Abstract. We have examined lidar and airglow data and National Weather Service analysis fields for a stratospheric sudden warming event in February 1993. The lidar and airglow measurements recorded temperature changes in the mesosphere and lower thermosphere over Eureka, Canada (80øN). In addition, the event was simulated by the National Center for Atmospheric Research TIME-GCM. The observations, analysis fields, and the simulation results taken together indicate a connection between the stratospheric warming of February 1993 and alternating regions of cooling and warming above the main warming in the lower stratosphere (however, movement of the polar vortex complicates the interpretation for the second of two warming episodes in the upper stratosphere during the event). The sudden warming was associated with cooling observed in the OH airglow and predicted by the model. This cooling preceded the warming in the lower stratosphere.

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We have examined Michelson Interferometer OH airglow temperature data to investigate solar cycle and long‐term variations of mesospheric temperatures at South Pole Station (SPS), Antarctica (90°S). The data set used here is continuous (24 hours a day) and taken during 1994–2004 austral winters. We have used a Multiple Linear Regression (MLR) technique to elucidate solar cycle and the trend term in the MI temperature time series data. The 11‐year time series of OH rotational temperature shows a strong correlation with F10.7 radio flux (R = 0.60). The amplitude of solar cycle response seen in the mesopause temperature records at South Pole is about 0.04 ± 0.01 K/sfu (Solar Flux Units), however, the trend term is statistically insignificant and is about 0.1 ± 0.2 K/year. Superposed epoch studies have been carried out in order to determine climatological variations in OH temperatures above South Pole derived from 11 years of austral winter observations. The mean amplitude of this variation is about 12.6 K and its maximum occurs near 30 May which is in agreement with the Fabry‐Perot Spectrometer (FPS) observations of OH temperatures at SPS (Hernandez, 2003). However, whereas Hernandez (2003) reported 35 K cooling in 2002, MI OH temperatures at SPS do not show any significant deviation from previous years.

We have examined the Michelson Interferometer (MI) OH airglow measurements at the South Pole Station and the National Center for Environment Prediction (NCEP) temperatures to investigate the dynamical effects of sudden stratospheric warming (SSW) events on the Antarctic mesosphere and stratosphere. Comparisons of stratospheric and mesospheric temperatures at the South Pole during the 1995 and 2002 observing seasons show evidence of mesospheric cooling preceding the SSW events. Spectral analyses of South Pole OH air glow brightness measurements from the 1995 and 2002 observing season and NCEP stratospheric temperatures show amplification of the 4‐day wave planetary wave before the start of the mesospheric cooling trend, the latter preceding the onset of SSW event. A similar behavior of planetary wave is also seen in the stratosphere where the 4‐day wave is seen to grow in amplitude just before the peak of the sudden increase in temperatures.

Intensities (I) and rotational temperatures (T) of the OH(8, 3) and (6, 2) bands were derived from spectrophotometric observations of airglow emissions, over Longyearbyen in Spitsbergen, made in December 1984. The high latitude of the Spitsbergen Observatory (78°15′N) permitted 24‐hour coverage of the wintertime polar airglow. These measurements yielded the following results: (1) T derived from P1 rotational lines of OH depend on the choice of A values (T (Honl‐London, A) > T (Mies, A) > T (Espy, A)); (2) P =,213= 2072 K 207 implying a 3‐ to 5‐K/km temperature gradient in the atmosphere around 85 km height; (3) Ī(8, 3) = 314 ± 30 R and Ī (6, 2) = 1025 ± 110 R; the corresponding OH(υ′) columnar abundances are (5.5 ± 0.6) × 108 cm−2 and (8.0 ± 0.8) × 108 cm−2 for υ′ = 8 and υ′ = 6 vibrational levels. These results are compared with the predictions of a one‐dimensional oxygen‐hydrogen model which shows that (1) the reaction rate of OH H + O 2 may be much higher than the laboratory‐measured k6 value for OH(υ′ = 0); (2) the higher k6 value accounts for the separation of OH layers for different υ′ levels observed in various rocket measurements of OH*(υ′) profiles and implies a positive temperature gradient in the atmosphere around 85 km; (3) Llewellyn et al.’s (1978) rate for quenching of OH* by M(N2 and O2) is required in the model to match the calculated column abundance of OH* in υ′ = 8 to the value derived from the observed intensities of the airglow OH(8, 3) band; and (4) a perhydroxyl source must be invoked for the model to yield a column abundance of OH* in υ′ = 6 consistent with the intensity of the airglow OH(6, 2) band observed in Spitsbergen.

OH nightglow emissions from the (6, 2) band were observed during February 12–14, 1986, at Sondre Stromfjord, Greenland. The data were analyzed using time series analysis techniques to determine , where ΔI and ΔT represent correlated fluctuations from the mean OH intensity (Ī) and temperature ( ) in various frequency bands. For correlated fluctuations due to measurement error, |η| < 1, while for correlated fluctuations caused by atmospheric gravity waves (AGWs) that pass through the OH emission layer the measured |η| should be generally greater than 1.5. While some of the observed OH intensity‐temperature fluctuations were correlated and had an |η| < 1, two correlated intensity‐temperature waves with periods of 4 and 2 hours were seen with an |η| > 1.5. The 4‐hour (2‐hour) period wave had an |η| equal to 3.1 ± 1.1 (1.6 ± 0.5) and a phase angle, between the intensity and temperature components, of 5° ± 23° (40° ± 20°). These results are consistent with a recent theoretical model for the passage of AGWs through an OH emission layer. Agreement is closest for the 4‐hour (2‐hour) period wave when the layer is peaked at 87 km (83 km) and the O scale height is −2.0 (−4.0km).

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[1] The local ionospheric response to an auroral intensification at the poleward auroral boundary has been investigated using the incoherent scatter radar (ISR) and optical instrumentation at Sondrestrom, Greenland, in conjunction with space-borne measurements by the IMAGE and FAST satellites. ISR elevation scans through the illuminated region revealed filamentary columns of enhanced plasma density, $5 km in latitude by $200 km in altitude. Column densities were typically 5 Â 10 11 /m 3 above background and often constant over a broad range of altitudes. The brightness of the O + 732-733 nm multiplet, monitored simultaneously by a near-infrared spectrometer, exceeded 1.2 kR during one 4-min period (a factor of $4 brighter than previously reported auroral measurements). A time-dependent model was developed to relate O + emission intensities to O + column densities for a given illumination time. The results suggested that the electron source was composed of kilometer-scale flux tubes locked in the E Â B flow for several minutes whose average energy varied temporally between <100 eV and >1 keV over their illumination lifetime. Conjugate electrons measured by the FAST satellite at 1700 km showed evidence for energization by inertial Alfvén waves. Ionization rates computed from these spectra were sufficient to account for the observed filamentary ionospheric structure. The implications of such ionization patterns for electrodynamic coupling with the magnetosphere are discussed.