Abstract
It is believed that a southward interplanetary magnetic field (IMF) is mainly responsible for the energy input from solar wind into the magnetosphere. This paper presents an unusual case of strong anti-sunward plasma flow (up to 2 km/s) in the polar cap ionosphere and large cross-polar cap potential (CPCP) during a period of horizontal IMF (|B Z | < 2 nT) observed by both ACE (at the L1 point) and Geotail (on the dusk flank of the magnetosheath). The CPCP is even higher than that under preceding B Z ≈ −23 nT. Furthermore, GOES8 observed that the magnetosheath field turns northward as the anti-sunward plasma flow and CPCP start to increase, which implies that the magnetosheath field interacting with the Earth’s magnetopause has significantly rotated and differs from the IMF observed by ACE and Geotail. In accordance with previous theoretical work, we suggest that the magnetic field line draping produces a southward magnetosheath field and enhances anti-sunward plasma flow and the CPCP.
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References
Shepherd S G. Polar cap potential saturation: Observations, theory, and modeling. J Atmos Sol Terr Phys, 2006, 3: 234–248
Richmond A D, Kamide Y. Mapping electrodynamic features of the high-latitude ionosphere from localized observations: Technique. J Geophys Res, 1988, A6: 5741–5759
Ridley A J, Lu G, Clauer C R, et al. A statistical study of the ionospheric convection response to changing interplanetary magnetic field conditions using the assimilative mapping of ionospheric electrodynamics technique. J Geophys Res, 1998, A3: 4023–4039
Coleman I J. A multi-spacecraft survey of magnetic field line draping in the dayside magnetosheath. Ann Geophys. 2005, 3: 885–900
Shepherd S G, Greenwald R A, Ruohoniemi J M. A possible explanation for rapid, large-scale ionospheric responses to southward turnings of the IMF. Geophys Res Lett, 1999, 20: 3197–3200
Šafránková J, Hayosh M, Gutynska O, et al. Reliability of prediction of the magnetosheath B Z component from interplanetary magnetic field observations. J Geophys Res, 2009, 114: A12213
Němeček Z, Šafránková J, Přech L, et al. Structure of the outer cusp and sources of the cusp precipitation during intervals of a horizontal IMF. J Geophys Res, 2003, A12: 1420
Zong Q G, Fritz T A, Spence H, et al. Plasmoid in the high latitude boundary/cusp region observed by Cluster. Geophys Res Lett, 2005, 32: L01101
Pu Z Y, Zhang X G, Wang X G, et al. Global view of dayside magnetic reconnection with the dusk-dawn IMF orientation: A statistical study for Double Star and Cluster data. Geophys Res Lett, 2007, 34: L20101
Crooker N. Dayside Merging and Cusp Geometry. J Geophys Res, 1979, A3: 951–959
Kobel E, Flückiger E. A Model of the Steady State Magnetic Field in the Magnetosheath. J Geophys Res, 1994, A12: 23617–23622
Sandholt P E, Farrugia C J, Cowley S W H, et al. Excitation of transient lobe cell convection and auroral arc at the cusp poleward boundary during a transition of the interplanetary magnetic field from south to north. Ann Geophys, 2001, 19: 487
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Wei, Y., Zong, Q., Pu, Z. et al. Enhanced anti-sunward flow near local noon during a period of horizontal IMF and high solar wind velocity V Y . Chin. Sci. Bull. 56, 1117–1122 (2011). https://doi.org/10.1007/s11434-011-4353-y
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DOI: https://doi.org/10.1007/s11434-011-4353-y