Localized High-Latitude Ionosphere-Thermosphere Ionization Events during the High Speed Stream Interval of 29 April – 5 May 2011

Tuesday, 16 December 2014: 9:02 AM
Olga P Verkhoglyadova1, Anthony J Mannucci2, Bruce T. Tsurutani1, Martin G Mlynczak3, Linda A Hunt4, Robert J Redmon5 and Janet C Green6, (1)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (2)Jet Propulsion Laboratory, Pasadena, CA, United States, (3)NASA Langley Research Ctr, Hampton, VA, United States, (4)SSAI, Hampton, VA, United States, (5)Natl Geophysical Data Ctr, Boulder, CO, United States, (6)GeoSynergy, Golden, CO, United States
We analyze localized ionospheric – thermospheric (IT) events in response to external driving by a high-speed stream (HSS) event during the ascending phase of the solar cycle 24. The HSS event occurred from 29 April to 5 May, 2011. The HSS (and not the associated co-rotating interaction region) caused a moderate geomagnetic storm with peak SYM-H = -55 nT and prolonged auroral activity. We analyze TIMED/SABER measurements of nitric oxide (NO) cooling emission during the interval as a measure of thermospheric response to auroral heating. We identify several local cooling emission (LCE) events in high- to sub-auroral latitudes that are presumed to be in response to external driving. Individual cooling emission profiles during these LCE events are enhanced at ~100 to 150 km altitude (ionospheric E layer). For the first time, we present electron density profiles in the vicinity of the LCE events using COSMIC radio-occultation measurements. Measurements at local nighttime show the formation of an enhanced E-layer (about 2.5 times increase over the undisturbed value) at the same approximate altitudes as the LCE peaks. Daytime electron density profiles show relatively smaller enhancements in the E-layer. We suggest that the IT response is due to additional ionization caused by medium energy electron (>20 keV) precipitation into the sub-auroral to high-latitude atmosphere during the HSS event. POES/MEPED electron precipitation data are presented to support this hypothesis. Consequences for space weather forecasting are discussed.