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  • 1. Aikio, A T
    et al.
    Blomberg, Lars
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Marklund, Göran
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Yamauchi, M
    On the origin of the high-altitude electric field fluctuations in the auroral zone1996In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 101, no A12, p. 27157-27170Article in journal (Refereed)
    Abstract [en]

    Intense fluctuations in the electric field at high altitudes in the auroral zone are frequently measured by the Viking satellite. We have made an analysis of the origin of electric and magnetic fluctuations in the frequency range of 0.1 - 1 Hz by assuming four different sources for the signals: (I) spatial structures, (2) spatial structures with a parallel potential drop below the satellite, (3) traveling; shear Alfven waves, and (4) interfering shear Alfven waves. We will shaw that these different sources of the signals may produce similar amplitude ratios and phase differences between the perpendicular electric and magnetic fields. Since the different sources have different frequency dependencies, this can be used as an additional test if the signals are broadband. In other cases, additional information is needed, for example, satellite particle measurements or ground; magnetic measurements. The ideas presented in the theory were tested for one Viking eveningside pass over Scandinavia, where ground-based magnetometer and EISCAT radar measurements were available. The magnetic conditions were active during this pass and several interfering shear Alfven waves were found. Also, a spatial structure with a parallel potential drop below the satellite was identified. The magnitude of the 10-km-wide potential drop was at least 2 kV and the upward field-aligned current 26 mu A m(-2) (value mapped to the ionospheric level). The held-aligned conductance was estimated as 1.3 - 2.2x10(-8) S m(-2).

  • 2. Aikio, A. T.
    et al.
    Mursula, K.
    Buchert, S.
    Forme, F.
    Amm, O.
    Marklund, Göran T.
    KTH, Superseded Departments, Alfvén Laboratory.
    Dunlop, M.
    Fontaine, D.
    Vaivads, A.
    Fazakerley, A.
    Temporal evolution of two auroral arcs as measured by the Cluster satellite and coordinated ground-based instruments2004In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 22, no 12, p. 4089-4101Article in journal (Refereed)
    Abstract [en]

    The four Cluster s/c passed over Northern Scandinavia on 6 February 2001 from south-east to north-west at a radial distance of about 4.4 R-E in the post-midnight sector. When mapped along geomagnetic field lines, the separation of the spacecraft in the ionosphere was confined to within 110 km in latitude and 50 km in longitude. This constellation allowed us to study the temporal evolution of plasma with a time scale of a few minutes. Ground-based instrumentation used involved two all-sky cameras, magnetometers and the EISCAT radar. The main findings were as follows. Two auroral arcs were located close to the equatorward and poleward edge of a large-scale density cavity, respectively. These arcs showed a different kind of a temporal evolution. (1) As a response to a pseudo-breakup onset, both the up- and downward field-aligned current (FAC) sheets associated with the equatorward arc widened and the total amount of FAC doubled in a time scale of 1-2 min. (2) In the poleward arc, a density cavity formed in the ionosphere in the return (downward) current region. As a result of ionospheric feedback, a strongly enhanced ionospheric southward electric field developed in the region of decreased Pedersen conductance. Furthermore, the acceleration potential of ionospheric electrons, carrying the return current, increased from 200 to 1000 eV in 70 s, and the return current region widened in order to supply a constant amount of return current to the arc current circuit. Evidence of local acceleration of the electron population by dispersive Alfven waves was obtained in the upward FAC region of the poleward arc. However, the downward accelerated suprathermal electrons must be further energised below Cluster in order to be able to produce the observed visible aurora. Both of the auroral arcs were associated with broad-band ULF/ELF (BBELF) waves, but they were highly localised in space and time. The most intense BBELF waves were confined typically to the return current regions adjacent to the visual arc, but in one case also to a weak upward FAC region. BBELF waves could appear/disappear between s/c crossings of the same arc separated by about 1 min.

  • 3.
    Alfvén, Hannes
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Fälthammar, Carl-Gunne
    KTH, Superseded Departments, Alfvén Laboratory.
    Can the Big Bang Survive in the Space Age?1990Report (Other academic)
  • 4.
    Andersson, Hans
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. KTH, Superseded Departments, Alfvén Laboratory.
    Currrent disruptions in a magnetised plasma stream1997Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 5. Andersson, L
    et al.
    Ivchenko, Nickolay
    KTH, Superseded Departments, Alfvén Laboratory.
    Clemmons, J
    Namgaladze, A
    Gustavsson, B
    Wahlund, E
    Eliasson, L
    Yurik, Y
    Electron signatures and Alfven waves2002In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 107, no A9Article in journal (Refereed)
    Abstract [en]

