On the Cause of the Post‐Sunset Nocturnal OI 630 nm Airglow Enhancement Over Low‐Latitude Thermosphere

Saha, Sovan; Pallamraju, Duggirala; Pant, Tarun Kumar; Chakrabarti, Supriya

doi:10.1029/2021ja029146

Cited by 6 publications

(29 citation statements)

References 57 publications

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“…Therefore, these simulations provide an independent confirmation of the interpretation made in our earlier work that the poleward turning of the usually equatorward meridional wind, or cessation of equatorward wind during post-sunset hours is the cause for the observed enhancements in the OI 630.0 nm emissions from Mt. Abu (Saha et al, 2021). The question we ask in this study is what is the cause for the reversal of meridional wind from its usual equatorward direction at post-sunset hours over low-latitudes?…”

Section: Introductionsupporting

confidence: 87%

“…The nightglow emission intensities continue to be small throughout the night and again start increasing towards morning twilight time. In one of our recent studies, an enhancement in OI 630.0 nm nightglow emissions after sunset was reported (Saha et al, 2021) in measurements over Mt. Abu (24.6 o N, 72.7 o E, 19 o N Mag), a low-latitude location in the Indian longitude sector.…”

Section: Introductionmentioning

confidence: 77%

“…This observation was explained in terms of the altitudinal movement of the ionosphere to be responsible for the observed enhancements in the redline airglow. As the poleward wind contributes to a decrease in the ionospheric height (Saha et al, 2021), thereby, it provides greater reactants for the dissociative recombination mechanism to cause an enhancement in the emissions. Such a decrease in the height of the ionosphere in the nighttime has been observed during midnight hours, and it is called as the midnight temperature maximum (MTM) (e.g., Mayr et al, 1979;Herrero and Spencer, 1982;Herrero et al, 1983;Sastri and Rao, 1993;Colerico et al, 1996;Fesen, 1996;Mesquita et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

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OI 630.0 nm Post-Sunset Emission Enhancement as an Effect of Tidal Activity over Low-Latitudes

Saha

Pallamraju

Kumar

et al. 2023

Preprint

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The OI 630.0 nm airglow emission variability provides salient information of the dynamical changes taking place in the upper atmosphere at around 250 km altitudinal region. The emission rates vary with the changes in the ambient electron densities and the neutral constituents which are associated with these emissions. On several occasions enhancements in these emissions are observed during post-sunset hours as measured from Mt. Abu (24.6oN, 72.7oE, 19oN Mag), a low-latitude location in the Indian longitude sector. These enhancements occur following the typical monotonic decrease in emission intensity after sunset. The presence of poleward meridional wind was shown to be the cause for such observed emission enhancements. However, climatologically, meridional winds are equatorward during these times. In this study, the cause of such reversal in winds in the post-sunset hours has been investigated using the variation in electron densities and winds simulated by the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCM-X) which also shows enhancements similar to those observed in the post-sunset OI 630.0 nm nightglow emissions. The amplitudes and phases of different components of tides obtained in WACCM-X meridional winds reveal a significant contribution of quarter-diurnal tides to be responsible for the observed reversal in the meridional winds during post-sunset hours. The change in the tidal amplitudes is proportional to the changes in wind magnitude during that wind reversal.

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Section: Introductionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

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OI 630.0 nm Post-Sunset Emission Enhancement as an Effect of Tidal Activity over Low-Latitudes

Saha

Pallamraju

Kumar

et al. 2023

Preprint

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“…At midlatitudes, the situation concerning upward/downward ion drift becomes more complex because two more drivers play significant roles: field‐aligned ambipolar diffusion and neutral wind (Chen et al., 2014; Saha et al., 2021, Equation 1). The ambipolar diffusion is upward during daytime and downward at night (Chen et al., 2014).…”

Section: Discussionmentioning

confidence: 99%

Isolated Peak of Oxygen Ion Fraction in the Post‐Noon Equatorial F‐Region: ICON and SAMI3/WACCM‐X

et al. 2021

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In the equatorial region, the fraction of oxygen ions (O+) in the topside ionosphere contains information on the source altitude of the plasma, which is controlled, in part, by the vertical plasma motion in the F‐region. Previous studies on this topic are restricted by limited coverage of local time, latitude, and season, leaving a significant knowledge gap in the distribution of the topside ionospheric composition. In this study, we statistically investigate the O+ fraction measured by ICON/IVM over all the local time sectors and seasons at low‐/midlatitudes. For the first time, we have found that an isolated peak in the O+ fraction emerges in the post‐noon equatorial region. The peak is most prominent during equinoxes, while during solstices it is connected to the O+ fraction bulges in the local summer midlatitudes. Simulations with SAMI3 coupled with thermospheric parameters from WACCM‐X reproduce the peak of the O+ fraction. The post‐noon equatorial peak can be explained by the net vertical motion of plasma consisting of transports either parallel or perpendicular to geomagnetic field lines.

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“…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.…”

Section: Discussionmentioning

confidence: 99%

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

Gao,

Xu,

Chen

et al. 2024

JGR Space Physics

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Observations from the Michelson Interferometer for Global High‐Resolution Thermospheric Imaging onboard the Ionospheric Connection Explorer spacecraft are used to study the response of OI630.0 and OI557.7 nm dayglow to a moderate geomagnetic storm on 27 August 2021. The storm reaches a minimum Dst index of −82 nT, significantly impacting the dayglow within the latitudinal range of approximately 20°N–42°N, where the dayglow observations are of good quality. During the geomagnetic storm, the OI630.0 dayglow intensity slightly increases, while the peak volume emission rate (VER) decreases, and the peak height rises noticeably. The F‐layer intensity, peak VER, and the entire‐layer intensity of OI557.7 dayglow decrease significantly. The rise in peak height is not noticeable for the OI557.7 dayglow. The VERs of the both dayglow emissions respond differently to the geomagnetic storm at different altitudes. The OI630.0 dayglow layer as a whole extends upward and rises in altitude. For dayglow averaged above 35°N, the OI630.0 dayglow VER increases above approximately 225 km but decreases below this altitude. The largest increase occurs near 300 km, reaching approximately 82.8%, while the largest decrease occurs around 160 km, reaching about −22.0%. The OI630.0 dayglow intensity increases by approximately 6.3%, the peak VER decreases by about −8.0%, and the peak height rises by approximately 16.3 km, corresponding to a 7.8% increase. The F‐layer intensity, peak VER, and the entire‐layer intensity of OI557.7 dayglow decrease by approximately −27.5%, −32.4% and −17.4%, respectively. The response of the dayglow also depends on longitude and is accompanied by a southward meridional wind.

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On the Cause of the Post‐Sunset Nocturnal OI 630 nm Airglow Enhancement Over Low‐Latitude Thermosphere

Cited by 6 publications

References 57 publications

OI 630.0 nm Post-Sunset Emission Enhancement as an Effect of Tidal Activity over Low-Latitudes

OI 630.0 nm Post-Sunset Emission Enhancement as an Effect of Tidal Activity over Low-Latitudes

Isolated Peak of Oxygen Ion Fraction in the Post‐Noon Equatorial F‐Region: ICON and SAMI3/WACCM‐X

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

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