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Sökning: WFRF:(Rème H.)

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1.
  • Deng, X. H., et al. (författare)
  • Dynamics and waves near multiple magnetic null points in reconnection diffusion region
  • 2009
  • Ingår i: Journal of Geophysical Research. - : Blackwell Publishing. - 0148-0227 .- 2156-2202. ; 114:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Identifying the magnetic structure in the region where the magnetic field lines break and how reconnection happens is crucial to improving our understanding of three-dimensional reconnection. Here we show the in situ observation of magnetic null structures in the diffusion region, the dynamics, and the associated waves. Possible spiral null pair has been identified near the diffusion region. There is a close relation among the null points, the bipolar signature of the Z component of the magnetic field, and enhancement of the flux of energetic electrons up to 100 keV. Near the null structures, whistler-mode waves were identified by both the polarity and the power law of the spectrum of electric and magnetic fields. It is found that the angle between the fans of the nulls is quite close to the theoretically estimated maximum value of the group-velocity cone angle for the whistler wave regime of reconnection.
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2.
  • Fuselier, S. A., et al. (författare)
  • Ion chemistry in the coma of comet 67P near perihelion
  • 2016
  • Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 462, s. S67-S77
  • Tidskriftsartikel (refereegranskat)abstract
    • The coma and the comet-solar wind interaction of comet 67P/Churyumov-Gerasimenko changed dramatically from the initial Rosetta spacecraft encounter in 2014 August through perihelion in 2015 August. Just before equinox (at 1.6 au from the Sun), the solar wind signal disappeared and two regions of different cometary ion characteristics were observed. These 'outer' and 'inner' regions have cometary ion characteristics similar to outside and inside the ion pileup region observed during the Giotto approach to comet 1P/Halley. Rosetta/Double-Focusing Mass Spectrometer ion mass spectrometer observations are used here to investigate the H3O+/H2O+ ratio in the outer and inner regions at 67P/Churyumov-Gerasimenko. The H3O+/H2O+ ratio and the H3O+ signal are observed to increase in the transition from the outer to the inner region and the H3O+ signal appears to be weakly correlated with cometary ion energy. These ion composition changes are similar to the ones observed during the 1P/Halley flyby. Modelling is used to determine the importance of neutral composition and transport of neutrals and ions away from the nucleus. This modelling demonstrates that changes in the H3O+/H2O+ ratio appear to be driven largely by transport properties and only weakly by neutral composition in the coma.
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3.
  • Fuselier, S. A., et al. (författare)
  • ROSINA/DFMS and IES observations of 67P : Ion-neutral chemistry in the coma of a weakly outgassing comet
  • 2015
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 583
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. The Rosetta encounter with comet 67P/Churyumov-Gerasimenko provides a unique opportunity for an in situ, up-close investigation of ion-neutral chemistry in the coma of a weakly outgassing comet far from the Sun. Aims. Observations of primary and secondary ions and modeling are used to investigate the role of ion-neutral chemistry within the thin coma. Methods. Observations from late October through mid-December 2014 show the continuous presence of the solar wind 30 km from the comet nucleus. These and other observations indicate that there is no contact surface and the solar wind has direct access to the nucleus. On several occasions during this time period, the Rosetta/ROSINA/Double Focusing Mass Spectrometer measured the low-energy ion composition in the coma. Organic volatiles and water group ions and their breakup products (masses 14 through 19), COP, and CO, (masses 28 and 44) and other mass peaks (at masses 26, 27, and possibly 30) were observed. Secondary ions include H3O+ and HCO+ (masses 19 and 29). These secondary ions indicate ion-neutral chemistry in the thin coma of the comet. A relatively simple model is constructed to account for the low H3O /H2O+ and HCO /CO+ ratios observed in a water dominated coma. Results from this simple model are compared with results from models that include a more detailed chemical reaction network. Results. At low outgassing rates, predictions from the simple model agree with observations and with results from more complex models that include much more chemistry. At higher outgassing rates, the ion-neutral chemistry is still limited and high HCO /CO+ ratios are predicted and observed. However, at higher outgassing rates, the model predicts high H3O /H2O+ ratios and the observed ratios are often low. These low ratios may be the result of the highly heterogeneous nature of the coma, where CO and CO2 number densities can exceed that of water.
