Open Geospace General Circulation Model simulation of a substorm: Axial tail instability and ballooning mode preceding substorm onset

Raeder, J.; Zhu, Ping; Ge, Yasong; Siscoe, G. L.

doi:10.1029/2010ja015876

Cited by 62 publications

(70 citation statements)

References 67 publications

(92 reference statements)

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“…Such mode, named K Y 0 mode, indeed was found unexpectedly during numerical modeling (Raeder et al, 2010). The instability growth rate increases with the increase of k y in the range k y a 1, and reaches the saturation for the azimuthal wave numbers k y a 1.…”

Section: Discussionmentioning

confidence: 97%

“…The computer experiments with advanced models of the magnetosphere showed that the substorm onset was caused by violation of the balance between the thermal plasma pressure and Ampere's force, resulting into the plasma expulsion and field lines extension into the magnetotail (Raeder et al, 2010).…”

Section: Introduction: Ballooning Instability Of Nearearth Plasma As mentioning

confidence: 99%

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Ballooning modes and their stability in a near-Earth plasma

2013

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As a possible trigger of the substorm onset, the ballooning instability has been often suggested. The ballooning disturbances in a finite-pressure plasma immersed into a curved magnetic field are described with the system of coupled equations for the Alfven and slow magnetosonic modes. The spectral properties of ballooning disturbances and instabilities can be characterized by the local dispersion equation. The basic system of equations can be reduced to the dispersion equation for the small-scale in transverse direction disturbances. From this relationship the dispersion, instability threshold, and stop-bands of the Alfvenic and slow magnetosonic modes have been determined. The field-aligned structure of unstable mode is described with the solution of the eigenvalue problem in the Voigt model. We have also analyzed in a cylindrical geometry an eigenvalue problem for the stability of ballooning disturbances with a finite scale along the plasma inhomogeneity. The account of a finite scale in the radial direction raises the instability threshold as compared with that in the WKB approximation.

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Section: Discussionmentioning

confidence: 97%

Section: Introduction: Ballooning Instability Of Nearearth Plasma As mentioning

confidence: 99%

Ballooning modes and their stability in a near-Earth plasma

2013

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“…A similar scenario emphasizing the role of the high beta on closed field lines has also been suggested for solar flares [Shibasaki, 2003]. The stability of 2D (x, z) magnetotail in a high beta plasma has been examined both theoretically and numerically by various authors studying the ballooning instability [e.g., Miura et al, 1989;Lee and Wolf, 1992;Hurricane, 1997;Pu et al, 1997;Bhattacharjee et al, 1998;Cheng and Lui, 1998;Horton et al, 2001;Zhu et al, 2007;Pritchett and Coroniti, 2010;Raeder et al, 2010] and also the tearing instability [Sitnov and Schindler, 2010]. Collisionless plasmas in inhomogeneous magnetic fields are subject to various kinetic effects such as bounce motion of particles.…”

Section: Introductionmentioning

confidence: 99%

Structure, force balance, and evolution of incompressible cross-tail current sheet thinning

Saito

Fairfield

et al. 2011

J. Geophys. Res.

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[1] THEMIS five-point observations on April 8, 2009 were used to study thinning of the current sheet in the near-Earth tail that led to the onset of a small substorm. Taking advantage of a fortuitous alignment of the five spacecraft near 2300 LT and 11 R E and within 1.5 R E of the current sheet center, latitudinal gradients are analyzed. A significant latitudinal pressure gradient is present indicating the necessity of a (J × B) z force to maintain the pre-onset equilibrium state. During thinning the total pressure remained approximately constant at all spacecraft rather than increasing. Within the plasma sheet, magnetic field strength increased while plasma pressure decreased due to decreasing temperature. We present a comprehensive explanation for the relationship between the thinning, the stretched structure, and development of intense current density. Our analysis of this event suggests that (1) the thinning in this event is an MHD force-balanced self-evolving process and is not a forced process due to an increased lobe field; (2) the thinning changes flux tube structure in length and curvature but not significantly in volume; (3) the thinning evolves with a change of the radial plasma pressure profile in the near-Earth tail, which is associated with a locally intensified current sheet. The conclusion is that the increased lobe field strength is not the necessary and the primary cause for cross tail current sheet thinning but rather thinning can occur within the plasma sheet as a result of unknown internal processes.

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“…[5] In this paper, we will present detailed results from an idealized OpenGGCM MHD simulation, based on a substorm event that occurred on 23 March 2007-an event that has been studied by Raeder et al [2008], Zhu et al [2009], Hu et al [2010], and Raeder et al [2010] using realistic solar wind and IMF input. We show that a bubble-blob pair forms naturally in the simulation and discuss the reason for their formation.…”

Section: Introductionmentioning

confidence: 99%

Consequences of violation of frozen-in-flux: Evidence from OpenGGCM simulations

Wolf

Toffoletto

et al. 2011

J. Geophys. Res.

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[1] It is widely believed that during a substorm, plasma instabilities occur before the onset of magnetic reconnection, signaling the end of the growth phase. Despite many years of effort, however, the details of how the instability and the onset of reconnection develop from closed field line configuration with finite normal magnetic field are not well understood. In this paper, we study an idealized simulation of a substorm that occurred on 23 March 2007, based on the Open Geospace General Circulation Model (OpenGGCM). Our analysis emphasizes the time development of the distribution of the entropy parameter and its convective time derivative, which should be zero in ideal MHD. In the late growth phase, the simulation exhibits, over a range of local times, a systematic violation of conservation of entropy that corresponds to what is called "antidiffusion." Out of this background, a more localized disturbance develops in a region of high magnetic stretching, resulting in formation of a strong reduction of entropy (bubble) earthward of a local enhancement (blob). The process is accelerated when the current density exceeds a threshold for triggering an explicit resistivity in the code. The bubble moves earthward and the blob tailward, which leads to a reduction of the normal magnetic field and a thinning of the current sheet between them, making the magnetospheric configuration more conducive to tearing and other instabilities (we do not address specifically which instability has occurred). This positive feedback gives rise to increased violation of the perfect conductivity relation and eventually reconnection.

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Open Geospace General Circulation Model simulation of a substorm: Axial tail instability and ballooning mode preceding substorm onset

Cited by 62 publications

References 67 publications

Ballooning modes and their stability in a near-Earth plasma

Ballooning modes and their stability in a near-Earth plasma

Structure, force balance, and evolution of incompressible cross-tail current sheet thinning

Consequences of violation of frozen-in-flux: Evidence from OpenGGCM simulations

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