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

Farrugia, C. J. and Lund, E. and Sandholt, P. E. and Wild, J. A. and Cowley, S. W. H. and Balogh, A. and Mouikis, C. and Mobius, E. and Dunlop, M. W. and Bosqued, J. M. and Carlson, C. W. and Parks, G. K. and Cerisier, J. C. and Kelly, J. D. and Sauvaud, J.-A. and Rème, H. (2004) Pulsed flows at the high-altitude cusp poleward boundary, and associated ionospheric convection and particle signatures, during a cluster - FAST - SuperDARN - sondrestrom conjunction under a southwest. Annales Geophysicae, 22 (8). pp. 2891-2905. ISSN 0992-7689

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    Abstract

    Particle and magnetic field observations during a magnetic conjunction Cluster 1-FAST-Søndrestrøm within the field of view of SuperDARN radars on 21 January 2001 allow us to draw a detailed, comprehensive and self-consistent picture at three heights of signatures associated with transient reconnection under a steady south-westerly IMF (clock angle ≈130◦). Cluster 1 was outbound through the high altitude (∼12RE ) exterior northern cusp tailward of the bifurcation line (geomagnetic Bx>0) when a solar wind dynamic pressure release shifted the spacecraft into a boundary layer downstream of the cusp. The centerpiece of the investigation is a series of flow bursts observed there by the spacecraft, which were accompanied by strong field pertur- bations and tailward flow deflections. Analysis shows these to be Alfven waves. We interpret these flow events as being due to a sequence of reconnected flux tubes, with field-aligned currents in the associated Alfven waves carrying stresses to the underlying ionosphere, a view strengthened by the other observations. At the magnetic footprint of the region of Cluster flow bursts, FAST observed an ion energy- latitude disperison of the stepped cusp type, with individual cusp ion steps corresponding to individual flow bursts. Simultaneously, the SuperDARN Stokkseyri radar observed very strong poleward-moving radar auroral forms (PMRAFs) which were conjugate to the flow bursts at Cluster. FAST was traversing these PMRAFs when it observed the cusp ion steps. The Søndrestrøm radar observed pulsed ionospheric flows (PIFs) just poleward of the convection reversal boundary. As at Cluster, the flow was eastward (tailward), implying a coherent eastward (tailward) motion of the hypothesized open flux tubes. The joint Søndrestrøm and FAST observations indicate that the open/closed field line boundary was equatorward of the convection reversal boundary by ∼2 deg. The unprecedented accuracy of the conjunction argues strongly for the validity of the interpretation of the various signatures as resulting from transient reconnection. In particular, the cusp ion steps arise on this pass from this origin, in consonance with the original pulsating cusp model. The observations point to the need of extending current ideas on the response of the ionosphere to transient reconnection. Specifically, it argues in favor of re-establishing the high-latitude boundary layer downstream of the cusp as an active site of momentum transfer.

    Item Type: Article
    Journal or Publication Title: Annales Geophysicae
    Uncontrolled Keywords: Cluster ; SuperDARN DCS-publications-id ; art-676 ; DCS-publications-credits ; iono ; DCS-publications-personnel-id ; 104
    Subjects: T Technology > T Technology (General)
    Departments: Faculty of Science and Technology > School of Computing & Communications
    Faculty of Science and Technology > Physics
    ID Code: 6647
    Deposited By: ep_importer_dcs
    Deposited On: 21 Apr 2008 12:23
    Refereed?: Yes
    Published?: Published
    Last Modified: 26 Jul 2012 18:16
    Identification Number:
    URI: http://eprints.lancs.ac.uk/id/eprint/6647

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