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4.
  • Hietala, H., et al. (författare)
  • Supermagnetosonic Jets behind a Collisionless Quasiparallel Shock
  • 2009
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 103:24, s. 245001-
  • Tidskriftsartikel (refereegranskat)abstract
    • The downstream region of a collisionless quasiparallel shock is structured containing bulk flows with high kinetic energy density from a previously unidentified source. We present Cluster multispacecraft measurements of this type of supermagnetosonic jet as well as of a weak secondary shock front within the sheath, that allow us to propose the following generation mechanism for the jets: The local curvature variations inherent to quasiparallel shocks can create fast, deflected jets accompanied by density variations in the downstream region. If the speed of the jet is super(magneto)sonic in the reference frame of the obstacle, a second shock front forms in the sheath closer to the obstacle. Our results can be applied to collisionless quasiparallel shocks in many plasma environments.
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5.
  • Hietala, H., et al. (författare)
  • Supermagnetosonic subsolar magnetosheath jets and their effects : from the solar wind to the ionospheric convection
  • 2012
  • Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 30:1, s. 33-48
  • Tidskriftsartikel (refereegranskat)abstract
    • It has recently been proposed that ripples inherent to the bow shock during radial interplanetary magnetic field (IMF) may produce local high speed flows in the magnetosheath. These jets can have a dynamic pressure much larger than the dynamic pressure of the solar wind. On 17 March 2007, several jets of this type were observed by the Cluster spacecraft. We study in detail these jets and their effects on the magnetopause, the magnetosphere, and the ionospheric convection. We find that (1) the jets could have a scale size of up to a few RE but less than similar to 6 R-E transverse to the XGSE axis; (2) the jets caused significant local magnetopause perturbations due to their high dynamic pressure; (3) during the period when the jets were observed, irregular pulsations at the geostationary orbit and localised flow enhancements in the ionosphere were detected. We suggest that these inner magnetospheric phenomena were caused by the magnetosheath jets.
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8.
  • Waara, Martin, 1980-, et al. (författare)
  • Oxygen ion energization observed at high altitudes
  • 2010
  • Ingår i: Annales Geophysicae. - : Copernicus Publications on behalf of the European Geosciences Union. - 0992-7689 .- 1432-0576. ; 28, s. 907-916
  • Tidskriftsartikel (refereegranskat)
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9.
  • Waara, M., et al. (författare)
  • Oxygen ion energization observed at high altitudes
  • 2010
  • Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 28:4, s. 907-916
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a case study of significant heating (up to 8 keV) perpendicular to the geomagnetic field of outflowing oxygen ions at high altitude (12 R-E) above the polar cap. The shape of the distribution functions indicates that most of the heating occurs locally (within 0.2-0.4 R-E in altitude). This is a clear example of local ion energization at much higher altitude than usually reported. In contrast to many events at lower altitudes, it is not likely that the locally observed wave fields can cause the observed ion energization. Also, it is not likely that the ions have drifted from some nearby energization region to the point of observation. This suggests that additional fundamentally different ion energization mechanisms are present at high altitudes. One possibility is that the magnetic moment of the ions is not conserved, resulting in slower outflow velocities and longer time for ion energization.
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10.
