HEIGHT-RESOLVED JOULE HEATING RATES IN THE HIGH-LATITUDE-E REGION ANDTHE INFLUENCE OF NEUTRAL WINDS

Height-resolved and height-integrated estimates of the Joule heating r ate in the high-latitude E region that include the effects of the neut ral wind have been derived from measurements made by the Sondrestrom i ncoherent-scatter radar. Analyzed in derail are two Sondrestrom radar data sets that represent solar minimum, daytime conditions with period s of moderate to strong geomagnetic activity. These measurements show much more structure in the height-resolved Joule heating rate when neu tral winds are included in the analysis. The neutral wind impact was p resent during all periods of elevated Joule heating and displayed an a ltitude-dependent influence that led to both positive and negative con tributions within the E region. Most often, the wind impact was to cre ate a much narrower region of Joule heating. The influence of the neut ral wind on the height-integrated Joule heating rate from 90 to 140 km was significant, at times, with observed reductions of 40% and observ ed enhancements of as much as 400%. However, the height-integrated Jou le heating rate often did not reflect the degree of neutral wind influ ence on the local Joule heating rate because the altitude-dependent be havior of the wind would tend to cancel out during the height-integrat ion process. Evidence of electric field behavior controlling the neutr al wind influence on the Joule heating rate was also observed. During directional changes in the electric field, the neutral winds tended to enhance the Joule heating rate, while directionally steady electric f ields resulted in an overall reduction of the Joule heating rate by th e neutral wind.