Physics Department Seminar University of Alaska Fairbanks

J O U R N A L    C L U B

An Investigation of the Characteristics of the Convection-Reversal Boundary under Southward Interplanetary Magnetic Field
William Bristow
Geophysical Institute and Electrical Engineering Department

The convection-reversal boundary (CRB) is a feature of the large-scale high-latitude convection pattern that separates sunward plasma flow from anti-sunward plasma flow, which originate from distinct magnetospheric regions. When the interplanetary magnetic field (IMF) is southward, magnetic merging at the nose of the magnetopause leads to a region within which the Earth's magnetic field lines connect to the IMF. This region, the polar cap, generally exhibits antisunward convection because of momentum imparted by the solar wind flow. At lower latitudes magnetic field lines close within the magnetosphere and generally convect sunward to replenish the demand for flux at the dayside merging site. Between the two regions there is another region of antisunward flow due to the so-called viscous interaction that maps within the magnetosphere. Hence, the CRB should occur on closed magnetic field lines at a latitude close to but below the open-closed field line boundary (OCB). Direct comparisons of OCB latitudes determined from particle precipitation to the CRB latitudes determined from SuperDARN observations have shown that on average the boundaries are separated by less than a degree of latitude at most magnetic local times (MLT). This close association with the OCB makes the CRB a good proxy, which can be used to determine the size of the polar cap and the level of magnetic activity.
This work examines the CRB as determined from Super Dual Auroral Radar Network (SuperDARN) observations of convection. Convection patterns were calculated for all intervals within the eleven-year period 2000-2010 when the IMF met a restrictive set of criteria. When there were sufficient observations, the CRB was determined and binned as a function of latitude and magnetic local time. The CRB was modeled as a linear sum of terms dependent on the IMF, the solar wind, and the SymH indicies. Finally, the dynamic behavior of the boundary is discussed and modeled in an attempt to reproduce the observed distributions.

Friday, 4 October 2013
Globe Room, Elvey Building
3:45 PM