Observations of Strong Vertical Winds within the Auroral Zone during Active Geomagnetic Disturbances
Abstract
Many nights of vertical wind observations using a narrow field redline Fabry-Perot interferometer obtained at Alaskan sites located at Eagle (64.8 N, 141.2), Poker Flat (65.1 N,147.5 W), and Ft. Yukon (66.6 N,145.2 W) show strong responses of thermospheric upwelling to significant auroral activity as represented by the Kp index exceeding 3 or the AE index that is in excess of 500 gammas. In geomagnetic quiet periods the vertical wind speed is generally less than 5-10 ms-1 which is associated with the presence of a long period wave structure. In the more active periods the typical range of the upwelling winds observed is of order of 50 to 100 ms-1. For several cases of stormtime geomagnetic activity with Kp and AE as high as 8 and 1500 gammas, respectively, the observed upward vertical wind speed can be as large as 200 ms-1. Examination of the 630-nm Doppler shifts for the central zone element of the Poker Flat Scanning Doppler Imager that is most closely aligned with the vertical direction also show evidence for such vigorous response of the auroral thermosphere dynamics during active geomagnetic disturbances. Also seen during these periods of upward vertical wind is a significant enhancement of the thermosphere temperature of 200 to 500 K. TIEGCM modeling for the St. Patrick geomagnetic storm of 17 March 2015 using a high resolution grid model (1.25 deg x 1.25 deg x 1/8 scale height) for the auroral region combined with PFISR measurements of plasma convection speeds that were typically 1000 ms-1 eastward showed that extended Joule heating could cause the vertical upwelling and temperature enhancement effects observed. These calculations included allowance for the electric field variability as well as the utilization of the THEMIS ASI auroral representation of the particle energy flux and mean particle energy for the auroral zone.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMSA025..06M
- Keywords:
-
- 2427 Ionosphere/atmosphere interactions;
- IONOSPHERE;
- 2431 Ionosphere/magnetosphere interactions;
- IONOSPHERE;
- 2704 Auroral phenomena;
- MAGNETOSPHERIC PHYSICS;
- 2736 Magnetosphere/ionosphere interactions;
- MAGNETOSPHERIC PHYSICS