Distribution of plasma density and potential around a mesothermal ionospheric object

Abstract

For an object moving at mesothermal speeds in a collisionless plasma it is shown that the ion thermal motion as well as the coupling of the disturbances in front of the object to the wake region play significant roles in modifying the plasma environment around the object. The case considered here is a dielectric cylinder moving transverse to its axis in ionospheric plasma. The radius of the cylinder is taken as much larger than the Debye shielding length of the ambient plasma but smaller than the mean free path of the charged particles. For this model, the Vlasov‐Poisson system of equations is numerically solved to determine the distribution of charged particle densities and potential around the cylinder. An important feature of the present work is that a self‐consistent solution is obtained without assuming any decoupling of the plasma in the wake and front regions and without neglecting thermal motion of the ions. The significance of this unified treatment of the environmental plasma in the prediction of possible ion shock wave disturbances is discussed. A range of ion Mach numbers which are typical of conditions found in the ionosphere is used to parameterize the dependence of the distribution of charged particle density on the object velocity. Finally, comparison of our results in the wake region with corresponding in situ measurements shows that the present model underestimates the measured ion depletion by less than an order of magnitude, in contrast to previous theoretical models which overestimate the measured ion depletion by several orders of magnitude.