Abstract
Abstract. On 6 January 1998 an interplanetary shock hit the magnetosphere around 14:15 UT and caused a reconfiguration of the northern high-latitude ionospheric convection. We use SuperDARN, spacecraft and ground magnetometer data to study such reconfiguration. We find that the shock front was tilted towards the morning flank of the magnetosphere, while the Interplanetary Magnetic Field (IMF) was By-dominated, with By<0, IMF Bz>0 and |By|>>Bz. As expected, the magnetospheric compression started at the first impact point of the shock on the magnetopause causing an increase of the Chapman-Ferraro current from dawn to dusk and yielding an increase of the geomagnetic field at the geostationary orbit and on the ground. Moreover, the high-latitude magnetometer data show vortical structures clearly related to the interaction of the shock with the magnetosphere-ionosphere system. In this context, the SuperDARN convection maps show that at very high latitudes above the northern Cusp and in the morning sector, intense sunward convection fluxes appear, well correlated in time with the SI arrival, having a signature typical for Bz>0 dominated lobe reconnection. We suggest that in this case the dynamic pressure increase associated to the shock plays a role in favouring the setting up of a new lobe merging line albeit |By|>>Bz≥0.
Highlights
The global patterns of the high-latitude ionospheric convection are mostly determined by magnetic reconnection at the magnetopause and in the tail
We have used SuperDARN convection maps, spacecraft data and ground magnetometer data to study the effect of a Sudden Impulse (SI) of solar wind dynamic pressure on the magnetosphere-ionosphere system
We have found that the shock front associated with the Sudden Impulses (SI) was tilted towards the dawn flank of the magnetopause, and occurred during an Interplanetary Magnetic Field (IMF) By-dominated period, with Bz>0
Summary
The global patterns of the high-latitude ionospheric convection are mostly determined by magnetic reconnection at the magnetopause and in the tail. For short rise times strong transient perturbations are observed both in the magnetosphere and in the ionosphere until a new location of the magnetopause boundary is established; on the other hand, the duration of a pressure perturbation determines whether the effects will be localized or global (Boudouridis et al, 2003). Prikryl et al, 1998; Francia et al, 1999; Motoba et al, 2003) As these effects are thought to take place on closed field lines, one does not expect to observe relevant ground SI signatures at very high latitudes, where the footprints of the Cusps and of the Low Latitude Boundary Layer (LLBL) usually map. The paper is structured as follows: Sect. 2 offers an overview of the observations made by spacecraft in the solar wind and in the magnetosphere (Sect. 2.1), by ground-based magnetometers (Sect. 2.2), and by SuperDARN in the Northern Hemisphere (Sect. 2.3); the observations are discussed in detail in Sect. 3 and Sect. 4 contains a brief summary of our conclusions
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