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Daytime Mesosphere and Lower Thermosphere Neutral Winds and their relationship with lower E region layers over Arecibo
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  • Eliana Nossa,
  • Jonathan Krall,
  • Joseph Huba,
  • Douglas Drob
Eliana Nossa
US Naval Research Laboratory

Corresponding Author:[email protected]

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Jonathan Krall
Naval Research Laboratory
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Joseph Huba
Syntek Technologies
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Douglas Drob
Naval Research Lab
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The formation of layers at mid-latitudes has been related to neutral winds activity at altitudes below 130km in the Mesosphere and Lower Thermosphere (MLT). Recent SAMI3 simulations by Krall et al. (2020) of ionospheric metallic layers at Arecibo suggest that forces induced by the meridional winds cause low altitude layers near 100 km. However, the classic mechanism, originally proposed by Whitehead (1961), correctly states that zonal wind shear has a bigger effect than meridional wind shear in the lower E region. Haldoupis and Shalimov (2021), referring to observations of ionosonde-based sporadic E statistics and radio occultation sporadic E measurements using low Earth orbiting satellites, support the idea that zonal winds dominate layer formation at these altitudes, apparently disputing the findings of Krall et al. (2020). Perhaps the latest technique to continuously measure mid-latitude MLT daytime neutral winds was developed by Hysell et al. (2014). That technique used a unique configuration of the Arecibo radar dual-beam. Unfortunately, since Arecibo lost the capability of the dual-beam in 2017 (when one antenna was destroyed by Hurricane Maria), there are only few valuable data sets that can help elucidate the origin of the lower altitude layers at Arecibo. We present Arecibo neutral wind data correlated with lower altitude layers. While not disputing current theory, we find that, near 100 km, meridional neutral wind shear can be much stronger than zonal wind shear when a layer is present, with the meridional shear correctly positioned to support the layer. We also present a complete analysis of the vertical ion drift, including declination, where the meridional winds become more important and with a reversed mechanism for altitudes below 115km for Arecibo conditions. References: Haldoupis et al. (2021), https://doi.org/10.1016/j.jastp.2021.105537 Hysell et al. (2014), http://doi.org/10.1002/2013JA019621 Krall et al. (2020), https://doi.org/10.1029/2019JA027297