Radio atmospheric the Earth's surface and the ionospheric D- and E- layers. Whistlers generated by lightning strokes can propagate into the magnetosphere along the geomagnetic lines of force. Finally, upper-atmospheric lightning or sprites, that occur at mesospheric altitudes, are short-lived electric breakdown phenomena, probably generated by giant lightning events on the ground. In a typical cloud-to-ground stroke (R stroke), negative electric charge (electrons) of the order of Q = 1 C stored within the lightning channel is lowered to the ground within a typical impulse time interval of τ = 100 μs. This corresponds to an average current flowing within the channel
Atmospheric tide The latitudinal structure of the tides is described by the "horizontal structure equation" which is also called "Laplace's tidal equation": with "Laplace operator" using formula_30, formula_31 and "eigenvalue" Hence, atmospheric tides are eigenoscillations (eigenmodes)of Earth's atmosphere with eigenfunctions formula_33, called Hough functions, and eigenvalues formula_34. The latter define the "equivalent depth" formula_35 which couples the latitudinal structure of the tides with their vertical structure. Longuet-Higgins has completely solved Laplace's equations and has discovered tidal modes with negative eigenvalues ε (Figure 2). There exist two kinds of waves: class 1 waves, (sometimes called gravity waves), labelled by positive n, and class