Tail-Lobe Current Loops Powered Directly by the Solar Wind Drive Magnetic Storms and Auroral Substroms

Abstract:

Abstract: The solar wind (SW) dynamo currents generated in the tail magnetopause close spontaneously by the cross-tail currents to form tail-lobe current loops (TLCLs), which convert SW kinetic energy directly to kinetic-thermal energy in the plasma sheet. The Lorentz force of the cross-tail current drives the global earthward convection against the pressure-gradient force leading to enhanced plasma pressure at the expense of the convection. Dayside reconnection produces open field lines to turn on the SW dynamo. Tail reconnection ejects flow bursts and replenishes closed field lines to sustain the plasma sheet to function as a motor. The tail-lobe current loops enhance the plasma pressure in the plasma sheet, not only to intensify the storm-time ring current, but also to enhance the oval conductance to form the Cowling electrojet current loop (CECL). An Alfvén wavefront leads the propagation of CECL towards the plasma sheet. Impingement of the Alfvén wavefront on the near-Earth plasma sheet disrupts the cross-tail current to trigger the dipolarization onset. The energy generated by the tail-lobe current loops in the plasma sheet during the main phase of a storm with Dst ~ -150 nT is estimated at W_PS ~ 2.0×10¹⁷ J, based on the TS05 empirical field model. Energy of the storm-time ring current with Dst ~ -150 nT is estimated at W_RC ~ 1.9 ×10¹⁶ J. Energy dissipated in a substorm with AL ~ -1000 nT is estimated at W_AS ~1.6×10¹⁵ J.