Laboratory simulations of suprauroral mechanisms leading to perpendicular ion heating and conic formation

Abstract

Laboratory experiments are presented simulating aspects of perpendicular ion heating and conic formation that are observed or hypothesized to occur in the terrestrial ionosphere and magnetosphere. Previous laboratory observations of ion conics in the presence of the current-driven electrostatic ion cyclotron wave are reviewed. Field-aligned ion beams, accompanied by beam-generated electrostatic ion cyclotron modes, resulted in perpendicular energization of beam ions and also the heating of background plasma ions. Antenna-launched broadband and narrow-band lower hybrid waves produced considerable perpendicular ion heating and non-Maxwellian "tail" formation. Laboratory results are discussed in light of in situ measurements by the S3-3 satellite and the MARIE sounding rocket.

Adjustable levels of strong turbulence in a positive/negative ion plasma

“…27 By increasing the concentration of SF 6 , the electron density in the plasma column can be reduced down to less than 0.01 of its initial value. The mass ratio of SF 6 to Ba, msF/maa = 146/137 = 1.07, is very close to unity. A more detailed discussion of this and other PNIP sources is found in Sheehan and Rynn.…”

“…The vessel's base pressure is 1 X 10- 6 Torr. The initial Ba+ le-plasma is produced by contact ionization of an atomic beam of Ba impinging on a rhenium-coated tung-sten disk (5 cm diam) heated to over 2000 K by electron bombardment.…”

“…Positive-negative ion plasmas are created from the Q-machine plasma by introducing gaseous SF 6 into the vacuum chamber. Sulfur hexafluoride is an electron scavenger with particular affinity for electrons with energies less than about 0.2 eV ( :::::2000 K).…”

“…The magnitude of this turbulence can be simply determined by setting a single experimental parameter: the vessel partial pressure of an electronscavenging gas, SF 6 • We are aware of no other plasma system whose turbulence level can be varied so simply between such marked extremes-from quiescent to strongly turbulent. As such, this plasma may serve as · a testing ground for models of strong turbulence.…”

“…PNIP's are interesting both experimentally and theoretically. They are found in gas laser discharges, combustion products, 1 plasma discharges for semiconductor device manufacture,2 stellar atmospheres, 3 pulsar magnetospheres, 4 the Earth's ionosphere, s, 6 and neutral beam sources for controlled fusion experiments. 7 In recent years, PNIP's have been created artificially in the ionosphere by rocket releases of electron scavengers such as CF 3 Br, Ni(C0) 4 , and SF 6 , Ref.…”