The three-dimensional co-seismic and co-tsunami ionospheric perturbations related to the 2011 M9.0 Tohoku earthquake in Japan

The three-dimensional (3-D) ionospheric electron density disturbances (dNe) concerning the 2011 M9.0 Tohoku-Oki earthquake were reconstructed using the total electron content data monitored by the ground-based Global Navigation Satellite System receivers and an improved constraint least-square fitting algorithm based on the computerized ionospheric tomography technique. First, we studied the overall 3-D dNe structures caused by different waves, such as Rayleigh waves (RWs), acoustic waves (AWsepi) and gravity waves (GWsepi) generated by the epicenter rupture and the internal gravity waves (IGWstsu) launched by the following tsunami. Then, we investigated these wave propagation characteristics in the ionosphere in the height interval of 190 - 490 km. RWs mainly existed below the F2 peak height, with propagating speeds ranging from 1.3 km/s to 3.3 km/s. The propagation speeds of AWsepi showed significant height dependence, that was about 0.65 km/s in 190 km and 0.90 km/s above the F2 peak height. GWsepi propagated at speed about 0.45 km/s became obvious 30 min after the earthquake. IGWstsu with a horizontal phase velocity of about 0.27 km/s was distinguished in the height interval of 190 - 490 km successively 42 min after the main shock. Finally, we studied the vertical dNe phase evolution in the F2 layer. While dNe induced by the AWsepi coupled with RWs was featured by steep-slope ascending phase variation structure, the GWsepi-induced perturbation was featured by steep-slope descending phase or near-vertical structure. The vertical dNe phase caused by IGWstsu presented remarkable curving descending structure.