Churchill Research Range Research Articles

Acceleration of electrons in strong beam‐plasma interactions

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 region.

1302Å absorption measurement of atomic oxygen concentrations in the high latitude winter upper atmosphere

The first measurement of atomic oxygen concentration in the upper atmosphere using the resonance absorption lamp method was made 23 January 1974 in a flight from the Churchill Research Range (58.4°N, 94.1°W, geographic) in northern Canada. Earlier difficulties with the data analysis have been resolved to a limited extent, and a concentration profile over the range 90–155 km is presented here. In the interim period, the same technique has been employed by a number of investigators, but the importance of the present data is that the atomic oxygen concentration was measured by three independent methods on the same flight, aeronomical and mass spectrometric methods being used as well as resonance absorption. The results are in good agreement when current aeronomical understanding is employed. Comparison is made with other measurements and it is concluded that the high degree of variability observed may well be real. A simple argument based on these data shows that O 2( c 1 Σ) cannot be the sole source of O( 1S) and O 2( b 1 Σ) in the aurora.

Measurements of the stability of energetic electron beams in the ionosphere

A Nike Black Brant V rocket was launched from the Churchill Research Range (Manitoba) on December 3, 1979, into a bright east‐west oriented auroral arc. The rocket payload consisted of two separable sections, each containing its own telemetry and a full set of wave and charged particle detectors. An electron gun, carried in the main payload, produced a pulsed electron beam with energies of 1.9, 4, and 8 keV at 1, 10, and approximately 100 mA in a programed format. Charged particle observations from the flight are used to define the spatial distribution of perturbed volume surrounding the accelerator during gun firing. The radial dimensions of the perturbation were found to scale with the primary electron beam gyroradius and current and were also dependent on the beam injection angle. On magnetic field lines near the gun, the induced return electron energy spectrum is characterized by a monotonically decreasing intensity with increasing energy out to the approximate beam energy. At increasing distances across field lines the energy spectrum takes on a monoenergetic appearance peaked near the beam energy. All beam‐induced electron fluxes drop rapidly to background at the edge of the perturbed volume. The intense flux of low‐energy electrons observed on field lines near the rocket are shown to be accelerated ambients, whereas the particles at or near the beam energy and at large radial distances are presumably beam primaries. The ambient thermal ion plasma was not measurably affected by the beam while the local electron temperature increased during gun pulses. Results from this flight are compared with the corresponding observations made in a large vacuum tank simulation, and it is concluded that certain features in the data are consistent with the beam‐plasma instability observed in the laboratory.

Preliminary results from Project Waterhole — an auroral modification experiment

A sounding rocket carrying 100 kg of high explosives and plasma diagnostic instrumentation was launched from Churchill Research Range on 6 April 1980 over a premidnight auroral arc. The object of the experiment was to produce an ionospheric hole or plasma density depletion near 300 km altitude on field lines connected to an auroral arc. The plasma depletion is produced when the explosive by-products (mostly water) charge-exchange with the ambient O+ ions and then rapidly recombine. It was speculated that the presence of the "hole" would interfere with the field aligned current systems associated with the arc and would in turn perturb the auroral source mechanism. The release occurred about 10 km poleward of the auroral arc fieldlines. As expected, a large ionospheric hole was detected by the rocket-borne plasma sensors. Within a few seconds following the release (a) the energetic electron precipitation observed in the hole dropped to background levels, (b) the luminosity of the auroral arc observed by a ground-based auroral scanning photometer decreased by a factor of two, and (c) the ionospheric E region density below the hole decayed at a rate consistent with a sudden reduction in particle precipitation. The simultaneous onset of these gross changes in electron precipitation coincident with the release strongly suggests a cause and effect relationship and demonstrates the intimate relationship that exists between the state of the ionospheric plasma and the auroral acceleration mechanism.

