The e l e ~t r o ~t a t i ~ character of the self-excited drift wave in a magnetized plasma column is demonstrated. The level of the self-excited mdgnetic fluctuation is small. With the help of external coils fixed onto the glass tube a rotating field component perpendicular to the steady state axial magnetic field is produced and the inhence nn i'ne self-excited electrostatic drift wave spectrum is siudied. Positive frequency shifts, modulation of the drift-wave amplitude and phase, suppression of the drift wave and mode competition and locking effects are studied. Furthermore, enhanced plasma losses arc observed which increase approximately with the square of the amplitude of the oscillating magnetic field. 1. I N T R O D U C T I O N ELECTROSTATIC PLASMA EDGE INSTABILITTES and turbulence Of illhOmOgeneOUS magneticaiiy confined piasma devices have been subject t o several studies during the iast decades [see for instance the review articles of LIEWER (1985) and HORTON (1984, 1990)]. The density gradient driven electrostatic drift wave is discussed to be one possible origin of these fluctuations (Vn-model), while another is the resistivity gradient driven mode (Vq-model), see for instance W ~T T O N er al. (1990).The understanding of the edge fluctuations is important with respect to the understanding of the induced particle and heat transport. Moreover, the low frequency fluctuations scatter and damp high frequency waves, for example lower hybrid waves, that are transmitted through the plasma device for the purpose of plasma heating. These low frequency waves are a good example for basic wave studies in dispersive media, such as coherent nonlinear structures as well as turbulence (KAUSCHKE and SCHLUTER, 1990, 1991).In addition to the electrostatic turbulence magnetic fluctuations are also a central topic in the description and understanding of the edge turbulence and particle and heat transport in several studies (HORTON, 1984; THYAGARAJA and HAAS, 1989; WOOTTON et al., 1988). A comparison of theory and experiment concerning heat transport induced by magnetic fluctuations is given by MCCOOL et al. (1989). HOW-LING and ROBINSON (1986) demonstrate on the TOSCA Tokamak that the electrostatic convective thermal transport due to fluctuations is the dominant heat loss mechanism. 'See footnote opposite. * I n this paper we use the following notations. The index " E indicates oscillating quantities caused by the externally coupled perlurbation(l,, B E : effective r.m.s. value^ of current and magnelic induction and B, the amplitude, respectively). The index "0" indicates non-time dependent steady slate quantities. The index "1" indicates time-dependent (fluctuating) quantities (amplitudes), n , / n , is therefore the level of rclativc density fluctuation.