    [1] We identify two distinct electron populations associated with Alfven waves in the Freja data set using the high time resolution state of the art electron detector. One of the populations, detected together with an Alfven wave, is field-aligned and can be seen as trapped within the wave. The other electron population is detected before the wave and consists of electrons which have left the wave at a point with a velocity higher than the local Alfven speed. In the paper, the electrons leaving wave are modeled for different density profiles and are compared with the observed data. Depending on the density profile, the model can produce the same energy-time and pitch angle-time dispersion that is observed in the Freja data. The conclusion of the paper is that the Alfven wave can explain the observed particle signatures. It is shown that the Alfven wave acceleration can create electron signatures similar to inverted-V structures. The density distribution along a flux tube has an important role in the type of particle signatures that can be detected at low altitudes.

  • 6. Andre, M.
    et al.
    Behlke, R.
    Wahlund, J. E.
    Vaivads, A.
    Eriksson, A. I.
    Tjulin, A.
    Carozzi, T. D.
    Cully, C.
    Gustafsson, G.
    Sundkvist, D.
    Khotyaintsev, Y.
    Cornilleau-Wehrlin, N.
    Rezeau, L.
    Maksimovic, M.
    Lucek, E.
    Balogh, A.
    Dunlop, M.
    Lindqvist, Per-Arne
    KTH, Superseded Departments, Alfvén Laboratory.
    Mozer, F.
    Pedersen, A.
    Fazakerley, A.
    Multi-spacecraft observations of broadband waves near the lower hybrid frequency at the Earthward edge of the magnetopause2001In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 19, no 12-okt, p. 1471-1481Article in journal (Refereed)
    Abstract [en]

    Broadband waves around the lower hybrid frequency (around 10 Hz) near the magnetopause are studied, using the four Cluster satellites. These waves are common at the Earthward edge of the boundary layer, consistent with earlier observations, and can have amplitudes at least up to 5 mV/m. These waves are similar on all four Cluster satellites, i.e. they are likely to be distributed over large areas of the boundary. The strongest electric fields occur during a few seconds, i.e. over distances of a few hundred km in the frame of the moving magnetopause, a scale length comparable to the ion gyroradius. The strongest magnetic oscillations in the same frequency range are typically found in the boundary layer, and across the magnetopause. During an event studied in detail, the magnetopause velocity is consistent with a large-scale depression wave, i.e. an inward bulge of magnetosheath plasma, moving tailward along the nominal magnetopause boundary. Preliminary investigations indicate that a rather flat front side of the large-scale wave is associated with a rather static small-scale electric field, while a more turbulent backside of the large-scale wave is associated with small-scale time varying electric field wave packets.

  • 7. Andre, M
    et al.
    Norqvist, P
    Andersson, L
    Eliasson, L
    Eriksson, A I
    Blomberg, Lars
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Erlandson, R E
    Waldemark, J
    Ion energization mechanisms at 1700 km in the auroral region1998In: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, ISSN 0148-0227, Vol. 103, no A3, p. 4199-4222Article in journal (Refereed)
    Abstract [en]

    Observations obtained by the Freja satellite at altitudes around 1700 km in the high-latitude magnetosphere are used to study ion energization perpendicular to the geomagnetic field. Investigations of ions, electrons, plasma densities, electric and magnetic wave fields, and field-aligned currents are used to study O+ heating mechanisms. Three ion heating events are studied in detail, and 20 events are used in a detailed statistical study. More than 200 events are classified as belonging to one of four major types of ion heating and are ordered as a function of magnetic local time. The most common types of ion heating are associated with broadband low-frequency electric wave fields occurring at all local times. These waves cover frequencies from below one up to several hundred hertz and correspond to the most intense O+ energization. Heating by these waves at frequencies of the order of the O+ gyrofrequency at 25 Hz seems to be the important energization mechanism, causing O+ ion mean energies up to hundreds of eV. The broadband waves are associated with Alfven waves with frequencies up to at least a few hertz and with field-aligned currents. Other types of O+ energization events are less common. During these events the ions are heated by waves near the lower hybrid frequency or near half the proton gyrofrequency. These waves are generated by auroral electrons or in a few cases by precipitating ions.

