Abstract
The disturbances of the ionosphere caused by thunderstorms or lightning events in the troposphere have an impact on global navigation satellite system (GNSS) signals. Gravity waves (GWs) triggered by thunderstorms are one of the main factors that drive short-period Travelling Ionospheric Disturbances (TIDs). At mid-latitudes, ionospheric GWs can be detected by GNSS signals. However, at low latitudes, the multi-variability of the ionosphere leads to difficulties in identifying GWs induced by thunderstorms through GNSS data. Though disturbances of the ionosphere during low-latitude thunderstorms have been investigated, the explicit GW observation by GNSS and its propagation pattern are still unclear. In this paper, GWs with periods from 6 to 20 min are extracted from band-pass filtered GNSS carrier phase observations without cycle-slips, and 0.2–0.8 Total Electron Content Unit (TECU) magnitude perturbations are observed when the trajectories of ionospheric pierce points fall into the perturbed region. The propagation speed of 102.6–141.3 m/s and the direction of the propagation indicate that the GWs are propagating upward from a certain thunderstorm at lower atmosphere. The composite results of disturbance magnitude, period, and propagation velocity indicate that GWs initiated by thunderstorms and propagated from the troposphere to the ionosphere are observed by GNSS for the first time in the low-latitude region.
Highlights
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This study mainly focuses on 1, determining the observability and magnitude of gravity waves (GWs) induced by lightning at low latitudes; 2, investigating the period, propagation direction, distance, and speed of GWs in the ionosphere; and 3, the relationship between the period characteristics of GWs and the propagation distance considering the atmospheric conditions
global navigation satellite system (GNSS) signals and presents clear cases that the GWs induced by thunderstorms can be observed from low latitudes by GNSS
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The solar activities have effects on the ionospheric electron content from the top, which can be retrieved by the global navigation satellite system (GNSS) [1,2]. Perturbations from the underlying atmosphere have been found to be another important factor in ionospheric variability [3]. In addition to earthquakes [4] and typhoons [5], which have been explored extensively, lightning or thunderstorms can drive significant ionospheric perturbations. Ionospheric perturbations induced by thunderstorms can be propagated by gravity waves (GWs) as carriers, which have been reported both in midlatitudes and low-latitudes [6,7]
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