A statistical study of magnetopause structures: Tangential versus rotational discontinuities

Chou, Yu-Chen; Hau, L.‐N.

doi:10.1029/2011ja017155

Cited by 23 publications

(22 citation statements)

References 38 publications

(69 reference statements)

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“…Only 18, respectively, 14 of these crossings, had Walén regression slopes above 0.5. These fractions of cases indicating an RD‐like magnetopause are comparable to the results reported by Chou and Hau () and only slightly higher than the Cluster results in Haaland et al (). For comparison, the MMS dayside study by Paschmann et al () found Walén slopes above 0.5 in around 30% of the cases.…”

Section: Resultssupporting

confidence: 89%

Characteristics of the Flank Magnetopause: THEMIS Observations

et al. 2019

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The terrestrial magnetopause is the boundary that shields the Earth's magnetosphere on one side from the shocked solar wind and its embedded interplanetary magnetic field on the other side. In this paper, we show observations from two of the Time History of Events and Macroscales Interactions during Substorms (THEMIS) satellites, comparing dayside magnetopause crossings with flank crossings near the terminator. Macroscopic properties such as current sheet thickness, motion, and current density are examined for a large number of magnetopause crossings. The results show that the flank magnetopause is typically thicker than the dayside magnetopause and has a lower current density. Consistent with earlier results from Cluster observations, we also find a persistent dawn‐dusk asymmetry with a thicker and more dynamic magnetopause at dawn than at dusk.

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Section: Resultssupporting

confidence: 89%

Characteristics of the Flank Magnetopause: THEMIS Observations

et al. 2019

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“…The change of V x , V y , and V z are in phase (antiphase) with the corresponding magnetic field components on the B z < 0 (B z > 0) side. Such spatial structures are consistent with being rotational discontinuities, or large-amplitude Alfvén waves, as have been found in previous 1-D and 2-D simulations and statistical studies [Lin and Swift, 1996;Lee et al, 1996;Chou and Hau, 2012].…”

Section: Case 3: Infinite X Line Length Finite Guide Fieldsupporting

confidence: 91%

Kinetic Alfvén waves in three‐dimensional magnetic reconnection

et al. 2016

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Alfvénic waves are believed to be fundamentally important in magnetic reconnection. Kinetic dynamics of particles can break the Alfvén speed limit in the evolution and propagation of perturbations during reconnection. In this paper, the generation and signatures of kinetic Alfvén waves (KAWs) associated with magnetic reconnection in a current sheet is investigated using a three‐dimensional (3‐D) hybrid code under a zero or finite guide field. In order to understand the wave structures in the general cases of multiple X line reconnection, cases with a single X line of various lengths are examined. The KAWs are identified using the wave dispersion relation, electromagnetic polarization relations, as well as spectral analysis. In the cases in which the X line is so long to extend through the entire simulation domain in the current direction, quasi 2‐D configurations of reconnection are developed behind a leading flux/plasma bulge. KAWs with perpendicular wave number k⊥ρi∼1 (with ρi being the ion Larmor radius) are found throughout the transient plasma bulge region and propagate outward along magnetic field lines with a slightly super‐Alfvénic velocity. These KAWs are generated from the X line and coexist with the whistler structure of the ion diffusion region under a small guide field. In the cases in which the X line has a finite length 2ξ ∼ 10di, with ξ being the half length of the X line and di the ion inertial length, the KAWs originated from the X line are of 3‐D nature. Under a finite guide field, KAWs propagate along the oblique magnetic field lines into the unperturbed regions in the current direction, carrying parallel electric field and Poynting fluxes. The critical X line length for the generation of 3‐D‐like structures is found to be 2ξc≤30di. The structure, propagation, energy, spectrum, and damping of the KAWs are examined. Dependence of the structure of KAWs on the guide field is also investigated.

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“…For various reasons, including pressure anisotropy and composition effects (see discussion in, e.g., Paschmann and Sonnerup [] about this), values close to unity are rarely observed, however. Both Paschmann et al [] and Chou and Hau [] therefore classified cases with Walén slopes greater than 0.5 as RDs. We will adapt these thresholds also for classifications of our events.…”

Section: Characteristics Of the Magnetopause Flanksmentioning

confidence: 99%

Characteristics of the flank magnetopause: Cluster observations

et al. 2014

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Key Points:• The magnetopause posesses a dawn-dusk asymmetry • The flank magnetopause is thicker than the dayside magnetopause • The magnetopause often consists of layered current sheets Abstract The magnetopause is a current sheet forming the boundary between the geomagnetic field on one side and the shocked solar wind on the other side. This paper discusses properties of the low-latitude dawn and dusk flanks of the magnetopause. The reported results are based on a large number of measurements obtained by the Cluster satellites during magnetopause traversals. Using a combination of single-spacecraft and multispacecraft techniques, we calculated macroscopic features such as thickness, location, and motion of the magnetopause. The results show that the typical flank magnetopause is significantly thicker than the dayside magnetopause and also possesses a pronounced and persistent dawn-dusk asymmetry. Thicknesses vary from 150 to 5000 km, with an median thickness of around 1400 km at dawn and around 1150 km at dusk. Current densities are on average higher on dusk, suggesting that the total current at dawn and dusk are similar. Solar wind conditions and the interplanetary magnetic field cannot fully explain the observed dawn-dusk asymmetry. For a number of crossings we were also able to derive detailed current density profiles. The profiles show that the magnetopause often consists of two or more adjacent current sheets, each current sheet typically several ion gyroradii thick and often with different current direction. This demonstrates that the flank magnetopause has a structure that is more complex than the thin, one-dimensional current sheet described by a Chapman-Ferraro layer.

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A statistical study of magnetopause structures: Tangential versus rotational discontinuities

Cited by 23 publications

References 38 publications

Characteristics of the Flank Magnetopause: THEMIS Observations

Characteristics of the Flank Magnetopause: THEMIS Observations

Kinetic Alfvén waves in three‐dimensional magnetic reconnection

Characteristics of the flank magnetopause: Cluster observations

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