Dayside and nightside segments of a polar arc: The particle characteristics

Abstract

[1] Using multiple satellites and a ground-based radar network, the physical characteristics of a polar arc and its evolution are investigated under quiet solar wind conditions. The average electron energy is higher at the near-midnight segment than at the sunward extension of the polar arc. Both polar arc segments are positioned primarily on closed magnetic field lines. The convection reversal boundary in the fitted convection pattern was located close to the transition region in the average electron energy seen by the satellites. The topside plasma density at an altitude of 680 km is clearly enhanced around the polar arc, although the enhancement boundary does not coincide precisely with that of the precipitation. The temporal sequence of auroral images suggests that the polar arcs emerged from a double oval structure. This suggestion is supported by the observed physical characteristics of the polar arc, which are quite similar to those of double oval structures that have been reported previously.

Transpolar arc observation after solar wind entry into the high‐latitude magnetosphere

“…There exist several other observations showing different flow directions on the same transpolar arc, which strengthens the idea suggested by Eriksson et al's [2005] [e.g., Liou et al, 2005;Nielsen et al, 1990]. The observations of the electron precipitation at the dayside and nightside parts [Park et al, 2012] also point to the difference between these regions. For the event of 27 September 2004 event, the GUVI high-resolution data also show some fine structure of the transpolar arc.…”

“…The average energy of the electrons is about several hundreds eV. The values are in a good agreement with typical values reported in previous studies [see, for example, Park et al, 2012]. Ion precipitations are much weaker than the electron precipitations, which mean that DMSP passes an aurora precipitation region, where electrons move toward the Earth and ions flow in opposite direction [Iijima et al, 1984].…”

“…'s [] [e.g., Liou et al , ; Nielsen et al , ]. The observations of the electron precipitation at the dayside and nightside parts [ Park et al , ] also point to the difference between these regions. For the event of 27 September 2004 event, the GUVI high‐resolution data also show some fine structure of the transpolar arc.…”