The equatorial neutral thermospheric response to geomagnetic

Abstract

Listen

Translate article

Thermospheric temperature and neutral density measurements from Dynamics Explorer 2 (DE 2) have been used to study the time‐dependent response of the equatorial thermosphere to geomagnetic forcing. Data taken following the onsets of several different isolated geomagnetic storms have been used in a superposed‐epoch scheme to investigate the characteristic response of the density and temperature structure of the equatorial thermosphère at ∼350 lcm altitude in the rooming and evening local‐time sectors. The principal post‐storm‐onset features that have been observed are as follows: 1) Two travelling waves, one generated at northern high latitudes and one at southern high latitudes, pass through the equatorial thermosphere, with wave crests crossing the equator at a time lag of 3–6 hours after the storm onset. The maximum neutral density perturbations associated with these waves are ∼15–25% for atomic oxygen and ∼30–40% for molecular nitrogen. 2) Following the passage of these travelling waves, the densities and temperatures in the evening sector return relatively rapidly to their undisturbed state, whereas those in the morning sector have significant variations at longer lag times. In particular, significant increases in neutral density and temperature occur in the morning sector about 12 hours after the onset of the storm. The N2 density enhancements are seen earliest in the summer hemisphere, while the O density enhancements are seen earliest in the winter hemisphere.