Observations of Traveling Ionospheric Disturbances at Midlatitudes during Geomagnetic Storm of 1 - 3 September 2016

Geomagnetic storms represent appreciable variations in space weather and result in global perturbations in characteristics of the magnetosphere, ionosphere, magnetic and electric field, including generation of acoustic-gravity waves (AGW). These structures together with traveling ionospheric disturbances (TIDs) play an important role in coupling different atmospheric and ionospheric regions. The detection and parameter estimation of such AGW/TIDs enable better understanding of storm energetics and stimulate further improvement of modelling efforts focused on disturbed conditions. Since magnetic storm effects are global, it is important to conduct quasi-simultaneous observations at different longitudes for correct interpretation of obtained results. Furthermore, the study of longitudinal differences is of great interest due to the fact that high energy sources of ionospheric perturbations are located in the polar regions and TIDs often propagate from auroral ionosphere toward equatorial one.

The current research is devoted to identifying TIDs at middle latitudes of European and east American longitudinal sectors using the data of Kharkiv incoherent scatter (IS) radar and dense GNSS networks acquired during moderate magnetic storm of 1 - 3 September, 2016. We detected an amplification of TIDs in IS power, electron density, ion and electron temperatures with periods of 70 - 100 min at the altitudes of 200 - 300 km during geomagnetic storm period over Kharkiv, Ukraine (50N, 36E), as compared with magnetically quiet day of 31 August 2016. We estimated the characteristics of prevailing TIDs in IS power. Their relative amplitudes during 1 - 2 September appear to enhance by a factor of two over quiet day. The vertical and horizontal phase velocities fall into the range of 30 - 50 and 300 - 500 m/s, respectively, and horizontal wavelength is 1200 - 3000 km. These parameters are consistent with characteristics of large-scale TIDs that are often generated during magnetically disturbed conditions.

The GNNS TEC results show the similar behaviour of TIDs over east America and Europe. Enhancement in both large- and medium-scale TID amplitudes is observed. A joint use of IS and GNSS techniques is very effective for detection of altitudinal and spatial characteristics of TIDs generated by natural and artificial sources.