On magnetic curl in front of the magnetosphere boundary

Energetic electron (E >20 keV) and ion (E >25 keV) enhancements have been observed using the Isee 1 and 2 spacecraft during magnetic flux transfer events in the dayside magnetosheath just outside the magnetopause. The ions are seen to be streaming along the magnetic field, filling the 90°–180° pitch angle region. The electrons are more isotropic and yet exhibit slight anisotropy in the direction opposite to that of the ions. From their intensities and spectra the ions appear to be of magnetospheric origin. With the interpretation of the flux transfer events as ‘patchy’ interconnection of magnetosheath and magnetospheric field lines, the ions are then seen to be previously trapped magnetospheric particles escaping along freshly opened field lines.

Section: Discussionmentioning

confidence: 83%

Particle signature of magnetic flux transfer events at the magnetopause

Daly

Williams²,

Russell³

et al. 1981

“…The antiparallel merging lines in this case lie along the y and z axes [Crooker, 1979] Following Sonnerup's [1980] suggestion that the magnetic curl may be very thin, Podgorny et al [1980] give evidence in a later paper that the curl collapses into a series of X-and O-type neutral points, consistent with being subject to the tearing mode instability. Further, their simulated boundary For other than purely southward IMF, Podgorny et al [1978bPodgorny et al [ , 1980 suggest that the large magnetic curl or loop becomes a coil. If, like the large curl, the large coil collapses by the tearing mode instability, then a series of small coils rather than small loops will result.…”

Section: Analysis and Resultsmentioning

confidence: 94%

A split separator line merging model of the dayside magnetopause

Crooker¹

1985

A new magnetic field configuration in the magnetopause of an open magnetosphere is constructed by superposing a uniform field and the idealized Chapman‐Ferraro field. A straightforward interpretation of the results synthesizes previously unrelated models and observations: antiparallel and subsolar merging, uniform‐field‐plus‐dipole models, merging by the tearing mode instability, the magnetic curl configuration in laboratory terella experiments, flux transfer events, and accelerated boundary layer flows.

“…Although our simulation does not produce the signatures associated with standard FTEs, it does produce several other features that are commonly associated with magnetopause crossings, namely, those obtained experimentally by Podgorny et al [1980], Saunders [ 1989], and Elphic [1990] concerning the location, repetition rate, and size of FTEs. Furthermore, it allows us to examine a suggestion by Cowley [ 1982] that tension in draped magnetosheath/magnetospheric magnetic field lines effectively flattens FIEs against the magnetopause.…”

Section: Introductionmentioning

confidence: 99%

Flux transfer events produced by bursty merging at a single X line

Ku¹,

Sibeck²

1998

Abstract. We present predictions for the signatures of flux transfer events (FTEs) at the dayside magnetopause produced by bursty merging at a single extended X line. In this MHD model, the time-dependent enhanced local resistivity tums on at a low northern latitude for a brief time and then tums off. Realistic ratios of magnetosheath to magnetosphere parameters are chosen to conform with observations and our previous simulations [Ku and Sibeck, 1997]: Pmsh/Psph = 10, Bmsh/Bsp h = 0.5, and rmsh/rsp h = 0.175. The burst of merging produces FTEs marked by strongly asymmetric bipolar magnetic field and plasma velocities normal to the magnetopause in the magnetosheath and no significant signatures in the magnetosphere, just as in the previously studied case for the step-function onset of merging [Ku and Sibeck, 1997]. However, the simulation produces other FTE signatures that differ strikingly from those generated by the step-function onset of merging. After the resistivity is switched off, one or more secondary reconnection sites appear on the trailing edge of the events. Merging at these sites inflates and propels the main FTE as it moves out of the simulation domain. Merging at these sites also fills a magnetic island with hot tenuous plasma near the subsolar (symmetry) point. Transient magnetic islands form on the trailing edge of the main FTE, but these remain small and may disappear. Scatterplots of various parameters versus the plasma density reveal that steep changes for the temperature kT, magnetic field B z, and the Alfv6n velocity occur on the magnetosheath side immediately adjacent to the magnetopause and also reflect the fact that the events scarcely deform the magnetopause.