Cluster Observations of the Magnetospheric Low-Latitude Boundary Layer and Cusp during Extreme Solar Wind and Interplanetary Magnetic Field Conditions: I. 10 November 2004 ICME |
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| Authors: | Y V Bogdanova C J Owen G Siscoe A N Fazakerley I Dandouras O Marghitu Z Kaymaz H Rème E A Lucek |
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| Institution: | (1) Mullard Space Science Laboratory, University College London, London, UK;(2) Center for Space Physics, Boston University, Boston, MA, USA;(3) Centre d’Etude Spatiale des Rayonnements, Toulouse, France;(4) Institute for Space Sciences, Bucharest, Romania;(5) Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany;(6) Faculty of Aeronautics and Astronautics, Istanbul Technical University, Istanbul, Turkey;(7) Space and Atmospheric Physics Group, Imperial College London, London, UK |
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| Abstract: | We present a study of the magnetospheric cusp response to extreme external parameters during passage of the ICME over the
Earth on 10 November 2004, based on Cluster observations of the plasma properties inside the low-latitude boundary layer (LLBL)/cusp regions. Two separate events are
observed while Cluster is in the dawn sector, 07 – 08 h magnetic local time (MLT). First, a LLBL/cusp crossing occurs during a period of strong
southward IMF. During this time, the LLBL/cusp is very small, ∼0.8 – 1° invariant latitude (ILAT) and moves equatorward, down
to 67° ILAT. This can be explained by the occurrence of significant magnetopause erosion due to enhanced dayside sub-solar
reconnection. The energy of the plasma inside this region is higher than normal, and the low-energy cut-off often observed
in the ion data is also unusually high. This might be explained by the suggestion that the local magnetosheath Alfvén velocity
and deHoffmann – Teller velocity are also both extremely high. However, the plasma convection and parallel velocity inside
this region are not very high. The second event discussed in this paper is a LLBL/cusp crossing during strong equatorial IMF
(mostly due to the dominant dawn – dusk component). Under these conditions, occurring at the same time as pulses of solar
wind dynamic pressure, the observations are very complicated. However, we suggest that in the polar region of the southern
hemisphere, Cluster cross two LLBLs/cusps, spatially separated by polar cap plasma. The first LLBL/cusp is formed by anti-parallel reconnection
in the dusk sector of the southern hemisphere and the second is formed by anti-parallel reconnection in the dawn sector of
the northern hemisphere. The second LLBL/cusp is located at extremely low latitude, less than ∼66.3° ILAT. During all LLBL/cusp
crossings, strong ionospheric O+ ion outflow is detected in the form of a narrow beam with limited pitch-angle range. |
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