  • 8. Antoni, V.
    et al.
    Bergsåker, Henric
    KTH, Superseded Departments, Alfvén Laboratory.
    Cavazzana, R.
    Carbone, V.
    Drake, James R.
    KTH, Superseded Departments, Alfvén Laboratory.
    Martines, E.
    Regnoli, G.
    Serianni, G.
    Spada, E.
    Spolaore, M.
    Vianello, N.
    Turbulence and anomalous transport in magnetized plasmas: Hints from the reversed field pinch configuration2004In: Contributions to Plasma Physics, ISSN 0863-1042, E-ISSN 1521-3986, Vol. 44, no 06-maj, p. 458-464Article in journal (Refereed)
    Abstract [en]

    The properties of plasma turbulence in the outer region of the Reversed Field Pinch experiments RFX and EXTRAP-T2R are reviewed. The statistical properties of fluctuations in the range of scales relevant for transport are presented. The observation of coherent structures emerging from the background turbulence and their interpretation in terms of vortices is reported. The interplay between these structures and the mean ExB flow of the plasma is demonstrated with emphasis to the action on the preferential rotation direction. The effect on the particle transport induced by the background turbulence and by the structures is discussed. Finally the methods tested to control turbulence and to mitigate the related transport are illustrated and discussed.

  • 9. Antoni, V.
    et al.
    Bergsåker, Henric
    KTH, Superseded Departments, Alfvén Laboratory.
    Serianni, G.
    Spolaore, M.
    Vianello, N.
    Cavazzana, R.
    Regnoli, G.
    Spada, E.
    Martines, E.
    Bagatin, M.
    Drake, James R.
    KTH, Superseded Departments, Alfvén Laboratory.
    Anomalous particle transport and flow shear in the edge region of RFP's2003In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 313, p. 972-975Article in journal (Refereed)
  • 10. Antoni, V
    et al.
    Cavanazza, R
    Martines, E
    Serianni, G
    Spada, E
    Spolaore, M
    Vianello, N
    Drake, James Robert
    KTH, Superseded Departments, Alfvén Laboratory.
    Bergsåker, Henric
    KTH, Superseded Departments, Alfvén Laboratory.
    Brunsell, Per R
    KTH, Superseded Departments, Alfvén Laboratory.
    Cecconello, Marco
    KTH, Superseded Departments, Alfvén Laboratory.
    Regnoli, G
    Turbulent transport and plasma flow in the reversed field pinch2004In: IAEA-CN-116, 2004Conference paper (Refereed)
  • 11.
    Axnäs, Ingvar
    et al.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Brenning, Nils
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Experiments on the Magnetic Field and Neutral Density Limits on CIV Interaction1988Report (Other academic)
  • 12.
    Axnäs, Ingvar
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Brenning, Nils
    KTH, Superseded Departments, Alfvén Laboratory.
    Laboratory Experiments on the Magnetic Field and Neutral Density Limits on CIV Interaction1990Report (Other academic)
  • 13. Bahnsen, A.
    et al.
    Ungstrup, E.
    Fälthammar, Carl-Gunne
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Fahleson, Ulf
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Olesen, J.K.
    Primdahl, F.
    Spangslev, F.
    Pedersen, A.
    Electrostatic Waves Observed in an Unstable Polar Cap Ionosphere1978In: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol. 83, p. 5191-5197Article in journal (Refereed)
  • 14. Bahnsen, Axel
    et al.
    PEDERSEN, BM
    JESPERSEN, M
    UNGSTRUP, E
    ELIASSON, L
    MURPHREE, JS
    ELPHINSTONE, RD
    Blomberg, Lars
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    HOLMGREN, G
    ZANETTI, LJ
    Viking observations at the source region of auroral kilometric radiation1989In: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, ISSN 0148-0227, Vol. 94, no A6, p. 6643-&Article in journal (Refereed)
  • 15.
    Bergkvist, Tommy
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Hellsten, Torbjörn
    KTH, Superseded Departments, Alfvén Laboratory.
    Johnson, T
    Laxåback, Martin
    KTH, Superseded Departments, Alfvén Laboratory.
    Nonlinear interaction between RF-heated high-energy ions and MHD-modes2003In: RADIO FREQUENCY POWER IN PLASMAS / [ed] Forest C.B., 2003, Vol. 694, p. 459-462Conference paper (Refereed)
    Abstract [en]

    Excitation of global Alfven eigenmodes by fast ions during ICRH is frequently observed in tokamaks. The importance of the phasing of the ICRH antennae for the excitation of these modes have been seen in experiments. The Alfven eigenmodes will drive the distribution function of the fast ions towards a state where the gradient in phase space is reduced. In general, the fast ions are displaced outwards, which can have a significant effect on the ICRH power deposition and lead to reduced heating efficiency. To calculate the effect on the heating profiles by the excitation of Alfven eigenmodes and the, effect on the resonating ions the Monte Carlo code FIDO, used for ICRH, has been upgraded to include particle interactions with MHD-waves. This allows self-consistent calculations of the mode amplitude and the distribution function during RF heating.

