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This paper discusses results of the Explorer 34 plasma detector obtained during three magnetic storms, May 30, June 5, and June 25, 1967. Detailed comparisons with magnetic field observations on the same satellite are used to interpret the observations and to identify shocks and tangential discontinuities. A relation between the magnitude of such sudden changes in the earth's magnetic field and the solar wind parameters has been derived by Siscoe. Our observations are consistent with this relationship. The local shock speeds are derived from data obtained at the time of the sudden commencements. An example of an si+ si− pair is discussed, and in this case the negative impulse is shown to be due to a tangential discontinuity rather than a shock, whereas the positive impulse is associated with a shock. Helium observations are described that show that during the main phase of some geomagnetic storms the abundance ratio na/np shows a marked increase. In the May 30 storm it attained a value of 0.15 ± 0.02, 5½ hours after the sc, an increase of seven times over the value observed earlier.

Abstract. Rayleigh lidar observations of mesosphere temperature profiles obtained from 40 to -100 km from Logan, Utah (41.7, 111.8 W, altitude, 1.9 km) over 10 nights in late February, 1995, revealed an interesting development between 60 to 75 km of a winter mesosphere inversion layer with an amplitude of -20-30 K and a downward phase progression of -1 km/hr. The data also showed two altitude regions exhibiting significant cooling of 10-30 K in extent. These were located below and above the peak of the inversion layer, respectively, at altitudes of-50-55 km and -70-80 km. When these results were compared with the predictions of a global wave scale model (GSWM), the observed thermal mesosphere structure is similar to the computed composite tidal structure based upon the semi-diurnal and diurnal tides with the exception that observed amplitudes of heating and cooling are -10x larger than predicted GSWM values. We suggest that these events over Utah are caused through a localized mechanism involving the coupling of gravity waves to the mesopause tidal structure.

A ground-based differential absorption lidar (DIAL) system is described which has been developed for vertical range-resolved measurements of water vapor. The laser transmitter consists of a ruby-pumped dye laser, which is operated on a water vapor absorption line at 724.372 nm. Part of the ruby laser output is transmitted simultaneously with the dye laser output to determine atmospheric scattering and attenuation characteristics. The dye and ruby laser backscattered light is collected by a 0.5-m diam telescope, optically separated in the receiver package, and independently detected using photomultiplier tubes. Measurements of vertical water vapor concentration profiles using the DIAL system at night are discussed, and comparisons are made between the water vapor DIAL measurements and data obtained from locally launched rawinsondes. Agreement between these measurements was found to be within the uncertainty of the rawinsonde data to an altitude of 3 km. Theoretical simulations of this measurement were found to give reasonably accurate predictions of the random error of the DIAL measurements. Confidence in these calculations will permit the design of aircraft and Shuttle DIAL systems and experiments using simulation results as the basis for defining lidar system performance requirements.

Long electrical spark discharges have been directed through air along predetermined paths defined by a concentrated laser beam. At apparent optical power densities of 50–100 giga W/cm2, 35-nsec half-width laser pulses at 10 600 Å have been effective in channeling streamer discharges from a 350-kV positively charged electrode for distances up to 28 cm in a total streamer length of 71 cm. The average E field required to obtain a discharge between electrodes was reduced from 7.3 to 5.5 kV/cm with the laser powers employed.