  We present a follow up study of the sensitivity of the Earth's magnetosphere
to solar wind activity using a particles-in-cell model [Baraka and Ben Jaffel,
2007], but here during northward IMF. The formation of the magnetospheric
cavity and its elongation is obtained with the classical structure of a
magnetosphere with parallel lobes. An impulsive disturbance is then applied to
the system by changing the bulk velocity of the solar wind to simulate a
decrease in the solar wind dynamic pressure followed by its recovery. In
response to the imposed disturbance, a gap [abrupt depression] in the incoming
solar wind plasma appears moving toward the Earth. The gap's size is a ~15 RE
and is comparable to the sizes previously obtained for both Bz<0 and Bz =0.
During the initial phase of the disturbance, the dayside magnetopause (MP)
expands slower than the previous cases of IMF orientations as a result of the
depression. The size of the MP expands nonlinearly due to strengthening of its
outer boundary by the northward IMF. Also, during the initial 100 {\Delta}t,
the MP shrank down from 13.3 RE to ~9.2 RE before it started expanding; a
phenomenon that was also observed for southern IMF conditions but not during
the no IMF case. As soon as they felt the solar wind depression, cusps widened
at high altitude while dragged in an upright position. For the field's
topology, the reconnection between magnetospheric and magnetosheath fields is
clearly observed in both northward and southward cusps areas. Also, the tail
region in the northward IMF condition is more confined, in contrast to the
fishtail-shape obtained in the southward IMF case. An X-point is formed in the
tail at ~110 RE compared to ~103 RE and ~80 RE for Bz =0 and Bz <0
respectively. Our findings are consistent with existing reports from many space
observatories for which predictions are proposed to test furthermore our
simulation technique.
