Climatology of thermospheric neutral winds over Oukaïmeden Observatory in Morocco

Abstract

Abstract. In order to explore coupling between the thermosphere and ionosphere and to address the lack of data relating to thermospheric neutral winds and temperatures over the African sector, a new system of instruments was installed at the Oukaïmeden Observatory located in the high Atlas Mountains, 75 km south of Marrakesh, Morocco (31.206 • N, 7.866 • W, 22.84 • N magnetic). In this work we present the first multi-year results of the climatology of meridional and zonal winds obtained during the period from January 2014 to February 2016, including observations from 648 nights. The measurements are obtained using an imaging Fabry-Pérot interferometer, which measures the 630.0 nm emissions caused by dissociative recombination of O + 2 . The basic climatology of the winds is as expected, showing zonal winds that are strongly eastward in the early evening just after sunset with a speed of 50 to 100 m s −1 decreasing in magnitude, and reversing directions in the local summer months, towards sunrise. The meridional winds are slightly poleward in the early evening during the local winter, before reversing directions around 21:00 LT. In the local summer months, the meridional winds are equatorward for the entire night, reaching a maximum equatorward speed of 75 m s −1 . We compare the observed climatologies of neutral winds to that provided by the recently updated Horizontal Wind Model (HWM14) in order to validate that model's predictions of the thermospheric wind patterns over the eastern portion of Africa. The model captures much of the features in the observational climatologies. The most notable exception is for the zonal winds during local summer, when the maximum eastward wind in the observations occurs approximately 4 h later than seen in the model results.

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

“…Among these studies, there are the climatologies of nighttime upper thermospheric winds measured by ground-based FPIs above several stations during geomagnetically quiet conditions as a function of the local time, latitudinal, seasonal, and cycle dependence was discussed (Emmert et al, 2006a). In parallel, there is a study using the same data set as ours, but analyzed regardless of geomagnetically conditions presented by Kaab et al (2017). The effect of the 27 February 2014 geomagnetic storm on the thermosphere and the ionosphere is discussed in Malki et al (2018).…”

“…The Fabry-Prot interferometer used in this study is located at the Oukaimeden Observatory in Morocco (31.206°N, 7.866°W; 22.84°N magnetic; 2,700 m altitude) and is described in detail in Makela et al (2009), Kaab et al (2017), and Malki et al (2018). To estimate the thermospheric wind speed, the FPI measures the Doppler shift of the 630.0-nm spectral emission emanating from the thermosphere located around an altitude of 250 km.…”

“…For creating climatologies of the thermospheric winds, we adopt the method detailed in Fisher et al (2015) and Kaab et al (2017). We sort and bin the filtered data into 15-min intervals and, for each interval, calculate a weighted average, v m , and sample variability, e, such that…”

Ionospheric and thermospheric response to the 27–28 February 2014 geomagnetic storm over north Africa

“…The GPS data needed to determine the TEC are (1) data extracted from files stored in RINEX (Receiver INdependent EXchange) format, (2) data in IONEX format (IONosphere EXchange Format), (3) almanacs of the GPS satellite position and (4) the satellite clock biases. The procedure for extracting the TEC from GPS data is well documented in the literature (Sardon et al, 1994;Klobuchar, 1996;Schaer, 1999;Zoundi et al, 2012;Christian et al, 2013).…”

“…Before commenting on the behavior of thermospheric winds over Oukaïmeden Observatory during the study period (25 to 28 February 2014), we first begin by summarizing their basic climatology (Kaab et al, 2017). In summertime, the meridional winds are equatorward for the entire night, reaching a maximum speed of 75 m s −1 .…”