Thermospheric temperatures above Poker Flat, Alaska, during the stratospheric warming event of January and February 2009

Abstract

[1] We report observations of neutral and ion temperatures at approximately 240 km altitude above Poker Flat, Alaska, taken during the stratospheric warming event of January and February 2009. Neutral temperatures were recorded by a single-etalon Fabry-Perot spectrometer observing the nighttime airglow and aurora at 630 nm wavelength, whereas ion temperatures were obtained with the Poker Flat Incoherent Scatter Radar, mostly during daylight. Neutral and ion temperatures generally tracked each other closely; both data sets exhibited a similar overall seasonal trend during January to April 2009 and even showed similar short-term day-to-day fluctuations. Further, the daily fluctuations correlated highly with geomagnetic activity. Both the short-term temperature fluctuations and their overall seasonal trend matched expectations based on the MSIS model evaluated for this period at hourly intervals. A cooling response was seen in neutral temperature over a 2-3 week period during the main phase of the stratospheric warming. The magnitude of this cooling was around 50 K relative to the seasonal trend. A corresponding signature was also discernible in the ion temperatures, although it was less prominent than the neutral response. This was largely because the cooling was masked by ion temperature perturbations driven by magnetic activity. The strength of the response in ion temperature was observed to depend on the local time of the observations, which is consistent with results presented previously.

The phases and amplitudes of gravity waves propagating and dissipating in the thermosphere: Application to measurements over Alaska

“…Figure 9 (bottom) shows T measured by PKZ and T i measured by PFISR, and the band‐pass filtered signals. The absolute temperature values agree well, in agreement with Conde and Nicolls [2010]. Additionally, the perturbation amplitudes are quite similar.…”

Winter-time dependence of the global TEC on the stratospheric temperature and solar radiation

“…Some incoherent scatter radar and Fabry-Perot observations at middle and high latitudes shed some light on the SSW response of the thermosphere as well. They identified large perturbations of ion and neutral temperatures at heights above 100 km revealing some increase of temperature in the height range of 100-140 km and its decrease above 150 km (Goncharenko and Zhang, 2008;Conde and Nicolls, 2010;Kurihara et al, 2010). Nevertheless that the above mentioned neutral temperature changes have been observed at single stations (Millstone Hill, Poker Flat and ESCAT) they supported to some extent the result obtained from the global circulation model reported by Liu and Roble (2002).…”

Variation of Small‐Scale Gravity Wave Activity in the Ionosphere During the Major Sudden Stratospheric Warming Event of 2009

“…It was devoid of any major geomagnetic disturbance which could help interpret the effects due to internal sources. Second, the 2009 SSW event has been studied extensively (Azeem et al, ; Chau et al, ; Conde & Nicolls, ; Fagundes et al, ; Fang et al, ; Forbes & Zhang, ; Fuller‐Rowell, Akmaev, et al, ; Fuller‐Rowell, Wang, et al ; Goncharenko, Coster, et al, ; Goncharenko, Chau, et al, ; He et al, ; Klimenko et al, ; Korenkov et al, ; Lin et al, ; Liu et al, , ; McDonald et al, ; Oyama et al, ; Patra et al, ; Pedatella et al, ), which gives us an advantage to use it as an ideal testbed. However, we must emphasize that none of the studies focused on small‐scale GWs.…”