Response of the lower equatorial ionosphere to strong tropospheric disturbances

A morphological analysis of the results of sounding the lower equatorial ionosphere (the D region) in the region of action of strong tropospheric vortex disturbances (tropical cyclones, TC) is presented in this work. Based on the rocket sounding of the lower ionosphere at Thumba rocket site (8° N, 77° E) in May–June 1985 and on the satellite monitoring of TC in the northern Indian Ocean, it is demonstrated that a sharp depletion (by a factor of 2–4) of the electron concentration at altitudes of 60–80 km could be a response of the ionosphere during the TC active phase. In this case the lower boundary of the D region rose by several kilometers (not more than 5 km), and the temperature in the region of the stratopause slightly (by 2°–3°) increases. It is assumed that internal gravity waves (IGWs) generated by TC cause the effect on the lower ion-osphere.