  • Yamauchi, M., et al. (författare)
  • Magnetospheric solitary structure maintained by 3000 km/s ions as a cause of westward moving auroral bulge at 19 MLT
  • 2009
  • Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 27:7, s. 2947-2969
  • Tidskriftsartikel (refereegranskat)abstract
    • In the evening equatorial magnetosphere at about 4 R-E geocentric distance and 19 MLT, the four Cluster spacecraft observed a solitary structure with a width of about 1000 similar to 2000 km in the propagation direction. The solitary structure propagates sunward with about 5 similar to 10 km/s carrying sunward electric field (in the propagation direction) of up to about 10 mV/m (total potential drop of about 5 similar to 10 kV), depletion of magnetic field of about 25%, and a duskward E x B convection up to 50 km/s of He+ rich cold plasma without O+. At the same time, auroral images from the IMAGE satellite together with ground based geomagnetic field data showed a westward (sunward at this location) propagating auroral bulge at the magnetically conjugate ionosphere with the solitary structure. The solitary structure is maintained by flux enhancement of selectively 3000 km/s ions (about 50 keV for H+, 200 keV for He+, and 750 keV for O+). These ions are the main carrier of the diamagnetic current causing the magnetic depletion, whereas the polarization is maintained by different behavior of energetic ions and electrons. Corresponding to aurora, field-aligned accelerated ionospheric plasma of several keV appeared at Cluster from both hemispheres simultaneously. Together with good correspondence in location and propagation velocity between the auroral bulge and the solitary structure, this indicates that the sunward moving auroral bulge is caused by the sunward propagation of the solitary structure which is maintained by energetic ions. The solitary structure might also be the cause of Pi2-like magnetic variation that started simultaneously at Cluster location.
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11.
  • Yao, S. T., et al. (författare)
  • Propagation of small size magnetic holes in the magnetospheric plasma sheet
  • 2016
  • Ingår i: Journal of Geophysical Research - Space Physics. - : Wiley-Blackwell. - 2169-9380 .- 2169-9402. ; 121:6, s. 5510-5519
  • Tidskriftsartikel (refereegranskat)abstract
    • Magnetic holes (MHs), characteristic structures where the magnetic field magnitude decreases significantly, have been frequently observed in space plasmas. Particularly, small size magnetic holes (SSMHs) which the scale is less than or close to the proton gyroradius are recently detected in the magnetospheric plasma sheet. In this study of Cluster observations, by the timing method, the minimum directional difference (MDD) method, and the spatiotemporal difference (STD) method, we obtain the propagation velocity of SSMHs in the plasma flow frame. Furthermore, based on electron magnetohydrodynamics (EMHD) theory we calculate the velocity, width, and depth of the electron solitary wave and compare it to SSMH observations. The result shows a good accord between the theory and the observation.
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12.
  • Arvelius, S., et al. (författare)
  • Statistical study of relationships between dayside high-altitude and high-latitude O+ ion outflows, solar winds, and geomagnetic activity
  • 2005
  • Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 23, s. 1909-1916
  • Tidskriftsartikel (refereegranskat)abstract
    • The persistent outflows of O+ ions observed by the Cluster CIS/CODIF instrument were studied statistically in the high-altitude (from 3 up to 11 RE) and high-latitude (from 70 to ~90 deg invariant latitude, ILAT) polar region. The principal results are: (1) Outflowing O+ ions with more than 1keV are observed above 10 RE geocentric distance and above 85deg ILAT location; (2) at 6-8 RE geocentric distance, the latitudinal distribution of O+ ion outflow is consistent with velocity filter dispersion from a source equatorward and below the spacecraft (e.g. the cusp/cleft); (3) however, at 8-12 RE geocentric distance the distribution of O+ outflows cannot be explained by velocity filter only. The results suggest that additional energization or acceleration processes for outflowing O+ ions occur at high altitudes and high latitudes in the dayside polar region.
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14.
