ALBERT

Beschreibung: Fast azimuthal auroral expansion and poleward expansion are characteristic features of the expansion phase of substorms. In the first study of its kind, we have investigated the azimuthal auroral expansion and its magnetospheric counterpart using data from Time History of Events and Macroscale Interactions during Substorms (THEMIS) all-sky imagers and multiple spacecraft. During the tail season in 2008–2009, we found 16 events of azimuthally expanding aurora that passed near the magnetic footprints of the multiple spacecraft operating in the near-Earth plasma sheet. In the magnetosphere, these events commonly showed fast azimuthal and earthward flows associated with intense electric fields and magnetic dipolarization. The speed of the propagating structure, which was estimated from the time difference of the depolarization observed by the multiple spacecraft, was close to the measured azimuthal plasma flow velocity. We also found that this azimuthal plasma transport was dominated by the E × B drift speed associated with the enhanced electric field. In a statistical analysis, the averaged speeds of the leading edge of the westward and eastward auroral expansion were 8.8 and 5.3 km/s, respectively. When mapped onto the equatorial magnetosphere, these speeds (267 and 162 km/s) were comparable to the averaged azimuthal plasma (E × B) flow speeds observed by the spacecraft, which were 193 (239) km/s in the westward direction and 112 (139) km/s in the eastward direction. Our events showed that E × B flows and auroral expansion predominantly propagated westward, indicating an effect of westward background convection in the Harang flow shear. From these results, we concluded that the azimuthal auroral expansion was closely related to magnetic dipolarization which expanded azimuthally at the E × B drift speed. On the basis of the abrupt formation of the fast E × B flows and their propagation away from the onset location, we suggest that the effects of the intense large-scale electric fields, which are possibly generated through substorm onset turbulence, propagate to the ionosphere along the magnetic field lines and lead to azimuthal expansion of an auroral arc.

Beschreibung: The neutron profile monitor stably operated at a high-count-rate for deuterium operations in the Large Helical Device has been developed to enhance the research on the fast-ion confinement. It is composed of a multichannel collimator, scintillation-detectors, and a field programmable gate array circuit. The entire neutron detector system was tested using an accelerator-based neutron generator. This system stably acquires the pulse data without any data loss at high-count-rate conditions up to 8 × 10 5 counts per second.

Beschreibung: Abstract Molecular ions in the magnetosphere can be a tracer of fast ion outflows from the deep ionosphere. Statistical properties of molecular ions (O2+/NO+/N2+) in the ring current are investigated based on ion composition measurements (〈180 keV/q) by MEPi and LEPi instruments onboard the Arase (ERG) satellite. The investigated period from late March to December 2017 includes 11 geomagnetic storms with the minimum Dst index less than ‐40 nT. The molecular ions are observed in the region of L=2.5‐6.6 and clearly identified at energies above ~12 keV during most magnetic storms. During quiet times, molecular ions are not observed. The average energy density ratio of the molecular ions to O+ is ~3 percent. The ratio tends to increase with the size of magnetic storms. Existence of molecular ions even during small magnetic storms suggests that the fast ion outflow from the deep ionosphere occurs frequently during geomagnetically active periods.