Premium
Ion Friction and Quantification of the Geomagnetic Influence on Gravity Wave Propagation and Dissipation in the Thermosphere‐Ionosphere
Author(s) -
Medvedev Alexander S.,
Yiğit Erdal,
Hartogh Paul
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2017ja024785
Subject(s) - thermosphere , physics , earth's magnetic field , ionosphere , geophysics , computational physics , ion , dissipation , zonal and meridional , atmospheric sciences , equator , gravity wave , magnetic field , mechanics , atomic physics , gravitational wave , latitude , astrophysics , quantum mechanics , astronomy
Motions of neutrals and ions in the thermosphere‐ionosphere (TI) do not, generally, coincide due to the presence of the geomagnetic field and associated electromagnetic forces affecting plasma. Collisions of ions with gravity wave (GW)‐induced motions of neutrals impose damping on the latter. We derive a practical formula for the vertical damping rate of GW harmonics that accounts for the geometry of the geomagnetic field and the direction of GW propagation. The formula can be used in parameterizations of GW effects developed for general circulation models extending from the lower atmosphere into the mesosphere and thermosphere. Vertical damping of GW harmonics by ion‐neutral interactions in the TI depends on the geometry of the geomagnetic field but not the strength of the latter. The ion damping of harmonics propagating in the meridional direction (in the geomagnetic coordinates) maximizes over the poles and reduces to zero over the equator. Waves propagating in the zonal direction are uniformly affected by ions at all latitudes. Accounting for the anisotropy produces changes in the GW drag in the F region of more than 100 m s −1 d −1 , cooling/heating rates of more than 15 K d −1 , and in GW temperature variance of disturbances by more than 5 K.