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Article Dans Une Revue Annales Geophysicae Année : 1999

The dynamic cusp aurora on 30 November 1997: response to southward turning of the IMF

Résumé

We document the detailed dynamics of the dayside aurora in the \sim1200-1600 MLT sector in response to a sharp southward turning of the interplanetary magnetic field (IMF) under negative IMF By conditions. Features not documented in previous work are elucidated by using two meridan scanning photometers (separated by 2 h) and an all-sky auroral imager in Ny Ålesund, Svalbard (75.5°MLAT) in combination with magnetograms from stations on Svalbard, covering the latitude range 71°75°MLAT. The initial auroral response may be divided into three phases consisting of: (1) intensification of both the red (630.0 nm) and green (557.7 nm) line emissions in the cusp aurora near 1200 MLT and ~100 km equatorward shift of its equatorward boundary, at ~75°MLAT, (2) eastward and poleward expansions of the cusp aurora, reaching the 1430 MLT meridian after 5-6 min, and (3) east-west expansion of the higher-latitude aurora (at ~77°78°MLAT) in the postnoon sector. The associated magnetic disturbance is characterized by an initial positive deflection of the X-component at stations located 100-400 km south of the aurora, corresponding to enhanced Sunward return flow associated with the merging convection cell in the post-noon sector. The sequence of partly overlapping poleward moving auroral forms (PMAFs) during the first 15 min, accompanied by corresponding pulsations in the convection current, was followed by a strong westward contraction of the cusp aurora when the ground magnetograms indicated a temporary return to the pre-onset level. These observations are discussed in relation to the Cowley-Lockwood model of ionospheric response to pulsed magnetopause reconnection.
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Dates et versions

hal-00316661 , version 1 (18-06-2008)

Identifiants

  • HAL Id : hal-00316661 , version 1

Citer

P. E. Sandholt, C. J. Farrugia, B. Lybekk. The dynamic cusp aurora on 30 November 1997: response to southward turning of the IMF. Annales Geophysicae, 1999, 17 (9), pp.1155-1165. ⟨hal-00316661⟩

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