  • Hasegawa, H., et al. (författare)
  • Kelvin-Helmholtz waves at the Earth's magnetopause : Multiscale development and associated reconnection
  • 2009
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 114:12, s. A12207-
  • Tidskriftsartikel (refereegranskat)abstract
    • We examine traversals on 20 November 2001 of the equatorial magnetopause boundary layer simultaneously at similar to 1500 magnetic local time (MLT) by the Geotail spacecraft and at similar to 1900 MLT by the Cluster spacecraft, which detected rolled-up MHD-scale vortices generated by the Kelvin-Helmholtz instability (KHI) under prolonged northward interplanetary magnetic field conditions. Our purpose is to address the excitation process of the KHI, MHD-scale and ion-scale structures of the vortices, and the formation mechanism of the low-latitude boundary layer (LLBL). The observed KH wavelength (>4 x 10(4) km) is considerably longer than predicted by the linear theory from the thickness (similar to 1000 km) of the dayside velocity shear layer. Our analyses suggest that the KHI excitation is facilitated by combined effects of the formation of the LLBL presumably through high-latitude magnetopause reconnection and compressional magnetosheath fluctuations on the dayside, and that breakup and/or coalescence of the vortices are beginning around 1900 MLT. Current layers of thickness a few times ion inertia length similar to 100 km and of magnetic shear similar to 60 degrees existed at the trailing edges of the vortices. Identified in one such current sheet were signatures of local reconnection: Alfvenic outflow jet within a bifurcated current sheet, nonzero magnetic field component normal to the sheet, and field-aligned beam of accelerated electrons. Because of its incipient nature, however, this reconnection process is unlikely to lead to the observed dusk-flank LLBL. It is thus inferred that the flank LLBL resulted from other mechanisms, namely, diffusion and/or remote reconnection unidentified by Cluster.
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15.
  • Hasegawa, H., et al. (författare)
  • Reconstruction of a bipolar magnetic signature in an earthward jet in the tail : Flux rope or 3D guide-field reconnection?
  • 2007
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 112:A11, s. A11206-
  • Tidskriftsartikel (refereegranskat)abstract
    • Southward-then-northward magnetic perturbations are often seen in the tail plasma sheet, along with earthward jets, but the generation mechanism of such bipolar B-z ( magnetic flux rope created through multiple X-line reconnection, transient reconnection, or else) has been controversial. At similar to 2313 UT on 13 August 2002, Cluster encountered a bipolar B-z at the leading edge of an earthward jet, with one of the four spacecraft in the middle of the current sheet. Application to this bipolar signature of Grad-Shafranov ( GS) reconstruction, the technique for recovery of two-dimensional ( 2D) magnetohydrostatic structures, suggests that a flux rope with diameter of similar to 2 R-E was embedded in the jet. To investigate the validity of the GS results, the technique is applied to synthetic data from a three-dimensional ( 3D) MHD simulation, in which a bipolar B-z can be produced through localized ( 3D) reconnection in the presence of guide field B-y ( Shirataka et al., 2006) without invoking multiple X-lines. A flux rope-type structure, which does not in fact exist in the simulation, is reconstructed but with a shape elongated in the jet direction. Unambiguous identification of a mechanism that leads to an observed bipolar B-z thus seems difficult based on the topological property in the GS maps. We however infer that a flux rope was responsible for the bipolar pulse in this particular Cluster event, because the recovered magnetic structure is roughly circular, suggesting a relaxed and minimum energy state. Our results also indicate that one has to be cautious about interpretation of some ( e. g., force-free, or magnetohydrostatic) model-based results.
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16.
  • Hasegawa, H., et al. (författare)
  • Retreat and reformation of X-line during quasi-continuous tailward-of-the-cusp reconnection under northward IMF
  • 2008
  • Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 35:15, s. L15104-
  • Tidskriftsartikel (refereegranskat)abstract
    • We present observations on 19-20 November 2006 by the Cluster spacecraft that were skimming the high-latitude dusk-flank magnetopause, which are consistent with more than one reconnection X-line present on the tailward side of the cusp under northward IMF. Evidence of quasi-continuous reconnection over 16 hours exists in the form of Alfvenic acceleration of magnetosheath ions found almost always when either of the satellites traversed the boundary. The data indicate that a dominant X-line was sunward of Cluster for most of the time, but ion velocity distributions consisting of two magnetosheath populations demonstrate that for part of the time, more than one X-line existed. Further, the motion of reconnected field lines shows that some X-line(s) retreated tailward. It is inferred that following the X-line retreat, another X-line reformed sunward of Cluster, leading tomultiple X-lines.