Observations of particle precipitation, electric field, and optical morphology of an artificially perturbed auroral arc: Project Waterhole

A sounding rocket carrying 88 kg of high explosives and plasma diagnostic instrumentation was launched from Churchill Research Range on April 6, 1980, over a premidnight auroral arc, as part of Project Waterhole, a joint NRC/LASL experiment. The object of the experiment was to produce an ionospheric hole, or plasma density depletion, at about 300‐km altitude on field lines connected to an auroral arc. The plasma depletion is produced when the explosive by‐products (mostly water) charge exchange with the ambient O+ ions to produce molecular ions (mostly H2O+) which then rapidly recombine with ambient electrons. It was speculated that the presence of the ‘hole’ would interfere with the field‐aligned current systems associated with the arc and would in turn perturb the auroral source mechanism. The release occurred about 10 km poleward of the auroral arc field lines. As expected, a large ionospheric hole was detected by the rocket‐borne plasma sensors. Within a few seconds following the release (1) the energetic electron precipitation observed in the hole dropped to background levels, (2) the luminosity of the auroral arc observed by a ground‐based auroral scanning photometer decreased by a factor of 2, and (3) the ionospheric E region density below the hole decayed at a rate consistent with a sudden reduction in particle precipitation. The simultaneous onset of these gross changes in electron precipitation coincident with the release strongly suggests a cause and effect relationship. Relevant observations of the particle precipitation, electric field, and optical morphology of the auroral arc system in the experiment are presented and their interpretations discussed in terms of current theories of auroral field‐aligned currents and auroral arc formation. Our observations suggest that the ionospheric plasma and the field‐aligned current systems play a crucial role in the auroral acceleration process.

A rocket-borne radar study of aurora

A coherent-pulse auroral radar was flown in a Black Brant VI rocket from the Churchill Research Range in February 1978, into a moderate radio-auroral event. The characteristic Doppler spectrum of i...

Do field‐aligned auroral particle distributions imply acceleration by quasi‐static parallel electric fields?

Charged particle observations from several high‐altitude sounding rocket flights launched from Churchill Research Range into auroral events when magnetic‐field‐aligned electron precipitation was observed are presented. Large field‐aligned enhancements were observed near the edges of regions of intense electron precipitation (auroral arcs), while only small or no enhancements were observed inside these regions. Field alignment was spread over a large energy range, at times from 0.5 to 60 keV, and showed no enhancement near the characteristic peak in the energy spectrum. These and other observations are compared with predictions of models involving acceleration by quasi‐static parallel electric fields, including the possibility of beam‐plasma instability effects, and are shown to be inconsistent. Acceleration by broadband electrostatic waves is suggested as a possible energization mechanism for field‐aligned particles.

Characteristics of auroral proton precipitation observed from sounding rockets

A summary of auroral proton observations from 12 sounding rockets launched from Churchill Research Range is presented. Although these rockets were launched into different auroral conditions and at various local times, certain characteristics were observed in all flights. Energy spectra were peaked in the 5- to 10-keV energy intervals with typical intensities near 10$sup 5$ cm$sup -2$ s$sup -1$ sr$sup -1$ keV$sup -1$. Proton pitch angle distributions in the loss cone were isotropic at all energies less than 20 keV. At higher energies, distributions were either isotropic or anisotropic peaked near 90degree pitch angle. Temporal and spatial structure was observed in proton precipitation with typical time scales of the order of 100 equatorial gyroperiods and scale lengths of the order of 100 gyrodiameters. No obvious electron proton correlations were apparent in any of the data. Observations of interactions of the primary proton beam with the neutral atmosphere are presented. Beam spreading effects due to charge exchange interactions are demonstrated, and equilibrium fractions for protons in the atmosphere are measured and compared with relevant laboratory observations. The implication of these results concerning auroral proton source regions and precipitation mechanisms is discussed. (AIP)

Simultaneous investigation of parent electrons and Bremsstrahlung X rays by rocket-borne detectors

Simultaneous measurements of the energy spectrum of precipitating electrons and the resulting bremsstrahlung X-ray spectrum were carried out during an auroral event on March 3, 1971, at the Churchill Research Range, Manitoba, Canada. The electron data were obtained with detectors on a Black Brant VB sounding rocket (275-km apogee), while the X-ray flux was measured by an instrument package that was boosted to 60 km on an Arcas rocket. The X-ray package was deployed on a parachute at apogee to provide a slow descent through the atmosphere. Thick-target bremsstrahlung theory is used to calculate the X-ray flux produced by the incident electrons, and a Monte Carlo method is used to predict the X-ray spectrum at various altitudes appropriate for comparison with the measured X-ray data. Satisfactory agreement between theory and experiment is obtained, and the value of the constant in the thick target theory has been estimated to be about 0.00002.