  • 16.
    Berglund, Mari
    KTH, Superseded Departments, Alfvén Laboratory.
    Spin-Orbit Maps and Electron Spin Dynamics for the Luminosity Upgrade Project at HERA2001Doctoral thesis, monograph (Other scientific)
  • 17.
    Bergsåker, H
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Larsson, D
    KTH, Superseded Departments, Alfvén Laboratory.
    Brunsell, P
    KTH, Superseded Departments, Alfvén Laboratory.
    Möller, A
    KTH, Superseded Departments, Alfvén Laboratory.
    Tramontin, L
    Wall conditioning and particle control in Extrap T21997In: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 241-243, p. 993-997Article in journal (Refereed)
  • 18.
    Bergsåker, Henric
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Ilyinsky, L.
    Portnoff, G.
    Ion beam analysis of sputter-deposited gold films for quartz resonators2000In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 30, no 1, p. 620-622Article in journal (Refereed)
    Abstract [en]

    Sputter deposition using a focused ion beam has been investigated as an alternative to magnetron sputtering for the deposition of thin-film gold electrodes onto quartz resonators. One potential concern is the inclusion of argon in the growing film when argon ions are used for sputtering. Argon retention in sputter-deposited gold films using an 11.5 keV argon ion beam was investigated with Rutherford backscattering spectrometry and it was found that in layers deposited at close to normal ejection angles the argon trapping was at the level of less than or equal to 1 at,%, similar to magnetron-deposited layers, whereas argon incorporation increased with the ejection angle up to several per cent at large angles.

  • 19.
    Block, Lars P
    et al.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Fälthammar, Carl-Gunne
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Mechanisms that may support magnetic-field-aligned electric fields in the magnetosphere1976In: ANNALES DE GEOPHYSIQUE, ISSN 0003-4029, Vol. 32, p. 161-174Article in journal (Refereed)
  • 20.
    Block, Lars P
    et al.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Fälthammar, Carl-Gunne
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    The Role of Magnetic-Field-Aligned Electric Fields in Auroral Acceleration1990In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 95, p. 5877-5888Article in journal (Refereed)
  • 21.
    Block, Lars P
    et al.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Fälthammar, Carl-Gunne
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lindqvist, Per-Arne
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Marklund, Göran
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Mozer, F.S.
    Pedersen, A.
    Potemra, T.A.
    Zanetti, L.J.
    Electric field measurements on Viking - 1st results1987In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 14, p. 435-438Article in journal (Refereed)
  • 22.
    Block, Lars P
    et al.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Fälthammar, Carl-Gunne
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Rothwell, P L
    Silevitch, M B
    Advantages of electric circuit models for treating the substorm breakup problem1998In: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, Vol. 103, p. 6913-6916Article in journal (Refereed)
    Abstract [en]

    It is shown, by using a circuit model for the magnetospheric current system, that the substorm breakup can be triggered either by some instability anywhere in the circuit or by a decrease in the generator emf, i.e., a northward turning of the interplanetary magnetic field.

  • 23.
    Block, Lars P
    et al.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lazutin, L. L.
    Riedler, W.
    The Role of Scientific Ballooning for Exploration of the Magnetosphere1984Report (Other academic)
  • 24.
    Blomberg, Lars
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Mercury's magnetosphere, exosphere and surface: Low-frequency field and wave measurements as a diagnostic tool1997In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 45, no 1, p. 143-148Article in journal (Refereed)
    Abstract [en]

    Diagnostics that can be made with combined electric and magnetic field measurements at Mercury are reviewed. Fundamental electrodynamic questions which can be answered by means of a Mercury Orbiter are discussed. These include, solar wind-magnetosphere coupling, coupling to low altitude, exospheric or planetary surface conductivity, auroral particle acceleration, and magnetospheric substorms. It is concluded that a comprehensive instrumentation package for low-frequency fields and waves on a future Mercury Orbiter mission may yield significant new information of interest to magnetospheric as well as to planetary physics in general. (C) 1997 Elsevier Science Ltd.

  • 25.
    Blomberg, Lars
    KTH, Superseded Departments, Alfvén Laboratory.
    Micro-satellite Mission Analysis: Theory Overview and Some Examples2003Report (Other academic)
    Abstract [en]

    Rudimentary mission analysis for micro-satellites has been carried out, in particular for ionospheric/thermospheric “dipper” missions. The basic equations of orbital mechanics are summarized and commented on. General properties of near-Earth orbits are discussed and exemplified in figures and tables. In addition, a few specific mission scenarios are described and discussed.

