90 seconds.
The team detected short-term reactions in the low ionosphere that did not lead to intense long-term reactions. The brief perturbations occurred at different times related to the bursts, indicating that there might be some secondary processes that influence ionization in the low ionosphere. In the future, gamma ray bursts could be detected by some of these secondary processes.
Further studies will help to shape these conclusions and improve gamma ray burst detection—fundamental to expanding scientific knowledge of our solar system. (Geophysical Research Letters, doi:10.1002/2015GL065726, 2015)
—Lily Strelich, Freelance Writer
Citation: Strelich, L. (2016), Gamma ray bursts leave their mark in the low ionosphere, Eos, 97, doi:10.1029/2016EO047639. Published on 10 March 2016.