Storm-time response of the mid-latitude thermosphere: Observations from a network of Fabry-Perot interferometers
Location
Yosemite National Park
Start Date
2-12-2014 6:40 PM
End Date
2-12-2014 6:55 PM
Description
Observations of thermospheric neutral winds and temperatures obtained from a network of five Fabry-Perot interferometers deployed in the midwest United States during a geomagnetic storm on 2 October 2013 showed that coincident with the commencement of the storm, the horizontal wind was observed to surge westward and southward (towards the equator). Simultaneous with this surge in the horizontal winds, an apparent downward wind of approximately 100 m/s lasting for 6 hours was also observed. The neutral temperature was observed to increase by approximately 400 K over all of the sites. Similar results of downward vertical winds and sustained heating have been seen in other geomagnetic storm events. The large sustained apparent downward winds are interpreted as arising from the contamination of the nominal spectral profile of the 630.0-nm population distribution, which is thermalized within the thermosphere region, by fast O related to the infusion of low-energy O+ ions that are generated by charge exchange and momentum transfer collisions. This interpretation is supported through simultaneous observations made by the Helium, Oxygen, Proton, and Electron spectrometer instruments on the twin Van Allen Probes spacecrafts, which show an influx of low-energy ions well correlated with the period of apparent downward winds. These results emphasize the importance of distributed networks of instruments in understanding the complex dynamics that occur in the upper atmosphere during disturbed conditions and represent an example of magnetosphere-ionosphere coupling.
Storm-time response of the mid-latitude thermosphere: Observations from a network of Fabry-Perot interferometers
Yosemite National Park
Observations of thermospheric neutral winds and temperatures obtained from a network of five Fabry-Perot interferometers deployed in the midwest United States during a geomagnetic storm on 2 October 2013 showed that coincident with the commencement of the storm, the horizontal wind was observed to surge westward and southward (towards the equator). Simultaneous with this surge in the horizontal winds, an apparent downward wind of approximately 100 m/s lasting for 6 hours was also observed. The neutral temperature was observed to increase by approximately 400 K over all of the sites. Similar results of downward vertical winds and sustained heating have been seen in other geomagnetic storm events. The large sustained apparent downward winds are interpreted as arising from the contamination of the nominal spectral profile of the 630.0-nm population distribution, which is thermalized within the thermosphere region, by fast O related to the infusion of low-energy O+ ions that are generated by charge exchange and momentum transfer collisions. This interpretation is supported through simultaneous observations made by the Helium, Oxygen, Proton, and Electron spectrometer instruments on the twin Van Allen Probes spacecrafts, which show an influx of low-energy ions well correlated with the period of apparent downward winds. These results emphasize the importance of distributed networks of instruments in understanding the complex dynamics that occur in the upper atmosphere during disturbed conditions and represent an example of magnetosphere-ionosphere coupling.