Evidence of different magnetotail responses to small solar wind pressure pulses depending on IMF Bz polarity

The response of the magnetotail to small flux rope associated pressure puls es depends on the IMF Bz polaxity. Clear and large amplitude magnetotail re verse polarity South-then-North traveling compression regions (SN TCRs) are observed when the pressure pulse is associated with the northward IMF inte rval of the flux rope. These tail signatures correspond to small-scale (< 1 0 minute duration) pulses of the solar wind dynamic pressure located in fro nt of and within the. small-scale flux ropes. Pressure pulses associated wi th IMF Bz southward are either absent or give rise to smaller amplitude com pressions and less systematic lobe Bz rotations. These results suggest that the orientation of the IMF Bz plays a critical role in modulating the magn etotail response to solar wind dynamic pressure pulses.