  • 26.
    Blomberg, Lars
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. KTH, Superseded Departments, Alfvén Laboratory.
    Potential- och konduktivitetsfördelningar i jonosfären under inflytande av Birkelandströmmar1986Independent thesis Advanced level (degree of Master (Two Years)), 12 credits / 18 HE creditsStudent thesis
  • 27.
    Blomberg, Lars
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Viking observations of dayside high-latitude electric fields1994In: Physical Signatures of Magnetospheric Boundary Layer Processes, 1994Conference paper (Refereed)
  • 28.
    Blomberg, Lars G.
    et al.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Cumnock, J. A.
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. KTH, Superseded Departments, Alfvén Laboratory.
    Eriksson, A. I.
    The martian plasma environment: Electric field and Langmuir probe diagnostics2003In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 31, no 6, p. 1232-1236Article in journal (Refereed)
    Abstract [en]

    The plasma environment of Mars has been studied by a small handful of spacecraft. From the sparse observations that exist, one may conclude that the solar wind-Martian magnetosphere interaction is different in significant ways from the solar wind's interaction with Earth's magnetosphere. Mars offers an opportunity to make significant advances in our understanding of the fundamentals of the solar wind's interaction with cold celestial bodies, with suitable plasma instrumentation orbiting the planet. We briefly review what is known about Mars' plasma environment and address some scientific topics that can be studied by proper plasma instrumentation in Mars' vicinity, in particular the scientific potential of Langmuir probe measurements. Finally, we exemplify how the studies may contribute to an enhanced understanding not only of the plasma surrounding Mars, but also of the planet itself and its neutral atmosphere.

  • 29.
    Blomberg, Lars G.
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Cumnock, Judy
    KTH, Superseded Departments, Alfvén Laboratory.
    On electromagnetic phenomena in Mercury's magnetosphere2004In: Mercury, Mars and Saturn / [ed] Grard, R; Masson, PL; Gombosi, TI, OXFORD: Pergamon Press, 2004, Vol. 33, no 12, p. 2161-2165Conference paper (Refereed)
    Abstract [en]

    Mercury has a small but intriguing magnetosphere. In this brief review, we discuss some similarities and differences between Mercury's and Earth's magnetospheres. In particular, we discuss how electric and magnetic field measurements can be used as a diagnostic tool to improve our understanding of the dynamics of Mercury's magnetosphere. These points are of interest to the upcoming ESA-JAXA BepiColombo mission to Mercury.

  • 30.
    Blomberg, Lars G.
    et al.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Eriksson, Stefan
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Cumnock, Judy A.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Yamauchi, M.
    Clemmons, J. H.
    Marklund, Göran T.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lindqvist, Per-Arne
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Karlsson, Tomas
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lundin, R.
    Solar windmagnetosphere-ionosphere coupling: an event study based on Freja data2004In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 66, no 5, p. 375-380Article in journal (Refereed)
    Abstract [en]

    Freja data are used to study the relative contributions from the high-latitude (reconnection/direct entry) and low-latitude (viscous interaction) dynamos to the cross-polar potential drop. Convection streamlines which are connected to the high-latitude dynamo may be identified from dispersed magnetosheath ions not only in the cusp/cleft region itself but also several degrees poleward of it. This fact, together with Freja's orbital geometry allows us to infer the potential drop from the high-latitude dynamo as well as to obtain a lower limit to the potential drop from the low-latitude dynamo for dayside Freja passes. All cases studied here are for active magnetospheric conditions. The Freja data suggest that under these conditions at least one third of the potential is generated in the low-latitude dynamo. These observations are consistent with earlier observations of the potential across the low-latitude boundary layer if we assume that the low-latitude dynamo region extends over several tens of Earth radii in the antisunward direction along the tail flanks, and that the majority of the potential drop derives from the sun-aligned component of the electric field rather than from its cross-boundary component, or equivalently, that the centre of the dynamo region is located quite far down tail. A possible dynamo geometry is illustrated.

