English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

We propose a simple model of the flow and currents in\udSaturn's polar ionosphere. This model is motivated by theoretical reasoning,\udand guided quantitatively by <I>in situ </I>field and flow data from space missions,\udground-based IR Doppler measurements, and Hubble Space Telescope images. The\udflow pattern consists of components which represent (1) plasma\udsub-corotation in the middle magnetosphere region resulting from plasma\udpick-up and radial transport from internal sources; (2) the Vasyliunas-cycle\udof internal plasma mass-loss down the magnetospheric tail at higher\udlatitudes; and (3) the polar Dungey-cycle flow driven by the solar wind\udinteraction. Upstream measurements of the interplanetary magnetic field\ud(IMF) indicate the occurrence of both extended low-field rarefaction\udintervals with essentially negligible Dungey-cycle flow, and few-day\udhigh-field compression regions in which the Dungey-cycle voltage peaks at a\udfew hundred kV. Here we model the latter conditions when the Dungey-cycle is\udactive, advancing on previous axi-symmetric models which may be more\uddirectly applicable to quiet conditions. For theoretical convenience the\udoverall flow pattern is constructed by adding together two components - a\udpurely rotational flow similar to previous axi-symmetric models, and a\udsun-aligned twin vortex representing the dawn-dusk asymmetry effects\udassociated with the Vasyliunas-and Dungey-cycle flows. We calculate the\udhorizontal ionospheric current associated with the flow and the\udfield-aligned current from its divergence. These calculations show that a\udsheet of upward-directed field-aligned current flows at the boundary of open\udfield lines which is strongly modulated in local-time by the Dungey-cycle\udflows. We then consider implications of the field-aligned current for\udmagnetospheric electron acceleration and aurorae using two plasma source\udpopulations (hot outer magnetospheric electrons and cool dense magnetosheath\udelectrons). Both sources display a strong dawn-dusk asymmetry in the\udaccelerating voltages required and the energy fluxes produced, resulting\udfrom the corresponding asymmetry in the current. The auroral intensities for\udthe outer magnetosphere source are typically ~50 kR at dawn and\ud~5 kR at dusk, in conformity with recent auroral observations under\udappropriate conditions. However, those for the magnetosheath source are much\udsmaller. When the calculated precipitating electron energy flux values are\udintegrated across the current layer and around the open closed field line\udboundary, this yields total UV output powers of ~10 GW for the hot\udouter magnetosphere source, which also agrees with observations

A model of the plasma flow and current in Saturn's polar ionosphere under conditions of strong Dungey cycle driving