[PEM12-P29] GNSS-TECを用いた中規模伝搬性電離圏擾乱の成長率の統計解析
キーワード：電離圏、E-F結合、GNSS
Medium scale traveling ionospheric disturbance is one of phenomenon in ionosphere and has been studied after 1960th [Hines, 1960].We think two mechanisms, E-F coupling and Perkins Instability, will relate to growth for MSTID at night in mid-latitude [Tsunoda and Cosgrove, 2001 ; Perkins, 1973].Perkins instability can explain propagating direction,but not for generation. Maximum linear growth rate of perturbation intensity of Pedersen conductivity expected from E-F coupling is less than 5 minutes [Yokoyama et al., 2009], which is far shorter than one expected from Perkins Instability [Fukao and Kelley, 1991 ; Miller et al., 1997 ; Shiokawa et al., 2003]. However, Es layer's spatial and temporal scale is less than 100km and 15min [Maeda et al., 2013 ; S.Saito et al., 2007],which is different from E-F coupling model's ones [Yokoyama, 2009]. And also they are different from MSTID’s ones, which are 200-400 km and around 2hours [Otsuka et al., 2011].
So we can't explain MSTID's saturating process only by E-F coupling and we have not observed the rletaion between that process and two mechanisms about growth rate. Therefore, to decide which instability is responsible for growth of nighttime MSTID after generating frontal structure, the growth rate of MSTID was observationally determined with ground-based GNSS network data.
We statistically investigated the growth rate of nighttime-MSTID in Japan in 2014 observed with GNSS-TEC. We applied twospace and time spectral analysis to calculate MSTID’s growth rates. We compared growth rate observed with linear growth rate of Perkins Instability for two method. We calculated latter using by ion temperature, neutral wind velocity, electric field and O mass density of GAIA model [Jin et al., 2008] and magnetic field of IGRF model.
The growth rate of nighttime -MSTID observed was 1.0 - 6.0 × 10-4 s-1 during 1800LT-2400LT in summer.Linear growth rate of Perkins instability in summer was 1.0 - 6.0 × 10-4 s-1 during 1800LT - 2400LT, so they were less than one of the E-F coupling instability.And we observed Es layer by Ionozonde at Kokubunji in 2014 and compared with LT distribution of growth rates in summer. At the result, the peak time of Es layer after midnight was consistent with that of growth rates.However, seasonal distribution of linear growth rates was different from observed growth rates, because we didn't considered about the effect about southern hemisphere for linear growth rates.
In presentation, we talk the detail about the relation between growth rates and two mechanisms, also relation between north and sourthern hemishphere about
nighttime MSTID's generation.
So we can't explain MSTID's saturating process only by E-F coupling and we have not observed the rletaion between that process and two mechanisms about growth rate. Therefore, to decide which instability is responsible for growth of nighttime MSTID after generating frontal structure, the growth rate of MSTID was observationally determined with ground-based GNSS network data.
We statistically investigated the growth rate of nighttime-MSTID in Japan in 2014 observed with GNSS-TEC. We applied twospace and time spectral analysis to calculate MSTID’s growth rates. We compared growth rate observed with linear growth rate of Perkins Instability for two method. We calculated latter using by ion temperature, neutral wind velocity, electric field and O mass density of GAIA model [Jin et al., 2008] and magnetic field of IGRF model.
The growth rate of nighttime -MSTID observed was 1.0 - 6.0 × 10-4 s-1 during 1800LT-2400LT in summer.Linear growth rate of Perkins instability in summer was 1.0 - 6.0 × 10-4 s-1 during 1800LT - 2400LT, so they were less than one of the E-F coupling instability.And we observed Es layer by Ionozonde at Kokubunji in 2014 and compared with LT distribution of growth rates in summer. At the result, the peak time of Es layer after midnight was consistent with that of growth rates.However, seasonal distribution of linear growth rates was different from observed growth rates, because we didn't considered about the effect about southern hemisphere for linear growth rates.
In presentation, we talk the detail about the relation between growth rates and two mechanisms, also relation between north and sourthern hemishphere about
nighttime MSTID's generation.