Eine Modellvorstellung für das „Auroral Afterglow“ und das „Pink Afterglow“

Abstract

Based on own measurements of the decay of light intensity and electron density, a simple model for the auroral afterglow and the pink afterglow is proposed.

To a certain extent the model can account for the influence of pressure and tube diameter on the behaviour of the afterglow. The first decay of the electron density towards the first minimum seems not to be influenced by creation processes for electrons during 3 to 15 ms. Therefore, the first decay can be used to measure the neutralization processes of electrons and positive ions. At pressures lower than 3 torr the electrons are removed by ambipolar diffusion with a rate given byD _a ·p≈2100 torr·cm²·s⁻¹. From this value an electron temperature of about 7200 °K could be derived. Assuming that ambipolar diffusion will remain the dominant loss process the time dependence of the electron creation rate has been evaluated. At a pressure of 1,75 torr the maximum electron creation rate was 4·10¹² s⁻¹·cm⁻³. At the same time the emission density rate of the first negative bands was found to be 2.7·10¹³ cm⁻³ s⁻¹. During one decay process about five times more electrons are created than the initial number. To explain the proportionality found between the electron density and the emission of the first negative bands, it is assumed that the ions, presumable N ⁺₂ -ions, are repeatedly excited to theB ² Σ ⁺ _u -state by metastables.