Evidence for anomalous cowling conductivity in the strongly driven equatorial electrojet and a reconciliation of magnetic field data with theory

Abstract

Several days of continuous incoherent scatter radar observations during the November 2004 magnetic superstorm are available, as well as data from the CHAMP [CHAllenging Minisatellite Payload] satellite magnetic fiel d detector. We have found that, for zonal electric fields greater than about 1 mV/m, the linear relationship between CHAMP-deduced electric fields and Jicamarca-measured electric fields breaks down. We find that the observed magnetic field is a factor of two smaller than expected for the largest zonal electric field (3.2 mV/m) observed simultaneously in time and nearby spatially with CHAMP. The fact that similar decreases in the effective conductivity occurred during both normal and counter-electrojet conditions indicates that Farley-Buneman waves must be the source of the physical mechanism for the reduced current. In addition, we provide an explanation for a long standing (more than 35 years) discrepancy between theory and (rocket) experiments, concerning the peak height of the electrojet and the magnetic field perturbation. The correction by a factor of four of the electron-neutral collision frequency thought to explain this problem is not necessary if the field line integrated conductivities are used.