Separator reconnection at Earth's dayside magnetopause under generic northward interplanetary magnetic field conditions

Dorelli, J.; Bhattacharjee, A.; Raeder, J.

doi:10.1029/2006ja011877

Cited by 86 publications

(149 citation statements)

References 71 publications

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“…Energy exchange E J 0 · < is rather low and peaks at the subsolar point and not in the null. Such a single null configuration is similar to the separator magnetopause reconnection occuring under northward IMF in a closed magnetosphere (Dorelli et al 2007). In the open (upper) hemisphere, a ring of nulls disappears, producing a collection of A-and B-type nulls, contrary to the solar wind-dipole interaction, where most nulls in the magnetosphere are spiral (see Section 5, Figure 5).…”

Section: Results: Quadrupolementioning

confidence: 66%

Magnetic Null Points in Kinetic Simulations of Space Plasmas

Olshevsky

Deca

Divin

et al. 2016

ApJ

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We present a systematic attempt to study magnetic null points and the associated magnetic energy conversion in kinetic particle-in-cell simulations of various plasma configurations. We address three-dimensional simulations performed with the semi-implicit kinetic electromagnetic code iPic3D in different setups: variations of a Harris current sheet, dipolar and quadrupolar magnetospheres interacting with the solar wind,and a relaxing turbulent configuration with multiple null points. Spiral nulls are more likely created in space plasmas: in all our simulations except lunar magnetic anomaly (LMA) and quadrupolar mini-magnetosphere the number of spiral nulls prevails over the number of radial nulls by a factor of 3-9. We show that often magnetic nulls do not indicate the regions of intensive energy dissipation. Energy dissipation events caused by topological bifurcations at radial nulls are rather rare and short-lived. The so-called X-lines formed by the radial nulls in the Harris current sheet and LMA simulations are rather stable and do not exhibit any energy dissipation. Energy dissipation is more powerful in the vicinity of spiral nulls enclosed by magnetic flux ropes with strong currents at their axes (their crosssections resemble 2D magnetic islands). These null lines reminiscent of Z-pinches efficiently dissipate magnetic energy due to secondary instabilities such as the two-stream or kinking instability, accompanied by changes in magnetic topology. Current enhancements accompanied by spiral nulls may signal magnetic energy conversion sites in the observational data.

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Section: Results: Quadrupolementioning

confidence: 66%

Magnetic Null Points in Kinetic Simulations of Space Plasmas

Olshevsky

Deca

Divin

et al. 2016

ApJ

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“…12,13 3D nulls have additionally been observed using in situ measurements from the Cluster satellites in the Earth's magnetotail 14 and are a prominent feature of the polar cusp regions. 15,16 When combined with current sheets, null points are also excellent particle accelerators, 17,18 and may be a contributing source of high energy particles in some solar flares. 6,8 It is well established that under the right conditions, current sheets will fragment via the tearing instability.…”

Section: Introductionmentioning

confidence: 99%

Dynamic topology and flux rope evolution during non-linear tearing of 3D null point current sheets

Wyper

Pontin

2014

Physics of Plasmas

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Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. In this work, the dynamic magnetic field within a tearing-unstable three-dimensional current sheet about a magnetic null point is described in detail. We focus on the evolution of the magnetic null points and flux ropes that are formed during the tearing process. Generally, we find that both magnetic structures are created prolifically within the layer and are non-trivially related. We examine how nulls are created and annihilated during bifurcation processes, and describe how they evolve within the current layer. The type of null bifurcation first observed is associated with the formation of pairs of flux ropes within the current layer. We also find that new nulls form within these flux ropes, both following internal reconnection and as adjacent flux ropes interact. The flux ropes exhibit a complex evolution, driven by a combination of ideal kinking and their interaction with the outflow jets from the main layer. The finite size of the unstable layer also allows us to consider the wider effects of flux rope generation. We find that the unstable current layer acts as a source of torsional magnetohydrodynamic waves and dynamic braiding of magnetic fields. The implications of these results to several areas of heliophysics are discussed. V C 2014 AIP Publishing LLC.

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“…Indeed, that the displacement of the null increases with reducing η shows that at realistic coronal values a 3D null will be severely rattled around by buffeting driving flows. This rapid movement could be a potential mechanism to crash together nulls of opposite type (A or B) leading to the null cancellation observed in the null clusters that connect large scale reconnecting separators (Dorelli et al 2007;Parnell et al 2010;Maclean et al 2009). …”

Section: Discussionmentioning

confidence: 99%

“…Single and multiple nulls have been observed in the reconnecting current sheet in the earth's magnetotail through in situ measurements from the cluster satellites (Xiao et al 2006(Xiao et al , 2007, as well as being inferred through fully 3D simulations in the polar cusp regions (Dorelli et al 2007). Their importance has also been noted in reconnection within laboratory plasmas (Gray et al 2010).…”

Section: Introductionmentioning

confidence: 97%

Spine-fan reconnection

Wyper

Jain

Pontin

2012

A&A

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Context. From observations, the atmosphere of the Sun has been shown to be highly dynamic with perturbations of the magnetic field often lacking temporal or spatial symmetry. Despite this, studies of the spine-fan reconnection mode at 3D nulls have so far focused on the very idealised case with symmetric driving of a fixed spatial extent. Aims. We investigate the spine-fan reconnection process for less idealised cases, focusing on asymmetric driving and drivers with different length scales. We look at the initial current sheet formation and whether the scalings developed in the idealised models are robust in more realistic situations. Methods. The investigation was carried out by numerically solving the resistive compressible 3D magnetohydrodynamic equations in a Cartesian box containing a linear null point. The spine-fan collapse was driven at the null through tangential boundary driving of the spine foot points. Results. We find significant differences in the initial current sheet formation with asymmetric driving. Notable is the displacement of the null point position as a function of driving velocity and resistivity (η). However, the scaling relations developed in the idealised case are found to be robust (albeit at reduced amplitudes) despite this extra complexity. Lastly, the spatial variation is also shown to play an important role in the initial current sheet formation through controlling the displacement of the spine foot points. Conclusions. We conclude that during the early stages of spine-fan reconnection both the temporal and spatial nature of the driving play important roles, with the idealised symmetrically driven case giving a "best case" for the rate of current development and connectivity change. As the most interesting eruptive events occur in relatively short time frames this work clearly shows the need for high temporal and spatial knowledge of the flows for accurate interpretation of the reconnection scenario. Lastly, since the scalings developed in the idealised case remain robust with more complex driving we can be more confident of their use in interpreting reconnection in complex magnetic field structures.

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Separator reconnection at Earth's dayside magnetopause under generic northward interplanetary magnetic field conditions

Cited by 86 publications

References 71 publications

Magnetic Null Points in Kinetic Simulations of Space Plasmas

Magnetic Null Points in Kinetic Simulations of Space Plasmas

Dynamic topology and flux rope evolution during non-linear tearing of 3D null point current sheets

Spine-fan reconnection

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