Coordinated interhemispheric SuperDARN radar observations of the ionospheric response to flux transfer events observed by the Cluster spacecraft at the high-latitude magnetopause

Abstract

Abstract. At 10:00 UT on 14 February 2001, the quartet of ESA Cluster spacecraft were approaching the Northern Hemisphere high-latitude magnetopause in the post-noon sector on an outbound trajectory. At this time, the interplanetary magnetic field incident upon the dayside magnetopause was oriented southward and duskward (B Z negative, B Y positive), having turned from a northward orientation just over 1 hour earlier. As they neared the magnetopause the magnetic field, electron, and ion sensors on board the Cluster spacecraft observed characteristic field and particle signatures of magnetospheric flux transfer events (FTEs). Following the traversal of a boundary layer and the magnetopause, the spacecraft went on to observe further signatures of FTEs in the magnetosheath. During this interval of ongoing pulsed reconnection at the high-latitude post-noon magnetopause, the footprints of the Cluster spacecraft were located in the fields-of-view of the SuperDARN Finland and Syowa East radars located in the Northern and Southern Hemispheres, respectively. This study extends upon the initial survey of Wild et al. (2001) by comparing for the first time in situ magnetic field and plasma signatures of FTEs (here observed by the Cluster 1 spacecraft) with the simultaneous flow modulations in the conjugate ionospheres in the two hemispheres. During the period under scrutiny, the flow disturbances in the conjugate ionospheres are manifest as classic "pulsed ionospheric flows" (PIFs) and "poleward moving radar auroral forms" (PMRAFs). We demonstrate that the ionospheric flows excited in response to FTEs at the magnetopause are not those expected for a spatially limited reconnection region, somewhere in the vicinity of the Cluster 1 spacecraft. By examining the large-and small-scale flows in the high-latitude ionosphere, and the inter-hemispheric correspondence exhibited during this interval, we conclude that the reconnection processes that result in the generation of PIFs/PMRAFs must Correspondence to: J. A. Wild (j.wild@ion.le.ac.uk) extend over many (at least 4) hours of magnetic local time on the pre-and post-noon magnetopause.

Simultaneous tracking of reconnected flux tubes: Cluster and conjugate SuperDARN observations on 1 April 2004

“…Owen et al, 2001;Fear et al, 2005;Zheng et al, 2005;Hasegawa et al, 2006) have been combined with a variety of groundbased instruments (e.g. Lockwood et al, 2001;Wild et al, 2001Wild et al, , 2003Wild et al, , 2007Marchaudon et al, 2004), and with other spacecraft located at the magnetopause (Dunlop et al, 2005). Statistically, the distribution of the repetition rates of pulsed ionospheric flows and poleward moving auroral forms is in agreement with the distribution of FTE occurrence at the magnetopause (McWilliams et al, 2000), although the data sets are typically restricted from the point of view of one-toone measurements.…”

The azimuthal extent of three flux transfer events

“…Observations at scales between 100 and 5000 km have enabled the study of FTE motion at the magnetopause (Owen et al, 2001;Wild et al, 2005a;Dunlop et al, 2005;Fear et al, 2005Fear et al, , 2007, FTE structure (Hasegawa et al, 2006;Owen et al, 2008), further study of the statistics of FTE occurrence (Wang et al, , 2006Fear et al, 2005Fear et al, , 2007 and conjugated magnetopause/ionospheric studies using the SuperDARN radar network (Wild et al, 2001(Wild et al, , 2003(Wild et al, , 2005b(Wild et al, , 2007Marchaudon et al, 2004;Amm et al, 2005). In this paper we present the first observations of FTEs from the Cluster 10 000 km separation magnetopause crossing season, enabling in situ examination of the scale lengths of an FTE in all three dimensions.…”

A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions

“…However, there have been attempts to characterize this 2-D signature. Although not making 2-D observations, Prikryl et al (1999) suggested that the Wild et al (2003), copyright by the European Geophysical Union Surv Geophys (2007) 28:33-109 49 ionospheric flow bursts could be associated with poleward progressing DPY currents (Hall currents modulated by variations in IMF B y ). Many of the recent SuperDARN 2-D observations of dayside flow transients appear to fit with a simple picture of polewardmoving FAC systems which are associated with PMAFs, poleward-moving local convection reversals, and other poleward-moving velocity structures (Chisham et al 2000b;Thorolfsson et al 2000;Lockwood et al 2001).…”

“…In a study of 87 FTEs measured by the Equator-S spacecraft, 69 (77%) of these had a measurable convection flow burst signature and hence the two signatures were statistically associated with greater than 99% confidence. Wild et al (2001Wild et al ( , 2003 later presented coincident observations of highlatitude magnetopause FTEs measured by the Cluster spacecraft and convection flow transients measured at conjugate locations in both hemispheres by SuperDARN. The flow transients were found to pulse in close synchronization with the occurrence of the FTEs observed by Cluster.…”

“…The flow transients were found to pulse in close synchronization with the occurrence of the FTEs observed by Cluster. Figure 6, from Wild et al (2003), presents line-of-sight velocity data from the Finland SuperDARN radar in the northern hemisphere (top panel) and the Syowa East SuperDARN radar in the southern hemisphere (bottom panel). The velocity data are characterized by transient flow enhancements which can be seen most clearly in the middle panel which illustrates the average velocity variation from between the latitudes highlighted by the dashed lines in the top and bottom panels.…”