[1] Magnetopause reconnection is investigated with our 3-D self-consistent global hybrid simulation model. The magnetic configuration and evolution of Flux Transfer Events (FTEs) and the associated ion density and ion velocity distribution at various locations on the magnetopause are investigated. The results reveal the following. (1) Multiple X lines are formed during the magnetopause reconnection, which lead to both FTEs and quasi-steady-type reconnection under a steady solar wind condition. The resulting bipolar signature of local normal magnetic field of FTEs is consistent with satellite observations. (2) A greater-than-20% plasma temperature rise is seen at the center of a FTE, compared to that of the upstream plasma in the magnetosheath. The temperature enhancement is mainly in the direction parallel to the magnetic field because of the mixing of ion beams. (3) Flux ropes that lead to FTEs form between X lines of finite lengths and evolve relatively independently. The ion density is enhanced within FTE flux ropes because of the trapped particles, leading to a filamentary global density. (4) Different from the previous understanding based on the asymmetric density across the magnetopause, a quadrupole magnetic field signature associated with the Hall effects is found to be present around FTEs.

[1] Magnetic reconnection is an important process in astrophysical, space and laboratory plasmas. The magnetic null pair structure is theoretically suggested to be a crucial feature of the three-dimensional magnetic reconnection. The physics around the null pair, however, has not been explored in combination with the magnetic field configuration deduced from in situ observations. Here, we report the identification of the configuration around a null pair and simultaneous electron dynamics near one null of the pair, observed by four Cluster spacecraft in the geomagnetotail. Further, we propose a new scenario of electron dynamics in the null region, suggesting that electrons are temporarily trapped in the central reconnection region including electron diffusion region resulting in an electron density peak, accelerated possibly by parallel electric field and electron pressure gradient, and reflected from the magnetic cusp mirrors leading to the bi-directional energetic electron beams, which excite the observed high frequency electrostatic waves.

[1] A three-dimensional (3-D) global hybrid simulation is carried out for the generation and structure of magnetic reconnection in the magnetosheath because of the interaction of an interplanetary tangential discontinuity (TD) with the bow shock and magnetosphere. Runs are performed for solar wind TDs possessing different polarization senses of magnetic field (north-to-south or south-to-north from the leading to trailing side of the incident TD) and initial half-widths. Two-step compression processes are shown in the transmitted TD, including a "shock compression," as the TD passes through the shock followed by a subsequent "convective compression" while the TD is moving in the magnetosheath toward the magnetopause. In cases with a relatively thin solar wind TD, 3-D patchy reconnection is initiated in the transmitted TD, forming magnetosheath flux ropes. Differences between these flux ropes and those due to magnetopause reconnection are discussed. Multiple components of ion particles are present in the velocity distribution in the magnetosheath merging, accompanied by ion heating. For cases with a relatively wide initial TD, a dominant single X line appears in the subsolar magnetosheath after the transmitted TD is narrowed through the two-step compression process. Specifically, in the cases with a south-to-north field rotation across an incident thin TD, the magnetosheath flux ropes could re-reconnect with the closed geomagnetic field lines to generate a closed field line region with mixed magnetosheath and magnetospheric plasmas, which may contribute to the transport of solar wind plasma into the magnetospheric boundary layer.

Experiments are described on the propagation of corona discharges over the surfaces of cylindrical PTFE and porcelain insulators under positive impulse voltages. A rod-plane electrode arrangement has been used to which a single value of peak voltage, with the same impulse profile, has been applied throughout. Quantities measured were inception times and voltages, corona current and light output at selected axial regions of the corona. Still photographs of the corona appearance have been taken. Comparison has been made between the surface corona and that in air alone. Interpretation is based on knowledge of the electric field profiles, as modified by the insulators and the possible effects of the surface on the discharge. These are discussed in terms of the presence or absence of charge attachment, the effects of the surface on electron production and the effect of the permittivity of the materials.

[1] With a 3-D global-scale hybrid simulation model, we investigate the energy spectra of cusp precipitating ions and issues associated with magnetopause reconnection under a southward IMF. Both the spatial and temporal energy spectra of cusp precipitating ions are computed by tracing trajectories of the transmitted magnetosheath ions. The spatial spectrum shows a dispersive feature consistent with satellite observations, with higher energy particles at lower latitudes and lower energy particles at higher latitudes. The simulation reveals (1) how and where particles are transmitted from the solar wind into the magnetosphere via direct magnetic reconnection on the dayside; (2) how the features of the spectra are related to ongoing magnetic FTEs; and (3)