A rocket instrument for imaging the aurora by means of high speed photometric scanning

A high resolution rocket-borne mechanical flying spot scanner has evolved from similar ground-based instruments. The spinning motion of the rocket together with that of a motor-driven prism are used to scan a narrow-angle photometer systematically and repetitively over the full 4π sr region around the rocket. Outputs from two wavelengths selected by narrow-band interference filters are available from the one instrument. The large quantity of data thus obtained are first reproduced in pictorial form making it relatively easy to identify auroral and airglow features which can then be studied quantitatively. Computer reduction of the data also makes it possible to determine the attitude of the vehicle carrying the scanner to an accuracy better than can be achieved with an aspect magnetometer. Results illustrating the capabilities of the instrument and data analysis system have been obtained from rocket AKD-VB-27 which was launched from the Churchill Research Range, 20 January 1971.

Churchill Research Range Auroral Launcher Facility

Churchill Research Range Auroral Launcher Facility

Noctilucent cloud observation in connection with the flight of a sounding rocket

The frequency of occurrence of noctilucent clouds over a fixed geographical location has been studied in connection with a sounding rocket flight to collect noctilucent cloud particles for analysis in the laboratory. The major objectives of this study were to document, both visually and photographically, that the sounding rocket did pass through a noctilucent cloud and to correlate the cloud properties with the particles collected. On the night of July 31 and August 1, 1968, a sounding rocket was launched from the Churchill Research Range, Manitoba, Canada, into a weak noctilucent cloud. The photograph in this report documents the presence of a noctilucent cloud during the time of its penetration by a sounding rocket. Only 4 of 13 displays observed from Thompson, Manitoba, Canada, during the period from July 1 to August 1 were over the launch range. On the basis of these data, one would expect noctilucent clouds over a specific geographic point, 59° latitude, only 15% to 25% of the nights during the optimum period for noctilucent clouds.

Temporal behavior of energetic particle precipitation during an auroral substorm

Results from two rocket experiments launched from Fort Churchill Research Range into the breakup and post-breakup phases of an auroral substorm are described. Unusual characteristics were observed in energy spectra and pitch-angle distributions of energetic electrons (E> 3 kev) and protons ( >28 kev) simultaneously with the arrival of the northern edge of a series of northward-propagating auroral arcs. When the northern edge passed the rocket, electron intensities increased and the spectrum hardened appreciably, both changes occurring with time constants less than about 2 seconds. Dispersion in arrival times of electrons was observed with the low-energy particles arriving first. After the initial injection the particle fluxes were observed to decay at rates consistent with the maximum decay rates for these latitudes. Decay times of the order of a few minutes for electrons and a few hours for protons were observed. Electron angular distribution characteristics were found to be energy dependent. The recovery-phase of the substorm was found to be characterized by soft isotropic electron precipitation.

Mass spectrometric investigation of the thermosphere at high latitudes

The number densities for N2, O2, O, and Ar in the 115–155 km range were measured by means of a monopole spectrometer flown aboard a Black Brant 3 rocket launched at the Churchill Research Range on December 12, 1966, at 1320 CST. The N2 density at 150-km altitude was found to be higher by a factor of 1.3 than the average of mass spectrometric determinations performed at temperate latitudes during the years 1966 and 1967. A low Ar content and a High He content (the latter measured by a mass filter aboard the same rocket) both point toward an altitude of the turbopause below 100 km. Unexpected high O2 densities in the ion source could only be explained by a considerable degree of recombination of O to O2 at the ion source walls. Similar to the ESRO CO7 flight, but less pronounced, a wave-like structure was found superimposed on the density profiles of all constituents. Neutral gas temperatures did not significantly deviate from the CIRA 1965 values.