The local dayside reconnection rate for oblique interplanetary magnetic fields

Komar, C. M.; Cassak, P. A.

doi:10.1002/2016ja022530

Cited by 15 publications

(14 citation statements)

References 66 publications

(106 reference statements)

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“…For the inflow speed, it has been shown that the 2‐D asymmetric reconnection theory [ Cassak and Shay , ] quantitatively describes the local reconnection rate at the dayside magnetopause in the global geometry for due southward IMF and no dipole tilt [ Borovsky et al , ; Ouellette et al , ; Komar and Cassak , ]. So we use v in, s = E / B s , with

E = \frac{B_{s} B_{m}}{B_{s} + B_{m}} v_{out} \frac{2 δ}{L},

where δ / L is the aspect ratio of the diffusion region, assumed to be 0.1 for fast reconnection (even in the asymmetric case) [ Cassak and Shay , ; Malakit et al , ], the m subscript denotes the values measured just on the magnetospheric side of the magnetosheath, and the asymmetric outflow speed is

v_{out}^{2} = \frac{B_{s} B_{m}}{μ_{0}} \frac{B_{s} + B_{m}}{ρ_{s} B_{m} + ρ_{m} B_{s}} .

Equations and of the present study are direct copies of equations (19) and (13) from Cassak and Shay [].…”

Section: Resultsmentioning

confidence: 99%

Transition from global to local control of dayside reconnection from ionospheric‐sourced mass loading

et al. 2017

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We have conducted a series of controlled numerical simulations to investigate the response of dayside reconnection to idealized, ionosphere‐sourced mass loading processes to determine whether they affect the integrated dayside reconnection rate. Our simulation results show that the coupled solar wind‐magnetosphere system may exhibit both local and global control behaviors depending on the amount of mass loading. With a small amount of mass loading, the changes in local reconnection rate affects magnetosheath properties only weakly and the geoeffective length in the upstream solar wind is essentially unchanged, resulting in the same integrated dayside reconnection rate. With a large amount of mass loading, however, the magnetosheath properties and the geoeffective length are significantly affected by slowing down the local reconnection rate, resulting in an increase of the magnetic pressure in the magnetosheath, with a significant reduction in the geoeffective length in the upstream solar wind and in the integrated dayside reconnection rate. In this controlled simulation setup, the behavior of dayside reconnection potential is determined by the role of the enhanced magnetic pressure in the magnetospheath due to magnetospheric mass loading. The reconnection potential starts to decrease significantly when the enhanced magnetic pressure alters the thickness of the magnetosheath.

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E = \frac{B_{s} B_{m}}{B_{s} + B_{m}} v_{out} \frac{2 δ}{L},

v_{out}^{2} = \frac{B_{s} B_{m}}{μ_{0}} \frac{B_{s} + B_{m}}{ρ_{s} B_{m} + ρ_{m} B_{s}} .

Equations and of the present study are direct copies of equations (19) and (13) from Cassak and Shay [].…”

Section: Resultsmentioning

confidence: 99%

Transition from global to local control of dayside reconnection from ionospheric‐sourced mass loading

et al. 2017

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“…Observations suggest that ( δ / L ) eff is of order 0.1. Numerical simulations have also confirmed this scaling and demonstrated that ( δ / L ) eff ∼0.1; these include local magnetohydrodynamic (MHD) simulations with a localized resistivity (Birn et al, ), local two‐fluid (Cassak & Shay, ) and local particle‐in‐cell (PIC) (Malakit et al, ; Pritchett, ) simulations, global magnetospheric MHD simulations (Borovsky, ; Borovsky & Birn, ; Komar & Cassak, ; Ouellette et al, ; Zhang et al, ), and global Vlasov simulations (Hoilijoki et al, ). This scaling along with ( δ / L ) eff ∼0.1 was then employed to develop a quantitative model of the coupling between the solar wind and Earth's magnetosphere (Borovsky, ; Borovsky & Birn, ).…”

Section: Introductionmentioning

confidence: 88%

On the Collisionless Asymmetric Magnetic Reconnection Rate

Liu

Hesse

Cassak

et al. 2016

Geophysical Research Letters

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A prediction of the steady state reconnection electric field in asymmetric reconnection is obtained by maximizing the reconnection rate as a function of the opening angle made by the upstream magnetic field on the weak magnetic field (magnetosheath) side. The prediction is within a factor of 2 of the widely examined asymmetric reconnection model (Cassak & Shay, 2007, https://doi.org/10.1063/1.2795630) in the collisionless limit, and they scale the same over a wide parameter regime. The previous model had the effective aspect ratio of the diffusion region as a free parameter, which simulations and observations suggest is on the order of 0.1, but the present model has no free parameters. In conjunction with the symmetric case (Liu et al., 2017, https://doi.org/10.1103/PhysRevLett.118.085101), this work further suggests that this nearly universal number 0.1, essentially the normalized fast‐reconnection rate, is a geometrical factor arising from maximizing the reconnection rate within magnetohydrodynamic‐scale constraints.

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“…In section 4.4 we identified that B z was a causal parameter during southward IMF, that is, when below the threshold B z =0. Since we know that strongly negative values of B z correlate with higher reconnection rates at the dayside magnetopause (Komar & Cassak, ), we look at how this could relate to the generation of magnetospheric ULF waves.…”

Section: Physically Interpreting External Ulf Generation Mechanismsmentioning

confidence: 99%

ULF Wave Activity in the Magnetosphere: Resolving Solar Wind Interdependencies to Identify Driving Mechanisms

et al. 2018

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Ultralow frequency (ULF) waves in the magnetosphere are involved in the energization and transport of radiation belt particles and are strongly driven by the external solar wind. However, the interdependency of solar wind parameters and the variety of solar wind‐magnetosphere coupling processes make it difficult to distinguish the effect of individual processes and to predict magnetospheric wave power using solar wind properties. We examine 15 years of dayside ground‐based measurements at a single representative frequency (2.5 mHz) and a single magnetic latitude (corresponding to L ∼ 6.6RE). We determine the relative contribution to ULF wave power from instantaneous nonderived solar wind parameters, accounting for their interdependencies. The most influential parameters for ground‐based ULF wave power are solar wind speed vsw, southward interplanetary magnetic field component Bz<0, and summed power in number density perturbations δNp. Together, the subordinate parameters Bz and δNp still account for significant amounts of power. We suggest that these three parameters correspond to driving by the Kelvin‐Helmholtz instability, formation, and/or propagation of flux transfer events and density perturbations from solar wind structures sweeping past the Earth. We anticipate that this new parameter reduction will aid comparisons of ULF generation mechanisms between magnetospheric sectors and will enable more sophisticated empirical models predicting magnetospheric ULF power using external solar wind driving parameters.

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The local dayside reconnection rate for oblique interplanetary magnetic fields

Cited by 15 publications

References 66 publications

Transition from global to local control of dayside reconnection from ionospheric‐sourced mass loading

Transition from global to local control of dayside reconnection from ionospheric‐sourced mass loading

On the Collisionless Asymmetric Magnetic Reconnection Rate

ULF Wave Activity in the Magnetosphere: Resolving Solar Wind Interdependencies to Identify Driving Mechanisms

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