Generation of traveling atmospheric disturbances during pulsating geomagnetic storms

Abstract

Traveling atmospheric disturbances (TADs) are effective in transporting momentum and energy deposited at high latitudes to the midlatitude and low‐latitude regions of the thermosphere. They also act to transport momentum and energy from the lower thermosphere into the upper thermosphere. Previously, model studies have been conducted to determine the characteristics of isolated, single‐pulse TADs, but the generation of multiple TADs excited during pulsating storms have not been considered before. Here a high‐resolution global thermosphere‐ionosphere model was used to study the basic characteristics of multiple TADs excited during pulsating storms, including idealized weak and strong pulsating storms, and an approximation of the 4 May 1998 pulsating storm. For all three pulsating storm simulations, multiple TADs that propagated away from the auroral oval toward both the poles and the equator at all longitudes, with the maximum amplitudes between midnight and dawn, were excited. The TAD amplitudes were at maximum near the poles and diminished toward the equator and were larger on the nightside than on the dayside. The TADs propagated at a slightly upward angle to the horizontal, with the result that the lower boundary of the TADs increased with decreasing latitude. The TADs crossed the equator and propagated to midlatitudes in the opposite hemisphere, where wave interference occurred for the strong pulsating storm cases. The TAD wavelengths vary from 2500 to 3000 km and the phase speeds vary from 800 to 1000 m/s. The maximum TAD perturbations are 20% for the mass density, 14% for the neutral temperature, and 100 m/s for the winds.