Storm‐Time Thermospheric Winds Over Peru

Abstract

Abstract 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.