Model results for the ionospheric E region: solar and seasonal changes

摘要: A new, empirical model for NO densities is developed, to include physically reasonable variations with local time, season, latitude and solar cycle. Model calculations making full allowance secondary produc- tion, ionising radiations at wavelengths down 25 As , then give values the peak density N m E that are only 6% below IRI summer conditions minimum. At maximum di⁄erence in- creases 16%. Solar-cycle changes in EUVAC radi- ation seem insuƒcient explain observed E, any modifications current atmospheric constants. Hinteregger correct change, results just 2% throughout cycle, but too little ionisation E-F valley region. To match increase high-flux reference spectrum needs an overall of about 20% (or 33% if change confined less well defined j(150 ). Observed show a seasonal anomaly, mid-latitudes, 10% higher winter than (for constant zenith angle). Composition MSIS86 produce summer-to-winter !2% northern hemi- sphere, #3% southern hemisphere. Seasonal additional 5% winter, near minimum, anomaly 8% Near maximum, reported suggest much smaller E. Other mechanisms, such as e⁄ects winds or electric fields, inadequate It therefore seems possible satellite data may underestimate mean variation maximum. not unreasonable data, same 2:1 can