Case study of solar wind pressure variations and neutral atom emissions observed by IMAGE/LENA

Abstract

The Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft was designed to observe neutral atom emissions at low energy (10 eV-∼4 keV) from the high-latitude ionosphere. In this study we present data from an ion outflow event on 24 June 2000 showing increases in neutral flux that appear to be associated with dynamic pressure variations in the solar wind. Results from a correlation analysis show the neutral flux to be well correlated (∼0.64) with the solar wind dynamic pressure. The neutral atom data are most consistent with a source region at a radial distance of 2.2-2.3 RE, interpreted as the region over which the bulk ion outflow escapes the ionosphere and is partly converted to neutral atoms. Very short time delays (∼2 min) were calculated between the solar wind pressure increase and neutral atom response, indicating a prompt ionospheric response to the solar wind input.