A Rare Simultaneous Detection of a Mid‐Latitude Plasma Depleted Structure in O(1D) 630.0 and O(1S) 557.7 nm All‐Sky Airglow Images on a Geomagnetically Quiet Night

• Published in: Geophysical research letters 2024-07, Vol.51 (14), p.n/a
• Main Authors: Patgiri, D., Rathi, R., Yadav, V., Chakrabarty, D., Sunil Krishna, M. V., Kannaujiya, S., Pavan Chaitanya, P., Patra, A. K., Liu, Jann‐Yenq, Sarkhel, S.
• Format: Article
• Language: English
• Subjects: Airglow; all‐sky airglow imager; Amplification; Banded structure; Depletion; dissociative recombination; Electron density; Emission; Emissions; Equatorial ionization anomaly; Equatorial regions; F region; Geomagnetic field; Geomagnetism; Image enhancement; Ionization; Latitude; Lower mantle; Mesosphere; Night; O(1D) 630.0 nm emission; O(1S) 557.7 nm emission; Plasma; Recombination; Recombination reactions; Solar activity; Thermosphere; Traveling ionospheric disturbances; Wind
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL106900

This letter reports first simultaneous detection of F‐region plasma‐depleted structure in O(1D) 630.0 and O(1S) 557.7 nm airglow images on a geomagnetically quiet‐night (Ap = 3) of 26 June 2021 from mid‐latitude station (Hanle, India) due to enhanced thermospheric 557.7 nm emission. Since nighttime thermospheric 557.7 nm emission over mid‐latitudes is predominantly masked by significantly larger mesospheric component, F‐region plasma structures are rarely observed in 557.7 nm images. Interestingly, thermospheric 557.7 nm emission was not significant on the following geomagnetically quiet‐night as bands of medium‐scale traveling ionospheric disturbance were only observed in 630.0 nm images. Poleward wind generated by Equatorial Temperature and Wind Anomaly transported plasma from the boundary of equatorial ionization anomaly, causing significant electron density enhancement around 250 km and descent of F‐layer peak over Hanle on 26 June 2021. This amplified the dissociative recombination enabling the simultaneous detection of plasma‐depleted structure in 557.7 and 630.0 nm images. Plain Language Summary The thermospheric O(1S) 557.7 generated through dissociative recombination of O2+ in the F‐region is significantly lower than its mesospheric counterpart which is generated via the Barth mechanism in the Mesosphere‐Lower‐Thermosphere region. This causes difficulties in the simultaneous detection of mid‐latitude F‐region plasma structures in 630.0 and 557.7 nm airglow images during geomagnetically quiet nights of low solar active years. We report, for the first time, such simultaneous detection of plasma‐depleted structure from mid‐latitude station (Hanle, India) on a geomagnetically quiet night of 26 June 2021. Interestingly, the thermospheric 557.7 nm emission was not significant on the following geomagnetically quiet night as bands of medium‐scale traveling ionospheric disturbance were detected only in the 630.0 nm images. Results from multi‐instrument data sets showed the descent of F‐layer peak and significant electron density enhancement over Hanle. The local poleward wind generated by stronger Equatorial Temperature and Wind Anomaly on 26 June 2021 transported the plasma from the boundary of the equatorial ionization anomaly region to Hanle through geomagnetic field lines. This caused the enhancement of electron density around 250 km and descent of F‐layer peak over Hanle that created suitable condition for the amplification of dissociative recombinati