eprintid: 162631 rev_number: 44 eprint_status: archive userid: 608 dir: disk0/00/16/26/31 datestamp: 2010-11-01 13:00:38 lastmod: 2021-10-10 22:43:11 status_changed: 2012-07-25 14:08:33 type: article metadata_visibility: show item_issues_count: 0 creators_name: Escoubet, CP creators_name: Bosqued, JM creators_name: Berchem, J creators_name: Trattner, KJ creators_name: Taylor, MGGT creators_name: Pitout, F creators_name: Laakso, H creators_name: Masson, A creators_name: Dunlop, M creators_name: Reme, H creators_name: Dandouras, I creators_name: Fazakerley, A title: Temporal evolution of a staircase ion signature observed by Cluster in the mid-altitude polar cusp ispublished: pub divisions: UCL divisions: B04 divisions: C06 divisions: F63 keywords: Flux-transfer events, Interplanetary magnetic-field, Low-altitude observations, Magnetopause reconnection, Precipitation, Aurora, Edge note: Copyright 2006 by the American Geophysical Union abstract: We use the Cluster string of pearls configuration to investigate temporal variations of ion precipitation in the mid-altitude polar cusp. On 7 Aug. 2004, Cluster 4 was moving poleward through the Northern cusp, followed by Cluster 1, Cluster 2, and finally Cluster 3. The Wind spacecraft detected a Southward turning of the Interplanetary Magnetic Field ( IMF) at the beginning of the cusp crossings and IMF-Bz stayed negative throughout. Cluster 4 observed a high energy step in the ion dispersion around 1 keV on the equatorward side of the cusp. C1, entering the cusp around 1 minute later, did not observe the high energy step anymore but a partial dispersion with a low energy cut-off reaching 100 eV. About 9 min later, C3 entered the cusp and observed a full ion dispersion from a few keV down to around 50 eV. The open-closed boundary, identified by electron precipitation, was initially moving equatorward at a rate of -0.43 degrees ILAT/minute at the beginning of the event and then slowed down to -0.16 degrees ILAT/minute, suggesting the erosion of the dayside magnetosphere under IMF Southward. This event is explained by the onset of dayside reconnection when the IMF turned southward; the step being the first signature of the reconnection that would then evolve as a full dispersion as reconnection goes on. We observed 1-3 keV ions near the open-closed boundary on the three spacecraft crossings that suggests a continuous reconnection during about 9 minutes. date: 2006-04-12 publisher: Amer Geophysical Union official_url: http://dx.doi.org/10.1029/2005GL025598 vfaculties: VMPS oa_status: green language: eng primo: open primo_central: open_green article_type_text: Article verified: verified_manual elements_source: Manually entered elements_id: 124090 doi: 10.1029/2005GL025598 lyricists_name: Fazakerley, Andrew lyricists_id: ANFAZ75 full_text_status: public publication: Geophysical Research Letters volume: 33 number: 7 article_number: L07108 issn: 0094-8276 citation: Escoubet, CP; Bosqued, JM; Berchem, J; Trattner, KJ; Taylor, MGGT; Pitout, F; Laakso, H; ... Fazakerley, A; + view all <#> Escoubet, CP; Bosqued, JM; Berchem, J; Trattner, KJ; Taylor, MGGT; Pitout, F; Laakso, H; Masson, A; Dunlop, M; Reme, H; Dandouras, I; Fazakerley, A; - view fewer <#> (2006) Temporal evolution of a staircase ion signature observed by Cluster in the mid-altitude polar cusp. Geophysical Research Letters , 33 (7) , Article L07108. 10.1029/2005GL025598 <https://doi.org/10.1029/2005GL025598>. Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/162631/1/2005GL025598.pdf