[1] 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] We present the first systematic observational evidence for a traveling periodic structure in the pre-onset optical aurora -the longitudinally propagating arc wave (LPAW) -associated with flapping oscillations in the magnetotail. The LPAW is characterized by azimuthally moving intensity enhancements inside auroral arcs as seen by THEMIS ground-based all-sky imagers. It travels westward in the pre-midnight auroral sector during the 10-20 minutes preceding auroral breakup with a velocity of 2 -10 km/s, time period 40-110 s, and wavelength 250 -420 km. Magnetically conjugate measurements by THEMIS satellites show low frequency plasma oscillations consistent with the parameters of the arc wave in the course of current sheet thinning. When mapped into tail, wavelength (4800 -9400 km) and velocity (70 -190 km/s) of the LPAW are compatible with observations and theoretical predictions for current sheet flapping motions. Our results strongly suggest that LPAW is an auroral footprint of the drift wave mode (kink, sausage, ballooning, etc.) in a stretched magnetotail.Citation: Uritsky, V. M.,

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Abstract. We present riometer and in situ observations of a substorm electron injection on 27 August 2001. The event is seen at more than 20 separate locations (including ground stations and 6 satellites: Cluster, Polar, Chandra, and 3 Los Alamos National Laboratory (LANL) spacecraft). The injection is observed to be dispersionless at 12 of these locations. Combining these observations with information from the GOES-8 geosynchronous satellite we argue that the injection initiated near geosynchronous orbit and expanded poleward (tailward) and equatorward (earthward) afterward. Further, the injection began several minutes after the reconnection identified in the Cluster data, thus providing concrete evidence that, in at least some events, near-Earth reconnection has little if any ionospheric signature.

[1] The central plasma sheet is a complex magnetized plasma structure located in the equatorial plane of the magnetotail from where substorms are believed to originate. Dynamically, it may behave like a self-organized critical (SOC) system, driven by the slow energy input of the solar wind. The power law distributions for the sizes, energies, and durations of substorms that are reflected in observations can be reproduced using such SOC models. However, the expected scale invariance does not seem to hold for all scale ranges and observables. Recent observations of all-sky auroras have suggested a dual regime, where small and large events scale as different power laws, the smaller events having a steeper slope. On the other hand, scale-dependent substorm behavior can materialize as a consequence of an energy loading-unloading cycle. Accordingly, we designed a 2-D SOC model subject to global deterministic driving and a nonconservative redistribution law. This model can reproduce the coexistence of two scaling regimes, with the second regime appearing as a consequence of the enhanced spatial development of avalanches caused by a higher spatial intermittency in the energy gradients. Thresholded interevent waiting time statistics showed a well-defined peak with an exponential tail, consistent with observations and the expected dynamics of a loading-unloading cycle. Finally, we show that the coherency index extracted from the simulations decreases prior to large avalanches, as is in fact observed in auroral arcs. This suggests that the coherency index may be a useful substorm predictor.Citation: Vallières-Nollet, M.-A., P. Charbonneau, V. Uritsky, E. Donovan, and W. Liu (2010), Dual scaling for self-organized critical models of the magnetosphere,