Abstract
Due to the sparsity of space probes, it is still not clear on how the
magnetic structure of the magnetotail looks like and how it evolves when
the Interplanetary Magnetic Field (IMF) directs northward. This
simulation study uses two different global magnetosphere MHD models to
simulate two northward IMF events and study the evolution of the
magnetotail. Both models show that the magnetotail may form a structure
that is composed of a dawnside tail lobe and a duskside tail lobe
instead of a northern tail lobe and a southern tail lobe under southward
IMF conditions. In this magnetic configuration, a tail lobe extends a
domain from northern (southern) cusp to southern (northern) IMF. The
bigger the magnitude of IMF clock angle, the longer and wider the
magnetotail. Such magnetic configuration suggests that magnetotail
reconnection is possible to occur when the dawnside tail lobe contacts
with the duskside tail lobe and thus a substorm is also possible to
occur under northward IMF conditions with significant By.