  • 31.
    Blomberg, Lars G.
    et al.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Marklund, Göran T.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    High-Latitude Convection Patterns For Various Large-Scale Field-Aligned Current Configurations1991In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 18, no 4, p. 717-720Article in journal (Refereed)
    Abstract [en]

    The large-scale field-aligned current system for persistent northward interplanetary magnetic field (IMF) is typically different from that for persistent southward IMF. One characteristic difference is that for northward IMF there is often a large-scale field-aligned current system poleward of the main auroral oval. This current system (the NBZ current) typically occupies a large fraction of the region poleward of the region 1 and 2 currents. The present paper models the high-latitude convection as a function of the large-scale field-aligned currents. In particular, a possible evolution of the convection pattern as the current system changes from a typical configuration for southward IMF to a configuration representing northward IMF (or vice versa) is presented. Depending on additional assumptions, for example about the y-component of the IMF, the convection pattern could either turn directly from a two-cell type to a four-cell type, or a three-cell type pattern could show up as an intermediate state. An interesting although rather surprising result of this study is that different ways of balancing the NBZ currents has a minor influence on the large-scale convection pattern.

  • 32.
    Blomberg, Lars G.
    et al.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Marklund, Göran T.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lindqvist, Per-Arne
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Primdahl, F.
    Brauer, P.
    Bylander, Lars
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. KTH, Superseded Departments, Alfvén Laboratory.
    Cumnock, Judy
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. KTH, Superseded Departments, Alfvén Laboratory.
    Eriksson, Stefan
    KTH, Superseded Departments, Alfvén Laboratory.
    Ivchenko, Nickolay V.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Karlsson, Tomas
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Kullen, Anita
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics. KTH, Superseded Departments, Alfvén Laboratory.
    Merayo, J. M. G.
    Pedersen, E. B.
    Petersen, J. R.
    EMMA - the electric and magnetic monitor of the aurora on Astrid-22004In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 22, no 1, p. 115-123Article in journal (Refereed)
    Abstract [en]

    The Astrid-2 mission has dual primary objectives. First, it is an orbiting instrument platform for studying auroral electrodynamics. Second, it is a technology demonstration of the feasibility of using micro-satellites for innovative space plasma physics research. The EMMA instrument, which we discuss in the present paper, is designed to provide simultaneous sampling of two electric and three magnetic field components up to about 1 kHz. The spin plane components of the electric field are measured by two pairs of opposing probes extended by wire booms with a separation distance of 6.7 m. The probes have titanium nitride (TiN) surfaces. which has proved to be a material with excellent properties for providing good electrical contact between probe and plasma. The wire booms are of a new design in which the booms in the stowed position are wound around the exterior of the spacecraft body. The boom system was flown for the first time on this mission and worked flawlessly. The magnetic field is measured by a tri-axial fluxgate sensor located at the tip of a rigid. hinged boom extended along the spacecraft spin axis and facing away from the Sun. The new advanced-design fluxgate magnetometer uses digital signal processors for detection and feedback, thereby reducing the analogue circuitry to a minimum. The instrument characteristics as well as a brief review of the science accomplished and planned are presented.

  • 33.
    Blomberg, Lars
    et al.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lindqvist, Per-Arne
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Marklund, Göran
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Viking observations of electric fields1992In: Study of the Solar-Terrestrial System, 1992, Vol. 346, p. 269-274Conference paper (Other academic)
  • 34.
    Blomberg, Lars
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Marklund, Göran
    KTH, Superseded Departments, Alfvén Laboratory.
    A Numerical Model of Ionospheric Convection Derived From Field-Aligned Currents and the Corresponding Conductivity1991Report (Other academic)
  • 35.
    Blomberg, Lars
    et al.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Marklund, Göran
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    High-latitude electrodynamics and aurorae during northward IMF1993In: Auroral Plasma Dynamics, Washington, DC: American Geophysical Union (AGU), 1993, p. 55-68Chapter in book (Refereed)
    Abstract [en]

    The large-scale auroral morphology and its associated electrodynamics for northward interplanetary magnetic field (IMF) is characteristically different from that for southward IMF. For northward IMF significant auroral activity is often present poleward of the “normal” auroral oval, and a number of different polar auroral configurations can occur. Two extreme situations which are considered here are either one where one or more discrete arcs separated from the “normal” oval are present in the polar region, or one where diffuse auroral activity is found in a large fraction of this region. The latter case might be associated with so-called NBZ (field-aligned) currents. We briefly review the typical signatures in terms of optical emissions, field-aligned currents, electric fields, and plasma convection usually encountered in the polar region when IMF Bz<0, and their interrelationships. This is the starting point for a more detailed discussion, driven by modeling results, of the relationships between electric field, field-aligned current, and conductivity in the two distinct situations mentioned. In particular we discuss the influence the polar field-aligned currents have on the convection pattern, on the small as well as on the large scale. As expected, currents associated with discrete isolated arcs give rise mainly to small-scale modifications, whereas currents related to auroral activity in an expanded oval can modify the overall convection pattern substantially.

