Geomagnetopause surface fluctuations observed by Voyager 1

Lepping, R. P.; Burlaga, L. F.

doi:10.1029/ja084ia12p07099

Cited by 73 publications

(35 citation statements)

References 21 publications

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“…Note also that when Geotail crosses the boundary layer during the time interval C, with relatively large clock angle, the position of Geotail near the equator and close to the stagnation region (Figure 1) is not the most favorable for meaningful comparison with the wave activity at Cluster . Moreover, to derive properties, including the phase speed, of wave activity at Geotail , would require a single spacecraft method as employed by Lepping and Burlaga [1979], which assumes a sinusoidal shape of the waves. For these reasons, we leave out the comparison between the two‐point observations at Cluster and Geotail during the time interval C.…”

Section: Resultsmentioning

confidence: 99%

Evolution of Kelvin‐Helmholtz activity on the dusk flank magnetopause

et al. 2008

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[1] Our purpose is to characterize the evolution of the magnetopause Kelvin-Helmholtz (KH) wave activity with changes in thickness of the adjacent boundary layer, geomagnetic latitude and interplanetary magnetic field (IMF) orientation. As the IMF turns northward, wave activity may be generated at the dayside before propagating down the tail, where the boundary layer is expected to support longer wavelengths. We use two-point observations on the dusk magnetopause at low latitudes, from Geotail on the dayside and Cluster tailward of the dusk terminator. We quantify the wavelength, power, wavefront steepness and propagation direction at Cluster. An estimate of the thickness of the low-latitude boundary layer (LLBL) is obtained by correlating normal distances to the magnetopause, derived from two empirical solar-wind-driven models, with a systematic relationship (the ''transition parameter'') found between the electron number density and temperature; the correlation factor is used to infer the temporal evolution of the thickness of the locally sampled layer. We find that wavelengths are controlled by the IMF clock angle, as expected when generated by the KH mechanism at the dayside, although amplitudes, wavefront steepness and propagation directions are more closely correlated with the layer thickness. A survey of parameter space provides evidence of the contribution of the KH mechanism to the widening of the electron LLBL.

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Section: Resultsmentioning

confidence: 99%

Evolution of Kelvin‐Helmholtz activity on the dusk flank magnetopause

et al. 2008

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“…Such waves may be common; for example, Lepping and Burlaga [1979] saw oscillations of the dawn magnetopause which they interpreted as surface waves of amplitude 1/3 Re, and wavelength 4 Re. These more regular pulsations, with a period of -4.5 min, die out at -7.2 Re at -1145 UT, as the average magnetic field strength climbs to near 100 nT.…”

Section: Interpretation Of the Event Seen On Iseementioning

confidence: 99%

Pc 5 pulsations in the outer dawn magnetosphere seen by ISEE 1 and 2

et al. 1990

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A long‐lasting Pc 5 pulsation at the dawn flank of the magnetosphere is studied using particle and field instrumentation from the ISEE 1 and 2 satellites. Electric field and particle modulation signatures were clearer than magnetic field variations, consistent with the satellites' position in latitude near the equatorial node of a fundamental resonance. Pulsation flow velocities along the ISEE 1 trajectory were calculated from particle characteristics using data from several instruments and from electric and magnetic field data. These flow velocities were all consistent with each other, but the velocities derived from plasma and energetic particle observations were a factor of 2.5 larger than velocities derived from the fields data. We have not been able to find the source of this discrepancy; one possibility is that the field near the spacecraft differs from the large‐scale field. In contrast to observations of pulsations during magnetic storms, which often involve resonant or gyrating particle behavior, particles at all energies sampled (10 eV to 200 keV) appeared to respond passively to the pulsation throughout most of the period of interest. Comparison of data from the two spacecraft, which traveled from ∼15 RE to ∼7 RE with a time separation of ∼1 hour, suggests the propagation of relatively broadband pulsation energy from the magnetopause/low latitude boundary layer and subsequent resonance of independent L shells in the fundamental toroidal mode after the cessation of power input.

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“…Several studies have reported evidences of KH instability at the Earth's magnetopause since the early observation by Lepping and Burlaga (1979). These authors developed a method to infer the amplitude and the wavelength of the KH instability.…”

Section: Discussionmentioning

confidence: 99%

On the incidence of Kelvin-Helmholtz instability for mass exchange process at the Earth’s magnetopause

Smets

Delcourt²,

Chanteur³

et al. 2002

Ann. Geophys.

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Abstract. Due to the velocity shear imposed by the solar wind flowing around the magnetosphere, the magnetopause flanks are preferred regions for the development of a KelvinHelmholtz instability. Since its efficiency for momentum transfer across the magnetopause has already been established, we investigate its efficiency for mass transfer. Using nonresistive magnetohydrodynamic simulations to describe the magnetic field shape in the instability region, we use testparticle calculations to analyse particle dynamics. We show that the magnetopause thickness and the instability wavelength are too large to lead to nonadiabatic motion of thermal electrons from the magnetosphere.On the other hand, the large mass of H + , He + and O + ions leads to such nonadiabatic motion and we thus propose the Kelvin-Helmholtz instability as a mechanism for either magnetospheric ion leakage into the magnetosheath or solar wind ion entry in the magnetosphere. Test-particle calculations are performed in a dimensionless way to discuss the case of each type of ion. The crossing rate is of the order of 10%. This rate is anti-correlated with shear velocity and instability wavelength. It increases with the magnetic shear. The crossing regions at the magnetopause are narrow and localized in the vicinity of the instability wave front. As a KelvinHelmholtz instability allows for mass transfer through the magnetopause without any resistivity, we propose it as an alternate process to reconnection for mass transfer through magnetic boundaries.

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Geomagnetopause surface fluctuations observed by Voyager 1

Cited by 73 publications

References 21 publications

Evolution of Kelvin‐Helmholtz activity on the dusk flank magnetopause

Evolution of Kelvin‐Helmholtz activity on the dusk flank magnetopause

Pc 5 pulsations in the outer dawn magnetosphere seen by ISEE 1 and 2

On the incidence of Kelvin-Helmholtz instability for mass exchange process at the Earth’s magnetopause

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