Observations of the cusp plasma irregularity with the sounding rocket - ICI-3 Campaign -

第3回極域科学シンポジウム/第36回極域宙空圏シンポジウム 11月27日（火） 国立極地研究所 2階大会議

Dayside auroral configurations: Responses to southward and northward rotations of the interplanetary magnetic field

We report specific types of daytime auroral activities occurring in response to certain rotations of the interplanetary magnetic field (IMF). The IMF rotations we focus on consist of a sharp southward turning from an initial northward orientation, followed by slower rotations back to an intermediate state, which is dominated by the By component (small Bz). When the IMF turned from north to south, the day side auroral configuration changed from one typical of northward conditions to one typical of southward conditions. The type 2 cusp aurora in the north (∼78°–79°magnetic latitude) was replaced by activation of a sequence of moving auroral forms (type 1 cusp aurora) at lower latitudes, each form appearing at the equatorward boundary of the previous one, resulting in ∼100- to 200-km total displacements of the auroral equatorward boundary in the cusp region during intervals of ∼5- to 10-min duration. This auroral activity is accompanied by enhancement of ionospheric convection and onset of magnetic bays on the ground. Since southward rotations of the IMF are expected to give rise to enhancements of the magnetopause reconnection rate, we conclude that these auroral/convection events represent distinct ionospheric signatures of such reconnection rate enhancements. When the IMF turned partially northward again, into an intermediate state, the aurora responded as expected, i.e., the equatorward auroral displacement was halted or reversed, and the type 2 aurora reappeared. The coexistence of the types 1 and 2 cusp auroras in the intermediate state is interpreted in terms of the simultaneous occurrence of reconnections at low and high magnetopause latitudes. The dynamical configurations of particle precipitation and ionospheric convection in the cusp region in such cases are discussed

Optical airglow patches in relation to EISCAT Svalbard Radar electron density measurements

Drifting polar cap patches are localized regions of enhanced F-region plasma densities with scale sizes of several hundreds of kilometre. The patches are seen to drift antisunward with velocities of several hundreds meters per second, and can have densities up to 10 times the ambient background. We present simultaneous ground based optical and radar data of nightside polar cap patches. Using meridian scanning photometer data, the optical airglow signature of patches are seen to drift into the auroral oval. The field aligned radar shows high electron density, with low electron temperature during the period of interest. This indicates that there is no electron precipitation in the radar field of view, and that the radar electron density signal stems from the drifting polar cap patches. It is seen that there is a very good match between enhancements in the 6300 Å airglow signature and enhancements in the radar electron density measurements