On Estimation of Daytime Equatorial Vertical (E × B) Plasma Drifts Using Optical Neutral Dayglow Emission Measurements

Abstract

Vertical drift (E × B) over the geomagnetic equator of the Earth is one of the fundamental parameters that governs the equatorial electrodynamics, which is responsible for the formation of large-scale phenomena in low and equatorial latitudes. We present a novel approach using ground-based optical neutral oxygen dayglow emission intensity measurements to estimate the daytime equatorial vertical drifts. The diurnal patterns of the dayglow emission intensities at OI 557.7, 630.0, and 777.4 nm wavelengths obtained from a low-latitude location, Hyderabad (78.4°E, 17.5°N; 8.9°N MLAT), India, are observed to be symmetric with respect to local noon on some days and asymmetric on some other. The extent of asymmetric nature is characterized by a parameter called Asymmetricity in Time (AT), which shows similar variations with the integrated Equatorial Electrojet (EEJ) strength. AT values obtained from the dayglow measurements are used to infer the vertical drifts. Vertical drifts derived by this method match well with the global climatological model estimates and with radar measurements. This new approach provides an alternative method for obtaining vertical drifts to enable systematic investigations of equatorial electrodynamics. Plain Language SummaryIt is well-known that the ionospheric equatorial zonal electric fields of the Earth play a key role in the generation and development of all the large-scale coupled equatorial-and low-latitude processes. Thus, knowledge of the equatorial electric fields is essential for comprehensive investigations of the equatorial-and low-latitude upper atmospheric behavior. This information on equatorial electric fields can be obtained directly by measuring the vertical drift of plasma above the magnetic equator. The vertical drifts are conventionally measured by ground-based radars and space-based payloads. In this work, a novel technique to estimate the daytime equatorial vertical drifts is presented using ground-based optical dayglow emission measurements. The estimated drifts match well with the model estimates and both ground-and space-borne observations as reported in the published literature. This method of estimating vertical drifts can be used to carry out continuous and systematic investigations of the equatorial electrodynamics. To the best of our knowledge, such a possibility of deriving the daytime equatorial vertical drifts using ground-based optical methods has not been shown before.

First Zonal Drift Velocity Measurement of Equatorial Plasma Bubbles (EPBs) From a Geostationary Orbit Using GOLD Data

“…The cause for the perturbations at the bottom layer is still a topic of debate, and such perturbations are thought to "seed" the plasma irregularities. Sometimes the daytime ionospheric and thermospheric coupling processes and wave activity make the ionosphere conducive to the occurrence of nighttime plasma irregularities (Karan et al, 2016;Karan & Pallamraju, 2020;Mandal et al, 2019;Pallamraju et al, 2004Pallamraju et al, , 2016Sridharan et al, 1994). The depleted plasma density regions (depletions) can grow nonlinearly and rise to 500-1,500 km (Anderson & Mendillo, 1983).…”

Unique Combinations of Differently Shaped Equatorial Plasma Bubbles Occurring Within a Small Longitude Range

“…This could be due to the prevalent ambient ionospheric‐thermospheric conditions at the longitude where B2 was generated. Small spatial scale variations (∼3° longitude) in the daytime equatorial electric fields have been reported (Karan & Pallamraju, 2017, 2020). B1 and B3 are separated by ∼11.5° longitudes at 23:10 UT.…”

Response of ICON/MIGHTI Measured Low‐Mid Latitude OI630.0 and OI557.7 nm Dayglow Emissions to the 27 August 2021 Geomagnetic Storm

“…Ultimately, this leads to a reconfiguration of atmospheric composition densities across all latitudes (Bag et al., 2017; Pallamraju et al., 2004). Furthermore, the equatorward wind can also move the ionospheric layer up to higher altitudes (Karan et al., 2016; Karan & Pallamraju, 2020; Rishbeth, 1977; Titheridge, 1995), inducing an increase in F ‐layer electron concentration. Therefore, the elevation may play a role in the observed fluctuations in OI630.0 and OI557.7 dayglow emissions that manifest during geomagnetic storms.…”

“…As previously mentioned regarding the role of the equatorward wind, the equatorward wind observed during the studied geomagnetic storm can induce changes in neutral compositions and plasma within the mid‐low latitude region. These changes encompass heightened molecule densities, an elevated ionosphere (Karan et al., 2016; Karan & Pallamraju, 2020; Rishbeth, 1977; Titheridge, 1995), and thereby affect the airglow emission intensities (Kumar et al., 2022; Saha et al., 2021). According to the simulation by Culot et al.…”

“…As mentioned earlier, the excitation mechanisms of OI630.0 and OI557.7 dayglow emissions are intricate and related to both thermospheric and ionospheric parameters. How the emissions respond to a geomagnetic storm is influenced by various factors, such as the strength of geomagnetic activity, latitude, and season (see Karan et al., 2016; Karan & Pallamraju, 2020). In this context, we only suggest the possible processes responsible for the variations of OI630.0 and OI557.7 dayglow emissions during the geomagnetic storm.…”