High time and height resolution neutral wind profile measurements across the mesosphere/lower thermosphere region using the Arecibo incoherent scatter radar

Abstract

A method for estimating the vector neutral wind profiles in the mesosphere and lower thermosphere (MALT) region of the upper atmosphere from Arecibo dual‐beam incoherent scatter radar data is presented. The method yields continuous estimates of both the altitude‐averaged F region plasma drifts and all three components of the altitude‐resolved neutral wind profiles in the MALT using data taken while the Arecibo feed system swings in azimuth. The problem is mixed determined, and its solution is not inherently unique. Second‐order Tikhonov regularization is used to find solutions consistent with the available data while being minimally structured, additional structure being unsupported by the data. The solution is found using the method of conjugate gradient least squares and sparse matrix mathematics. Example data acquired during an interval of midlatitude spread F are used to illustrate the method. The estimated wind profiles exhibit characteristics broadly consistent with gravity waves but are impulsive, with features that generally persist for less than one and a half wave periods.