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A trimethyl aluminum (TMA) release rocket launched during the 1998 Coqui II sounding rocket campaign in Puerto Rico produced what appeared to be an artificially generated aurora. This phenomenon has been observed on several other occasions but has heretofore not been reported. In this paper we discuss the observation of artificially generated auroral light in relation to a kerosene-doped TMA release and propose an auroral generation mechanism involving motion of charged particulates associated with the TMA trail.

[1] The Aerospace Corporation's Nightglow Imager observed a large step function change in airglow in the form of a traveling front in the OH Meinel (OHM) and O2atmospheric (O2A) airglow emissions over Alice Springs, Australia, on 2 February 2003. The front exhibited nearly a factor of 2 stepwise increase in the OHM brightness and a stepwise decrease in the O2A brightness. There was significant (∼25 K) cooling behind the airglow fronts. The OHM airglow brightness behind the front was among the brightest for Alice Springs that we have measured in 7 years of observations. The event was associated with a strong phase-locked 2 day wave (PL/TDW). We have analyzed the wave trapping conditions for the upper mesosphere and lower thermosphere using a combination of data and empirical models and found that the airglow layers were located in a region of ducting. The PL/TDW-disturbed wind profile was effective in supporting a high degree of ducting, whereas without the PL/TDW the ducting was minimal or nonexistent. The change in brightness in each layer was associated with a strong leading disturbance followed by a train of weak barely visible waves. In OHM the leading disturbance was an isolated disturbance resembling a solitary wave. The characteristics of the wave train suggest an undular bore with some turbulent dissipation at the leading edge.

[1] Expressions for momentum and heat fluxes using density as the vertical coordinate are derived. These are applied in the evaluation of fluxes using data from super-pressure balloons drifting on constant density surfaces in the Antarctic lower stratosphere during the VORCORE campaign (September 2005 to February 2006). We focus on the core months of October and November. Vertical fluxes of zonal and meridional momentum are calculated using wind, pressure and height data and the vertical flux of sensible heat is calculated using temperature and height data. Calculations were performed in three band passes covering 1–13 h. We find that the largest fluxes are in the vicinity of the Antarctic Peninsula. In October the fluxes in the low period band pass (1–5 h) account for the main part of the total flux of zonal momentum, consistent with topographically forced waves. During November the vertical fluxes of zonal momentum are found mainly in longer period band passes, consistent with weaker winds. The peak campaign-averaged flux of zonal momentum in the vicinity of the Antarctic Peninsula is ∼−30 mPa. These values are ∼60% larger over the peninsula than those inferred by other authors. The flux of zonal momentum provides a zonal body force of ∼5 m s−1 day−1 assuming a saturated spectrum. We infer downward sensible heat fluxes of ∼3 W m−2. The corresponding cooling rates assuming a saturated spectrum are ∼0.6 K day−1, a significant fraction of the net radiative imbalance in the springtime Antarctic lower stratosphere.

[1] The quasi 2 day wave, with a nominal mean period just above 50 h, is a significant feature of the 80–100 km altitude region in both hemispheres. It becomes particularly prominent in the Southern Hemisphere summer at midlatitudes where, a short time after summer solstice, its amplitude rapidly increases and its mean period is found to be approximately 48 h, producing an oscillation phase locked in local time. This lasts for a few weeks. Presented here are observations of the meridional winds and airglow over two sites in Australia, for 4 years during the austral summers of 2003–2006. We show that during those times when the large-amplitude phase-locked 2 day wave (PL-TDW) is present the diurnal tide greatly decreases. This is consistent with the Walterscheid and Vincent (1996) model in which the PL-TDW derives its energy from a parametric excitation by the diurnal tide. These data also show that the diurnal tide is more suppressed and the PL-TDW amplitude is larger in odd-numbered years, suggesting a biannual effect. The airglow data indicated that, for the PL-TDW, the winds and temperature are nearly out of phase. When the PL-TDW is present airglow amplitudes can become quite large, a result dependent on the local time of the PL-TDW maximum. The airglow intensity response was, in general, much larger than what would be expected from the airglow temperature response, suggesting that the PL-TDW is causing a significant composition change possibly due to minor constituent transport.