  • 36.
    Blomberg, Lars
    et al.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Marklund, Göran
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    The influence of conductivities consistent with field-aligned currents on high-latitutde convection patterns1988In: Journal of Geophysical Research - Space Physics, ISSN 0148-0227, Vol. 93, no A12, p. 14493-14499Article in journal (Refereed)
  • 37.
    Blomberg, Lars
    et al.
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Marklund, Göran
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Lindqvist, Per-Arne
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Bylander, Lars
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Atrid-2: An advanced auroral microprobe1999Other (Other academic)
    Abstract [en]

    Astri-2 is an advanced auroral microprobe with dual primary mission objectives; to do high-quality in situ measurements of the physical processes behind the aurora, and to demonstrate the usefulness of microspacecraft as advanced research tools. Mission success will open up entirely new possibilities to carry out low-budget multipoint measurements in near-Earth space. This long-desired kind of in situ measurements are the next major step forward in experimental space physics. Astrid-2 has platform dimensions of 45×45×30 cm, a total mass of just below 30 kg, and carries scientific instruments for measuring local electric and magnetic fields, plasma density and density fluctuations, ions and electrons, as well as photometers for remote imaging of auroral emissions. Attitude determination is provided by a high-precision star imager. Some 250 Mbytes' worth of scientific data will be received each day at the two ground stations. Astrid-2 will be launched as a piggy-back on a Russian Kosmos-3M launcher into an 83 deg inclination circular orbit at 1000 km altitude. Nodal regression will give complete coverage of all local time sectors every 3.5 months. © 1999 Elsevier B.V. All rights reserved.

  • 38.
    Blomberg, Lars
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Marklund, Göran
    KTH, Superseded Departments, Alfvén Laboratory.
    Lindqvist, Per-Arne
    KTH, Superseded Departments, Alfvén Laboratory.
    Primdahl, F.
    Brauer, P.
    Bylander, Lars
    KTH, Superseded Departments, Alfvén Laboratory.
    Cumnock, Judy
    KTH, Superseded Departments, Alfvén Laboratory.
    Eriksson, S.
    Ivchenko, Nickolay
    KTH, Superseded Departments, Alfvén Laboratory.
    Karlsson, Tomas
    KTH, Superseded Departments, Alfvén Laboratory.
    Kullen, Anita
    KTH, Superseded Departments, Alfvén Laboratory.
    Merayo, J. M. G.
    Pedersen, E. B.
    Petersen, J. R.
    The EMMA Instrument on the Astrid-2 Micro-Satellite2003Report (Other academic)
  • 39. Boehm, M. H.
    et al.
    CLEMMONS, J
    WAHLUND, JE
    ERIKSSON, A
    ELIASSON, L
    Blomberg, Lars
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    KINTNER, P
    HOFNER, H
    Observations of an  upward-directed electron beam with the perpendicular temperature of the cold ionosphere1995In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 22, p. 2103-2106Article in journal (Refereed)
    Abstract [en]

    The Freja TESP electron spectrometer has repeatedly observed similar to 100 eV - 1 keV upward-directed, anti-field-aligned electron beams near 1700 km altitude in the auroral zone. A particularly intense event, at energies up to 2 keV, is described. The beam perpendicular temperature T perpendicular to(e)), was as low as 0.1-0.2 eV at 100-200 eV parallel energy. The 10-15 s period of upward fluxes was coincident with a low density (similar to 10 cm(-3)) period and a similar to 5 keV ion conic. Strong low frequency waves and the lack of any downward motion in the simultaneously observed ion conic suggest a strong element of wave acceleration, while electric field and ion loss cone measurements provide limited evidence of potential acceleration to a fraction of the observed energies.

  • 40. Bohlmark, J.
    et al.
    Helmersson, U.
    VanZeeland, M.
    Axnäs, Ingvar
    KTH, Superseded Departments, Alfvén Laboratory.
    Alami, J.
    Brenning, Nils
    KTH, Superseded Departments, Alfvén Laboratory.
    Measurement of the magnetic field change in a pulsed high current magnetron discharge2004In: Plasma sources science & technology (Print), ISSN 0963-0252, E-ISSN 1361-6595, Vol. 13, no 4, p. 654-661Article in journal (Refereed)
    Abstract [en]

