Event Title

A quantitative assessment of the role of soft electron precipitation on global ion upwelling

Location

Yosemite National Park

Start Date

2-12-2014 5:10 PM

End Date

2-12-2014 5:25 PM

Description

We find that, in general, existing models of electron precipitation underestimate the soft electron component which is a prime driver of O+ upwelling. Our conclusion is supported by a detailed study of the relative influence of electron precipitation on upwelling O+ during quiet times producing upwelling O+ in the nightside auroral zone. We use the Field Line Interhemispheric Plasma (FLIP) ionospheric model to study the upwelling O+ on 40 field lines distributed across the auroral zone and magnetic local times, turning precipitation on and off as field lines move in and out of the auroral zone. We investigate the efficacy of electron precipitation patterns derived from the OVATION Prime and Hardy et al., [2008] models to produce upwelling O+ as a function of MLT and latitude. Our results indicate that during quiet times soft e- precipitation in the evening hours plays a critical role in controlling upwelling O+ in the cold night-side ionosphere but plays a relatively modest role in facilitating energetic O+ escape on the dayside. Detailed comparisons between the model output and statistical DMSP observations at 850 km show that the combination of using the output of two standard precipitation models during a quiet equinoctial period (Kp = 2, Ap = 7) as a single Maxwellian precipitating electron distribution input to this model does not sufficiently reproduce average observed upwelling fluxes in the nightside auroral zone. It is likely that an influential quantity of electron energy flux at sub 100 eV characteristic energies is unaccounted for in the standard models of electron precipitation. We have then devised an auroral electron precipitation pattern consisting of single modal Maxwellian distributions, which produces upwelling O+ fluxes that are in reasonable agreement with the DMSP observations as reported by Redmon et al., [2010].

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Feb 12th, 5:10 PM Feb 12th, 5:25 PM

A quantitative assessment of the role of soft electron precipitation on global ion upwelling

Yosemite National Park

We find that, in general, existing models of electron precipitation underestimate the soft electron component which is a prime driver of O+ upwelling. Our conclusion is supported by a detailed study of the relative influence of electron precipitation on upwelling O+ during quiet times producing upwelling O+ in the nightside auroral zone. We use the Field Line Interhemispheric Plasma (FLIP) ionospheric model to study the upwelling O+ on 40 field lines distributed across the auroral zone and magnetic local times, turning precipitation on and off as field lines move in and out of the auroral zone. We investigate the efficacy of electron precipitation patterns derived from the OVATION Prime and Hardy et al., [2008] models to produce upwelling O+ as a function of MLT and latitude. Our results indicate that during quiet times soft e- precipitation in the evening hours plays a critical role in controlling upwelling O+ in the cold night-side ionosphere but plays a relatively modest role in facilitating energetic O+ escape on the dayside. Detailed comparisons between the model output and statistical DMSP observations at 850 km show that the combination of using the output of two standard precipitation models during a quiet equinoctial period (Kp = 2, Ap = 7) as a single Maxwellian precipitating electron distribution input to this model does not sufficiently reproduce average observed upwelling fluxes in the nightside auroral zone. It is likely that an influential quantity of electron energy flux at sub 100 eV characteristic energies is unaccounted for in the standard models of electron precipitation. We have then devised an auroral electron precipitation pattern consisting of single modal Maxwellian distributions, which produces upwelling O+ fluxes that are in reasonable agreement with the DMSP observations as reported by Redmon et al., [2010].