Artificial auroral experiment - Ground-based optical observations
Ground based optical observation of raylike artificial auroras produced by rocket-borne accelerator generated electron beams, using image orthicon TV system
Davis, T. N.↗
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Plasma physics abstracts, 1 January - 31 December 1971
Abstracts are presented on various aspects of plasma physics, including theoretical discussions and ionospheric plasmas. The topics considered cover Alfven waves, magnetized plasmas, plasma diffusion, Poynting flux measurements, electric fields, the magnetosphere, auroras, and plasma convection.
Montgomery, D. C.↗
Atmospheric sound propagation
The propagation of sound waves at infrasonic frequencies (oscillation periods 1.0 - 1000 seconds) in the atmosphere is being studied by a network of seven stations separated geographically by distances of the order of thousands of kilometers. The stations measure the following characteristics of infrasonic waves: (1) the amplitude and waveform of the incident sound pressure, (2) the direction of propagation of the wave, (3) the horizontal phase velocity, and (4) the distribution of sound wave energy at various frequencies of oscillation. Some infrasonic sources which were identified and studied include the aurora borealis, tornadoes, volcanos, gravity waves on the oceans, earthquakes, and atmospheric instability waves caused by winds at the tropopause. Waves of unknown origin seem to radiate from several geographical locations, including one in the Argentine.
Cook, R. K.↗
Determination of sounding rocket position and attitude from radar and magnetometer data
The techniques are described that were used to determine the trajectories and orientations of three sounding rockets instrumented to study the aurora. The radar plot board data were fitted to a near earth expansion of the force of gravity to determine the trajectory. Only onboard magnetometer data were used to determine the attitude of the payload with respect to the earth's magnetic field. Computer programs in the FORTRAN language are available which generate the trajectory and attitude parameters.
Pongratz, M.↗
Functional characteristics of the OGO main body airglow photometer
The OGO-4 main body airglow photometer used a trialkali cathode photomultiplier to sense light at selected wavelengths between 2500 and 6300A corresponding to important emissions in the aurora and night airglow at emission rates ranging from a few rayleighs to about 200 kilorayleighs. The optical, electronic, and mechanical systems are described in terms of their functional characteristics.
Reed, E. I.↗
SM91: Observations of interchange between acceleration and thermalization processes in auroral electrons
Results from a Nike-Tomahawk sounding rocket flight launched from Fort Churchill are presented. The rocket was launched into a breakup aurora at magnetic local midnight on 21 March 1968. The rocket was instrumented to measure electrons with an electrostatic analyzer electron spectrometer which made 29 measurements in the energy interval 0.5 KeV to 30 KeV. Complete energy spectra were obtained at a rate of 10/sec. Pitch angle information is presented via 3 computed average per rocket spin. The dumped electron average corresponds to averages over electrons moving nearly parallel to the B vector. The mirroring electron average corresponds to averages over electrons moving nearly perpendicular to the B vector. The average was also computed over the entire downward hemisphere (the precipitated electron average). The observations were obtained in an altitude range of 10 km at 230 km altitude.
Pongratz, M.↗
Physics of the space environment
Upper atmospheric physics and chemistry, auroras, and solar flare forecasting - colloquium
Smith, R. E.↗
Upper atmospheric spectroscopy
Atomic physics is so intimately entwined with planetary aeronomy that progress in this geophysical-astronomical discipline is dependent in large measure upon progress in certain phases of atomic physics. The interdependence is illustrated by a discussion of photon, electron, and proton stimulation of the dayglow and the aurora. Calculations are given for the excitation of various states in N2, O2, and O as a result of electron energy degradation, assuming a gas mixture appropriate to 120 km. Emphasis is given to the O2(a 1 Delta g) 1.27 micron emission and to the low energy region in areas where many competing mechanisms enhance or inhibit certain spectral emissions.
Green, A. E. S.↗
Midday auroral observations in the oval, cusp region, and polar cap.
Evaluation of combined photographic and photometric measurements made on the 1969 NASA airborne expedition, yielding a description of the midday oval, cusp region, and polar cap auroral precipitation at low magnetic activity (Kp = 0, 1+). The observations delineate three regions through the description of the type of aurora observed and the photometrically inferred change in energy of the particles: (1) the region in and equatorward of the oval where greater than 3-keV electrons are associated with 6300 A/4278 A ratios less than or equal to 1 and with a diffuse glow or structured arcs; (2) the cusp region where electrons of several hundred electron volts and spikes of more energetic electrons are associated with 6300 A/4278 A ratios between 10 and 35 in broken, fragmented, rayed features and patches; (3) the polar cap where discrete earth-sun-aligned arcs have height luminosity profiles in 5577 A, 6300 A (forbidden O I), and 4278 A (N2(+)) that suggest incoming electrons with an energy spectrum of 2-keV characteristic energy above a low-energy (few hundred electron volts) background.
Romick, G. J.↗
Observed correlations between auroral and vlf emissions.
This paper presents a series of simultaneous observations of very-low-frequency radio noise by the Injun 5 satellite and of visual aurora along the same geomagnetic-field line by the Fort Churchill Auroral Observatory. Seven observations from the period of August 29, 1968, to March 4, 1969, are discussed. In 5 of the 7 events studied vlf hiss is observed in association with auroral-light emissions. These observations typically show the occurrence of vlf hiss in the general region of the auroral arc, with significant changes in the vlf spectrum sometimes observed in the immediate vicinity of the auroral arc. One event for which the associated charged-particle fluxes have been analyzed is investigated in detail. The vlf radio noise intensity for this event is among the largest observed with Injun 5 and is much greater than can presently be explained by an incoherent Cerenkov radiation mechanism.
