We used Fabry‐Perot Interferometer (FPI) observations at Jicamarca, Nasca, and Arequipa, Peru, from 2011 to 2017 to study the nighttime zonal and meridional disturbance winds over the Peruvian equatorial region. We derived initially the seasonal‐dependent average thermospheric winds corresponding to 12 hr of continuous geomagnetically quiet conditions. These quiet‐time climatological winds, which are in general agreement with results from the Horizontal Wind Model (HWM14), were then used as baselines for the calculation of the disturbance winds. Our results indicate that the nighttime zonal disturbance winds are westward with peak values near midnight and with magnitudes much larger than predicted by the Disturbance Wind Model (DWM07). The premidnight equinoctial and June solstice westward disturbance winds have comparable values and increase with local time. The postmidnight westward disturbance winds decrease toward dawn and are largest during equinox and smallest during June solstice. The meridional average disturbance winds have small values throughout the night. They are northward in the premidnight sector, and southward with larger (smaller) values during December solstice (equinox) in the postmidnight sector. We also present observations showing that during the main and recovery phases of the April 2012 and May 2016 geomagnetic storms the zonal disturbance winds have much larger magnitudes and lifetimes (up to about 48 hr) than suggested by the HWM14. These observations highlight the importance of longer‐term disturbance wind effects. The large and short‐lived (about 2 hr) observed meridional wind disturbances are not reproduced by current climatological empirical models.
We used observations from the Peruvian Fabry‐Perot Interferometer network and from the Jicamarca radar to study the coupling of equatorial nighttime thermospheric winds and ionospheric drifts under moderate solar flux conditions. We show that the coupling of the extended quiet time zonal winds and drifts increases from dusk to midnight and is stronger during equinox than during June solstice. After midnight, they are strongly coupled, except during December solstice when the drifts are stronger. The nighttime disturbance zonal winds and drifts, derived by removing the corresponding quiet time values, are westward with peak magnitudes around midnight. They are in close agreement, except at early night when the winds are stronger, and have strongest (weakest) magnitudes during equinox (June solstice). We also present observations showing the strong neutral wind‐plasma drift coupling during the September 2017 and August 2015 large geomagnetic storms. We show that during the early phase of the September 2017 storm there were large and short‐lived, prompt penetration electric field‐driven, correlated oscillations (~1 hr) in the vertical and zonal plasma drifts, and in the zonal and meridional winds. These are the first observations of prompt penetration‐driven equatorial zonal and meridional wind disturbances. In this event, the vertical and zonal drift oscillations were anticorrelated, and the zonal winds followed the zonal drift oscillations with a delay of ~15 min. Our results illustrate the strong coupling of equatorial thermospheric winds and plasma drifts during geomagnetically quiet as well as during short‐lived prompt penetration and long‐lasting disturbance dynamo events.
more » « less- NSF-PAR ID:
- 10449101
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 125
- Issue:
- 9
- ISSN:
- 2169-9380
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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We introduce the implementation of a global climatological model of the equatorial ionospheric F-region zonal drifts (EZDrifts) that is made available to the public. The model uses the analytic description of the zonal plasma drifts presented by Haerendel et al. (1992) [ J Geophys Res 97(A2) : 1209–1223] and is driven by climatological models of the ionosphere and thermosphere under a realistic geomagnetic field configuration. EZDrifts is an expansion of the model of the zonal drifts first presented by Shidler & Rodrigues (2021) [ Prog Earth Planet Sci 8 : 26] which was only valid for the Jicamarca longitude sector and two specific solar flux conditions. EZDrifts now uses vertical equatorial plasma drifts from Scherliess & Fejer (1999) [ J Geophys Res 104(A4) : 6829–6842] model which allows it to provide zonal drifts for any day of the year, longitude, and solar flux condition. We show that the model can reproduce the main results of the Shidler & Rodrigues (2021) [ Prog Earth Planet Sci 8 : 26] model for the Peruvian sector. We also illustrate an application of EZDrifts by presenting and discussing longitudinal variabilities produced by the model. We show that the model predicts longitudinal variations in the reversal times of the drifts that are in good agreement with observations made by C/NOFS. EZDrifts also predicts longitudinal variations in the magnitude of the drifts that can be identified in the June solstice observations made by C/NOFS. We also point out data-model differences observed during Equinox and December solstice. Finally, we explain that the longitudinal variations in the zonal plasma drifts are caused by longitudinal variations in the latitude of the magnetic equator and, consequently, in the wind dynamo contributing to the resulting drifts. EZDrifts is distributed to the community through a public repository and can be used in applications requiring an estimate of the overall behavior of the equatorial zonal drifts.more » « less
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