Thermospheric Neutral Winds Above the Oukaimeden Observatory: Effects of Geomagnetic Activity

Abstract

In the context of space weather, we investigate the effect of geomagnetic activity on Earth's thermosphere above the Oukaimeden Observatory in Morocco (geographic coordinates: 31.206°N, 7.866°W; magnetic latitude: 22.77°N) over 3 years from 2014 to 2016. The observatory is equipped with a Fabry‐Perot interferometer (FPI) that provides measurements of thermospheric wind speed. In this study 41 disturbed nights (with SYM‐H ≤ −50 nT, Kp ≥ 5) were identified and analyzed. We have characterized the meridional and zonal winds variability and dependence on the solar cycle, during both quiet and disturbed conditions. We have classified the storm time meridional neutral winds into three types of variation. The first type is characterized by traveling atmospheric disturbance (TAD)‐induced circulation: the first TAD coming from the north and the second TAD being transequatorial, coming from the south. This type of storm with TAD‐induced circulation accounts for 59% of the cases. The second type exhibits only slight discrepancies between the disturbed and quiet night flows. These cases account for 33% of the cases. The third type is characterized by the transequatorial wind in whole the night. This last type accounts for 8% of the cases. Finally, we apply a superposed epoch analysis method on the FPI data, and the effect of each phase of the geomagnetic storm on the wind flow and vertical total electron content VTEC has been quantified.

Interhemispheric Asymmetry of the Equatorial Ionization Anomaly (EIA) on the African Sector Over 3 Years (2014–2016): Effects of Thermospheric Meridional Winds

“…From FPI data over Oukaimeden (left top panel), it is evident that EIA crest asymmetry is the most probable phenomena with the northern crest higher than the southern one ( a ≥ 0) along with equatorward winds (V ≤ 0). Indeed from FPI wind data climatology (Kaab et al., 2017; Loutfi et al., 2020), equatorward winds are most probable during the course of the night especially during September and March equinoxes and June solstice. The December solstice data (blue dots) are characterized with a negative asymmetry index a ≤ 0 (the southern crest higher than the northern one) and low wind speed.…”

“…Loutfi et al. (2020) have reported transequatorial neutral winds above the Oukaimeden Observatory from summer to winter. Solstice seasons, characterized by the winter anomaly, have been explained successfully by changes in thermospheric composition, the atomic/molecular ratio in winter is higher than in summer (e.g., Rishbeth & Setty, 1961; Rüster & King, 1973), and from global thermospheric circulation (e.g., Millward et al., 1996).…”

“…Furthermore, several studies suggest that the transequatorial neutral wind from summer to winter hemisphere can be the primary reason for the EIA crests asymmetry in solstice seasons (e.g., Dang et al, 2016;Hanson & Moffett, 1966;Lin et al, 2007;Luan et al, 2015). Loutfi et al (2020) have reported transequatorial neutral winds above the Oukaimeden Observatory from summer to winter. Solstice seasons, characterized by the winter anomaly, have been explained successfully by changes in thermospheric composition, the atomic/molecular ratio in winter is higher than in summer (e.g., Rishbeth & Setty, 1961;Rüster & King, 1973), and from global thermospheric circulation (e.g., Millward et al, 1996).…”

Thermospheric Wind Response to March 2023 Storm: Largest Wind Ever Observed With a Fabry‐Perot Interferometer in Tromsø, Norway Since 2009

“…This wind circulation model during geomagnetic storms has been widely supported by a wealth of observational evidence from ground‐based Fabry‐Perot interferometer (FPI) (Hernandez et al., 1982; Loutfi et al., 2020; Malki et al., 2018; Meriwether, 2008; Navarro & Fejer, 2019; Yang et al., 2020) and spaceborne instruments (Emmert et al., 2001; Fejer et al., 2000). During periods of geomagnetically disturbed conditions, in the nightside hemisphere of the mid/low‐latitudes, zonal wind perturbations are predominantly westward (Loutfi et al., 2020; Navarro & Fejer, 2019; Yang et al., 2020), and meridional wind perturbations are equatorward, which is attributed to successive streams from the wind surge at auroral latitudes (Buonsanto, 1995; Loutfi et al., 2020; Malki et al., 2018). A conceptual drawing illustrated by Hernandez et al.…”

MANGO: An Optical Network to Study the Dynamics of the Earth's Upper Atmosphere

“…This is accomplished by making high spectral resolution measurements of the 557.7‐ and 630.0‐nm emissions, respectively. Each instrument is based on the successful MiniME design that has been deployed in Peru (e.g., Meriwether et al., 2008), Brazil (e.g., Makela et al., 2013), North America (e.g., Harding et al., 2019; Makela et al., 2012), Morocco (e.g., Fisher et al., 2015; Loutfi et al., 2020; Malki et al., 2018), Ethiopia (e.g., Tesema et al., 2017), and South Africa (e.g., Katamzi‐Joseph et al., 2022; Ojo et al., 2022). The simple, robust design is intended to accommodate long‐term deployments with little need for on‐site user intervention, making it an ideal companion to the MANGO imaging system.…”