Coupling between atmospheric layers in gaseous giant planets due to lightning-generated electromagnetic pulses

Atmospheric electricity has been detected in all gaseous giants of our solar system and is therefore likely present also in extrasolar planets. Building upon measurements from Saturn and Jupiter, we investigate how the electromagnetic pulse emitted by a lightning stroke affects upper layers of a gaseous giant. This effect is probably significantly stronger than that on Earth. We find that electrically active storms may create a localized but long-lasting layer of enhanced ionization of up to 10³ cm^-3 free electrons below the ionosphere, thus extending the ionosphere downward. We also estimate that the electromagnetic pulse transports 10⁷ J to 10¹⁰ J toward the ionosphere. There emissions of light of up to 10⁸ J would create a transient luminous event analogous to a terrestrial "elve." Key Points The EMP from lightning has a stronger effect in gaseous planets than on EarthThe EMP creates ionization and light upper atmosphere of Saturn and JupiterLight emitted by the EMP is one tenth of the light from the lightning stroke