Driving dayside convection with northward IMF: Observations by a sounding rocket launched from Svalbard

The first sounding rocket flight into the dayside cusp with dark ground and northward interplanetary magnetic field (IMF) conditions was launched from the new SvalRak range at Ny-Alesund in the Svalbard archipelago in early D ecember 1997. Extensive ground observations of auroral emissions and radar backscatter provided contexts for in situ rocket measurements. Real-time in terplanetary measurements from the Wind satellite aided launch selection wi th foreknowledge of impending conditions. NASA rocket flight 36.153 was lau nched near local magnetic noon while the IMF was dominated by positive B-X and had lesser northward B-Z and negative B-Y components. The rocket's west ward trajectory carried it toward auroral forms associated with morningside boundary layers. The rich set of vector de electric and magnetic fields, e nergetic particles, thermal plasma, plasma waves, and optical emissions gat hered by the rocket reveal a complex electrodynamic picture of the cusp/bou ndary-layer region. Four factors were important in separating temporal and spatial effects: (1) Near the winter solstice the Earth's north magnetic po le tilts away from the Sun, (2) at the UT of the flight the dipole axis was rotated toward dawn, (3) the variability of solar wind driving was low, an d (4) B-X was the dominant IMF component. We conclude that no signatures of dayside merging in the Northern Hemisphere were detected in either the roc ket or ground sensors. Electric field variations in the interplanetary medi um directly correlate with those observed by the sounding rocket, with sign ificantly shorter lag times than estimated for simple propagation between W ind and the ionosphere. The correlation requires that the observed Northern Hemisphere convection structures were stirred in part by merging of the IM F with closed field lines in the Southern Hemisphere, thereby adding open f lux to the northern polar cap. Subsequent motions of adiaroic polar cap bou ndaries were detected in the rocket electric field measurements. The observ ations indicate that IMF B-X significantly affected the location and timing of merging interactions.