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[1] We use low- and mid-latitude wind data from the Wind Imaging Interferometer (WINDII) on board the Upper Atmosphere Research Satellite (UARS) to study the average response of nighttime upper thermospheric winds to geomagnetic activity. We calculate perturbation winds in magnetic coordinates and analyze them as a function of magnetic local time, latitude, geomagnetic activity, and solar EUV flux. The nighttime zonal disturbance winds are predominately westward, with the strongest effects extending from dusk at 70° to midnight at 45°. Westward disturbance winds are also observed throughout most of the night at low latitudes, where they change to eastward at dawn. Eastward perturbations occur in the post-midnight sector above 50°. The meridional disturbance winds are primarily equatorward above 40° and after 0300 MLT. In the midnight sector during low and moderate solar flux conditions, poleward winds are observed below 40°; during solar maximum, the perturbations are largely equatorward throughout the night.

[1] Thermospheric neutral winds exhibit strong altitudinal and latitudinal variation during geomagnetically quiet and active times. We use daytime middle and low-latitude neutral winds measured by the Wind Imaging Interferometer (WINDII) instrument on board the Upper Atmosphere Research Satellite (UARS) over the 90–275 km height range to study the altitude and season dependent climatology of disturbance winds (i.e., with quiet time patterns removed) in magnetic coordinates. The daytime perturbations winds are generally equatorward and westward and decrease toward the magnetic equator. Both the zonal and meridional components decrease sharply below 120 km and are essentially insignificant below 100 km. The seasonal dependence of the disturbance winds is strongest in the early morning sector. The zonal disturbance winds are predominantly westward with largest magnitudes near 150 km at late afternoon upper midlatitudes (magnetic latitudes 50°–60°) and near 120 km in the early morning winter between 25° and 45°. At upper midlatitudes in the early morning sector, the zonal perturbation winds are eastward above ∼120 km in the summer hemisphere and between ∼120 and 180 km in the winter hemisphere. Eastward perturbations are also observed near the magnetic equator with largest values near noon at 250 km. The meridional perturbation winds are mostly equatorward and nearly height-independent above ∼150 km, with the largest magnitudes occurring in the early morning winter hemisphere. In the late afternoon sector the upper midlatitude meridional disturbance winds are poleward, and there is a small winter-to-summer flow at lower latitudes. In general, the storm-time dependence of the disturbance winds is quite complex. The perturbation winds begin to develop after 0–9 hours and tend to saturate 12–24 hours after storm onset. The development does not change much with altitude, and the seasonal dependence is generally important only at storm times greater than 6–12 hours.

A method has been developed for the retrieval of mesospheric temperatures in the 65–90 km altitude range from satellite observations made by the Wind Imaging Interferometer (WINDII) aboard the Upper Atmosphere Research Satellite (UARS). Retrieved temperatures are derived from Rayleigh scattered sunlight observed in a wavelength band centered at 553 nm. Integrated line-of-sight radiance observations are inverted to tangent height volume scattering profiles, which are proportional to atmospheric density. From these, absolute temperature profiles are calculated using a technique derived from established Rayleigh lidar retrieval methods assuming that the atmosphere is in hydrostatic equilibrium and that it obeys the ideal gas law. Sources of error have been identified and typical temperature uncertainty values for individual profiles are determined to be < 2.5%, 5.5%, and 13% for altitudes of 70 km, 80 km, and 90 km, respectively. A thorough comparison of the derived WINDII temperatures is performed against a number of ground-based and satellite measurements, including ground-based lidar, falling spheres, the High Resolution Doppler Imager observations aboard UARS, and against common atmospheric models. The data consist of spring equinox observations in March and April 1992/1993, summer solstice data in July/August 1992/1993, fall equinox data in September/October 1992, and winter solstice data in December 1992/1993 and January 1993/1994. The results of the comparisons show that WINDII temperatures are in reasonable to excellent agreement with a number of established temperature studies. In particular, July Northern Hemisphere monthly averaged temperatures show that characteristics of the mesopause obtained by WINDII are in very good agreement with other measurements. This good agreement with other established data sets and a determination of the error bounds of our recovered temperatures have shown that WINDII data can be used to confidently derive near-global temperatures of the upper mesosphere between 65 and 90 km. Above 90 km the errors increase, and systematic differences may arise with other measurements.

Thermospheric neutral winds play important roles on the dynamics of the upper atmosphere. We use extensive F region zonal and meridional wind data measured by the Wind Imaging Interferometer (WINDII) instrument on board the Upper Atmosphere Research Satellite (UARS) to study the mid-and low-latitude daytime average perturbation winds during magnetically disturbed periods. We have determined the perturbation winds by subtracting the quiet time wind values along the satellite orbits. Our data indicate large changes in the latitudinal profiles of both the zonal and meridional disturbance winds from morning to afternoon hours. The early morning zonal disturbance winds are eastward near the equator and at upper mid-latitudes (above 50°), and westward at lower mid-latitudes. The mid-morning and afternoon zonal disturbance wind patterns show very small amplitudes at low latitudes and increasing westward winds at mid-latitudes. These latitudinal profiles are in excellent agreement with the patterns derived from zonal wind measurements on board the DE-2 satellite. The meridional daytime perturbation winds are equatorward and have magnitudes increasing linearly with latitude, with largest values in the early morning sector. The zonal and meridional disturbance winds show an approximately linear increase with the Kp index during geomagnetically active conditions.

The effects of grazing by barnacle geese Branta leucopsis on arctic vegetation was studied. Two plots where grazers had been excluded five and six years previously were compared with grazed vegetation nearby. The exclosed plots contained more live biomass than the area with grazed vegetation. However, there was no significant difference in density of shoots and number of leaves per shoot in the heavily grazed Poa arctica. Within the exclosed plots, there was a slow build-up of dead material and the moss carpet had grown thicker than in the grazed plots. The number of inflorescences was the most prominent feature, which differentiated the exclosed vegetation from the sated surrounding. There is no evidence for habitat deterioration caused by increased grazing pressure from the expanding barnacle goose population as has been reported for the snow goose on the Hudson Bay lowlands in Canada. The increased activity of nitrogen fixation by cyanobacteria in grazed vegetation might be a mechanism which compensates for the nitrogen deficit caused by the migratory geese.

Two different types of nitrogen-fixing root nodules are known - actinorhizal nodules induced by Frankia and legume nodules induced by rhizobia. While legume nodules show a stem-like structure with peripheral vascular bundles, actinorhizal nodule lobes resemble modified lateral roots with a central vascular bundle. To compare carbon metabolism in legume and actinorhizal nodules, sucrose synthase and enolase cDNA clones were isolated from a cDNA library, obtained from actinorhizal nodules of Alnus glutinosa. The expression of the corresponding genes was markedly enhanced in nodules compared to roots. In situ hybridization showed that, in nodules, both sucrose synthase and enolase were expressed at high levels in the infected cortical cells as well as in the pericycle of the central vascular bundle of a nodule lobe. Legume sucrose synthase expression was studied in indeterminate nodules from pea and determinate nodules from Phaseolus vulgaris by using in situ hybridization.