NASA/NOAA..
IIA. Geophysical Activity Summary 04/2100Z to 05/2100Z:
The geomagnetic field was at quiet levels. The Ace spacecraft observed an IP shock at 05/1804Z. The greater than 2 MeV electron flux at geosynchronous orbit was at high levels throughout the period.

IIB. Geophysical Activity Forecast: Geomagnetic field activity is expected to be at quiet to unsettled levels for the next three days (06 - 08 April) in response to the IP shock mentioned above and coronal hole high speed effects.

Harvard..
Interaction of interplanetary (IP) shocks with the Earth's magnetosphere is a key problem of the Space Weather Program because their interaction often (but not always) leads to major geomagnetic storms. According to already published papers, a fast forward shock passing through the bow shock would generate a train of new discontinuities that differ along the bow shock surface. However, IP shocks are often accompanied with a rotation of the interplanetary magnetic field (IMF) over a large angle and this rotation modifies the interaction process. Since the huge interaction region can be covered by simultaneous spacecraft observations only sporadically, global MHD modeling can help in our understanding of these processes. Using one IP shock observed by Geotail, we compare its passage through the magnetosphere with a model prediction of the global BATS-R-US MHD code. We slightly change upstream conditions in several model runs to order to separate effects of the IP shock itself from the effects of the IMF rotation. The results show that IMF rotations intensify the IP shock influence and lead to a more complex character of the resulting discontinuities.
[link to adsabs.harvard.edu]