Secular variation of auroral zone location

BRUNO S. ZOSSI; ANA G. ELIAS

Kuhlungsborn

Workshop; 9th Workshop on Long Term Changes and Trends in the Atmosphere; 2016

Leibniz-Institute of Atmospheric Physic, IAGA, SCOSTEP

Changes in the geomagnetic field can deeply modify the auroral zones, which are the regions of most frequent precipitation of energetic particles causing aurora. The present field can be approximated by a magnetic dipole that accounts for ~80% of the magnetic field of the Earth?s surface, plus multipolar components making up the remaining ~20%. During a polarity transition the field magnitude diminishes to about 10% of its normal value at the expense of decreasing the dipolar component and becoming mostly quadrupolar or multipolar in nature. The variation of auroral zones location and shape for different magnetic field configurations is analyzed through different simulations using charged particles path along the field lines and theoretical considerations. As the dipole strength decreases the auroral zones move equatorward and increase their latitudinal extents, modifying their structure when non-dipolar components dominate. In addition to bringing the aurora regularly to low-latitude regions, mid and low-latitude atmosphere may become vulnerable to the direct effects of energetic particle precipitation during these geomagnetic conditions.