ISSN:0094-8276    

DOI:10.1029/GL013i013p01363

年代:1986

数据来源: WILEY

摘要:

The evolution of newborn cometary ions that interact self‐consistently with the solar wind are studied with one‐dimensional hybrid computer simulations. Cometary ions are injected at a constant rate and in a constant direction; the associated free energy leads to growing electromagnetic fluctuations which scatter these ions. At relatively low fluctuating field amplitudes, this scattering leads to shell‐like velocity distributions that subtend approximately 4π in solid angle, but have relatively small spread in speed. Shell‐like distributions are favored when the ion injection rate is comparatively slow (i.e. thin shells should be observed at relatively large distances from the cometary nucleus), when the injected ion mass is relatively light (i.e. protons develop a thinner shell than oxygen ions), and when the energy density of the fluctuating magnetic fields exhibits linear, rather than exponential, tempora

ISSN:0094-8276    

DOI:10.1029/GL013i013p01364

年代:1986

数据来源: WILEY

摘要:

Simultaneous observations using two‐channel meridian scanning photometers were carried out at geomagnetically conjugate‐pair stations, Syowa Station in Antarctica and Husafell in Iceland (L=6.1), during August‐September 1984. The photometers were equipped with interference filters for OI 5577A and Hß 4861A emissions. During the conjugate campaign, the data obtained on September 26, 1984 was of the highest quality with a clear sky and no moon. The initial results on the conjugacy of Hß proton auroras and their relations to 5577A electron auroras are as follows; i) During the pre‐breakup phase the Hß auroras observed at Syowa were mostly located at a lower latitude than the simultaneous conjugate auroras observed at Husafell. Such Hß auroras showed high intensities at Syowa relatively to those at Husafell, ii) During the auroral breakup phase, enhancement of Hß emissions occurred almost simultaneously in the both hemispheres. However, the intensities of Hß auroras were higher at Husafell than at Syowa, iii) During the pre‐breakup phase, Hß auroras observed continuously in the equator boundary were associated with weak diffuse 5577A auroras in the conjugate regions, (iv) In the regions and time intervals where 5577A auroras showed poor conjugacy, the Hß auroras also show

ISSN:0094-8276    

DOI:10.1029/GL013i013p01368

年代:1986

数据来源: WILEY

摘要:

During an extended energetic particle event upstream of the earth's bow shock on September 5, 1984, a brief burst of energetic O+ions has been observed using the time‐of‐flight spectrometer SULEICA on the AMPTE/IRM spacecraft. The event occurred during very active geomagnetic conditions. The onset of the O+event coincides with a brief electron burst. O+is predominantly streaming into the sunward direction, while the H+and He2+ions exhibit a net flow toward the bow shock with a second order anisotropy perpendicular to the interplanetary magnetic field (which was almost radial throughout the whole event). The energy spectrum of O+is significantly harder than those of H+, He2+and CNO (Q>2). The observations of two particle populations, different in temporal evolution, anisotropies and energy spectra, are discussed in terms of bow shock accelerated ions over the entire time period accompanied by a brief injection of magnetospheric partic

ISSN:0094-8276    

DOI:10.1029/GL013i013p01372

年代:1986

数据来源: WILEY

摘要:

Energetic particle data from the AMPTE Charge Composition Explorer (CCE) spacecraft in the outer dayside magnetosphere are examined during the period of an upstream ion event observed by the AMPTE Ion Release Module (IRM) spacecraft on September 5, 1984 [Moebius et al., this issue]. The CCE data reveal the following: (a) an ion enhancement was observed at ∼0040 UT in near coincidence with a substorm onset at ∼0035 UT, approximately 15 minutes prior to the onset of the event upstream of the shock; (b) ions of both solar wind (He++, Fe‐group) and ionospheric (O+) origin over a broad energy range (∼20 keV to>1350 keV) were injected at substorm onset; (c) the time evolution of the H+, He++, and O+pitch angle distributions markedly differed, with O+exhibiting mostly enhancements at off‐90° angles for the first hour after injection; (d) an enhancement in the Fe‐group ions inside the magnetosphere at L ∼ 6.4 occurred simultaneously with the appearance of an O+burst upstream of the shock. The CCE observations, taken together with the simultaneously observed IRM ion event, suggest that a plausible explanation for the appearance of upstream ions is leakage from the magnetosphere into the upstream region, rather than the alternate explanation which requires in‐situ acceleration of solar wind ions via the

