Erick Agrimson

Effect of parallel velocity shear on the electrostatic ion-cyclotron instability in filamentary current channels

The effect of magnetic field-aligned ion flow with a transverse flow velocity gradient (parallel velocity shear) on the excitation of the electrostatic ion cyclotron (EIC) instability in narrow current channels (width<ion gyroradius) is studied experimentally in a double-ended Q machine. The presence of parallel velocity shear may lead to the excitation of the EIC instability even in current filaments too small to otherwise support the instability.

Amplification of electrostatic ion-cyclotron waves in a plasma with magnetic-field-aligned ion flow shear and no electron current

Experimental demonstration of the amplification of electrostatic ion-cyclotron waves in a plasma with parallel ion flow shear but no magnetic-field-aligned electron current is presented. Waves with frequencies near the ion gyrofrequency and multiple harmonics launched from an antenna are observed to grow in amplitude in a region of ion flow shear. Amplification of multiple cyclotron harmonics was observed when a broadband (white noise) signal was applied to the launching antenna. Implications of these results for plasma wave excitation in the Earth’s auroral region are discussed.