Relative timing of substorm processes as derived from multifluid/multiscale simulations: Internally driven substorms

[1] The role of tail reconnection in initiating substorm onset remains highly controversial. Multifluid/multiscale simulations are used to examine this problem with the unique capability of being able to resolve ion skin depth and ion cyclotron processes within a very thin tail current sheet within a global magnetosphere. It is shown that, consistent with the near-Earth neutral line model, a thin current sheet forms during the growth phase with the eventual formation of an X line and the ejection of a plasmoid. However, these processes do not produce substorm onset but are precursors to onset. The modeling indicates that in the wake of the plasmoid, a Y line forms within which there is the intermittent generation of flux ropes that can propagate either earthward or tailward with equal probability. The intensity and size of the flux ropes are seen to increase in time up to substorm onset. Depending on the size of the earthward moving flux rope, pseudobreakup or substorm onset occurs when the energy within the earthward moving flux rope is dissipated against the inner edge of the plasma sheet. This interaction leads to rapid (1 min) dipolarization, magnetospheric injection of energetic particles, and intensification of the nightside auroral currents that expand in local time and to higher latitudes. These processes are consistent with the current disruption model where onset occurs as a direct consequence of processes occurring at the inner edge of the plasma sheet. Ionospheric outflows and their energization with the thin current sheet play important roles in the buildup of energy in the plasma sheet that eventually produces substorm onset and drives breakup.

[1]  A. Stickle,et al.  Prompt ionospheric/magnetospheric responses 29 October 2003 Halloween storm: Outflow and energization , 2008 .

[2]  V. Angelopoulos,et al.  On the relationship between bursty flows, current disruption and substorms , 1999 .

[3]  K. Glassmeier,et al.  Kink mode oscillation of the current sheet , 2003 .

[4]  Kazue Takahashi,et al.  Initial signatures of magnetic field and energetic particle fluxes at tail reconfiguration : explosive growth phase , 1992 .

[5]  Michael C. Kelley,et al.  The Earth's Ionosphere : Plasma Physics and Electrodynamics , 1989 .

[6]  W. Hughes,et al.  Plasmoids as magnetic flux ropes , 1991 .

[7]  Rumi Nakamura,et al.  Cluster observation of a bifurcated current sheet , 2003 .

[8]  T. Sanderson,et al.  CDAW 8 observations of plasmoid signatures in the geomagnetic tail: An assessment , 1989 .

[9]  C. Mcilwain Substorm Injection Boundaries , 1974 .

[10]  T. Ogino A three-dimensional MHD simulation of the interaction of the solar wind with the earth's magnetosphere - The generation of field-aligned currents , 1986 .

[11]  R. L. Arnoldy,et al.  PARTICLE SUBSTORMS OBSERVED AT THE GEOSTATIONARY ORBIT. , 1969 .

[12]  Kazue Takahashi,et al.  Ion composition of the near-Earth plasma sheet in storm and quiet intervals: Geotail/EPIC measurements , 2001 .

[13]  Wolfgang Baumjohann,et al.  Plasma sheet oscillations and their relation to substorm development: cluster and double star TC1 case study , 2008 .

[14]  B. Anderson,et al.  Multipoint observations of a small substorm , 1990 .

[15]  Wolfgang Baumjohann,et al.  Characteristics of high‐speed ion flows in the plasma sheet , 1990 .

[16]  F. Frutos-Alfaro,et al.  Ion composition of substorms during storm-time and non-storm-time periods , 2002 .

[17]  W. Hughes,et al.  Plasmoid observations in the distant plasma sheet boundary layer , 1992 .

[18]  G. Parks,et al.  Global impact of ionospheric outflows on the dynamics of the magnetosphere and cross-polar cap potential , 2002 .

[19]  Robert M. Winglee,et al.  Ion cyclotron and heavy ion effects on reconnection in a global magnetotail , 2004 .

[20]  R. Winglee Circulation of ionospheric and solar wind particle populations during extended southward interplanetary magnetic field , 2003 .

[21]  M. Kivelson,et al.  Cluster electric current density measurements within a magnetic flux rope in the plasma sheet , 2003 .

[22]  R. Winglee,et al.  The role of ion cyclotron motion at Ganymede: Magnetic field morphology and magnetospheric dynamics , 2006 .

[23]  J. Eastwood,et al.  Observations of multiple X‐line structure in the Earth's magnetotail current sheet: A Cluster case study , 2005 .

[24]  C. Russell,et al.  ISEE‐1 and 2 observations of magnetic flux ropes in the magnetotail: FTE's in the plasma sheet? , 1986 .

[25]  R. D. Belian,et al.  Observations of magnetospheric substorms occurring with no apparent solar wind/IMF trigger , 1996 .

[26]  Freddy Christiansen,et al.  A new model of field‐aligned currents derived from high‐precision satellite magnetic field data , 2002 .

[27]  J. Kan A globally integrated substorm model: Tail reconnection and magnetosphere-ionosphere coupling , 1998 .

[28]  R. D. Belian,et al.  Radial propagation of substorm injections , 1996 .

[29]  E. Harnett,et al.  Multi‐scale/multi‐fluid simulations of the post plasmoid current sheet in the terrestrial magnetosphere , 2006 .

[30]  A. Lui Potential Plasma Instabilities For Substorm Expansion Onsets , 2004 .

[31]  Rumi Nakamura,et al.  Structure of the Hall current system in the vicinity of the magnetic reconnection site , 2003 .

