Space‐based imaging of nighttime medium‐scale traveling ionospheric disturbances using FORMOSAT‐2/ISUAL 630.0 nm airglow observations

Abstract

This paper reports the results of space‐based imaging of nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) in 630.0 nm emission by Imager of Sprites and Upper Atmospheric Lightnings (ISUAL), on board FORMOSAT‐2 satellite. The limb integrated measurements, after removing background, reveal multiple bands of intensity perturbation when projected to a horizontal plane corresponding to the altitude of peak emission, with distinct southwest to northeast orientation in the Southern Hemisphere. Simulations are carried out by artificially introducing MSTID fluctuations in model electron density to confirm if the MSTID could be identified in the ISUAL‐viewing geometry. The ISUAL observations in year 2007 are further used to investigate the MSTID features as well as occurrence characteristics in the Southern Hemisphere, most of which are over the ocean where no ground‐based observations are available. The preliminary statistics shows more MSTID occurrence in solstices with peak in June–July months. Majority of the MSTID perturbations have wavelength in the range 150–300 km, and the wavefronts are aligned at about 30°–50° from the east‐west plane. The statistic results of the orientation of wavefronts indicate that Es layer instability might be important in the MSTID generation.

Statistical analysis of nighttime medium‐scale traveling ionospheric disturbances using airglow images and GPS observations over central China

“…As suggested by Otsuka et al [2004], polarization electric fields (E p ) can be mapped along geomagnetic field lines (B) into the other hemisphere, then in both hemispheres, and polarization electric fields move the electron density in F region downward or upward by E × B drifts and cause plasma density perturbations with mirrored structures. The peak of the nighttime MSTID occurrences in June-July (summer) over the Southern Hemisphere was reported by Rajesh et al [2016], and it is in Table 3. Same as Table 2 but for the Southern Hemisphere accordance with the nighttime MSTID occurrences observed at the geomagnetic conjugate point, Mengcheng (Figures 4f and 4h).…”

Traveling Ionospheric Disturbances at Mars

“…At Earth TIDs have a temporal scale of tens of minutes to hours when viewed from the ground, corresponding to a wavelength between 150 and 500 km (Rajesh et al, ; Shiokawa et al, ). An orbiting spacecraft, however, takes only tens of seconds to pass through them (see Figure ).…”

“…They have typical wavelengths between 150 and 500 km (Rajesh et al, 2016; and 100to 300-m/s horizontal velocities (Jonah et al, 2018;.…”

“…Such medium‐scale traveling ionospheric disturbances (MSTIDs) have been associated with AGWs resulting from tropospheric weather convection and mountain ranges such as the Sierra Nevada and Rocky Mountains (Jonah et al, , ) and earthquakes and seismic activity (Kherani et al, ). They have typical wavelengths between 150 and 500 km (Rajesh et al, ; Shiokawa et al, ) and 100‐ to 300‐m/s horizontal velocities (Jonah et al, ; Shiokawa et al, ).…”

Relation of internal gravity wave anisotropy with neutral wind characteristics in the upper atmosphere

“…As seen from Table , most TIDs (~58%) are associated with IGWs; the percentage of the IGW‐induced TIDs is higher in the daytime (from ~55% in summer to ~88% in winter) and lower in the nighttime (49–55%). A higher percentage of the TIDs that are not associated with IGW during nighttime is consistent with the assumption that nighttime southwestward MSTIDs are caused by the Perkins instability [ Shiokawa et al ., , ; Kotake et al ., ; Martinis et al ., ; Otsuka et al ., ; Ichihara et al ., ; Oinats et al ., ; Rajesh et al ., ]. Further in the IISR‐DPS‐4 case, we analyze only the IGW‐induced TIDs denoting them as IGWs (implying that TID characteristics correspond to IGW characteristics).…”