  With the global view and high-cadence observations from SDO/AIA and STEREO,
many spatially separated solar eruptive events appear to be coupled. However,
the mechanisms for "sympathetic" events are still largely unknown. In this
study, we investigate the impact of an erupting flux rope on surrounding solar
structures through large-scale magnetic coupling. We build a realistic
environment of the solar corona on 2011 February 15 using a global
magnetohydrodynamics (MHD) model and initiate coronal mass ejections (CMEs) in
active region (AR) 11158 by inserting Gibson-Low analytical flux ropes. We show
that a CME's impact on the surrounding structures depends not only on the
magnetic strength of these structures and their distance to the source region,
but also on the interaction between the CME with the large-scale magnetic
field. Within the CME expansion domain where the flux rope field directly
interacts with the solar structures, expansion-induced reconnection often
modifies the overlying field, thereby increasing the decay index. This effect
may provide a primary coupling mechanism underlying the sympathetic eruptions.
The magnitude of the impact is found to depend on the orientation of the
erupting flux rope, with the largest impacts occurring when the flux rope is
favorably oriented for reconnecting with the surrounding regions. Outside the
CME expansion domain, the influence of the CME is mainly through field line
compression or post-eruption relaxation. Based on our numerical experiments, we
discuss a way to quantify the eruption impact, which could be useful for
forecasting purposes.