Mosier, S. R.↗
Ogo 5 observations of LHR noise, emissions, and whistlers near the plasmapause at several earth radii during a large magnetic storm.
On May 15, 1969, Ogo 5 crossed the plasmapause during a major storm that produced severe geomagnetic disturbances (Kp up to 8-), large and rapid variations in ring-current intensity (as measured by Dst), intense low-latitude aurora, and persistent SAR arcs. Near the highly structured plasmasphere boundary, the electric- and magnetic-field sensors on Ogo 5 detected lower-hybrid-resonance noise bursts, whistlers, ELF hiss, and other discrete signals or emissions. Some LHR noise bursts were associated with whistlers, and these high-altitude phenomena resembled the corresponding ionospheric ones. This report contains a description of the VLF observations. We also show that intense ULF magnetic signals were present near the plasmapause, and we attempt to relate these observations to the predictions of various theories of proton ring-current decay and SAR-arc formation.
Scarf, F. L.↗
N2 positive and N2/+/ band systems and the energy spectra of auroral electrons.
Use of the relative emission rates of the auroral N2 positive and N2(+) band systems to limit the permissible range of differential electron fluxes in auroras, due to remarkable differences in electron excitation functions for the two kinds of systems. Use of recently measured electron cross sections and many observational data from ground based and rocket studies shows that the results are consistent with spectra equivalent to a power law E to the minus 1.4 power for primaries and secondaries combined. The unified primary spectra of Rees (1969) and secondary spectra of Rees et al. (1969) fail seriously to predict the optical ratios. It is shown that Rees' primary spectrum is deficient in slow primaries, owing to the use of defective Monte Carlo results of Maeda (1965). Doubt is thereby cast on the validity of experimental results for the differential spectrum below 50 eV reported by Feldman et al. (1971) because of the rapid decrease in flux with energy shown by those measurements.
Shemansky, D. E.↗
Auroral emissions and particle precipitation in the noon sector.
Comparison of airborne optical measurements during December 1969 with satellite particle measurements made earlier in 1969. The latitudinal distributions of H beta, 4278-A and 6300-A emissions during quiet periods are observed to agree with what would be expected from the latitudinal distribution of particle precipitation during similar conditions. In particular, there is a belt 200 to 500 km wide (at ionospheric heights) in which the magnetosheath plasma penetrates down to low altitudes through the cusps in the dayside magnetosphere and in which both H beta and 6300-A emissions are observed. There are brighter red arcs with green lower borders within this belt. It is suggested that these are produced by narrow regions of precipitation of slightly more energetic electrons embedded in the cusp fluxes. Poleward of this belt the flux of particles is low, and the atmospheric emissions are very weak, except for occasional narrow regions of electron precipitation (without measurable protons) and the corresponding polar-cap aurora (without the H beta emission).
Heikkila, W. J.↗
Electron deposition in water vapor, with atmospheric applications.
Examination of the consequences of electron impact on water vapor in terms of the microscopic details of excitation, dissociation, ionization, and combinations of these processes. Basic electron-impact cross-section data are assembled in many forms and are incorporated into semianalytic functions suitable for analysis with digital computers. Energy deposition in water vapor is discussed, and the energy loss function is presented, along with the 'electron volts per ion pair' and the efficiencies of energy loss in various processes. Several applications of electron and water-vapor interactions in the atmospheric sciences are considered, in particular, H2O comets, aurora and airglow, and lightning.
Olivero, J. J.↗
Behavior of outer radiation zone and a new model of magnetospheric substorm.
This paper presents particle data obtained from synchronous altitudes and attempts to evaluate the origin and nature of particle flux variations observed during substorms. The correlated particle intensities, time variations, and energy spectrums are compared between the equatorial and auroral zones. The correlated particle and field observations during substorms are tied together and a model of magnetospheric substorms is derived. Among the features predicted by the model is the poleward expansion of visual auroras observed at the onset of magnetospheric substorms. The model also explains how substorms are triggered in a few minutes time scale during sudden commencements.
Parks, G. K.↗
Auroral data from Michigan airglow payload launch
Auroral studies are presented of flight data analysis from the Michigan airglow payload. Analysis of the stellar occultation data and results from the twilight flight are reported. Optical emissions from bottled aurora and an electron analyzer for measurement of distributions in energy of electrons along a beam are also presented. A list of related publications is included.
Hays, P. B.↗
The IR emission spectrum of N2 excited under auroral conditions.
Recently determined experimental and theoretical cross sections for electron impact excitation of six triplet states of N2 (A, B, W, C, E, D) have been utilized to predict the absolute IR volume emission rates from N2 under nighttime auroral conditions. Secondary electron fluxes appropriate to an IBC II normal aurora were used in the calculations. The cascade contributions coupling the various electronic states were included as well as the most important quenching processes. The results indicate that the B yields reversibly A and W yields reversibly B cascade processes, which are important in the population of the A, B, and W states, produce appreciable radiation in the 1- to 5-micron wavelength region.
Cartwright, D. C.↗
Magnetospheric processes and the behavior of the neutral atmosphere.
A review is given of the quiet time couplings which exist between the magnetosphere and the thermosphere. Joule heating arising from aurorae and the combination of Joule heating and ion drag arising from magnetospheric convection normally provide as much energy to the thermosphere as solar ultraviolet radiation. Ion drag is especially important for establishing wind systems in the thermosphere. Using the qualitative ideas of convective electric fields, a description of a possible model of the global wind system is given. It is pointed out that the existence of a convectively driven wind source at high latitudes consistent with magnetospheric convection leads to the possibility of a mean easterly wind, i.e., super-rotation.
Banks, P. M.↗