On the use of photometer data to map dynamics of the magnetotail current sheet during substorm growth phase

Wanliss, J. A.; Samson, J. C.; Friedrich, E.

doi:10.1029/2000ja000178

Cited by 24 publications

(41 citation statements)

References 41 publications

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“…We assume that during the growth phase stretching of the tail and plasma sheet thinning take place without a major reconfiguration of magnetic field lines. This is not an unreasonable assumption, and several studies have shown how this is consistent with data observations (Kaufmann, 1987;Wanliss et al, 2000). The important thing to note is that mapping is done during substorm growth phase when slow changes ensure that the models are most likely to provide results within reason.…”

Section: Magnetic Field Modelssupporting

confidence: 58%

“…Mapping from the ionosphere to the magnetotail would correspondingly result in magnetotail locations somewhat closer than actually was the case. They have also indicated that thin current sheets in the inner tail are an important governing component of the overall growth phase dynamics Wanliss et al, 2000Wanliss et al, , 2002. At substorm onset, the initial disturbance location and timing is sensitively dependent on the stability properties of the thin current sheet .…”

Section: Discussionmentioning

confidence: 99%

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Substorm onset location and dipole tilt angle

Wanliss

2006

Ann. Geophys.

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Abstract. From an initial data set of over 200 substorms we have studied a subset of 30 magnetospheric substorms close to magnetic midnight to investigate, in a statistical fashion, the source region of the auroral arc that brightens at the onset of expansive phase. This arc is usually identified as the ionospheric signature of the expansive phase onset that occurs in the magnetotail. All the substorm onsets were identified via ground-based magnetometer and photometer data from the CANOPUS array. Various Tsyganenko global magnetic field models were used to map magnetic field lines from the location of the onset arc out to its greatest radial distance in the magnetotail. The results appear to favour the current disruption model of substorms since the average onset location has an average of 14.1 Earth radii (R E ) and is therefore more consistent with theories that place the onset location in the inner magnetotail. For the narrow range of tilts available our modeling indicates the parameter that appears to strongly influence the location of the substorm onset is the dipole tilt angle; as tilt becomes less negative onsets occur further downtail.

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Section: Magnetic Field Modelssupporting

confidence: 58%

Section: Discussionmentioning

confidence: 99%

Substorm onset location and dipole tilt angle

Wanliss

2006

Ann. Geophys.

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“…[39] Liu et al [2007] elaborate that there are two scenarios for equatorward motion of aurora: 1) Earthward displacement of plasma which may lead to pressure buildup and 2) tailward stretching of field lines where nonadiabatic protons are pitch angle scattered by the small radius of the magnetic field line curvature closer to the Earth [Wanliss et al, 2000]. The latter scenario was suggested to account for both equatorward motion and fading of proton aurora.…”

Section: Equatorward Motion Of Aurora and Field-aligned Currentmentioning

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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“…The WFR creates a region of minimum-B in the near-Earth plasma sheet. Figure 1 of Wanliss et al (2000a) (not shown here) gives a profile of our model magnetic field in the current sheet, compared to observations, and shows the region of minimum-B. The WFR is located around 11 R E to accord with observations (Kaufmann, 1987;Baker and McPherron, 1990;Iijima et al, 1993;Baker et al, 1993;Sergeev et al, 1993;Nakai et al, 1997).…”

Section: Magnetic Fieldmentioning

confidence: 51%

“…It was used by Wanliss et al (2000a) to model the substorm growth phase, during which the midnight sector magnetic field becomes more stretched than at other times. We chose to use this simple model because it is easier to attain a stretched configuration than for the most commonly used statistical models.…”

Section: Magnetic Fieldmentioning

confidence: 99%

Origin of some anisotropic tailward flows in the plasma sheet

et al. 2002

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Abstract. We use a test particle model to explore anisotropy and fast flows in the central plasma sheet (CPS) that are a consequence of plasma sheet boundary layer (PSBL) ion beam dynamics. Ion distributions and flows (velocity moments) in the CPS and equatorial current sheet (CS) are compared and we find that mirroring of initially earthward beams from the PSBL, and their subsequent convection to the CS region, results in strong anisotropy throughout the CPS. At higher latitudes, velocity moments are field-aligned and feature earthward flow. Deeper in the CPS, velocity moments yield flows in the anti-earthward direction. There is no clear distinction between the PSBL and CPS, since velocity distributions with large streaming components occur throughout the model CPS, but in the CS region they are anisotropic and nongyrotropic. In the CS region velocity moments can feature anti-earthward cross field flows. These tailward flows (> 400 km/s) are observed in the CS region between X = −20 to −30 R E due to nonadiabatic effects. Model results suggest that fast tailward plasma flows can be obtained without necessarily appealing to magnetotail processes associated with dynamic geomagnetic activity.

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On the use of photometer data to map dynamics of the magnetotail current sheet during substorm growth phase

Cited by 24 publications

References 41 publications

Substorm onset location and dipole tilt angle

Substorm onset location and dipole tilt angle

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

Origin of some anisotropic tailward flows in the plasma sheet

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