A case study of the large-scale traveling ionospheric disturbances in the eastern Asian sector during the 2015 St. Patrick's Day geomagnetic storm

Abstract

This study presents a comprehensive observation of the large-scale traveling ionospheric disturbances (LSTIDs) in the eastern Asian sector during the 2015 St. Patrick 's Day (17 March 2015) geomagnetic storm. For the first time, three dense networks of GPS receivers in China and Japan are combined together to obtain the twodimensional (2-D) vertical total electron content (VTEC) perturbation maps in a wider longitudinal range than previous studies in this region. Results show that an LSTID spanning at least 60 • in longitude (80-140 • E) occurs as a result of possible atmospheric gravity waves (AGWs) propagating from high to lower latitudes at around 09:40-11:40 UT (universal time), and the crest of this LSTID shows a tendency of dissipation starting from the eastern side. The manifestation of the 2-D VTEC perturbation maps is in good agreement with the recordings from two high-frequency Doppler sounders and the iso-frequency lines from eight ionosondes. Then, the propagation parameters of the LSTIDs are estimated by applying least-square fitting methods to the distinct structures in the 2-D VTEC perturbation plots. In general, the propagation parameters are observably longitudinally dependent. For example, the propagation direction is almost due southward between 105 and 115 • E, while it is slightly southwest and southeast in the western and eastern sides of this region. This feature is probably related to the regional geomagnetic declination. The mean values of the period, trough velocity (V t ), crest velocity (V c ), and wavelength of the LSTIDs in the studied longitudinal bands are 74.8 ± 1.4 min, 578 ± 16 m s −1 , 617 ± 23 m s −1 , and 2691 ± 80 km, respectively. Finally, using the VTEC map data from the Madrigal database of the MIT Haystack Observatory, the characteristics of the ionospheric disturbances over the European sector (30-70 • N, 10-20 • E) are also studied. The results are very different from those in the eastern Asian sector in parameters like the occurrence time, oscillation period, and propagation velocities.

SABER Observation of Storm‐Time Hemispheric Asymmetry in Nitric Oxide Radiative Emission

“…It could be due to the fact that during a geomagnetic storm event, the Joule heating and particle heating create a composition bulge and upwelling of increased mean molecular mass (depleted O/N 2 ), which is subsequently transported to mid and low latitudes by background and storm‐induced circulation changes as discussed in the introduction (Fuller‐Rowell et al., 1994, 1996; Fuller‐Rowell & Rees, 1996). Similar propagation of storm‐time equatorward meridional wind during March 16–21, 2015 has been reported by many researchers (Borries et al., 2016; Figueiredo et al., 2017; Liu et al., 2019; Zakharenkova et al., 2016). The returns of the meridional wind to its prestorm condition during the recovery phase can be seen from Figure 1f4.…”

Evaluating Total Electron Content (TEC) Detrending Techniques in Determining Ionospheric Disturbances during Lightning Events in A Low Latitude Region

“…The unit of VTEC and DTEC is Total Electron Content Units (TECU; 1 TECU = 10 16 e/m 2 ). Orders of 3 and 6 and time window lengths 30, 60, 90 and 120 min [13,21,22] were selected for Savitzky-Golay, and orders of 3, 5 [23,24], 6, [1,12,25], and 10 [11] were used for polynomial fitting. The selected parameters for detrending are summarized below in Table 1.…”

Identification of potential precursors for the occurrence of Large-Scale Traveling Ionospheric Disturbances in a case study during September 2017

“…The size and the tilt of the slanted rays provide the information about wavelength, velocity and period. The parameters of the observed disturbances are obtained based on the method described in Liu et al (2019) in which the linear least-square method is used to fit pairs of crests and troughs for each disturbance, as depicted in Figure 5. The white dots are the minimum and maximum values around the trough and crest, respectively.…”