Electron Cyclotron Drift Instability

Abstract

out separately, by means of an axially and radially movable probe. We found, by interferometry, that the wave signals were primarily concentrated within the axial length of the T probes or grids. When the detecting probe was outside of this region, the signal dropped by 60 dB. Our measurements indicated that in the axial direction the waves were essentially standing waves, with the dominant Fourier components having twice the probe lengths; i.e., k^ir/l', etc. Thus, by approximating the standing waves in the axial direction with cosik^z), cos(k/z), we find from theory that for k ]l «k x the dominant contributions to the matrix elements are given by k || =k "' + k [,". By varying the lengths of the receiving and transmitting probes in the nonlinear Landau damping experiments, we have verified that this model of wave excitation gave good agreement with theory, In summary, we believe that we have observed experimentally nonlinear Landau damping of plasma waves in the presence of an external magnetic field. The qualitative features of the experimental results agreed well with the predictions of the nonlinear Landau damping theory. In particular, the observed decay of a finiteamplitude wave into a single perturbed wave cannot be explained by resonant mode-mode coupling or parametric theory. The amplitude variation of the perturbed wave as a function of the pump wave followed the predictions of the third-order theory, through at least four decades. The measured nonlinear wave-particle coupling coefficient was found to agree with theory within ex-perimental error. A detailed account of this work will be published elsewhere.We are very grateful to Professor M 0 N. Rosenbluth and Professor B c Coppi for invaluable discussions. . 5 M. Porkolab and R. P. H. Chang, Phys. Rev. Lett. 22, 826 (1969). 6 R. P. H. Chang and M. Porkolab, to be published. 7In the spatial case, the finite parallel wave number cannot be neglected in nonlinear Landau damping theory in a nearly collisionless plasma. 8 The dispersion curves shown in Fig. 1(b) are those with &n =0. Nevertheless, for the experimentally measured values of k^/hjfiw «kj), it can be shown that the real parts of k L and oo are closely approximated by the curves used.Electron cyclotron waves are shown to grow unstably in the presence of small relative drifts of a warm ion distribution perpendicular to the B field. Numerical simulations show that this instability causes anomalous diffusion of plasma across the magnetic field and heating of the electron thermal spread to values much greater than the relative ion-electron drift velocity.Most methods for heating and confining high-temperature plasma involve a flow of electric currents normal to magnetic field lines in the plasma. This Letter reports the theoretical properties of a highfrequency electrostatic plasma instability which is driven by the relative drift of ions and electrons in such a normal current flow and which is expected to occur and cause anomalous resistance to the current in a wide range of applications. The calcu...

Electron cyclotron microinstability in the foot of a perpendicular shock: A self-consistent PIC simulation

“…Forslund et al (1970), Gary (1971), and references in the review by Wu et al (1984)). It is a variety in the sense that the instability is not driven by the whole ions drifting as a bulk, yet just by an ion beam.…”

“…We believe that it is a variety of the electron cyclotron drift instability, which was studied in the 70's and has since been all but forgotten (e.g. Forslund et al, 1970). The idea is illustrated in Figure 6a which displays the two ion beam modes at ω = k(V d ± v ti ) intersecting with the first three branches of Bernstein modes.…”

Dynamics and microinstabilities at perpendicular collisionless shock: A comparison of large-scale two-dimensional full particle simulations with different ion to electron mass ratio

“…The relative bulk velocity between electrons and ions (which is proportional to u x1 /v te1 ) controls the type of microinstabilities, while the ratio of the plasma-tocyclotron frequency (ω pe /ω ce ) determines the dispersion relation of plasma waves. When the relative bulk velocity between electrons and ions exceeds the electron thermal velocity, electrostatic waves are excited by current-driven instabilities such as the Buneman-type instability (BI) 7 or the electron cyclotron drift instability (ECDI) 8,9 . At high-Mach-number perpendicular shocks, the relative velocity between incoming electrons and reflected ions commonly becomes much faster than the electron thermal velocity.…”

Quantified energy dissipation rates in the terrestrial bow shock: 2. Waves and dissipation

“…ECDI-driven waves are important for shock physics because they are capable of resonantly interacting with the bulk of the ion distribution and preferentially heating the electrons perpendicular to B o [Forslund et al, 1970[Forslund et al, , 1972Lampe et al, 1972]. More recent work has shown that the ECDI can produce a suprathermal tail on the ion distribution and can strongly heat the electrons [Muschietti and Lembège, 2013].…”