摘要:

Experimental evidence for a causal relationship between lightning and explosive equatorial spread F is presented. It is proposed that explosive spread F is produced by rapidly growing plasma instabilities, which are triggered by sudden increases of the F region ambient electric fields due to the penetration of lightning fields into regions of weak or marginal instability.

ISSN:0094-8276    

DOI:10.1029/GL011i012p01165

年代:1984

数据来源: WILEY

摘要:

Explosive spread F was first described by Woodman and LaHoz [1976]. In such events the 50 MHz radar signal rises at Jicamarca to 10‐20 db above the noise level within a few milliseconds but then disappears within 100 ms or less. Woodman has suggested that electric fields from thunderstorms might drive a plasma instability which could cause these echoes, and recent observations [Woodman and Kudeki, 1984]provide convincing evidence for this triggering. Here we discuss the instability mechanism and show that transient thunderstorm electric fields comparable to those recently observed by rockets in the midlatitude ionosphere could excite a rapidly growing two‐stream plasma instability that is driven by theE×Bdrift of the F region electrons in the short period (less than the ion gyroperiod) before the ions reach the same velo

ISSN:0094-8276    

DOI:10.1029/GL011i012p01168

年代:1984

数据来源: WILEY

摘要:

It is shown that oscillations of ionospheric Doppler velocity are associated with Pc3 geomagnetic pulsations recorded at ground level. Two mechanisms are proposed to account for this association, namely, variations in the refractive index of the ionosphere due to the oscillatingand verticaldrift of the ionosphere as a whole. The latter is used to determine the east‐west component of pulsation electric field in the ionospher

ISSN:0094-8276    

DOI:10.1029/GL011i012p01172

年代:1984

数据来源: WILEY

摘要:

The sounding rocket payload SCEX (Several Compatible Experiments to utilize an electron accelerator; NASA flight 27.045) launched on January 27, 1982 from the Churchill Research Range provided an opportunity to observe the effects of strong beam‐plasma interactions on the electron population in a region of space remote from the main payload carrying the accelerator. We present observations demonstrating that electron energies of up to four times the injection energy occurred during accelerator operations in high‐current mode. Detailed instrumental performance characteristics in flight and in the laboratory will be discussed. The acceleration events occurred at reception pitch angles between 54° and 126°. Long confinement times seem to be a necessary condition for generating the energetic electrons. It is proposed that they result from the length of the interaction r

ISSN:0094-8276    

DOI:10.1029/GL011i012p01176

年代:1984

数据来源: WILEY

摘要:

In this study it is shown that the upward moving electron beams observed by DE‐1 in the dayside polar cusp at 2 to 5 REdrive an electrostatic electron acoustic mode, rather than the whistler mode near resonance, as previously concluded. The characteristics of this instability are compared with the properties of hiss in the polar cusp observed by DE‐1. The hiss frequencies and funnel shaped frequency‐time spectra are consistent with the electron acoustic mode. However, because the hiss often has a fluctuating magnetic field component near the axis of the funnel shape, the hiss is probably composed of both electron acoustic and whistler mode

ISSN:0094-8276    

DOI:10.1029/GL011i012p01180

年代:1984

数据来源: WILEY

摘要:

The incoherent scatter radar facility (ISR) recently installed at Søndre Strømfjord, Greenland (inv. lat. = 74°) has been used to investigate events of substantially elevated E‐region temperatures related to the occurrence of strong horizontal electric fields. It has been found that a peculiar type of weak, slowly fluctuating cosmic noise absorption commonly observed in the daytime on riometers in the polar region could be caused by non‐deviative collisional absorption resulting from the strongly enhanced electron‐neutral collision frequencies in the heated

ISSN:0094-8276    

DOI:10.1029/GL011i012p01184

年代:1984

数据来源: WILEY

摘要:

Observations of auroral kilometric radiation (AKR) made with DE‐1 indicate the presence of both ordinary and extraordinary wave modes. Although the two modes usually occur separately, they are sometimes observed together. When both modes are present, the ordinary‐mode component tends to occur at lower frequencies and with lower amplitudes than those of the accompanying extraordinary‐mode component. On the other hand, the local electron gyrofrequency is an absolute lower frequency cutoff for both modes. Ordinary mode intensities are proportional to extraordinary mode intensities but less by roughly a factor of 50. Extraordinary mode ray paths are generally confined to a cone within 50° of the source magnetic field direction and ordinary mode emissions are typically observed outside of this cone. This behavior suggests that both components are produced within the same source region but are then refracted differently as they

ISSN:0094-8276    

DOI:10.1029/GL011i012p01188

年代:1984

数据来源: WILEY

摘要:

The optical glow induced by spacecraft‐environment interaction under daytime conditions is analyzed using photometric data obtained by the Visible Airglow Experiment on board the Atmosphere Explorer Satellite. Because of the increased ambient oxygen density, the glow is more intense in the daytime. The daytime production efficiency, measured in Rayleighs per oxygen atom, is similar to the nighttime value. No dependence of the glow intensity on the ambient plasma density was found. The production efficiency increased with time throughout the duration of the spacecraft in orbi

ISSN:0094-8276    

DOI:10.1029/GL011i012p01192

年代:1984

数据来源: WILEY

摘要:

We present the vacuum ultraviolet (VUV) spectrum of H2O produced by electron impact at 200 eV. A total of 25 spectral features is identified at a resolution of 0.5 nm over the wavelength range of 40 to 280 nm. Absolute emission cross sections were measured for each of these features. These features are all attributed to excited states of the dissociation products (H, O, O+). The Lyman‐α feature which is the brightest spectral feature for electron induced fluorescence of H2O from the UV to near‐IR has a cross section of 6.3 ± 1.0 × 10−18cm² at 200 eV and contributes 74% of the total measured emission cross section i

ISSN:0094-8276    

DOI:10.1029/GL011i012p01195

年代:1984

数据来源: WILEY

摘要:

The absorption cross‐sections of both O2, from 200 to 220 nm, and O3from 220 to 235 nm have been deduced from measurements of the atmospheric absorption performed at night aboard a stratospheric balloon launched from Aire sur 1'Adour (France)The ozone column content was previously determined using the absorption measured from 278 to 289 nm, assuming that the ozone absorption cross sections are well known in this wavelength interval. The O2and O3cross sections have been found to meet most of the laboratory measurements. From 200 to 210 nm the results concerning the O2cross‐sections do not confirm the low values measured recently in the stratosphere and in the laborat

ISSN:0094-8276    

DOI:10.1029/GL011i012p01199

年代:1984

数据来源: WILEY