Diffuse Glow Research Articles

Transient emissions on the wavelength of helium I, 5876 Å recorded during auroral break-up

During the break-up phase of two strong auroral events, emissions of short duration on the wavelength of He I, 5876 Å have been observed. These records are accurate within ∼0.5 Å and intensities of up to 120 R have been measured. This high value is not consistent with the theoretical limit suggested by other authors. Simultaneous observations of Hα, 6563 Å show that the He I and Hα emissions are not closely related to each other with time, which may be one reason for explaining the discrepancy with the predicted intensity derived from observed ratios of He ++/H + in the solar wind. The emission on 5876 Å has only been detected at the lowest border of very intense ray bundles towards north but not yet in auroral arcs and diffuse glow. It is suggested that two principally different helium events in aurora may be observable, one resulting in a low level He emission lasting for longer time and another in a stronger He emission of short duration. The observational difficulties caused by the presence of OH bands are discussed.

Far-Ultraviolet Spectrophotometry of Bright Stars in Orion

view Abstract Citations (6) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Far-Ultraviolet Spectrophotometry of Bright Stars in Orion Stuart, Frank E. Abstract A 12-inch telescope and low-resolution grating spectrophotometer were flown on an Aerobee rocket to obtain absolute vacuum-ultraviolet spectra of bright stars in Orion Nineteen stars, including the Trape- zium, were observed in the spectral range XX1050-2180. A 55 A region around Ly-a was purposely oc- culted to reduce the background due to geocoronal Ly-a light and to test for diffuse sources. The data shortward of Ly-a are not absolute, but are useful for relative comparison between different stars Absolute intensities were generally somewhat higher than those reported by others, although differ- ences were within the error limits of the calibration Agreement of observed spectra with a B 1.5 V model was generally good. A rapid divergence for wavelengths below 1800 A between observed data for an A3 star (i3 En) and a model was noted. Variation of the general slope of the spectra of the earlier-type stars with luminosity class can be observed. A large ultraviolet excess was found for 42 On and probably for BS 1923 Evidence is presented to indicate that in 42 On the excess is probably due to a diffuse glow around the star Publication: The Astrophysical Journal Pub Date: September 1969 DOI: 10.1086/150152 Bibcode: 1969ApJ...157.1255S full text sources ADS | data products SIMBAD (20)

The auroral electron energy spectrum extended to 45 ev

Direct measurements of the precipitated auroral electron energy spectrum above 1 kev indicate that the differential energy spectrum has a peak near 6 kev [Mcllwain, 1960; Albert, 1967; Evans, 1968]. This spectrum has been referred to in the literature as a monoenergetic electron beam, and theoretical models of the source mechanism have been developed accordingly [e.g., Taylor and Hones, 1965], It is the purpose of this Letter to report a recent observation of this auroral electron spectrum extended to 45 ev, which reveals the existence of a smooth continuum from which the 6-kev peak emerges to produce the auroral arcs. These observations were obtained from the Rice University Javelin Twins 1 sounding rocket experiment which was launched to an altitude of 800 km over an active IBC I-II aurora from Fort Churchill, Manitoba, at 2347 local time, March 17, 1967. The auroral conditions during the flight consisted of a general diffuse glow of about 5 kR (3914 A) with a system of arcs of more than 25 kR (3914 A), which moved across the payload trajectory.

The Development of Spark Discharges in Hydrogen

Streak photography has been used to supplement the earlier shutter photo. graphic investigation of Doran and Meyer (1967) using the same coaxial cable discharge circuit. Additional information has also been obtained from measurement of the potential distribution between the electrodes at two stages in the spark development. Redistribution of space charge is shown to give rise firstly to a transient diffuse glow discharge that has a close similarity with a normal d.c. glow discharge. It has also been shown that, even while the diffuse glow discharge expands, a partial constriction occurs in which most of the current flows along a narrow axial column. The resulting maximum in electron density eventually causes a rapid increase in dissociation of molecular hydrogen on the axis of the discharge brought about by a rise in the gas temperature. Owing to its greater electrical conductivity this axial column soon carries the entire current and the discharge becomes filamentary though still being maintained by a high cathode fall field, which exists until a sudden change in the cathode mechanism gives rise to the low voltage arc channel. Both the filamentary glow and arc columns are observed to expand according to an r cc ti law.

