[P-EM10] Dynamics of Magnetosphere and Ionosphere

[PEM10-17] Curved Trajectory Effect on Charge-Exchange Collision at Ionospheric Temperatures

*Akimasa Ieda¹ (1.Institute for Space-Earth Environmental Research, Nagoya University)

Keywords:charge-exchange collision, polarization collision, collision frequency, cross section , electron-transfer, momentum-transfer

Collision between ions and neutral particles is an essential characteristic of Earth's ionosphere. This ion-neutral collision is usually caused by the polarization of neutral particles. This collision can also be caused by charge exchange, if the particle pair is parental, such as atomic oxygen and its ion. The total collision frequency is not the sum of the polarization and charge-exchange components, but is essentially equal to the dominant component. The total is enhanced only around the classic transition temperature, which is near the ionospheric temperature range (typically 200–2000 K). However, the magnitude of this enhancement has differed among previous studies; the maximum enhancement has been reported as 41% and 11% without physical explanation. In the present study, the contribution of the polarization force to the charge-exchange collision is expressed as a simple curved particle trajectory effect. As a result, the maximum enhancement is found to be 22%. It is discussed that the enhancement has been neglected in classic ionospheric studies partly due to confusion with the glancing particle contribution, which adds 10.5% to the polarization component. The enhancement has been neglected presumably also because there has been no functional form to express it. Such an expression is derived in this study.

Ieda (JGR, 2022) https://doi.org/10.1029/2021JA029612