Magnetospheric sash dependence on IMF direction

Siscoe, G. L.; Erickson, G. M.; Sonnerup, B. U. Ö.; Maynard, N. C.; Siebert, K. D.; Weimer, D. R.; White, W. W.

doi:10.1029/2000gl003784

Cited by 21 publications

(35 citation statements)

References 9 publications

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“…In the vacuum superposition model, the polar angle of null M (θ M ) measured from the dipole‐based geomagnetic north is given in terms of the polar angle of the uniform IMF (θ IMF ) by θ M = tan −1 () [ Yeh , 1976], where 0° < θ IMF < 180°. This polar angle relationship approximately holds true for the MHD simulated magnetosphere in the case of IMF B X = 0 and no dipole tilt [ Siscoe et al , 2001a]. Thus the vacuum superstition topology is applicable to nonvacuum models fairly generally.…”

Section: Anatomy Of Reconnection‐driven Ionospheric Convectionmentioning

confidence: 86%

Synthesis of various ionospheric convection patterns for IMF B_Y‐dominated periods: Split crescent cells, exchange cells, and theta aurora formation

Watanabe

Sofko

2008

J. Geophys. Res.

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[1] When the dawn-to-dusk component of the interplanetary magnetic field (IMF B Y ) is dominant, ionospheric convection exhibits a distorted two-cell pattern with its dawn-dusk and interhemispheric asymmetries regulated by the IMF B Y polarity. For B Y > 0, the convection in the Northern (Southern) Hemisphere usually consists of a relatively round cell on the duskside (dawnside) and a crescent-shaped cell on the dawnside (duskside); for B Y < 0, the dawn-dusk relationship is reversed. However, deviations from the basic round/crescent cell pattern are sometimes seen. Such nonstandard convection patterns include the dayside-enhanced crescent cell pattern, nightside-enhanced crescent cell pattern, split crescent cell pattern, and exchange cell pattern. Although at times the nonstandard convection patterns appear to be quite different from the basic round/crescent cell pattern, the underlying physical processes (i.e., the types of reconnection) and field line topologies are basically the same. We show that these various convection patterns can be synthesized by considering the topologies of magnetic field lines involved in eight types of reconnection. We also discuss the formation mechanism of the theta aurora configuration in terms of magnetic topology and ionospheric convection.

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Section: Anatomy Of Reconnection‐driven Ionospheric Convectionmentioning

confidence: 86%

Synthesis of various ionospheric convection patterns for IMF B_Y‐dominated periods: Split crescent cells, exchange cells, and theta aurora formation

Watanabe

Sofko

2008

J. Geophys. Res.

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“…Siscoe et al [2001] presented an empirical relationship between the IMF clock angle and the clock angle of a magnetopause region of simulated minimum magnetic field strength at X = 0 R E with x-type magnetic topology that White et al [1998] referred to as the magnetospheric sash. It was found that the two angles closely followed the formula tan(θ mp ) = À (3 AE √ (9 + 8tan 2 (θ IMF ))) / 2tan(θ IMF ) based on a dipole-plus-uniform vacuum superposition model of null point locations in the X = 0 plane proposed by Yeh [1976] and Crooker et al [1990].…”

Section: Discussionmentioning

confidence: 99%

“…[13] The MHD simulation of the 15 May 2005 ICME has shown that a well-defined channel of sunward ExB flow existed poleward of the predicted location of magnetic reconnection from the vacuum superposition of the IMF and the geomagnetic field [Siscoe et al, 2001]. Its polar angle location θ FC in the YZ plane is directly determined by the IMF clock angle on the form θ FC = a * θ IMF + g with a = (0.30, 0.38, 0.43, 0.45) and g = (À2.1 , À1.5 , À0.8 , À0.8 ) for X = (4, 2, 0, À2) R E where θ FC and θ IMF are given in degrees.…”

Section: Discussionmentioning

confidence: 99%

Alfvén Mach number and IMF clock angle dependencies of sunward flow channels in the magnetosphere

Eriksson

Rastätter

2013

Geophysical Research Letters

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“…During periods of positive (negative) IMF B Y the northern‐hemisphere sash appears on the dusk (dawn) side magnetopause. Reverse sash locations appear along the southern hemisphere magnetopause Siscoe et al [2001]. demonstrated that sash locations follow loci of antiparallel merging sites [ Crooker , 1979; Luhmann et al , 1984].…”

Section: Introductionmentioning

confidence: 99%

Cluster observations of the dusk flank magnetopause near the sash: Ion dynamics and flow‐through reconnection

Maynard¹,

Farrugia²,

Burke³

et al. 2012

J. Geophys. Res.

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[1] Compared to the dayside, dynamics on the flanks of the magnetopause are poorly understood. To help bridge this knowledge gap we analyzed Cluster plasma and field measurements acquired during a 90-min period on 20 November 2003 when Cluster crossed the magnetopause four times in the vicinity of the sash. MHD simulations provide a context for Cluster observations. Crossings were between the magnetosheath and an S-shaped plasma sheet, rather than to the open-field lobes of the magnetotail. Cluster encountered two regions of MHD-breaking differences between perpendicular ion velocities and E Â B convection. Ion adiabatic expansion parameter (d i ) calculations show that ion gyrotropy was not broken during an episode of strong Alfvén wave activity in the magnetosheath. However, gyrotropy was broken (d i > 1) during the fourth magnetopause crossing. In the magnetosheath, ion guiding-center motion was maintained but inertial effects associated with temporally varying electric fields are probable sources of velocity differences. Regarding the magnetopause crossing, the generalized Ohm's law limits possible sources for breaking ion gyrotropy to inertial forces and/or electron pressure gradients associated with a nearby reconnection event. We suggest that Cluster witnessed effects of a temporally varying and spatially limited, flow-through reconnection event between open mantle field lines from the two polar caps adding new closed flux to the LLBL at the sash. Future modeling of flank dynamics must consider inertial forces as significant drivers at the magnetopause and in the adjacent magnetosheath.

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Magnetospheric sash dependence on IMF direction

Cited by 21 publications

References 9 publications

Synthesis of various ionospheric convection patterns for IMF B_Y‐dominated periods: Split crescent cells, exchange cells, and theta aurora formation

Synthesis of various ionospheric convection patterns for IMF B_Y‐dominated periods: Split crescent cells, exchange cells, and theta aurora formation

Alfvén Mach number and IMF clock angle dependencies of sunward flow channels in the magnetosphere

Cluster observations of the dusk flank magnetopause near the sash: Ion dynamics and flow‐through reconnection

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Magnetospheric sash dependence on IMF direction

Cited by 21 publications

References 9 publications

Synthesis of various ionospheric convection patterns for IMF BY‐dominated periods: Split crescent cells, exchange cells, and theta aurora formation

Synthesis of various ionospheric convection patterns for IMF BY‐dominated periods: Split crescent cells, exchange cells, and theta aurora formation

Alfvén Mach number and IMF clock angle dependencies of sunward flow channels in the magnetosphere

Cluster observations of the dusk flank magnetopause near the sash: Ion dynamics and flow‐through reconnection

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Synthesis of various ionospheric convection patterns for IMF B_Y‐dominated periods: Split crescent cells, exchange cells, and theta aurora formation

Synthesis of various ionospheric convection patterns for IMF B_Y‐dominated periods: Split crescent cells, exchange cells, and theta aurora formation