VLF reflection properties of the normal and disturbed polar ionosphere in northern Greenland

Abstract

This paper describes long‐wave reflection properties of the high‐latitude ionosphere, observed under both quiet and highly disturbed conditions. The data were obtained using a short‐pulse VLF ionosounder located within the polar cap, in northern Greenland. Under quiet ionospheric conditions, substantial diurnal, day‐to‐day, seasonal, and solar cycle variations were observed. During polar cap absorption events the VLF reflection properties of the disturbed ionosphere depended greatly on the solar illumination conditions, as well as the magnitude of the incoming energetic particle flux. The use of the steep‐incidence VLF reflection data to develop and validate models of the lower ionosphere is discussed; and electron density profiles are given, derived from reflection data obtained during quiet and disturbed conditions.