Interaction of gravity waves with ionospheric plasma: Implications for Jupiter's ionosphere

The J0-ingress radio occultation of the Galileo orbiter by Jupiter exhibits a system of well-defined, regularly spaced electron layers in the altitude range where the presence of gravity waves have been previously inferred. B ased on the terrestrial analog of sporadic E and spread F ionospheric layer s, we argue that the observed layers are a result of dynamical processes ra ther than chemistry. We consider the impact of upward propagating gravity w aves on the plasma distribution in a H+ dominated ionosphere. The relevant physics is discussed and illustrated with an analytic, small-amplitude mode l. A time-dependent, 2D, large-amplitude model is developed to simulate the observed large excursions in the J0-electron density profile. We show that gravity waves with parameters consistent with the thermal structure of Jup iter's upper atmosphere are capable of creating large peaks in the electron density similar to the observed ones. The ionospheric response is extremel y anisotropic with respect to the direction of wave propagation. We demonst rate that the location of the J0-ingress radio occultation on Jupiter favor s large ionospheric response for waves propagating along the magnetic merid ian. A wave driven plasma flux results in plasma removal above the altitude of maximum ionospheric response and plasma deposition in the region below, significantly modifying the initial steady state electron density profile. (C) 2001 Academic Press.