摘要:

Observations of interplanetary Lyman‐α obtained by the Galileo Extreme Ultraviolet Spectrometer (EUVS) experiment near solar maximum in 1990 show a distinct migration in the upwind brightness maximum from 36±5°N to 6±5°N ecliptic latitude over a period of several months. Our earlier models based on solar Lyman‐α flux proxies appropriate for use in the ecliptic plane ( Pryor et al., 1992; Ajello et al., 1994) capture the solar rotation effects present in the data, but do not reproduce this latitude migration. We introduce a new type of model that uses He 1083 nm images to produce a proxy for Lyman‐α as a function of both solar longitude and latitude. This model reproduces the observed latitude migration of the Lyman‐α bri

ISSN:0094-8276    

DOI:10.1029/96GL01978

年代:1996

数据来源: WILEY

摘要:

The exhaust plume of the Space Shuttle during its ascent is a very powerful source of energy that excites atmospheric acoustic perturbations. Because of the coupling between neutral particles and electrons at ionospheric altitudes, these low frequency acoustic perturbations induce variations of the ionospheric electron density. We computed ionospheric electron content time series using Global Positioning System data collected on Bermuda island during the STS‐58 Space Shuttle launch. The analysis of these time series shows a perturbation of the ionospheric electron content following the launch and lasting for 35 mn, with periods less than 10 mn. The perturbation is complex and shows two sub‐events separated by about 15 mn at 200 km from the source. The phase velocities and waveform characteristics of the two sub‐events lead us to interpret the first impulsive arrival as the direct propagation of the shock wave front, followed by oscillatory guided waves probably excited by the primary shock wave and propagating along horizontal atmospheric interfaces at 120 km altitude and

ISSN:0094-8276    

DOI:10.1029/96GL01256

年代:1996

数据来源: WILEY

摘要:

Observations of electron fluxes made by the PET and LICA instruments aboard SAMPEX have been used with NO measurements made by HALOE aboard UARS to provide evidence of mesospheric and lower thermospheric NO formation due to precipitating electrons. Results indicate significant NO increases from 70 to 120 km which are associated with the occurrence of enhanced electron populations in the outer trapping regions of the magnetosphere, 2.5 ≤ L ≤ 7, which precipitate into the atmosph

ISSN:0094-8276    

DOI:10.1029/96GL01787

年代:1996

数据来源: WILEY

摘要:

Simulations using SAMPEX and HALOE data suggest that NOyproduced by thermospheric processes and by relativistic electron precipitation in the mesosphere and lower thermosphere have been important to stratospheric NOyand O3during the austral spring in 1994. The relative importance of the two NOysources is discussed. The results are supported by an analysis of HALOE NOxand CH4data during October 1994 and are in agreement with ATMOS NOyobservations made in November 1994.

ISSN:0094-8276    

DOI:10.1029/96GL01788

年代:1996

数据来源: WILEY

摘要:

We have used, for the first time that we are aware of, the NASA/JPL Goldstone planetary radar to study the Earth's atmosphere. With its high bandwidth and power, we were able to achieve a height resolution of 20 m, which is significantly better than the usual 150‐m resolution for stratospheric radars. Here we discuss the observation of a very thin scattering layer that persisted over several hours at the same height just above the tropopause. We question the assumption of turbulent radar scatter based on the available evidence, and also investigate the two‐minute oscillation observed in the vertical veloc

ISSN:0094-8276    

DOI:10.1029/96GL01570

年代:1996

数据来源: WILEY

摘要:

Measured particle volumes in a type I polar stratospheric cloud near the Antarctic polar vortex during ASHOE/MAESA show that the onset of the cloud occurred near 193 K, 3 degrees colder than nitric acid trihydrate (NAT) saturation. The onset temperature, the smooth increase of volume with decreasing temperature, the inverse correlation of particle volume and enhanced NOy(HNO3in the particles) with temperature, and comparisons of observations with an equilibrium model of ternary droplet growth all support the notion that much of this type I PSC was ternary solution droplets. This provides confirmation of previous findings in the northern hemisphere. However, the ternary model does not fit the observations in all regions. This may be due to the presence of some solid phase growth in agreement with impactor observations.

ISSN:0094-8276    

DOI:10.1029/96GL01812

年代:1996

数据来源: WILEY

摘要:

A broad band radio interferometer for locating lightning emissions has been designed, constructed and tested. For a broad band interferometer, a single fixed pair of antennas is equivalent to having many baselines in a narrow band interferometer. So, a broad band system requires fewer antennas than a narrow band system to achieve equivalent angular resolution. In addition, frequency dependent locations of the radio emissions can be extracted for a more detailed look at the lightning breakdown processes. Such a system has been tested by a computer simulation and by measuring a man‐made broad band radiation source. The system consists of two antennas which are separated vertically. Bandwidth of the system is from 40 to 350 MHz. Measurements of the man‐made source indicate that with a signal‐to‐noise ratio (SNR) above 10 dB, the system is able to locate the source with an accuracy of about 2° over the detectable frequencies. Preliminary observations of lightning discharges with this new technique appear to indicate that breakdown processes of a dart leader to ground radiate solely at its descen

ISSN:0094-8276    

DOI:10.1029/96GL00474

年代:1996

数据来源: WILEY

摘要:

Using a soil‐derived dust emission scheme, the annual and monthly dust emissions in the western “dry” Sahara have been estimated for 1991 and 1992, respectively to 665 Mt and 586 Mt. Based on these simulations, an investigation of the seasonal and annual changes in dust emissions has been performed. The monthly dust emissions vary from 163 Mt in March 1991 to 8 Mt in December 1992. These seasonal variations are related to changes in the location and area of the source‐regions and in the frequency of dust events. On the opposite, the interannual variations of the dust emissions are due to changes in the occurrence of the most intense dust

ISSN:0094-8276    

DOI:10.1029/96GL01432

年代:1996

数据来源: WILEY

摘要:

The 18‐year data base for vertical column abundance measurements of atmospheric OH at Fritz Peak Observatory, Colorado (40°N, 105°W), exhibits a relatively abrupt change in seasonal behavior during 1991 through 1995. Late summer through early fall abundances, especially, for each year of the 1991–1995 period are significantly below the comparable seasonal average for 1980–1990. Early morning abundances for August through October at solar zenith angles greater than 45° exibit an average reduction of about 0.8 × 1013/cm², which at a solar zenith angle of 60° is a 15% colu

ISSN:0094-8276    

DOI:10.1029/96GL01811

年代:1996

数据来源: WILEY

摘要:

Raman lidar measurements of ozone, water vapor, and cirrus optical properties over northern Germany (53.4°N, 10.4deg;E) in autumn 1995 are presented. In contrast to smooth ozone profiles with values of 50 to 100 ppbv in a cloud‐free and dry upper troposphere, pronounced minima in the ozone distribution with values close to zero were found several times in the presence of ice cloud laye

ISSN:0094-8276    

DOI:10.1029/96GL01856

年代:1996

数据来源: WILEY