Comparison of SuperDARN radar boundaries with DMSP particle precipitation boundaries

[1] Auroral boundary algorithms for SuperDARN ionospheric convection observations are introduced. Both the equatorward boundary of scatter (EBS) and the convection reversal boundary (CRB) are found and compared with boundaries based on DMSP particle precipitation observations. These comparisons provide an intercalibration between the two schemes and insight into the relationship between disparate phenomena. The EBS is reliably poleward of the equatorward boundary of precipitation (EBP) at most local times but centers well on the equatorwardmost precipitation between 1600 and 2200 MLT when within 8° latitude of the radar station, indicating a correspondence with the SLERPS (slow long-lived E region plasma structures) of Jayachandran. Near dawn the EBS coincides better with the structured–unstructured boundary (SUB) than the EBP, as one might expect if the ionospheric irregularities responsible for this scatter were produced by the gradient-drift instability. The CRB correlates well with the open-closed boundary (OCB) as seen by DMSP. There is, however, an equatorward offset of the CRB relative to the OCB that varies from zero near noon to ∼1° near dawn and dusk and is largest near midnight. This offset is consistent with a small viscous-like interaction between the magnetosheath and the low-latitude boundary layer, resulting in a degree of antisunward flow on closed field lines. The offset decreases under the influence of southward interplanetary magnetic field, as one might expect if increased dayside merging interfered with this effect.