סמינר בחוג לגיאופיזיקה: Solar Activity, and Planetary Atmospheric Escape
Prof. Leon Ofman, NASA-Goddard Space Flight Center
Planetary atmospheres are subject to losses due to thermal (Jeans) escape, induced by solar radiation, as well as other loss mechanisms. Energetic processes in the Earth’s upper atmosphere induced by solar plasma activity, such as geomagnetic storms and the solar wind produce the ring current and energetic ions. These processes result in heated magnetized plasma in Earths’ ionosphere, and likely similar processes in other solar system bodies, leading to preferential energization of ions such as O+, and their eventual escape from the Earth’s atmosphere. I will provide an overview of planetary atmospheric loss mechanisms, and present the results of the model of O+ ion pickup and thermalization using the 2.5D hybrid simulation method (with fluid electrons and kinetic ions) of the ion ring distributions, formed in the auroral ionosphere, with a range of ring velocities and thermal to magnetic pressure ratios. Using the model, we find that the collsionless regime the plasma becomes unstable, and the relaxation of the instability leads to ion heating, facilitating enhanced atmospheric escape. I will discuss the results and the implications for the Earth and other planetary atmospheres.
מארגן הסמינר: פרופ' איל חפץ