Abstract. In this work, we study ionospheric disturbances excited by the passage of the solar terminator (ST) during tropical cyclones, using total electron content (TEC) data. We have considered 16 intense tropical cyclones (typhoons) that acted in the northwest of the Pacific Ocean near the territory of Japan. We analyze two-dimensional distributions of the number of registered wave packets (WPs) depending on various parameters: local time, WP maximum amplitude, and distance to typhoon. It is shown that in most cases the maximum number of WPs is observed at a distance less than 500-1500 km from the typhoon center and near the time of evening solar terminator passage. For typhoons occurring during autumn periods, the maximum number of WPs is recorded at daytime, and, apparently, is not associated with ST. Distributions of the number of WPs depending on their amplitude have a similar form for all the cases considered, with a maximum of about 0.2 TECU. At the same time, for some typhoons there are a large number of WPs with amplitude up to 0.6-0.8 TECU, which is significantly higher than WP amplitudes under quiet conditions. We briefly discuss the mechanism of possible interaction between ionospheric disturbances caused by two different sources (tropical cyclones and ST passage).
Аннотация. Проведено исследование уровня возмущенности полного электронного содержания (ПЭС) в среднеширотных и высокоширотных обла-стях ионосферы в течение 2013 г. Ряды вариаций ПЭС рассчитывались по двухчастотным фазовым измерениям на всех радиолучах для GPS-станций MOND (Монды), NRIL (Норильск). Рассматрива-лись колебания ПЭС в двух диапазонах периодов: 10 и 40 мин, которые соответствуют средне-и круп-номасштабным ионосферным возмущениям. Для характеристики общего уровня возмущенности ПЭС использовался специальный индекс W TEC , который позволяет получать многодневные непре-рывные ряды усредненной интенсивности вариа-ций ПЭС. Выявлено, что в высоких широтах пове-дение W TEC хорошо согласуется с вариациями AE и хуже -с поведением индекса D st ; минимальный уровень возмущенности ПЭС не зависит от сезона; суточные вариации W TEC более выражены для сред-немасштабных ионосферных возмущений, чем для крупномасштабных. В средних широтах поведение W TEC хорошо согласуется с вариациями D st и K p только во время сильных магнитных бурь; значе-ние минимального уровня возмущенности летом выше, чем зимой; суточные вариации W TEC в средних широтах ярко выражены в течение года. В средних широтах солнечный терминатор генерирует грави-тационные волны, в Арктическом регионе возму-щения, вызванные солнечным терминатором, не наблюдаются.Ключевые слова: GPS, ионосфера, полное элек-тронное содержание, Арктический регион, геомаг-нитные вариации. Аbstract.We study the level of total electron content (TEC) disturbance in ionospheric mid-latitude and high-latitude regions during 2013. TEC behavior is calculated using data from two GPS stations: MOND (Mondy) and NRIL (Norilsk). TEC variations are calculated from two-frequency phase measurements for all radio rays. We analyze the TEC variations in two time ranges: 10 and 40 min. These ranges correspond to middle-and large-scale ionospheric disturbances respectively. The TEC disturbance level is characterized using the special index W TEC . W TEC allows us to receive multi-day continuous series of average TEC variation intensity. We reveal that at high latitudes W TEC variations agree well with AE ones. The correlation between W TEC and D st variations is much less. The minimum level of TEC disturbance is independent of the season in the Arctic region; diurnal W TEC variations are more pronounced for medium-scale ionospheric disturbances than for largescale ones. At mid-latitudes, the W TEC behavior agrees well with the D st and K p variations only during strong magnetic storms. The minimum level of TEC disturbance is higher in summer than in winter. At midlatitudes, the sunset terminator generates gravitational waves. In the Arctic region, terminator-generated waves are not observed.
We study the level of total electron content (TEC) disturbance in ionospheric mid-latitude and high-latitude regions, which occurred during 2013. TEC behavior is calculated using data from two GPS stations: MOND (Mondy) and NRIL (Norilsk). TEC variations are estimated from dual-frequency phase measurements for all radio signal paths. We analyze the TEC variations in two time ranges: 10 and 40 min. These ranges correspond to medium- and large-scale ionospheric disturbances respectively. The TEC disturbance level is characterized using a special index WTEC. It allows us to receive multi-day continuous series of average TEC variation intensity. We reveal that at high latitudes WTEC variations correlate well with AE ones. The correlation between WTEC and Dst variations is much lower. The minimum level of TEC disturbance is independent of the season in the Arctic region; diurnal WTEC variations are more pronounced for medium-scale ionospheric disturbances than for large-scale ones. At mid-latitudes, the WTEC variation concurs with Dst and Kp variations only during strong magnetic storms. The minimum level of TEC disturbance is higher in summer than in winter. At middle latitudes, the sunset terminator generates gravity waves. In the Arctic region, terminator-induced waves are not observed.
In this work, we study ionospheric disturbances excited by the passage of the solar terminator (ST) during tropical cyclone periods, using total electron content (TEC) data. We have considered 16 intense tropical cyclones (typhoons) that acted in the northwest of the Pacific Ocean near the territory of Japan. We analyze two-dimensional distributions of the number of registered wave packets (WPs) depending on various parameters: local time, maximum amplitude of packets, and distance to typhoon. It is shown that in most cases the maximum num-ber of WPs is observed at a distance less than 500–1500 km from the typhoon center and near the time of evening solar terminator passage. For typhoons occurring during autumn periods, the maximum number of WPs is recorded at daytime, and, apparently, is not associated with ST. Distributions of the number of WPs depending on their amplitude have a similar form for all the cases considered, with a maximum of about 0.2 TECU. At the same time, for some typhoons there are a large number of WPs with amplitude up to 0.6–0.8 TECU, which is significantly higher than WP amplitudes under quiet conditions. We briefly discuss the mechanism of possible interaction between ionospheric disturbances caused by two different sources (tropical cyclones and ST passage).
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