<i>Letter to the Editor</i> Simultaneous observations of the ionospheric footprint of flux transfer events and dispersed ion signatures

Abstract

Abstract. We perform a case study of a favourable conjunction of overpasses of the DMSP F11 and F13 spacecraft with the field of view of the Hankasalmi HF coherent scatter. At the time, pulsed ionospheric flows (PIFs) were clearly observed at a high-latitude in the radar field of view. The PIFs were associated with medium spectral width values and were identified as the fossilized signatures of pulsed dayside reconnection. Simultaneously, DMSP spectrograms from the two spacecraft showed dispersed ion signatures, observed equatorwards of the PIF signatures. We identified dayside high-latitude magnetosphere boundaries; these boundaries agreed well with those defined using the algorithm on the JHU/APL auroral particle website (Haerendel et al., 1978; Meng, 1988, 1995;Newell et al., 1991aNewell et al., , 1991bNewell et al., , 1991cTraver et al., 1991). We conclude that in this case study the dispersed ion signatures map to regions of very newly-opened flux. It is only when this flux has convected polewards that the signatures of the PIFs with medium spectral widths are observed by the HF radars. These particular PIF signatures map to regions of mantle precipitation, i.e. recently reconnected flux.

Multi-site observations of the association between aurora and plasma convection in the cusp/polar cap during a southeastward(<i>B<sub>y</sub></i> <u>~</u> |<i>B<sub>z</sub></i>|) IMF orientation

“…Steady-state aspects of the high-latitude dynamo process for the actual IMF orientation (IMF B y > 0) are discussed by, for example, Taguchi et al (1993). Our aurora-convection results are in good agreement with the recent study of Provan et al (2002), showing that the high-latitude pulsed ionospheric flows are observed within the regime of mantle precipitation and can be considered as "fossilized signatures of dayside reconnection, observed as the field lines are being pulled antisunward by the magnetosheath flow. "…”

“…The high-latitude phase (ii) observations appear as the recently reconnected field lines are being pulled antisunward by the magnetosheath flow. The observed flow excitation in this phase is in agreement with the previous observations/interpretations reported by for example, Sandholt et al (1993) and Provan et al (2002). PMAFs are found to be tracers of electron precipitation along poleward moving flux tubes in the convection throat which are present during a ∼5-min long phase following the initial equatorward boundary intensification.…”

“…The detailed observations of the evolution of the auroral events, including poleward moving/expanding auroral forms (PMAFs), are placed in the proper context of large-scale plasma convection at high temporal and spatial resolution. First of all, we demonstrate a close association between the sequence of auroral brightenings/PMAFs and pulsed ionospheric flows (Provan et al, 1999;Greenwald et al, 1999;Provan et al, 2002). Each episode of enhanced merging cell convection may be divided in two phases, for example, (i) enhanced westward convection at the cusp equatorward boundary, followed by, (ii) a "patch" of strong (∼1 km/s), poleward convection at high latitudes, >500 km poleward of the cusp equatorward boundary.…”

Pulsed flows at the high-altitude cusp poleward boundary, and associated ionospheric convection and particle signatures, during a Cluster - FAST - SuperDARN- Søndrestrøm conjunction under a southwest IMF

“…These flow pertubations corrugate the convection reversal boundary, as predicted by Cowley et al (1991) and Lockwood (1997). The flows at Søndrestrøm are examples of pulsed ionospheric flows which are coupled to the solar wind-magnetosphere dynamo in the HBL, along old open flux tubes that were generated at an earlier stage by a transient reconnection process (Pinnock et al, 1993(Pinnock et al, , 1995Rodger and Pinnock, 1997;Neudegg et al, 1999;Provan et al, 2002). The pulsed flows equatorward of the convection reversal (directed westward) are related to newly-opened field lines, while the channel of strong eastward flows poleward of the convection reversal is situated on older open flux coupled to the solar wind-magnetosphere dynamo in the HBL.…”

“…Individual signatures include: poleward-moving auroral forms (PMAFs; Sandholt et al, 1986Sandholt et al, , 1990Sandholt et al, , 2003, pulsed ionospheric flows/flow channels (PIFs; Pinnock et al, 1993Pinnock et al, , 1995Rodger and Pinnock, 1997;Neudegg et al, 1999;Provan et al, 2002), poleward-moving radar auroral forms (PMRAFs; Wild et al, 2001), an ion energy-latitude dispersion signature in the cusp of the staircase variety ("stepped cusp"; Cowley et al, 1991;Newell et al, 1989;Escoubet et al, 1992). The reliable and unique association of these signatures to transient reconnection requires in general multi-point observations.…”