Interferometric measurements of [formula omitted] emission temperatures in aurora

Observations of the λ5577 A ̊ [OI] line profiles in aurora made with a photoelectric pressure scanning Fabry-Perot interferometer at Fort Churchill, Canada located near the auroral zone maximum are described. The deduced Doppler temperatures for faint diffuse glows yielded values in the range 170°K–690°K, with about 80 per cent of the values lying in the range 200°K–400°K. Temperatures for sub-visual aurora were found in the general range 400°K–700°K, which suggests that this auroral form is a distinct type originating at higher altitudes. A large number of observations during one night showed no definite trend of nocturnal variation of auroral temperatures.

Simultaneous observation of electron fluxes, ionization, and luminosity in an aurora

Electron energy spectra, number density of ambient electrons, and 5577 Å luminosity have been measured in a rocket which passed through a well-defined westward-moving auroral band embedded in a widespread diffuse glow. In the band there was excellent spatial correlation among the electron number density, the luminosity as seen from both the ground and the rocket, and the electron flux of energy 1–7 keV. A peak of higher-energy electrons apparently trailed the band by ~ 10 km. The electron fluxes appeared to be not quite sufficient to account for the observed electron number density, still less for the luminosity. Fluxes of electrons having energies of the order of 100 eV were observed, too large and too uncorrelated with the higher-energy electron fluxes to be secondaries produced in the atmosphere by the electrons of higher energy. Since 100-eV electrons cannot penetrate from above to such heights [Formula: see text], there is a suggestion that they must have been locally accelerated. When these electrons are included in the calculations, it is possible under certain assumptions to obtain quantitative agreement between electron flux, electron density, and 5577 Å photon production in the diffuse glow.

Correlation of the formative time lags with the light emitted from spark discharges

Measurements of the formative time lags in homogeneous fields for different gases up to pd values of 3000 mmHg cm have been made. For overvolted gaps in dry air and oxygen a discontinuity is found in the logarithmic plot of overvoltage against formative time. This is considered to be evidence of a transition from a Townsend- to a streamer-type of discharge. No definite sign of this change has been found in hydrogen, nitrogen and pure argon. Additional evidence that the discontinuity is the transition from one initiating mechanism to another is obtained from still photographs of the sparks. These indicate that at low values of overvoltage the discharge consists of a diffuse glow and spark channel while the streamer initiated spark has a narrow constricted glow. The position of the bright constriction or knob in the gap varies with overvoltage and its position agrees with the value predicted by the Meek criterion αx crit. = 20. The value of overvoltage at which the transition occurs decreases with pd and is about 5 % at pd = 1000 mm Hg cm and 1-5 % at pd = 3000 mmHg cm. By extrapolation it seems unlikely that the streamer mechanism will occur at minimum break-down for pd values less than 7000 mmHg cm. Oscillographic studies have shown that the disappearance of the glow to arc step is not always a satisfactory Townsend to streamer criterion. Spectra of the sparks in air show a continuum associated with the constriction in the streamer together with bright atomic lines and weakening of the band spectra.

Transillumination of fingertip as aid in examination of nail changes.

Transillumination is used in dermatology in the examination of the breast, in the examination of the skull of infants, for superficial soft tissue tumors, and for large foreign bodies. In addition, transillumination can provide a technique of examination of the nails. This technique is possible without removal of the covering nail polish. This is appreciated by many woman patients. The nail lesions for which transillumination is especially effective include varying degrees of nail plate markings, onycholysis, subungual thickening, and leukonychia. Transillumination, then, helps in following the course of nail changes especially in psoriasis and in onychomycosis. In a dark room, a single, narrow, strong beam of light is used underneath the flexor pad of the fingertip. The blackish lines of nail plate pits, separations of nail plate, and thicknesses are seen and differentiated readily from the diffuse homogenous reddish glow of the normal nail plate.

