Airglow observations over the equatorial ionization anomaly zone in Taiwan

Abstract

Abstract. Airglow imaging at mid-latitude stations often show intensity modulations associated with medium scale travelling ionospheric disturbances (MSTID), while those carried out near the equatorial regions reveal depletions caused by equatorial plasma bubbles (EPB). Two all sky cameras are used to observe plasma depletions in the 630.0 nm emission over the equatorial ionization anomaly (EIA) region, Taiwan (23 • N, 121 • E; 13.5 • N Magnetic) during 1998-2002 and 2006-2007. The results show EPB and MSTID depletions in different solar activity conditions. Several new features of the EPB depletions such as bifurcation, secondary structure on the walls, westward tilt, etc., are discussed in this paper. Evidence of tilted depletions with secondary structures developing on the eastern wall that later evolve to appear as bifurcations, are presented for the first time. Moreover, detail investigations are carried out using International Reference Ionosphere (IRI) model as well as the electron density from Ionosonde and Global Positioning System (GPS) Occultation Experiment (GOX) onboard FORMOSAT-3/COSMIC satellite, to understand the conditions that favor the propagation of MSTID to the latitude of Taiwan.

Spread F occurrence and drift under the crest of the equatorial ionization anomaly from continuous Doppler sounding and FORMOSAT-3/COSMIC scintillation data

“…However, the observation of plasma bubbles by the CHAMP satellite (Stolle et al 2006(Stolle et al ) in 2001(Stolle et al -2004 the measurements of prereversal enhancement of vertical plasma drift (Huang and Hairston 2015) are closer to our findings such that spread F is more frequently observed around equinoxes. Our results concerning the propagation velocities are consistent with previous reports based on optical and GPS total electron content measurements for South America (e.g., Haase et al 2011) and for Taiwan (Huang 1990;Liu et al 2011). Our results are based on larger numbers of events and cover the entire year.…”

“…However, we note that the velocities were determined by two independent methods that gave consistent results within the estimated uncertainties; thus, it is unlikely that both methods would give systematically larger values. In addition, the OSS velocities are consistent with propagation velocities obtained from airglow measurements at 630 nm in Taiwan (Liu et al 2011). Hence, we consider the first possibility to be the most probable.…”

Intrinsic parameters of periodic waves observed in the OI6300 airglow layer over the Brazilian equatorial region

“…Several airglow emissions come from thermospheric heights, which coincides with the bottom side of the ionospheric F region. These emissions have been used to study the morphology and dynamics of phenomena in the ionosphere, such as equatorial plasma bubbles (e.g., Fagundes et al, 1999;Taori et al, 2010;Paulino et al, 2011;Shiokawa et al, 2015;Fukushima et al, 2015), equatorial ionization anomaly (e.g., Liu et al, 2011;Narayanan et al, 2013), traveling ionospheric disturbances and gravity waves (e.g., Taylor et al, 1998;Kubota et al, 2000;Garcia et al, 2000;Shiokawa et al, 2005Shiokawa et al, , 2006Otsuka et al, 2007;Candido et al, 2008;Martinis et al, 2011;Makela et al, 2011;Amorim et al, 2011;Fukushima et al, 2012;Narayanan et al, 2014), etc. The most important emission in the thermosphere is the OI 630.0 nm (hereafter, OI6300) which is a spectral red line and has an intensity strong enough to be detected by airglow imaging systems.…”

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

“…Liu et al . [] show that the strength and location of equatorial anomaly crests play an important role in restricting the equatorward MSTID propagation.…”