SPP - Space and Plasma Physics Laboratory
Centre de recherche public Accréditation CIR
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Téléphone : 46 (0)8 790 60 00
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Adresse :
KTH, School of Electrical Engineering
Osquldas väg 10
100 44 Stockholm
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Description
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The research aims to further our understanding of fundamental properties of matter in the plasma state, especially its electrodynamic properties, such as ability to carry electric current, to support electric fields, and to rapidly release magnetically stored energy. Laboratory activities deal with double layers and dusty plasmas whereas space experiments aim to further understand the aurora, space weather, solar wind - magnetosphere - ionosphere interaction, and the plasma environments of other planets.
The research profits from a fruitful combination of space experiments and laboratory experiments as well as theory and numerical simulation. We participate in a number of spacecraft missions and we also run a programme of ground based observations. Laboratory experiments are carried out in-house as well as in collaboration with others. The research activities can be divided into seven main research areas, further described under each of the headings below. - Auroral Physics - Magnetospheric Physics - Solar System Plasma Physics - Complex Plasmas - Plasma Propulsion - Applied Plasma Physics - Basic Plasma Physics |
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Profil scientifique partiel |
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Domaines étudiés partiels
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Domaines scientifiques
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Quelques documents de Space and Plasma Physics Laboratory
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A bulk plasma model for dc and HiPIMS magnetrons
Auteurs :
Nils Brenning
Masquer le résumé
A plasma discharge model has been developed for the bulk plasma (also called the extended presheath) in sputtering magnetrons. It can be used both for high power impulse magnetron sputtering (HiPIMS) and conventional dc sputtering magnetrons. Demonstration calculations are made for the parameters of the HiPIMS sputtering magnetron at Link oping University, and also benchmarked against results in the literature on dc magnetrons. New insight is obtained regarding the structure and time development of the currents, the electric fields and the potential profiles. The transverse resistivity eta(perpendicular to) has been identified as having fundamental importance both for the potential profiles and for the motion of ionized target material through the bulk plasma. New findings are that in the HiPIMS mode, as a consequence of a high value of eta(perpendicular to), (1) there can be an electric field reversal that in our case extends 0.01-0.04m from the target, (2) the electric field in the bulk plasma is typically an order of magnitude weaker than in dc magnetrons, (3) in the region of electric field reversal the azimuthal current is diamagnetic in nature, i.e. mainly driven by the electron pressure gradient, and actually somewhat reduced by the electron Hall current which here has a reversed direction and (4) the azimuthal current above the racetrack can, through resistive friction, significantly influence the motion of the ionized fraction of the sputtered material and deflect it sideways, away from the target and towards the walls of the magnetron.
Cluster observations of an auroral potential and associated field-aligned current reconfiguration during thinning of the plasma sheet boundary layer
Auteurs :
Göran Marklund
Masquer le résumé
Cluster observations are used to illustrate the reconfiguration of an auroral potential structure encountered at the poleward boundary of the central plasma sheet within the Southern Hemisphere premidnight auroral oval. The reconfiguration from a symmetric U shape to an asymmetric S shape takes place between two consecutive crossings by Cluster spacecraft 1 and 2, moving along roughly the same orbits and separated in time by 16 min. During this time the plasma conditions poleward of the boundary changed dramatically. The fluxes of energetic electrons decreased, as did the intensities of the associated small-scale field-aligned currents (FACs) and the ambient plasma density. These changes were particularly pronounced in a narrow region adjacent to the boundary. The reconfiguration of the potential structure, and of the associated FAC system consistent with this, are consistent with the predictions by Marklund et al. (2004).
Keywords :
PARALLEL ELECTRIC-FIELDS; RETURN CURRENT REGION; PARTICLE-ACCELERATION; BLACK AURORA; MAGNETOSPHERE; EVOLUTION; ARCS ; NATURAL SCIENCES
Source :
Libris SwePub
Cluster observations of an auroral potential and associated field-aligned current reconfiguration during thinning of the plasma sheet boundary layer
Auteurs :
Göran Marklund
Masquer le résumé
Cluster observations are used to illustrate the reconfiguration of an auroral potential structure encountered at the poleward boundary of the central plasma sheet within the Southern Hemisphere premidnight auroral oval. The reconfiguration from a symmetric U shape to an asymmetric S shape takes place between two consecutive crossings by Cluster spacecraft 1 and 2, moving along roughly the same orbits and separated in time by 16 min. During this time the plasma conditions poleward of the boundary changed dramatically. The fluxes of energetic electrons decreased, as did the intensities of the associated small-scale field-aligned currents (FACs) and the ambient plasma density. These changes were particularly pronounced in a narrow region adjacent to the boundary. The reconfiguration of the potential structure, and of the associated FAC system consistent with this, are consistent with the predictions by Marklund et al. (2004).