[32]  R. M. Winglee,et al.  High-resolution multifluid simulations of the plasma environment near the Martian magnetic anomalies , 2007 .

[33]  R. Winglee Mapping of ionospheric outflows into the magnetosphere for varying IMF conditions , 2000 .

[34]  B. Mauk,et al.  Acceleration of oxygen ions of ionospheric origin in the near-Earth magnetotail during substorms , 2000 .

[35]  A. Lui,et al.  A synthesis of magnetospheric substorm models , 1991 .

[36]  Rumi Nakamura,et al.  Structure and dynamics of magnetic reconnection for substorm onsets with Geotail observations , 1998 .

[37]  R. Lin,et al.  Flux rope structures in the magnetotail: Comparison between Wind/Geotail observations and global simulations , 1998 .

[38]  Kan Liou,et al.  Substorm timings and timescales: A new aspect , 2004 .

[39]  R. Elphic,et al.  The auroral current circuit and field‐aligned currents observed by FAST , 1998 .

[40]  C. Owen,et al.  Geotail observations of magnetic flux ropes in the plasma sheet , 2003 .

[41]  D. Baker,et al.  Cluster observations of earthward flowing plasmoid in the tail , 2004 .

[42]  D. Baker,et al.  Timing of magnetic reconnection initiation during a global magnetospheric substorm onset , 2002 .

[43]  Robert M. Winglee,et al.  Mapping of the heavy ion outflows as seen by IMAGE and multifluid global modeling for the 17 April 2002 storm , 2005 .

[44]  G. Paschmann,et al.  Bursty bulk flows in the inner central plasma sheet , 1992 .

[45]  Robert L. McPherron,et al.  Growth phase of magnetospheric substorms , 1970 .

[46]  G. Parks,et al.  The geopause in relation to the plasma sheet and the low‐latitude boundary layer: Comparison between Wind observations and multifluid simulations , 2000 .

[47]  R. Winglee Non-MHD influences on the magnetospheric current system , 1994 .

[48]  Peter A. Delamere,et al.  Three‐dimensional multi‐fluid simulations of Pluto's magnetosphere: A comparison to 3D hybrid simulations , 2005 .

[49]  A. Lui,et al.  Current disruption in the Earth's magnetosphere: Observations and models , 1996 .

[50]  I. J. Rae,et al.  Tail Reconnection Triggering Substorm Onset , 2008, Science.

[51]  Syun-Ichi Akasofu,et al.  The development of the auroral substorm. , 1964 .

[52]  E. Harnett,et al.  2.5‐D fluid simulations of the solar wind interacting with multiple dipoles on the surface of the Moon , 2003 .

[53]  Wolfgang Baumjohann,et al.  Fast flow during current sheet thinning , 2002 .

[54]  J. Horwitz The substorm as an internal magnetospheric instability Substorms and their characteristic time scales during intervals of steady interplanetary magnetic field , 1985 .

[55]  R. McPherron,et al.  Substorm signatures at synchronous altitude , 1981 .

[56]  R. Winglee,et al.  Multi‐fluid simulations of Ganymede's magnetosphere , 2004 .

[57]  T. Moretto,et al.  Coordinated observations demonstrating external substorm triggering , 1997 .

[58]  J. Slavin,et al.  Magnetotail flux ropes , 1984 .

[59]  Daniel N. Baker,et al.  Neutral line model of substorms: Past results and present view , 1996 .

[60]  S. Wing,et al.  Magnetic dipolarization with substorm expansion onset , 2002 .

[61]  A. Stickle,et al.  Model/data comparisons of ionospheric outflow as a function of invariant latitude and magnetic local time , 2008 .

[62]  A. Stickle,et al.  Multiscale/multifluid simulations of flux ropes at the magnetopause within a global magnetospheric model , 2008 .

[63]  A. Lazarus,et al.  Magnetic field line draping in the plasma depletion layer , 1990 .

[64]  J. Slavin,et al.  Analysis of Magnetotail Flux Ropes with Strong Core Fields : ISEE 3 Observations , 1996 .

[65]  Steven Paul Slinker,et al.  Plasmoid formation and evolution in a numerical simulation of a substorm , 1995 .

[66]  Wolfgang Baumjohann,et al.  Multi-point study of the magnetotail current sheet , 2006 .

[67]  Y. Feldstein,et al.  The auroral luminosity structure in the high-latitude upper atmosphere: Its dynamics and relationship to the large-scale structure of the Earth's magnetosphere , 1985 .

[68]  R. Lepping,et al.  Cross‐tail magnetic flux ropes as observed by the GEOTAIL spacecraft , 1995 .

[69]  Wolfgang Baumjohann,et al.  Braking of high‐speed flows in the near‐Earth tail , 1997 .

[70]  C. Owen,et al.  ISEE 3 observations of plasmoids with flux rope magnectic topologies , 1995 .

[71]  B. Anderson,et al.  Current disruptions in the near-Earth neutral sheet region , 1992 .

[72]  R. Winglee,et al.  Multi‐fluid simulations of the magnetosphere: The identification of the geopause and its variation with IMF , 1998 .

[73]  J. Sauvaud,et al.  Contribution of nonadiabatic ions to the cross-tail current in an O+ dominated thin current sheet , 2005 .

[74]  G. Le,et al.  Strong interplanetary magnetic field By‐related plasma convection in the ionosphere and cusp field‐aligned currents under northward interplanetary magnetic field conditions , 2002 .