Effect of auroral electrojets and solar wind parameters on variations in the intensity of low-latitude geomagnetic disturbances and Dst during the extremely large magnetic storm of November 20-21, 2003

摘要

The effect of auroral electrojets on the variations in the low-latitude geomagnetic disturbances and Dst during a strong magnetic storm of November 20-21, 2003, with Dst approximate to -472 nT has been studied based on the global magnetic observations. It has been indicated that the magnetospheric storm expansive phase with Delta t approximate to 1-2 h results in positive low-latitude disturbances (Delta H) of the same duration and with an amplitude of similar to 30-100 nT in the premidnight-dawn sector. A growth of negative low-latitude Delta H values and Dst is mainly caused by regular convection electrojets with Delta t >= 10 h, the centers of which shift to latitudes of similar to 50 degrees-55 degrees during the storm development. It has been established that the maximal low-latitude values of the field Delta H component at 1800-2400 MLT are observed when the auroral luminosity equatorward boundary shifts maximally southward during an increase in the negative values of the IMF B-z component. It has been assumed that, during this storm, a magnetic field depression at low latitudes was mainly caused by an enhancement of the partially-ring current which closes through field-aligned currents into the ionosphere at the equatorward boundary of the auroral luminosity zone.