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We present ground-based and in situ observations from March 13, 2007. The THEMIS satellites were in the evening sector conjugate to THEMIS ground-based imagers. At ∼0507 UT there was an optical onset on inner CPS field lines. This involved near-simultaneous brightening of 1 MLT hour longitudinal segment of the onset arc. The part of the arc that brightened was that closest to the equatorward boundary of the diffuse (proton) aurora. Within one minute, a dipolarization front moved across four THEMIS satellites. Based on their locations, the order in which they detected the dipolarization front, and the auroral evolution, we assert that the expansion phase began earthward of the four satellites and evolved radially outwards. We conclude that this onset occurred in an azimuthally localized region of highly stretched field lines.

[1] Recently, Robinson et al. [2000] presented a brief report on the artificial generation of ULF waves by high power ionospheric modification and their subsequent detection by the Fast Auroral Snapshot ( FAST) spacecraft. The radio frequency "heating'' facility at Tromso was employed to impose a 3-Hz modulation on the current system that constitutes the auroral electrojet, resulting in the injection of field-guided ULF waves into the magnetosphere. The electric and magnetic field signatures of the waves were detected directly by the FAST spacecraft. Furthermore, a signature in the downgoing field-aligned electron flux, also observed by the satellite, was postulated to have resulted from the interaction of the ULF waves with the upper boundary of the ionospheric Alfven resonator. This paper evaluates these results in the context of the prevailing ionospheric conditions during the experiment and discusses the significance of the substorm activity, which occurred during this interval. The technique of artificial ULF wave injection, which can be used to "tag'' narrow flux tubes, could play an important part in overcoming mapping issues between ground-based and space-based observations of phenomena that couple the ionosphere and magnetosphere.

We report in-situ detection by two spacecraft of oppositely directed jets of plasma emanating from a magnetic reconnection site at the Earth’s dayside magnetopause, confirming a key element inherent in all reconnection scenarios. The dual-spacecraft (Equator-S and Geotail) observations at the flank magnetopause, together with SuperDARNHalley radar observations of the subsolar cusp region, reveal the presence of a rather stable and extended reconnection line which lies along the equatorial magnetopause. These observations were made under persistent southward interplanetary magnetic field (IMF) conditions, implying that under these conditions the reconnection sites are determined by the large-scale interactions between the solar wind magnetic field and the dayside magnetosphere, rather than by local conditions at the magnetopause. Control by local conditionswould result in patchy reconnection, distributed in a less well-organized fashion over the magnetopause surface.

Results are reported from an experiment in which the HF high power facility at Tromsø was utilised to inject artificial ULF waves into the magnetosphere by means of modulated heating of the auroral electrojet. Local electric field oscillations associated with the artificially stimulated ULF waves were detected on board the FAST spacecraft, at an altitude of 2550 km. In addition, a modulated downward flux of electrons was also detected. The artificially excited waves, together with these energised downward electrons, were observed in a narrow region only a few tens of km across the geomagnetic field, which mapped down the geomagnetic field line to the heated volume in the ionosphere. Furthermore, the downward flux exhibited energy dispersion in a manner that was consistent with the artificially excited waves having followed the geomagnetic field line out beyond the spacecraft, where they appear to have stimulated electron precipitation back down the field line.