Nonlinear correlations in phase-space resolved fluctuations at drift wave frequencies
In an effort to better understand plasma transport, we measure fluctuations associated with drift instabilities resolved in the ion phase-space. Primary attention is given to fluctuations near the electron drift frequency where there are two general components to the observed fluctuations. From two (spatial) point measurements of the ion distribution function with a variable separation along the magnetic field, a number of statistical measures of the fluctuations are calculated including cross-correlation and cross-bicoherence. Both fluid (omega/k >>upsilon(ti)) and kinetic (omega/k similar to upsilon(ti)) components are observed in the fluctuations. The nonlinear interactions are found to depend strongly on the ion particle velocity.