Negative-energy perturbations in cylindrical equilibria with a radial electric field

The impact of an equilibrium radial electric field {bold E} on negative-energy perturbations (NEP{close_quote}s) in cylindrical equilibria of magnetically confined plasmas is investigated within the framework of Maxwell-drift kinetic theory. It turns out that for wave vectors with a nonvanishing component parallel to the magnetic field, the conditions for the existence of NEP{close_quote}s in equilibria with {bold E}={bold 0} [G. N. Throumoulopoulos and D. Pfirsch, Phys. Rev. E {bold 53}, 2767 (1996)] remain valid, while the condition for the existence of perpendicular NEP{close_quote}s, which are found to be the most important perturbations, is modified. For {vert_bar}e{sub i}{phi}{vert_bar}{approx}T{sub i}, a scaling which is satisfied in the edge region of magnetic confinement systems ({phi} is the electrostatic potential), the impact of {bold E} on perpendicular NEP{close_quote}s depends on the value of T{sub i}/T{sub e}, i.e., (a) for T{sub i}/T{sub e}{lt}{beta}{sub c}{approx}P/(B{sup 2}/8{pi}) (P is the total plasma pressure) the electric field does not have any effect; and (b) for T{sub i}/T{sub e}{gt}{beta}{sub c}, a case which is of operational interest in magnetic confinement systems, the existence of perpendicular NEP{close_quote}s depends on e{sub {nu}}{bold E}, where e{sub {nu}} is the charge of the particle species {nu}. In the latter case, for tokamaklike equilibria and H mode parameters pertaining to the plasma edge two regimes of NEP{close_quote}s exist. In the one of them the critical value (2) /(3) of {eta}{sub i}{equivalent_to}{partial_derivative}lnT{sub i}/{partial_derivative}lnN{sub i} plays a role in the existence of ion NEP{close_quote}s, as in equilibria with {bold E}={bold 0}, while a critical value of {eta}{sub e} does not occur for the existence of electron NEP{close_quote}s. (Abstract Truncated)