Ion resonances and ELF wave production by an electron beam injected into the ionosphere: Echo 6

Abstract

The interaction with the ionospheric plasma of two separately controllable electron beams injected from the Echo 6 sounding rocket in the auroral zone has been studied using orthogonal electric double probes and other instruments on a separate plasma diagnostics payload. The gun pulses produced a myriad of large electric probe signals covering the entire ion gyro range between dc and 1250 Hz. In particular a signal driven at the 1‐kHz gun frequency and a naturally occurring resonance at 840 Hz near the 799‐Hz proton gyrofrequency were studied. The 1‐kHz signal decreased by a factor of 100 between 45 and 90 m from the beam field line but was detectable in the 1‐mV/m range at 120 m, confirming previous findings that pulsed electron beams may serve as ELF wave sources in space. The 840‐Hz resonance was excited by a beam injected parallel to the magnetic field but could be quenched by the addition of a transverse beam in what appears to be a case of controlled damping. The 840‐Hz and 1‐kHz signals were superposed on large‐amplitude fluctuations and were extracted using power spectral analysis. The data contain a large variety of ion gyro range frequencies which are under study. The paper discusses the interpretation of the electric probe responses and large turbulent payload floating potential effects produced by the hot plasma generated by the beams.

Actively produced high-energy electron bursts within the magnetosphere: the APEX project

“…These dimensions are similar to those reported from a joint US/Canadian electron accelerator experiment (Duprat et al, 1983). The Echo 6 flight (Winckler et al, 1984) with a higher beam power showed a disturbed plasma region greater than 140 m of radius. Large disturbed regions of radius up to 800 m were reported by Sagdeev et al (1981) in a lower altitude region.…”

Double‐probe potential measurements near the Spacelab 2 electron beam

“…During events 2, 3, 4, and 5 the peaks in Vdif• are associated with specific orientations of the antenna with respect to the velocity and the magnetic field, and therefore can be primarily attributed to shadowing effects. Shadowing effects of this type were observed by Winckler et al [1984] during the Echo 6 experiment. In that experiment, large signals at the payload spin frequency were attributed to shadowing of one probe from a magnetic field aligned plasma flow.…”

Floating bare tether as upper atmosphere probe

“…Active experiments using electron beam sources on board rockets to produce artificial auroras started in 1969 [ Hess et al , 1971; Davis et al , 1971]. This pioneer work was followed by a series of rocket missions such as Echo, for upward injection [ Israelson and Winckler , 1975; Hallinan et al , 1978; Winckler et al , 1984], Excede, for low‐altitude injection [ O'Neil et al , 1978a, 1978b; Paulsen et al , 1990], and TEP/Charge, involving tethers [ Sasaki et al , 1987; Myers et al , 1990; Gilchrist et al , 1990]. Beam sources have also been used onboard the shuttle [ Wilhelm et al , 1984; Beghin et al , 1984; Banks et al , 1987].…”