We present a careful statistical analysis of pulsating aurora (PA) using all‐sky green line (557.7 nm) images obtained at 3.3 Hz. Six well‐defined individual PA patches are identified and extracted using a contouring technique. Quantitative parameters such as the patch duration (on‐time and off‐time), peak intensity, and integrated intensity are determined for each patch and each pulsation. The resulting characteristics serve as strict observational constraints that any of the many competing theories attempting to explain PA must predict. The purpose of this paper is to determine the characteristics of PA patches in order to provide better observational constraints on the suggested mechanisms. All aspects of the temporal behavior of the individual patches appear to be erratic. Historically, PA has been defined very loosely and we argue that the use of the term “pulsating” is inappropriate since our findings and other published results are not regularly periodic and thus a more appropriate term may be fluctuating aurora. Further, we find that the observational constraints do not fit well with the flow cyclotron maser theory, which in particular is suggested to create PA patches. There is no clear candidate of the suggested mechanisms and drivers to explain the observational constraints set by the PA patches in a satisfactory manner.

Five hours of simultaneous global imaging data from the conjugate hemispheres are used to examine the dynamics of the auroral substorm. Earlier studies have demonstrated that substorm onset locations in the two hemispheres are systematically displaced due to the orientation of the interplanetary magnetic field. In this paper we present, for the first time, how the asymmetric auroras induced by the IMF orientation at substorm onset disappears during the expansion phase. We suggest that this is the large scale manifestation of auroral arcs as being the sites of magnetic stress release. Magnetic stress on field lines with asymmetric footpoints can lead to a net hemispherical difference in parallel electric field strength which implies that the auroras move with different speeds in the two hemispheres to release the magnetic stress. The relative velocity can be derived from the potential between the hemispheres. During expansion phase the twisted magnetic fields are rectified, bringing the closed magnetic field lines back to the configuration defined by the Earth's interior.

Large thermospheric neutral density enhancements in the cusp region have been examined for many years. The Challenging Minisatellite Payload (CHAMP) satellite for example has enabled many observations of the perturbation, showing that it is mesoscale in size and exists statistically over solar cycle timescales. Further studies examining the relationship with magnetospheric energy input have shown that fine‐scale Poynting fluxes are associated with the density perturbations on a case‐by‐case basis, whilst others have found that mesoscale downward fluxes also exist in the cusp region statistically. In this study, we use nearly 8 years of the overlapping Super Dual Auroral Radar Network and Active Magnetosphere and Planetary Electrodynamics Response Experiment datasets to generate global‐scale patterns of the high‐latitude and height‐integrated Poynting flux into the ionosphere, with a time resolution of 2 min. From these, average patterns are generated based on the interplanetary magnetic field orientation. We show the cusp is indeed an important feature in the Poynting flux maps, but the magnitude does not correlate well with statistical neutral mass density perturbations observed by the CHAMP satellite on similar spatial scales. Importantly, the lack of correlation between mesoscale height‐integrated Poynting fluxes and the cusp neutral mass density enhancement gives possible insight into other processes that may account for the discrepancy, such as energy deposition at finer scale sizes or at higher altitudes than captured.

The pulsating aurora covers a broad range of fluctuating shapes that are poorly characterized.The purpose of this paper is therefore to provide objective and quantitative measures of the extent to which pulsating auroral patches maintain their shape, drift and fluctuate in a coherent fashion. We present results from a careful analysis of pulsating auroral patches using all-sky cameras. We have identified four well-defined individual patches that we follow in the patch frame of reference. In this way we avoid the space-time ambiguity which complicates rocket and satellite measurements. We find that the shape of the patches is remarkably persistent with 85-100% of the patch being repeated for 4.5-8.5 min. Each of the three largest patches has a temporal correlation with a negative dependence on distance, and thus does not fluctuate in a coherent fashion. A time-delayed response within the patches indicates that the so-called streaming mode might explain the incoherency. The patches appear to drift differently from the SuperDARN-determined ⃗ E × ⃗ B convection velocity. However, in a nonrotating reference frame the patches drift with 230-287 m/s in a north eastward direction, which is what typically could be expected for the convection return flow.