Abstract
A review is given of the effects observed during injections of powerful electron beams from sounding rockets into the upper atmosphere. Data come from in situ particle and wave measurements near a beam emitting rocket and ground-based optical, wideband radiowave, and radar observations. The overall data cannot be explained solely by collisional degradation of energetic electrons but require collisionless beam plasma interactions (BPI) be taken into account. The beam-plasma discharge theory describes the features of the region near a beam-emitting rocket, where the beam-excited plasma waves energize plasma electrons, which then ignite the discharge. The observations far beneath the rocket reveal a double-peak structure of artificial auroral rays, which can be understood in terms of the beam-excited strong Langmuir turbulence being affected by collisions of ionospheric electrons. This leads to the enhanced energization of ionospheric electrons in a narrow layer termed the plasma turbulence layer (PTL), which explains the upper peak. Similar double-peak structures or a sharp upper boundary in rayed auroral arcs have been observed in the auroral ionosphere by optical, radar, and rocket observations, and called Enhanced Aurora. A striking resemblance between Enhanced and Artificial Aurora altitude profiles indicates that they are created by the above BPI process which results in the PTL.
Highlights
The effects of powerful electron beams injected from sounding rockets into the upper atmosphere to create artificial aurora are outlined
The basic processes of the near-rocket region are described in terms of the beam-plasma discharge (BPD) ignited by plasma electrons energized by the beam-excited plasma turbulence
The observations of artificial auroral rays far beneath the rocket indicate that turbulence regime and the relaxation of radially expanded beams are strongly affected by collisions of plasma electrons
Summary
It is straightforward to employ electron beams injected from a space vehicle with controlled parameters to explore Artificial Aurora (AA) generated in the upper atmosphere Such (active) AA experiments have been conducted from sounding rockets and the Spacelab (e.g., Davis et al, 1971, 1980; Hess et al, 1971; Cambou et al, 1975, 1978, 1980; O’Neil et al, 1978a,b; Maehlum et al, 1980a; Jacobsen, 1982; Obayashi et al, 1984; Neubert et al, 1986; Kawashima, 1988; Goerke et al, 1992; Burch et al, 1993). Before presenting the principal experimental results, it is instructive to discuss briefly the “classical” auroral features that follow from collisional interaction of energetic electrons with the neutral atmosphere
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