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18.
  • Keika, K., et al. (författare)
  • Response of the inner magnetosphere and the plasma sheet to a sudden impulse
  • 2008
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 113:A7, s. A07S35-
  • Tidskriftsartikel (refereegranskat)abstract
    • [1] The passage of an interplanetary shock caused a sudden compression of the magnetosphere between 0900 UT and 0915 UT on 24 August 2005. An estimate of the shock normal from solar wind data obtained by Geotail upstream of the bow shock indicates symmetric compression with respect to the noon-midnight meridian. Compression-related disturbances of the magnetic and electric field and plasma motion were observed by Double Star Program (DSP) Tan Ce 1 (TC1) and Tan Ce 2 (TC2) in the inner magnetosphere and by the Cluster spacecraft in the dawnside plasma sheet. DSP/TC1 and TC2 observations suggest that the disturbances in the inner magnetosphere are propagating from the dayside magnetopause. Cluster S/C 4 observations indicate that the front normal of the disturbances in the dawnside plasma sheet is phi similar to 180 degrees at 0902: 50 UT and phi = 107 degrees at 0904: 34 UT, where phi is the longitude in GSM coordinates, if we assume that the measured electric field is on the front plane and the normal lies on the X-Y plane. The timing analysis applied to magnetic field data from the four Cluster spacecraft independently gives a front normal, which is calculated to be phi =131 degrees at about 0904: 20 UT. Shock-associated magnetic and electric field disturbances propagating from both the dayside and flank magnetopauses are detected in the plasma sheet; the latter makes the dominant contribution. Substorms are, however, not triggered at the passage of the disturbances.
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19.
  • Langlais, B., et al. (författare)
  • Mars environment and magnetic orbiter model payload
  • 2009
  • Ingår i: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 23:3, s. 761-783
  • Tidskriftsartikel (refereegranskat)abstract
    • Mars Environment and Magnetic Orbiter was proposed as an answer to the Cosmic Vision Call of Opportunity as a M-class mission. The MEMO mission is designed to study the strong interconnections between the planetary interior, atmosphere and solar conditions essential to understand planetary evolution, the appearance of life and its sustainability. MEMO provides a high-resolution, complete, mapping of the magnetic field (below an altitude of about 250 km), with an yet unachieved full global coverage. This is combined with an in situ characterization of the high atmosphere and remote sensing of the middle and lower atmospheres, with an unmatched accuracy. These measurements are completed by an improved detection of the gravity field signatures associated with carbon dioxide cycle and to the tidal deformation. In addition the solar wind, solar EUV/UV and energetic particle fluxes are simultaneously and continuously monitored. The challenging scientific objectives of the MEMO mission proposal are fulfilled with the appropriate scientific instruments and orbit strategy. MEMO is composed of a main platform, placed on a elliptical (130 x 1,000 km), non polar (77A degrees inclination) orbit, and of an independent, higher apoapsis (10,000 km) and low periapsis (300 km) micro-satellite. These orbital parameters are designed so that the scientific return of MEMO is maximized, in terms of measurement altitude, local time, season and geographical coverage. MEMO carry several suites of instruments, made of an 'exospheric-upper atmosphere' package, a 'magnetic field' package, and a 'low-middle atmosphere' package. Nominal mission duration is one Martian year.
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20.
