摘要:

New results on the spatial and temporal variability of the auroral emissions from Jupiter have been obtained from three IUE observations of the south pole made during the period July 1983 to March 1984. The current observations, together with previous IUE studies of the north pole aurora, provide convincing evidence for persistent longitudinal asymmetries in the Jovian auroral emissions. The strongest emissions appear to originate from regions centered near λIII∼ 0° at the south pole and λIII∼ 185° at the north pole. Differences in surface magnetic field strength seem inadequate to explain the extent to which particles precipitating along field lines into a given longitude sector in one hemisphere are inhibited from precipitating along the same field lines into the opposite hemisphere. Thus, the IUE auroral results present a challenge to existing models of auroral pro

ISSN:0094-8276    

DOI:10.1029/GL011i011p01107

年代:1984

数据来源: WILEY

摘要:

The trajectories of mainly low‐energy ionospheric ions injected near the polar cusp into the polar magnetosphere are presented for a model polar magnetosphere including the effects of convection electric fields and gravitation. The trajectories display the ion mass and energy differentiation which has been seen in recent satellite observations of low‐energy ionospheric ions injected into the polar magnetosphere, and indicate that for reasonable ranges of injection energy, pitch angle and convection electric field: 1. Transport of low‐energy ‘polar cusp’ O+to the ∼1 Re altitude nightside auroral acceleration region is feasible; and 2. Preferential trapping of energetic O+relative to H+and He+energetic ions occurs in the closed field line region of the magnetotail plasma sheet. Two interesting classes of polar region very low‐energy heavy ion trajectories are noted: 1. ‘Parabolic’ trajectories, in which heavy ions injected at the polar cusp at small pitch angles rise then fall into the polar cap atmosphere, and 2. ‘Hopping’ trajectories, in which heavy ions injected at large pitch angles at the polar cusp mirror between the gravitational stopping location and magnetic mirror point as they convect at low to intermediate altitudes across the polar cap. It is also illustrated how during conditions of sunward convection in the central polar cap, a pronounced ‘spray’ of ions injected on the nightside may occur, in which such ions may appear in the nightside or dayside magnetosphere depending upon injection characteristics and dusk‐to‐dawn convection electric field magnitude; such ion dynamics may be of interest in

ISSN:0094-8276    

DOI:10.1029/GL011i011p01111

年代:1984

数据来源: WILEY

摘要:

Observations made on the space shuttle during the STS‐3 flight indicate that generation of dense plasma from sources aboard the orbiter was accompanied by substantial reduction of electric potential measured by probes fixed on the orbiter. In a separate experiment increased plasma densities were observed to follow the release of neutral gas. In this letter, it is argued that both observations are consistent with the shielding of the electric field, , associated with the motion of the orbiter across the earth's field from the interior of the spacecraft generated plasma. As a consequence the downstream drift of the part of the plasma cloud near the vehicle may be much less than the drift speedexperienced by a single charged particle released from rest in the vehicle's frame. Since the ion thermal velocities with which plasma expands along field lines are typically much less than , this consequence can have a substantial impact on the determination of spacecraft generated plasma densities near the orbite

ISSN:0094-8276    

DOI:10.1029/GL011i011p01115

年代:1984

数据来源: WILEY

摘要:

The quenching of N2(A³∑u+) by atomic oxygen in the auroral thermosphere offers an attractive method of determining atomic oxygen concentrations, using the emission rate ratio of the N2Second Positive bands and the N2Vegard‐Kaplan bands. In the first applications of this method it was necessary to derive the quenching rate constant, the production rate ratio and the 0 profile from the measurement of emission rate ratio versus altitude. Even with more recent laboratory measurements of the quenching rates, different analyses of the same datasets gave rise to conflicting results. In this paper the consequences of including a requirement of diffusive equilibrium are considered; it is concluded that at times the 0 concentration at 130 km can be lower than that of CIRA 72 by a factor of 5, while at other times it can agree with the CIRA m

ISSN:0094-8276    

DOI:10.1029/GL011i011p01117

年代:1984

数据来源: WILEY

摘要:

