Steady magnetospheric convection: Statistical signatures in the solar wind and AE

Abstract

We identify steady magnetospheric convection (SMC) whenever AE ≥ 200 nT and AL does not decrease by more than 25 nT in one minute. We demonstrate that the distribution of durations of SMCs has a larger tail than would be expected by assuming that long intervals of SMC are chance conjunctions of shorter SMCs. This implies that the magnetosphere can resist substorm onset and remain in a steady convective state. We also examine the distribution of interplanetary parameters during the long SMCs to determine what conditions are associated with SMCs. We document that solar wind velocity below 450 km s-1 and magnetic field Bz ∼ -3 nT are the hallmarks of the SMC intervals identified by our criteria. We note that the variability of Bz is only somewhat smaller during SMC intervals than during other times. We conclude by demonstrating that the appropriate solar wind conditions alone are not sufficient for producing an SMC.