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We present observations and analysis of seven horizontal wind profiles obtained by the trimethyl aluminum (TMA) tracer method on 27 March 2012 over the Atlantic ocean near Wallops Island, Virginia (37.9°N, 75.4°W). Payloads were launched in order to produce quasi‐simultaneous trails separated by tens to hundreds of kilometers. Tracer positions evolving in time and space were triangulated from three locations along the Atlantic seaboard and wind profiles between 90 and 140 km calculated. The wind profiles present a coherent wind structure dominated by very strong diurnal and semidiurnal tides up to 110 km and an upward propagating inertia‐gravity wave between 110 and 140 km. Properties such as horizontal and vertical wavelength could be extracted from the simultaneous observations at separate locations. A statistical analysis of the wind differences was performed to estimate power‐law coefficients of the second structure function at mesoscales. They show scale‐independence in the region of the largest wind shears, 100–110 km, and a scaling coefficient characteristic for isotropic wind fluctuations above and below this region. We present seven upper atmospheric wind profiles (90–140 km) measured with the tracer method. The winds were observed at seven different locations spaced over 500 km along a line from the Mid‐Atlantic coast. The winds show very similar structures below 110 km, presumably due to very large atmospheric tidal waves. A very distinct, smaller wave motion is evident above 110 km, because it was sampled at different locations. In some regions the variability of the winds show signs of large‐scale turbulence. Seven simultaneous wind profiles in the lower thermosphere, horizontally separated by up to 600 km, are dominated by strong tidesA large‐scale upward propagating inertia‐gravity wave is evident in the observationsThe region between 100 and 110 km shows the largest mesoscale variability of winds and wind shears, independent of separation scale Seven simultaneous wind profiles in the lower thermosphere, horizontally separated by up to 600 km, are dominated by strong tides A large‐scale upward propagating inertia‐gravity wave is evident in the observations The region between 100 and 110 km shows the largest mesoscale variability of winds and wind shears, independent of separation scale

Range‐time‐intensity (RTI) plots of 50 MHz radar backscatter detected at Jicamarca from the 150‐km region of the equatorial ionosphere exhibit necklace‐shaped multilayered structures first reported by Kudeki and Fawcett (1993, https://doi.org/10.1029/93GL01256). The backscatter layers also exhibit quasi‐periodic intensity fluctuations with periods of about 5–15 min and are separated from adjacent layers by thin and undulating regions of no detectible power returns. A study of the fluctuating backscatter layers and undulating gap regions will be presented using VIPIR ionosonde data taken at the Jicamarca Radio Observatory simultaneously with high‐resolution 50‐MHz radar backscatter data. VIPIR virtual reflection height variations in time are noted to match the RTI gap‐region undulations very closely at selected VIPIR frequencies (or, equivalently, electron densities at reflection heights). This matching enables assigning “true heights” to VIPIR virtual height contour maps, and a joint study of the contour maps with the 50‐MHz radar RTI maps strongly suggests that correlated fluctuations and undulations observed in VIPIR and 50‐MHz radar data are indicative of gravity wave‐induced variations in the 150‐km region ionosphere. Accordingly, a complete explanation of the 150‐km echo phenomenon will need to include gravity wave coupling and forcing effects in the enhancement and suppression processes that can account for the observed fluctuations and gap‐region features of necklace‐shaped 150‐km echo maps. VIPIR ionosonde and 50 MHz radar data are used jointly to investigate the equatorial 150‐km irregularitiesThe 150‐km echo layers seen in 50 MHz data are aligned with VIPIR isodensity contours in the region rippled by gravity wave modulationsThe 150‐km irregularity models need to account for gravity wave modulation and forcing effects

Radar echoes from the daytime lower Fregion near the magnetic equator, so‐called 150‐km echoes, have been puzzling researchers for decades. Neither the mechanisms that generate the enhanced backscatter at very high frequencies (typically 30–50 MHz), the sharp lower cutoff height, the intricate layering with multiple echo layers separated by narrow gaps, nor the modulation of the echoes by short‐period gravity waves is well understood. Here we focus on the diurnal variation of the echo layers—specifically, certain wide gaps in the vertical structure—which apparently descend in the morning, reach their lowest altitude near local noon, and ascend in the afternoon, sometimes described as necklace structure based on the appearance of the layers in range‐time‐intensity diagrams. Analyzing high‐resolution data obtained with the Jicamarca radar between 2005 and 2017, spanning more than one solar cycle, we find that (a) wide gaps and narrow lines occur in vertically stacked, systematically repeating pattern; (b) the gap heights vary with season and solar cycle; and (c) the gap heights can be associated with specific contours of plasma frequencies or electron densities. The last two findings are supported by simultaneous observations of VIPIR ionosonde reflection heights and by comparison of gap heights with electron density contours obtained with the WACCM‐X 2.0 global model. Finally, the wide gaps appear to coincide with the double resonance condition, where the upper hybrid frequency equals integer multiples of the electron gyrofrequency. This may explain why field‐aligned plasma irregularities are suppressed and enhanced radar backscatter is not observed inside the gaps. Specific gaps and lines in the 150‐km echo structure correspond to specific electron density contoursThe height of the gaps varies with season and solar activityWide gaps where echoes are suppressed likely correspond to regions of double resonance conditions