Keywords :
PARALLEL ELECTRIC-FIELDS; RETURN CURRENT REGION; PARTICLE-ACCELERATION; BLACK AURORA; MAGNETOSPHERE; EVOLUTION; ARCS ; NATURAL SCIENCES
Source :
Libris SwePub
Divergent electric fields in downward current channels
Auteurs :
Göran Marklund
Masquer le résumé
[ 1] The results from a numerical study on the formation and dynamics of the localized, diverging perpendicular electric fields found in the nightside auroral magnetosphere are presented. These fields are frequently observed inside the downward magnetic field-aligned current (FAC) channels where the electrons flow upward from the ionosphere. The present study focuses on one particular example of the dynamics of such structures that was recorded by the Cluster spacecrafts on 14 January 2001. Simulations show that the localized, divergent electric fields observed by Cluster can be provided by the interactions between downward FACs and the ionosphere. Conditions promoting the formation of these fields include low ionospheric conductivities and solitary downward current channels. Numerical simulations are used to explain the dynamics of the currents and electric fields observed by the Cluster satellites during this event and also show that such electric fields are not normally detected in the upward current channels.
Keywords :
alfven waves ; auroral arcs ; magnetosphere ; ionosphere ; reflection ; electrodynamics ; acceleration ; region ; freja
Source :
Libris SwePub
On the profile of intense high-altitude auroral electric fields at magnetospheric boundaries
Auteurs :
Göran Marklund
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The profile of intense high-altitude electric fields on auroral field lines has been studied using Cluster data. A total of 41 events with mapped electric field magnitudes in the range between 0.5-1 V/m were examined, 27 of which were co-located with a plasma boundary, defined by gradients in particle flux, plasma density and plasma temperature. Monopolar electric field profiles were observed in 11 and bipolar electric field profiles in 16 of these boundary-associated electric field events. Of the monopolar fields, all but one occurred at the polar cap boundary in the late evening and midnight sectors, and the electric fields were typically directed equatorward, whereas the bipolar fields all occurred at plasma boundaries clearly within the plasma sheet. These results support the prediction by Marklund et al. (2004), that the electric field profile depends on whether plasma populations, able to support intense field-aligned currents and closure by Pedersen currents, exist on both sides, or one side only, of the boundary.
Keywords :
magnetospheric physics ; auroral phenomena ; electric fields ; magnetosphere-ionosphere interactions ; current region ; double-layers ; cluster ; arcs ; plasma ; signatures ; sheet ; evolution ; waves
Source :
Libris SwePub
Evidence of standing waves during a Pi2 pulsation event observed on Cluster
Auteurs :
Lars G. Blomberg
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Observations of Pi2 pulsations at middle and low latitudes have been explained in terms of cavity mode resonances, whereas transients associated with field-aligned currents appear to be responsible for the high latitude Pi2 signature. Data from Cluster are used to study a Pi2 event observed at 18:09 UTC on 21 January 2003, when three of the satellites were within the plasmasphere (L=4.7,4.5 and 4.6) while the fourth was on the plasmapause or in the plasmatrough (L=6.6). Simultaneous pulsations at ground observatories and the injection of particles at geosynchronous orbit corroborate the occurrence of a substorm. Evidence of a cavity mode resonance is established by considering the phase relationship between the orthogonal electric and magnetic field components associated with radial and field-aligned standing waves. The relative phase between satellites located on either side of the geomagnetic equator indicates that the field-aligned oscillation is an odd harmonic. Finite azimuthal Poynting flux suggests that the cavity is effectively open ended and the azimuthal wave number is estimated as m similar to 13.5.
Keywords :
magnetospheric physics ; MHD waves and instabilities ; plasmasphere ; storms and substorms ; pi-2 pulsations ; power spectra ; magnetic pulsations ; ulf pulsations ; field-line ; geomagnetic micropulsations ; geosynchronous orbit ; hydromagnetic-waves ; inner magnetosphere ; substorm onsets
Source :
Libris SwePub
Statistics of a parallel Poynting vector in the auroral zone as a function of altitude using Polar EFI and MFE data and Astrid-2 EMMA data
Auteurs :
Lars G. Blomberg
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We study the wave-related (AC) and static (DC) parallel Poynting vector (Poynting energy flux) as a function of altitude in auroral field lines using Polar EFI and MFE data. The study is statistical and contains 5 years of data in the altitude range 5000-30 000km. We verify the low altitude part of the results by comparison with earlier Astrid-2 EMMA Poynting vector statistics at 1000km altitude. The EMMA data are also used to statistically compensate the Polar results for the missing zonal electric field component. We compare the Poynting vector with previous statistical DMSP satellite data concerning the electron precipitation power. We find that the AC Poynting vector (Alfvenwave related Poynting vector) is statistically not sufficient to power auroral electron precipitation, although it may, for K-P> 2, power 25-50% of it. The statistical AC Poynting vector also has a stepwise transition at R=4 R-E, so that its amplitude increases with increasing altitude. We suggest that this corresponds to Alfven waves being in Landau resonance with electrons, so that wave-induced electron acceleration takes place at this altitude range, which was earlier named the Alfven Resonosphere (ARS). The DC Poynting vector is similar to 3 times larger than electron precipitation and corresponds mainly to ionospheric Joule heating. In the morning sector (02:00-06:00 MLT) we find that the DC Poynting vector has a nontrivial altitude profile such that it decreases by a factor of similar to 2 when moving upward from 3 to 4 RE radial distance. In other nightside MLT sectors the altitude profile is more uniform. The morning sector nontrivial altitude profile may be due to divergence
Keywords :
magnetospheric physics ; auroral phenomena ; magnetosphere-ionosphere interactions ; space plasma physics ; wave-particle interactions ; electric-fields ; flux ; satellite ; frequency ; de-2
Source :
Libris SwePub
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