Abstract
Abstract. Cluster magnetic field data are studied during an outbound pass through the post-noon high-latitude magnetopause region on 14 February 2001. The onset of several minute perturbations in the magnetospheric field was observed in conjunction with a southward turn of the interplanetary magnetic field observed upstream by the ACE spacecraft and lagged to the subsolar magnetopause. These perturbations culminated in the observation of four clear magnetospheric flux transfer events (FTEs) adjacent to the magnetopause, together with a highly-structured magnetopause boundary layer containing related field features. Furthermore, clear FTEs were observed later in the magnetosheath. The magnetospheric FTEs were of essentially the same form as the original "flux erosion events" observed in HEOS-2 data at a similar location and under similar interplanetary conditions by Haerendel et al. (1978). We show that the nature of the magnetic perturbations in these events is consistent with the formation of open flux tubes connected to the northern polar ionosphere via pulsed reconnection in the dusk sector magnetopause. The magnetic footprint of the Cluster spacecraft during the boundary passage is shown to map centrally within the fields-of-view of the CUTLASS SuperDARN radars, and to pass across the field-aligned beam of the EISCAT Svalbard radar (ESR) system. It is shown that both the ionospheric flow and the backscatter power in the CUTLASS data pulse are in synchrony with the magnetospheric FTEs and boundary layer structures at the latitude of the Cluster footprint. These flow and power features are subsequently found to propagate poleward, forming classic "pulsed ionospheric flow" and "poleward-moving radar auroral form" structures at higher latitudes. The combined Cluster-CUTLASS observations thus represent a direct demonstration of the coupling of momentum and energy into the magnetosphere-ionosphere system via pulsed magnetopause reconnection. The ESR observations also reveal the nature of the structured and variable polar ionosphere produced by the structured and time-varying precipitation and flow.Key words. Ionosphere (auroral ionosphere) Magentospheric physics (magnetopause, cusp and boundary layers; magnetosphere-ionosphere interactions)
Highlights
Reconnection at the dayside magnetopause boundary is the dominant mechanism by which energy and momentum are transferred from the solar wind into the Earth’s magnetosphere
Signatures indicating that the reconnection process is often of a transient nature were first obtained by Haerendel et al (1978) using high-latitude magnetic field data from the HEOS-2 spacecraft, and by Russell and Elphic (1978, 1979) using lower latitude data from ISEE-1 and -2
This paper investigates magnetometer data from an outbound pass of the Cluster spacecraft through the post-noon highlatitude magnetopause region, together with simultaneous ionospheric data obtained in the conjugate ionosphere by the CUTLASS (SuperDARN) and EISCAT radars
Summary
Reconnection at the dayside magnetopause boundary is the dominant mechanism by which energy and momentum are transferred from the solar wind into the Earth’s magnetosphere. The EISCAT radar observations were limited to two pointing directions and a 5 min measurement cycle, Elphic and co-workers showed evidence of transient reconnection at the magnetopause and a simultaneous flow response in the polar ionosphere These data, obtained during one observing interval, remained unique until the advent of the EquatorS mission. Neudegg et al (1999) presented a single case study of a southward turning of the IMF which resulted in the observation of a clear magnetospheric FTE in the magnetometer data of the Equator-S spacecraft, located in the vicinity of the magnetopause This was accompanied almost simultaneously by the onset of transient poleward-propagating flow signatures in the SuperDARN Hankasalmi (CUTLASS) radar. We present the first simultaneous observations of FTEs in the magnetopause region by the Cluster spacecraft, and pulsed features in the conjugate ionosphere by the CUTLASS and EISCAT Svalbard radars
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
