Non-neutralized Electric Current Patterns in Solar Active Regions: Origin of the Shear-generating Lorentz Force

In addition to bringing nicely shaded colors into play, this cartoon illustrates an ambitious claim: that coronal currents can be non-neutralized. Recall that this implies the existence of an electrostatic potential and charge separation, which lie outside the MHD framework. The long-standing difference between two schools of thought, on this point, in principle ends here with this paper. The mechanism for the unbalanced currents may involve the behavior of the photospheric inversion region (PIL) line, shown here as an unmagnetized region (lower panels) separating two deforming flux tubes, in the plane of the photosphere, forced to interact. Somehow the sheath currents (dark boundaries) required for Parker's "fibril" fields in the solar interior can morph into unbalanced coronal currents via the azimuthal component of the shearing Lorentz force. The Longcope-Welsch cartoon aims at explaining how this happens.