  Here, we present a case study of THEMIS and ground-based observations on the
dayside magnetopause, and geomagnetic field perturbations related to the
interaction of an interplanetary directional discontinuity (DD), as observed by
ACE, within the magnetosphere on 16 June 2007. The interaction resulted in a
large-scale local magnetopause distortion of an
'expansion-compression-expansion' (ECE) sequence that lasted for 15 min. The
compression was caused by a very dense, cold, and fast high-beta magnetosheath
plasma flow, a so-called plasma jet, whose kinetic energy was approximately
three times higher than the energy of the incident solar wind. The plasma jet
resulted in the effective penetration of the magnetosheath plasma inside the
magnetosphere. A strong distortion of the Chapman-Ferraro current in the ECE
sequence generated a tripolar magnetic pulse 'decrease-peak-decrease' (DPD)
that was observed at low and middle latitudes by the INTERMAGNET network of
ground-based magnetometers. The characteristics of the ECE sequence and the
spatial-temporal dynamics of the DPD pulse were found to be very different from
any reported patterns of DD interactions within the magnetosphere. The observed
features only partially resembled structures such as FTE, hot flow anomalies,
and transient density events. Thus, it is difficult to explain them in the
context of existing models.
