Enhanced N2 and O2 densities inferred from EISCAT observations of Pc5 waves and associated electron precipitation

Abstract

AbstractAn advanced two‐dimensional numerical model of the coupled ionosphere and magnetosphere is used to analyze EISCAT observations of ULF waves that are accompanied by electron precipitation with a wide energy spectrum. The observations show columns of significantly enhanced electron density produced by pulsating precipitation at altitudes between 150 km and 300 km. After each precipitation pulse, the plasma density returns to its initial value within 2 min. Simulations reveal that such a high‐density decay rate cannot be reproduced with the composition of neutrals corresponding to a quiet time provided by the Mass Spectrometer Incoherent Scatter model. To explain the rapid density decay rate using the model of the coupled ionosphere and magnetosphere, the density of nitrogen and oxygen molecules was increased, while the density of oxygen atoms was decreased. The modified neutral densities improved not only the decay rate but also the altitude profile of plasma density which had no F2 layer maximum before the wave and the pulsating precipitation started.