The effects of an interplanetary shock on the high-latitude ionospheric convection during an IMF <I>B<sub>y</sub></I>-dominated period

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 B y -dominated, with B y <0, IMF B z >0 and |B y | B z . 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 B z >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 |B y | B z ≥0.

IMF-By dependence of transient ionospheric flow perturbation associated with sudden impulses: SuperDARN observations

“…Besides the geomagnetic field observations, the Super Dual Auroral Radar Network (SuperDARN) (Greenwald et al 1995) has played an important role in the measurement of the two-dimensional structure of ionospheric convection associated with SIs (Lyatsky et al 1999;Thorolfsson et al 2001;Vontrat-Reberac et al 2002;Coco et al 2008;Huang et al 2008;Kane and Makarevich 2010;Liu et al 2011;Gillies et al 2012;Hori et al 2012). A conclusion from these studies with the radar observations is that changes in flow direction and the polarity of flow shear are consistent with a PI-MI sequence on ground magnetograms described by the SC model proposed by Araki (1977Araki ( , 1994.…”

Review of the accomplishments of mid-latitude Super Dual Auroral Radar Network (SuperDARN) HF radars

“…These observations primarily occur in the high-latitude and polar cap regions owing to their origins in the solar wind and the favorable coupling on open magnetic field lines at higher latitudes. Studies of these transients include the response of large-and meso-scale convection to abrupt transitions in the IMF Bz (Ruohoniemi and Greenwald 1998;Shepherd et al 1999;Milan et al 2000;Nishitani et al 2002;Fiori et al 2012) and IMF By (Chisham et al 2000;Senior et al 2002) magnetic field components, the solar wind dynamic pressure (Boudouridis et al 2007;Coco et al 2008;Boudouridis et al 2011;Gillies et al 2012), and interplanetary shocks (e.g., Kane and Makarevich 2010). These studies show general agreement with a two-stage response consisting of a prompt initial perturbation in the convection velocity seen nearly simultaneously at all MLTs, followed by a slower reconfiguration of the large-scale convection pattern that progresses from the dayside to the nightside.…”

Circumpolar ground‐based optical measurements of proton and electron shock aurora

“…The high‐latitude indices AU and AL both show a relatively small response to the shock around 0102:30–0103:30 UT, while the equatorial SYM–H index does not increase appreciably until a couple of minutes later. The deflections of the former can result from a sudden increase in precipitating particle flux, and thus increased horizontal ionospheric conductivity, associated field‐aligned currents (FACs), and convection signatures from the dayside auroral zone [e.g., Han et al, ; Coco et al , ]. On the other hand, the increase in SYM–H results primarily from the shock's compression of the dayside magnetosphere leading to an intensified and/or nearer dawn‐dusk Chapman‐Ferraro current.…”

“…Since the sunward side of the magnetosphere is further compressed during impulsive shock or high‐pressure events, ground‐based studies have generally focused on dayside measurements [e.g., Vorobjev , ; Sandholt et al , , ; Lorentzen and Moen , ; Kozlovsky et al , ; Motoba et al , ; Zhou et al , ; Liu et al , ]. Exceptions are specific to geomagnetic storm times, studies considering influence of P ram with respect to substorms [e.g., Lyons et al , ; Meurant et al , ], or those that focus on high‐latitude convection enhancements [e.g., Cerisier et al, ; Coco et al , ; Boudouridis et al , , and references therein].…”