Electromagnetic Radiation from Extra-Terrestrial Sources

Rocket astronomy has mapped the spectrum of the sun from the ground level cutoff at 3000 A down to x-ray wavelengths as short as 0.1 A. The x-ray emissions are strongly dependent on solar activity with greatly enhanced intensities accompanying solar flares. Photographs from rockets have revealed the disk distribution of ultraviolet emission. The first measurements of ultraviolet light of the night sky have discovered the existence of extended ultraviolet nebulosities surrounding hot stars and a bright diffuse glow of Lyman-α radiation scattered from neutral hydrogen in space.

Rocket Observations of the Ionosphere

Daytime electron density profiles measured at Fort Churchill have been found to be similar to those observed at White Sands. One winter nighttime flight showed very little ionization, less than 20,000 electrons per cc up to 165 km. Polar blackout produced strong enhancement of the D-region electron density down to 55 km. NO+ is the predominant ion below 200 km during the night, but O+ becomes the most abundant ion above 150 km during the day. Solar flares are accompanied by X-ray bursts capable of penetrating to the 60-km level and sufficiently intense to account for sudden ionospheric disturbances. At night a diffuse glow of Lyman-? is visible over the entire sky. From the observed intensity it is possible to estimate the electron density of interplanetary space.

A short duration afterglow of nitrogen; survey of afterglows

When an electron beam of more than 10·5 eV energy traverses low pressure nitrogen the beam is surrounded by a diffuse glow emitting the first positive bands ( 1). This light is interpreted as an afterglow. It is attributed to metastable molecules, a 1 Π, which diffuse out of the space occupied by the beam, are thrown by collisions with normal molecules into the unstable state B 3 Π and then emit the first positive bands. The time required for diffusion is of the order 5 × 10 −5 sec. This afterglow is compared with four other types of nitrogen afterglow.

Uniform-field breakdown in air

Experiments on the breakdown processes in a uniform-field gap at the minimum d.c. breakdown voltage in air at atmospheric pressure are described. It is shown that the breakdown processes consist of two phases, (1) a diffuse glow completely bridging the gap, followed by (2) a filamentary channel moving from the cathode to the anode, and bridging a 0.77 cm gap in about 3 × 10-9 s in a 13 Ω coaxial system. Spectrograms of the stages of the discharge are also given. These experimental results are in disagreement with both the Townsend and the Streamer theories.

Negative Coaxial Cylindrical Corona Discharges in Pure N2, O2, and Mixtures Thereof

Direct-current corona studies were made on coaxial cylinders with inner cylinder at negative potentials in pure N2, pure O2, and mixtures of 1 percent 10 percent O2 in N2, and on clean dry air from 27-mm to 760-mm pressure. Observations of current potential relations from field intensified ionization currents to as near breakdown as possible were made noting thresholds for current transitions, pulsed discharges and other oscillographic as well as visual appearances. Negative wire corona does not exist as such in truly pure N2. Unless a high series resistance was in the line once the critical region of potential was reached, the gap broke down to an arc. With current limiting resistor bombardment of the filament with positive ions from the low order pre-discharge released enough gaseous impurity so that after six minutes the resistor could be removed and the internal resistance of the negative ion space charge near the anode held the current at 2000 μa. The behavior indicated that breakdown was preceded by a low current Townsend discharge that cleaned up or conditioned the filament. In all the negative wire studies the onset thresholds vary with the past history of the wire, and the threshold potential at higher pressures overshoots the minimum operating potential of the discharge once it has set in. Studies with 1 percent O2 indicate that the threshold discharge with clean gas is a continuous current with a diffuse glow which in time contracts to a cathode spot with Trichel pulses. Similar behavior applies to air at lower pressure. The negative wire in O2 shows very heavy predischarge currents with relatively small current jumps when random Trichel pulses appear, and further small current jumps when the fixed spot with regular Trichel pulses appears. There is evidence for a continuous heavy background of Townsend discharge along the whole wire until the visible spot and heavy pulsed discharge appears. The duration of Trichel pulses in pure O2 is two to ten times those in air with point to plane geometry and two to three times those in air with coaxial cylindrical geometry. Lower pressures in pure O2 show many current transitions and transitions between discharge forms.

Occult Phenomena and After-images

IF the hand be held against a dark background in a very subdued light, coming from behind the observer and falling on the hand, a diffuse glow will be observed round thumb and fingers, frequently uniting the finger tips. A little patience and a moderately clean hand are all that is required to observe the phenomenon