| Popis: |
The temporal as well as vertical and horizontal variations of the concentric traveling ionospheric disturbances (CTIDs) caused by hurricane Matthew on 7 October 2016 were reconstructed using 3-dimensional computerized ionospheric tomography (3DCIT) technology, based upon the GNSS data from the dense receiver network over North America. The frequency range of disturbances was determined by spectrum analysis, and a Butterworth band-pass filter was used to de-trend the total electron content (TEC) sequences in order to determine TIDs. A remarkable CTID segment was detected at a distance of 1000 – 1500 km from the hurricane eye at ~5:40 – 6:10 UT on 7 October 2016, moving westward with the horizontal phase velocity of ~153.4 m/s, the period of ~30 min and the horizontal wavelength of ~276.1 km. The positive and negative wavefronts dominated the CITD at different times during the event. From 4:00 to 8:00 UT, the altitudinal variation of the CTIDs in electron density exhibited clear downward phase progression predominately in the range of 150 – 400 km altitudes, however, the percentage electron density disturbances were larger below 250 km. The inverted cone-like geometry of CTID wavefronts was presented. The vertical phase velocities of the CTIDs ~1100 km away from the hurricane eye in the northwest direction near 88°W, 34°N were ~203.7 – 277.8 m/s, and at the same location, the horizontal phase velocities at 300 km altitude were ~149.1 – 181.5 m/s, slightly larger than those at 200 km altitude (~145.1 – 178.5 m/s). |
