Search Publications
First results from ideal 2-D MHD reconstruction: magnetopause reconnection event seen by Cluster
Teh, W. -L.; Ã-. Sonnerup, B. U.
We have applied a new reconstruction method (Sonnerup and Teh, 2008), based on the ideal single-fluid MHD equations in a steady-state, two-dimensional geometry, to a reconnection event observed by the Cluster-3 (C3) spacecraft on 5 July 2001, 06:23 UT, at the dawn-side Northern-Hemisphere magnetopause. The event has been previously studied by use …
On nonstationarity and rippling of the quasiperpendicular zone of the Earth bow shock: Cluster observations
Dudok de Wit, T.; Krasnoselskikh, V. V.; Lobzin, V. V. +1 more
A new method for remote sensing of the quasiperpendicular part of the bow shock surface is presented. The method is based on analysis of high frequency electric field fluctuations corresponding to Langmuir, upshifted, and downshifted oscillations in the electron foreshock. Langmuir waves usually have maximum intensity at the upstream boundary of t…
Observation of three distinct ion populations at the Kelvin-Helmholtz-unstable magnetopause
Lavraud, B.; Taylor, M. G. G. T.
We report Double Star spacecraft observations of the dusk-flank magnetopause and its boundary layer under predominantly northward interplanetary magnetic field (IMF). Under such conditions the flank low-latitude boundary layers (LLBL) of the magnetosphere are known to broaden. The primary candidate processes associated with the transport of solar …
Cluster observations of near-Earth magnetospheric lobe plasma densities a statistical study
Haaland, S.; Lybekk, B.; Pedersen, A. +1 more
The Cluster-mission has enabled a study of the near-Earth magnetospheric lobes throughout the waning part of solar cycle 23. During the first seven years of the mission the satellites crossed this region of space regularly from about July to October. We have obtained new and more accurate plasma densities in this region based on spacecraft potenti…
Dependence of the open-closed field line boundary in Saturn's ionosphere on both the IMF and solar wind dynamic pressure: comparison with the UV auroral oval observed by the HST
Belenkaya, E. S.; Badman, S. V.; Cowley, S. W. H. +2 more
We model the open magnetic field region in Saturn's southern polar ionosphere during two compression regions observed by the Cassini spacecraft upstream of Saturn in January 2004, and compare these with the auroral ovals observed simultaneously in ultraviolet images obtained by the Hubble Space Telescope. The modelling employs the paraboloid model…
The redshifted footpoints of coronal loops
Parenti, S.; Dwivedi, B. N.; Curdt, W. +1 more
The physics of coronal loops holds the key to understanding coronal heating and the flow of mass and energy in the region. However, the energy source, structure maintenance and mass balance in coronal loops are not yet fully understood. Observations of blue- and redshifted emissions have repeatedly been used in the construction of loop models. But…
Least-squares multi-spacecraft gradient calculation with automatic error estimation
de Keyser, J.
Multi-spacecraft missions allow the gradient of important physical quantities in the terrestrial environment to be determined. The gradient can be computed from four simultaneous measurements in a straightforward way, but this computation does not produce proper error estimates, making it hard to assess the meaningfulness of the result. Recently d…
GALS - Gradient Analysis by Least Squares
Hamrin, M.; Vaivads, A.; Rönnmark, K. +2 more
We present a method, GALS (Gradient Analysis by Least Squares) for estimating the gradient of a physical field from multi-spacecraft observations. To obtain the best possible spatial resolution, the gradient is estimated in the frame of reference where structures in the field are essentially locally stationary. The estimates are refined iterativel…
Foreshock density holes in the context of known upstream plasma structures
Parks, G. K.; Mazelle, C.; Harris, A. +4 more
We present case examples of foreshock density holes and results from a statistical survey, which provide additional characterizations of these recently-described structures. Specific effort is made to place these objects into context with well-studied foreshock phenomena, such as hot flow anomalies (HFAs) and large-amplitude magnetic pulsations (S…
Correlation length of magnetosheath fluctuations: Cluster statistics
Němeček, Z.; Gutynska, O.; Afránková, J. Å.
Magnetosheath parameters are usually described by gasdynamic or magnetohydrodynamic (MHD) models but these models cannot account for one of the most important sources of magnetosheath fluctuations the foreshock. Earlier statistical processing of a large amount of magnetosheath observations has shown that the magnetosheath magnetic field and plasma…