[1] During the Tropical Warm Pool International Cloud Experiment (TWPICE) an intense tropical low was situated between Darwin and Alice Springs, Australia. Observations made on 31 January 2006 by the Atmospheric Infrared Sounder instrument on the NASA Aqua satellite imaged the presence of atmospheric gravity waves (AGWs), at approximately 40 km altitude, with horizontal wavelengths between 200 and 400 km that were originating from the region of the storm. Airglow images obtained from Alice Springs (about 600 km from the center of the low) showed the presence of similar waves with observed periods of 1 to 2 h. The images also revealed the presence of 30- to 45-km-horizontal-wavelength AGWs with shorter observed periods of near 15 to 25 min. Ray tracing calculations show that (1) some of the long wavelength waves traveled on rays, without ducting, to the altitudes where the observations were obtained, and (2) shorter-period waves rapidly reached 85 km altitude at a horizontal distance close to the storm, thus occurring over Alice Springs only if they were trapped or ducted. The mesospheric inversion layer seen in the measured temperature data almost forms such a trapped region. The winds therefore critically control the formation of the trapped region. Wind profiles deduced from the available data show the plausibility for the formation of such a trapped region. Variations in the wind, however, would make ideal trapped region conditions short-lived, and this may account for the sporadic nature of the short-period wave observations.

[1] Aerospace imagers operating at Alice Springs (23°42′S, 133°53′E) and Adelaide (34°55′S, 138°36′E) have collected more than 4-year of OH and O2 atmospheric emission data. Images taken over the course of each moonless night at 5-min intervals were used to determine OH Meinel (6, 2) and O2 Atmospheric (0, 1) band emission intensities and temperatures, as well as atmospheric gravity wave parameters. The NCAR general circulation model TIME-GCM was run for years 2002–2005 for comparison with these data. The data presented here show the interannual variability of OH and O2A emissions at two sites, Alice Springs and Adelaide, over a 4-a period. It was found that the TIME-GCM successfully reproduces many observed features of the data, including equinoctial maxima associated with the diurnal tide, a 6-h phase shift between OH temperature and intensity maxima, and springtime OH intensity enhancements at Alice Springs. However, the model tends to underestimate the depth of the summertime temperature minimum at both sites, possibly due to inadequate specification of the seasonal variation of gravity waves in the model. The model does, however, successfully describe many of the mesospheric changes observed during the 2002 stratospheric warming event.

[1] We present data from a winter 2002 sounding rocket campaign for multiple observations of mesospheric charged dust. The campaign consisted of four identically instrumented payloads carrying detectors for charged mesospheric dust particles. The payloads reached an altitude of 100 km in the nighttime mesosphere and were flown from Poker Flat Research Range, Alaska, in conjunction with observations by the UAF sodium and iron resonance lidar system. Three of the four flights flew in sequence during the course of one night to study the temporal evolution of dust layers. Observations show good correlations between structure seen in the charged dust altitude profile, structure seen in the neutral metal layers observed by the lidars, and structure in the plasma density seen by the onboard Langmuir probes. The dust detector is sensitive to positively and negatively charged dust particles with ram energies of 1 to 11 eV for negatively and 3–11 eV for positively charged dust; that is, particles of approximately 5000 amu. The charged dust densities seen (estimated to be approximately 5 to 10 percent of the total dust density) are approximately 100 particles per cc, and the dust is negatively charged. Variations in the dust density of about 10% are seen in conjunction with structure in the plasma density and with the neutral metal layers. In this paper we present the details of the dust data and instrumentation; a companion paper explores the implications of the correlations seen between the dust and other mesospheric layers.

[1] On 11 March 1998 the Langmuir Turbulence sounding rocket was launched through the Arecibo heater beam during an experiment to measure electric fields and plasma densities in the heater interaction region. In spite of a serious degradation of the Arecibo heater, the rocket data has provided evidence of Z mode waves and field aligned striations above the O mode reflection height. These observations give credence to the theory that Z mode wave interactions with field-aligned striations may be, in part, responsible for some of the features of the reflected HF spectrum observed in heating experiments. We also find strong low-frequency electric fields where the local plasma frequency matches an electron cyclotron harmonic. This suggests that electron Bernstein modes must be generated in the interaction process and can propagate to regions where they are severely damped.