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FRIPRO-Fri prosjektstøtte

Gamma-ray-glow Effects on Atmospheric Electricity and Chemistry

Alternative title: Gammastråle-glødeffekter på atmosfærisk elektrisitet og kjemi

Awarded: NOK 12.0 mill.

A gamma ray glow is an x-ray and gamma radiation generated in thunderclouds, lasting from seconds to several minutes. This energetic radiation produces (1) chemical effects which modify the ozone layer and change the aerosol content in the stratosphere; and (2) electrical effects, i.e., modify currents flowing between the Earth and the sky which are the part of the so-called global electric circuit. The goal of our project is to theoretically and quantitatively study these effects and their difference from the effects of cosmic rays, which is the radiation coming downwards from the sky. We will use various numerical methods, including models of propagation of energetic radiation, models of evolution of chemical constituents and aerosols, and models of electric fields and currents in the atmosphere. The novel models developed in the course of the project will be available to other scientists working on physics of atmosphere and thunderstorms. The project will produce actionable knowledge through scientific publications, webinars and a dedicated website.

A gamma ray glow (GRG) is a long-lasting x-ray and gamma radiation generated in thunderclouds. It may last from seconds to several minutes and contain photons with energies exceeding 5 MeV. The brightest GRG may be one or two orders of magnitude higher than the background due to cosmic rays. Energetic x-rays produced by GRG and emitted upwards from the thundercloud may strongly affect the chemical-physical conditions of the stratosphere through additional ionization. The ionization has several effects that we plan to quantify in this project by theoretical modeling: 1. It interacts with the atmosphere to produce nitric oxide, a powerful agent which reduces the ozone layer. 2. The ions serve as seeds for condensation, which leads to an increase in stratospheric aerosol content. 3. The increased ionization leads to increased conductivity in stratosphere. This affects currents flowing in the global electrical circuit (GEC). The ionization effect of GRG is different from cosmic-ray-induced ionization, not only because the flux of x-rays in GRG may exceed that in cosmic rays by orders of magnitude. Unlike cosmic rays, GRG are localized both in time (last seconds to several minutes) and in space (only exist in the vicinity of a thunderstorm), which may lead to new effects. Preliminary estimates also show that the production of nitric oxide (item 1 above) may be of the same order as the strongest source of this chemical in the stratosphere, namely oxidation of nitrous oxide which diffuses upward from the Earth's surface.

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FRIPRO-Fri prosjektstøtte

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