Balloon observations of auroral X-rays in Canada. I. Determination of auroral X-ray illuminating regions.

Abstract

Two balloons each carrying a payload consisting of three sets of NaI(T1) scintillation counters have been launched from Thompson, Manitoba, Canada, in April 1975, to search precipitating mechanisms of auroral particles through observations of the bremsstrahlung X-rays in conjugation with the geo-stationary statellite ATS-6. Two omnidirectional counters, one of which had the modulation collimator, were used together with the directional counter inclined from the zenith. On the basis of the spin-modulated data obtained during the appearance of two distinct auroral X-ray bursts, two-dimensional source models, arc-and disc-shaped, are proposed for the auroral X-ray illuminating region. Also shown is an example of the eastward drift of another auroral X-ray source. Some of problems related to the analyses of data, i.e., background fluxes due to cosmic rays, and the response functions of the detectors are discussed.

Auroral X ray images

“…This information would allow for a separation of the effects of the two components. Some attempts at obtaining energetic spatial information have been made by balloon borne X ray detectors [Parks, 1967;Yamagami et at., 1978]. Also, satellite detectors have been employed to study X ray emission structures with resolution _>200 km [Mizera et at., 1978;Imhof et at., 1974Imhof et at., , 1978.…”

Defocusing characteristics of auroral X-ray images observed at balloon altitudes.

“…Balloon observations of auroral X-rays still supply an attractive means to form X-ray images, owing to various advantages such as easier handling in launch, longer 389 observing time at a location, heavier allowable payload and economical cost (YAMAGAMI et al, 1978;MAUK et al, 1981;HIRASIMA et al, 1983HIRASIMA et al, , 1987a. In parallel with experimental works, some simulative and analytical investigations have been performed from the standpoint of a theoretical approach of X-ray diffusions through the atmosphere (PILKINGTON and ANGER, 1971;BERGER and SELTZER, 1972;OGURA and KODAMA, 1980).…”

Spatial Characteristics of Bremsstrahlung X-Rays Associated with VLF Emissions.

“…On the other hand, a balloon usually stays at a site during fairly a long time, so that the local spatial distribution of auroral X-rays could be obtained as well as the temporal characteristics. Numerous works were made to take X-ray images by using a variety of balloon-borne instruments (PARKS, 1967;YAMAGAMI et al, 1978YAMAGAMI et al, ,1990MAUK et al,1981;ULLALAND et al, 1984;HIRASIMA et al, 1987 or disc-shaped Gaussian type X-ray source functions. The method of the simulation is described in SUZUKI et al (1988).…”