TY - JOUR

T1 - Flux closure during a substorm observed by cluster, double star, IMAGE FUV, SuperDARN, and greenland magnetometers

AU - Milan, S. E.

AU - Wild, J. A.

AU - Hubert, B.

AU - Carr, C. M.

AU - Lucek, E.

AU - Bosqued, J. M.

AU - Watermann, J. F.

AU - Slavin, J. A.

PY - 2006/3

Y1 - 2006/3

N2 - We examine magnetic flux closure during an ex- tended substorm interval on 29 August 2004 involving a two-stage onset and subsequent re-intensifications. Cluster and Double Star provide observations of magnetotail dy- namics, while the corresponding auroral evolution, convec- tion response, and substorm current wedge development are monitored by IMAGE FUV, SuperDARN, and the Greenland magnetometer chain, respectively. The first stage of onset is associated with the reconnection of closed flux in the plasma sheet; this is accompanied by a short-lived auroral intensification, a modest substorm current wedge magnetic bay, but no significant ionospheric convection enhancement. The second stage follows the progression of reconnection to the open field lines of the lobes; accompanied by prolonged auroral bulge and westward-travelling surge development, enhanced magnetic bays and convection. We find that the tail dynamics are highly influenced by ongoing dayside creation of open flux, leading to flux pile-up in the near-tail and a step-wise down-tail motion of the tail reconnection site. In all, 5 dipolarizations are observed, each associated with the closure of ∼0.1 GWb of flux. Very simple calculations indicate that the X-line should progress down-tail at a speed of 20 km s−1, or 6 RE between each dipolarization.

AB - We examine magnetic flux closure during an ex- tended substorm interval on 29 August 2004 involving a two-stage onset and subsequent re-intensifications. Cluster and Double Star provide observations of magnetotail dy- namics, while the corresponding auroral evolution, convec- tion response, and substorm current wedge development are monitored by IMAGE FUV, SuperDARN, and the Greenland magnetometer chain, respectively. The first stage of onset is associated with the reconnection of closed flux in the plasma sheet; this is accompanied by a short-lived auroral intensification, a modest substorm current wedge magnetic bay, but no significant ionospheric convection enhancement. The second stage follows the progression of reconnection to the open field lines of the lobes; accompanied by prolonged auroral bulge and westward-travelling surge development, enhanced magnetic bays and convection. We find that the tail dynamics are highly influenced by ongoing dayside creation of open flux, leading to flux pile-up in the near-tail and a step-wise down-tail motion of the tail reconnection site. In all, 5 dipolarizations are observed, each associated with the closure of ∼0.1 GWb of flux. Very simple calculations indicate that the X-line should progress down-tail at a speed of 20 km s−1, or 6 RE between each dipolarization.

KW - DCS-publications-id

KW - art-747

KW - DCS-publications-credits

KW - iono

KW - DCS-publications-personnel-id

KW - 104

U2 - 10.5194/angeo-24-751-2006

DO - 10.5194/angeo-24-751-2006

M3 - Journal article

VL - 24

SP - 751

EP - 767

JO - Annales Geophysicae

JF - Annales Geophysicae

SN - 0992-7689

IS - 2

ER -