To determine whether the 1982/83 El Nino event and the eruption of El Chichon in April 1982 are related, eleven similar eruptions at low latitudes (20°) show just the opposite behavior. They show significant cooling of the sea surface temperatures in this region especially in the fourth and fifth season after the eruption. The association is found to be significant at the

ISSN:0094-8276    

DOI:10.1029/GL011i011p01121

年代:1984

数据来源: WILEY

摘要:

Aerosol optical thicknesses were derived from solar spectral extinction measurements. These were made with a sunphotometer on board the NASA Convair 990 aircraft during May, July and December 1982 over a range of latitudes covered by the flight mission. Large increases in the optical thicknesses over the background levels for the stratosphere were found at all latitudes where observations were made; these are attributed to the El Chichon eruption cloud. The latitudinal variation of the optical thickness in May and July shows a maximum in the vicinity of the eruption, a minimum near 30°N and no appreciable change further north of the minimum. This is indicative of a thick portion of the cloud being confined between 0° and 30°N latitude. In December, the maximum was found near 8°N, the minimum near 25°N and an increase north of the minimum. The spectral dependence of the aerosol optical thickness which is different on one side of the 30°N latitude from the other suggests that the two portions of the cloud have different size distributions of aer

ISSN:0094-8276    

DOI:10.1029/GL011i011p01125

年代:1984

数据来源: WILEY

摘要:

Ozone data were obtained from 8 km to the surface and at latitudes from 38° to 76° N during January and February 1983. Flight lines covered northeastern U.S., Canada, and Greenland. The results of the latitudinal survey at 5‐ to 8‐km altitude showed O3mixing ratios to be ≃ 40 ppbv with little variation in latitude. One region of elevated O3was observed and extended from 54° N to 57° N latitude. Ozone reached 150 ppbv at 6.4‐km altitude. This sampling was stratospheric air as the tropopause height was 5.6‐km altitude. Profiles at 76°, 67°, and 53° N showed O3to be well mixed from about 5 km to the surface. In some cases, profiles identified a layer of 1 km to 100 m vertical dimension at the surface, in which O3destruct

ISSN:0094-8276    

DOI:10.1029/GL011i011p01129

年代:1984

数据来源: WILEY

摘要:

The concentration of polychlorinated hydrocarbons has been measured in air samples from 4 Arctic stations in 1980‐83. The measurements show that elevated concentrations are found during episodes of long range transport, and an accumulation of polychlorinated hydrocarbons seems to take plac

ISSN:0094-8276    

DOI:10.1029/GL011i011p01133

年代:1984

数据来源: WILEY

摘要:

There has been a resurgence of studies relating to Sea Surface Temperature (SST) variations in the equatorial Pacific and variations in atmospheric flow patterns over tropical as well as over middle latitudes. In this note, the SST variations over the equatorial eastern Pacific and the variations in the Indian monsoon rainfall (June ‐ September) are re‐examined with particular reference to drought and flood years. Our analysis reveals that major drought (flood) years are associated with warmer (cooler) than normal SST values before and after the monsoon season. A possible connection with a feedback mechanism between the SST variation in the equatorial Pacific and the monsoon rainfall over India and vicinity is hypothesi

ISSN:0094-8276    

DOI:10.1029/GL011i011p01137

年代:1984

数据来源: WILEY

摘要:

Two airborne surveys of atmospheric carbon dioxide (CO2) concentration have been conducted over the Gulf Stream off the east coast of Virginia and North Carolina on September 7‐8, 1983. In‐situ CO2data were acquired at an aircraft altitude of 300 m on trajectories that transected the Gulf Stream near 36°N 73°W. Data show evidence of a CO2concentration increase by 4 ppm to 15 ppm above the nominal atmospheric background value of 345 ppm. These enhanced values were associated with the physical location of the Gulf Stream prior to the passage of a weak cold

ISSN:0094-8276    

DOI:10.1029/GL011i011p01141

年代:1984

数据来源: WILEY