    In this paper we present a study of how the magnetic field of a circular planar magnetron is affected when it is exposed to a pulsed high current discharge. Spatially resolved magnetic field measurements are presented and the magnetic disturbance is quantified for different process parameters. The magnetic field is severely deformed by the discharge and we record changes of several millitesla, depending on the spatial location of the measurement. The shape of the deformation reveals the presence of azimuthally drifting electrons close to the target surface. Time resolved measurements show a transition between two types of magnetic perturbations. There is an early stage that is in phase with the axial discharge current and a late stage that is not in phase with the discharge current. The later part of the magnetic field deformation is seen as a travelling magnetic wave. We explain the magnetic perturbations by a combination of E x B drifting electrons and currents driven by plasma pressure gradients and the shape of the magnetic field. A plasma pressure wave is also recorded by a single tip Langmuir probe and the velocity (similar to10(3) m s(-1)) of the expanding plasma agrees well with the observed velocity of the magnetic wave. We note that the axial (discharge) current density is much too high compared to the azimuthal current density to be explained by classical collision terms, and an anomalous charge transport mechanism is required.

  • 41.
    Bohm, Martin
    KTH, Superseded Departments, Alfvén Laboratory.
    A users guide for the code XPDP1, version 3.1 and the modified version MODXPDP1. To be run on HP workstation 712/80 with HP-UX version 09.03 and a digital VXT 2000+ terminal1995Report (Other academic)
  • 42.
    Bohm, Martin
    KTH, Superseded Departments, Alfvén Laboratory.
    Experimental Observations of Anomalous Potential Drops over Ion Density Cavities1991Report (Other academic)
  • 43.
    Bohm, Martin
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Brenning, Nils
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Fälthammar, Carl-Gunne
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Dynamic trapping: Neutralization of positive space charge in a collisionless magnetized plasma1990In: Physical Review Letters, ISSN 00319007, Vol. 65, p. 859-866Article in journal (Refereed)
    Abstract [en]

    It is shown by numerical simulations that in a collisionless plasma electron inertia leads to inefficient neutralization of positive space charge and allows large positive potentials (φ ≫ kTe/e) to be established and maintained on the time scale of ion motion. This is true even if the buildup of positive space charge is so slow that it corresponds to a small fraction of the random electron current of the surrounding plasma. A simple physical model clarifies the physics of the process and provides an analytical expression for the potential.

  • 44. Bohm, Martin
    et al.
    Brenning, Nils
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Fälthammar, Carl-Gunne
    KTH, Superseded Departments, Alfvén Laboratory. KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Dynamic trapping of electrons in the porcupine ionospheric ion beam experiment1992In: Advances in Space Research, ISSN 02731177, Vol. 12, p. 9-14Article in journal (Refereed)
    Abstract [en]

    Electrons are needed to maintain quasineutrality in a case where positive ions are injected across the magnetic field into a limited volume in a magnetized plasma. In the absence of collisions, a positive potential builds up and traps the electrons which enter the region along the magnetic field. If the added density of ions exceeds the ambient density, large potential differences along the magnetic field can be maintained this way. The process explains several features of the Porcupine xenon ion beam injection experiment, where strong magnetic-field-aligned electric fields were measured in the vicinity of a xenon ion beam which was injected into the ambient ionosphere from a spinning subpayload. © 1992.

  • 45.
    Bohm, Martin
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Torvén, Staffan
    KTH, Superseded Departments, Alfvén Laboratory.
    Potential Drops Supported by Ion Density Cavities in the Dynamic Response of a Plasma Diode to an Applied Field1990Report (Other academic)
  • 46.
    Bohm, Martin
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Torvén, Staffan
    KTH, Superseded Departments, Alfvén Laboratory.
    The Dynamic Response of an Inhomogeneous Plasma Diode to an Applied Electric Field1990Report (Other academic)
  • 47.
    Bolin, Odd
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Brenning, Nils
    KTH, Superseded Departments, Alfvén Laboratory.
    A Numerical Study of the Electrodynamical Interaction Between Comet Shoemaker-Levy 9 and Jupiter1994Report (Other academic)
  • 48.
    Bolin, Odd
    et al.
    KTH, Superseded Departments, Alfvén Laboratory.
    Brenning, Nils
    KTH, Superseded Departments, Alfvén Laboratory.
    One-Dimensional Numerical Simulations of the Low-Frequency Electric Fields in the CRIT I and CRIT II Rocket Experiments1992Report (Other academic)
  • 49.
    Boström, Rolf
    KTH, Superseded Departments, Alfvén Laboratory.
    Auroral Electric Fields1966Report (Other academic)
  • 50.
    Boström, Rolf
    KTH, Superseded Departments, Alfvén Laboratory.
    The Magnetic Field of Three-dimensional Magnetospheric Model Current Systems and Currents Induced in the Ground1969Report (Other academic)
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