ISSN:0094-8276    

DOI:10.1029/GL013i013p01376

年代:1986

数据来源: WILEY

摘要:

This Letter presents a first step towards a substorm model including particle heating and transport in the plasma sheet boundary layer (PSBL). The heating mechanism discussed is resonant absorption of Alfven waves. For some assumed MHD perturbation incident from the tail lobes onto the plasma sheet, the local heating rate in the PSBL has the form of a resonance function of the one‐fluid plasma temperature. Balancing the local heating by convective transport of the heated plasma toward the central plasma sheet, an "equation of state" is found for the steady‐state PSBL whose solution has the form of a mathematical catastrophe: at a critical value of a parameter containing the incident power flux, the local density, and the convection velocity, the equilibrium temperature jumps discontinuously. Associating this temperature increase with the abrupt onset of the substorm expansion phase, the catastrophe model indicates at least three ways in which the onset may be triggered. Several other consequences related to substorm dynamics are suggested by the simple catastrophe m

ISSN:0094-8276    

DOI:10.1029/GL013i013p01380

年代:1986

数据来源: WILEY

摘要:

The theory of absolute and convective instabilities is discussed and we argue that the basis of the theory is questionable, since it describes the linear development of instabilities by their behaviour in the time asymptotic limit. In order to make sensible predictions on the linear development of instabilities, the problem should be studied on the finite time scale implied by the linear approximation.

ISSN:0094-8276    

DOI:10.1029/GL013i013p01384

年代:1986

数据来源: WILEY

摘要:

The spatial and temporal characteristics of ozone density measured from the SBUV (Solar Backscatter Ultraviolet) spectrometer on Nimbus‐7 and the UV and the IR spectrometers on SME (Solar Mesosphere Explorer) are compared in the altitude region near 50 km where the three data sets overlap. Their temporal characteristics, when averaged over the same longitude range, are remarkably similar with respect to seasonal variations and short term fluctuations induced by transient planetary waves. The long term trends in the three data sets, however, differ significantly with each other. Over the three year period after 1982 ozone mixing ratio at 1 mb decreased by about 10 percent based on SBUV measurements but increased by 12 and 30 percent respectively based on SME‐IR and SME‐UV measurements. None of these estimates are consistent with the predicted decrease of about 2 percent based on solar UV flux and temperature changes during this p

ISSN:0094-8276    

DOI:10.1029/GL013i013p01387

年代:1986

数据来源: WILEY

摘要:

A balloon‐borne experiment to measure midlatitude stratospheric [BrO] and [ClO]by NO chemical conversion/atomic resonance fluorescence was flown from Palestine, Texas, on 20 May 1986. In this first study of BrO, no signal attributable to BrO was detected, and upper limits (2σ uncertainty) between 35 and 24 km altitude give BrO mixing ratios less than 15 pptv. Current models predict mixing ratios that are 1.7 times larger. Measurements of [ClO] were obtained at less than .2 km altitude resolution from 41 to 22 km. The smoothly varying altitude profile lies within the range of 2‐D model calculat

ISSN:0094-8276    

DOI:10.1029/GL013i013p01391

年代:1986

数据来源: WILEY

摘要:

We have discovered a new type of reaction for atmospheric Na species and propose that this type of reaction will dominate its chemistry. The third order rate constants for NaO + O2+ M and NaO + CO2+ M were measured at 297 K in a flow tube study. The rate constants for NaO + O2with He, N2, and N2O as third bodies are (1.3±0.8), (3.5±0.7), and (11±4)×10−30cm6molecule−2s−1. The rate constants for NaO + CO2with N2and N2O as third bodies are (8.7±2.6) and (12±5)×10−28cm6molecule−2s−1. We show that these association reactions, and others like them, will produce Na compounds that are likely to render Na species inactive in stratospheric ozone chemistry. The reactivities of NaO, NaO2, NaO3, and NaCO3with O atom

ISSN:0094-8276    

DOI:10.1029/GL013i013p01395

年代:1986

数据来源: WILEY