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Using DMSP F13 data in conjunction with IMF datawe investigate the newly discoveredchannels of enhanced (1.5–3 km/s) antisunwardconvection occurring at the dawn (06:00–09:00 MLT) or dusk (15:00–18:00 MLT)flanks of the polar cap for different combinations ofIMF By polarity, hemisphere (NH/SH) and the dawn/dusk MLTs.Dawn-side cases where this flow channel appears occur for the followingcombinations:NH-dawn/By>0 and SH-dawn/By<0.The dusk-side cases are: NH-dusk/By<0 and SH-dusk/By>0.The flow channels areplaced in the context of particle precipitation regimes/boundariesand ionospheric conductivity gradients.They are found to be threadedby "old open field lines" ("time sincereconnection" >10 min) characterized bypolar rain precipitation. In the dawn-side cases(NH-dawn/By>0 and SH-dawn/By<0)and in a Parker spiral field,the polar rain containsthe "solar wind strahl" component.The convection enhancementis attributed to the Pedersen current closure of Birkeland currentsheets (C1 and C2) in the polar cap (C1) and at the polar cap boundary (C2).The low ionospheric conductivity in the polarcap, particularly in the winter hemisphere,is compensated by an enhancedelectric field driving the flow channel there.This is momentum transferfrom the solar wind via dynamo action taking place in thecombined current system of the high-and low-latitude boundary layers (HBL/LLBL).The conductivity gradient at the polar cap boundarycontributes to establishing the convection channel and theassociated enhancement of the dawn-dusk convectionasymmetry extending beyond the dawn-dusk terminatorduring intervals of nonzero IMF By component.The HBL/LLBL-ionosphere coupling via Birkeland currentsC1/C2 is a source of dawn-dusk convection asymmetryand Svalgaard-Mansurov effect whichmust be added to the effect of magnetic tension actingon "newly open field lines"

annales geophysicae

Plasma flow channels at the dawn/dusk polar cap boundaries: momentum transfer on old open field lines and the roles of IMF &amp;lt;I&amp;gt;B&amp;lt;sub&amp;gt;y&amp;lt;/sub&amp;gt;&amp;lt;/I&amp;gt; and conductivity gradients