  • Lockwood, M, et al. (författare)
  • Coordinated Cluster and ground-based instrument observations of transient changes in the magnetopause boundary layer during an interval of predominantly northward IMF : relation to reconnection pulses and FTE signatures
  • 2001
  • Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 19:10-12, s. 1613-1640
  • Forskningsöversikt (refereegranskat)abstract
    • We study a series of transient entries into the low-latitude boundary layer (LLBL) of all four Cluster spacecraft during an outbound pass through the mid-afternoon magnetopause ([X(GSM), Y(GSM), Z(GSM)] approximate to [2, 7, 9] R(E)). The events take place during an interval of northward IMF, as seen in the data from the ACE satellite and lagged by a propagation delay of 75 min that is well-defined by two separate studies: (1) the magnetospheric variations prior to the northward turning (Lockwood et al., 2001, this issue) and (2) the field clock angle seen by Cluster after it had emerged into the magnetosheath (Opgenoorth et al., 2001, this issue). With an additional lag of 16.5 min, the transient LLBL events cor-relate well with swings of the IMF clock angle (in GSM) to near 90degrees. Most of this additional lag is explained by ground-based observations, which reveal signatures of transient reconnection in the pre-noon sector that then take 10-15 min to propagate eastward to 15 MLT, where they are observed by Cluster. The eastward phase speed of these signatures agrees very well with the motion deduced by the cross-correlation of the signatures seen on the four Cluster spacecraft. The evidence that these events are reconnection pulses includes: transient erosion of the noon 630 nm (cusp/cleft) aurora to lower latitudes; transient and travelling enhancements of the flow into the polar cap, imaged by the AMIE technique; and poleward-moving events moving into the polar cap, seen by the EISCAT Svalbard Radar (ESR). A pass of the DMSP-F15 satellite reveals that the open field lines near noon have been opened for some time: the more recently opened field lines were found closer to dusk where the flow transient and the poleward-moving event intersected the satellite pass. The events at Cluster have ion and electron characteristics predicted and observed by Lockwood and Hapgood (1998) for a Flux Transfer Event (FTE), with allowance for magnetospheric ion reflection at Alfvenic disturbances in the magnetopause reconnection layer. Like FTEs, the events are about 1 R(E) in their direction of motion and show a rise in the magnetic field strength, but unlike FTEs, in general, they show no pressure excess in their core and hence, no characteristic bipolar signature in the boundary-normal component. However, most of the events were observed when the magnetic field was southward, i.e. on the edge of the interior magnetic cusp, or when the field was parallel to the magnetic equatorial plane. Only when the satellite begins to emerge from the exterior boundary (when the field was northward), do the events start to show a pressure excess in their core and the consequent bipolar signature. We identify the events as the first observations of FTEs at middle altitudes.
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24.
  • Savin, S., et al. (författare)
  • Experimental study of nonlinear interaction of plasma flow with charged thin current sheets : 2. Hall dynamics, mass and momentum transfer
  • 2006
  • Ingår i: Nonlinear processes in geophysics. - 1023-5809 .- 1607-7946. ; 13:4, s. 377-392
  • Tidskriftsartikel (refereegranskat)abstract
    • Proceeding with the analysis of Amata et al. (2005), we suggest that the general feature for the local transport at a thin magnetopause (MP) consists of the penetration of ions from the magnetosheath with gyroradius larger than the MP width, and that, in crossing it, the transverse potential difference at the thin current sheet (TCS) is acquired by these ions, providing a field-particle energy exchange without parallel electric fields. It is suggested that a part of the surface charge is self-consistently produced by deflection of ions in the course of inertial drift in the nonuniform electric field at MP. Consideration of the partial moments of ions with different energies demonstrates that the protons having gyro-radii of roughly the same size or larger than the MP width carry fluxes normal to MP that are about 20% of the total flow in the plasma jet under MP. This is close to the excess of the ion transverse velocity over the cross-field drift speed in the plasma flow just inside MP (Amata et al., 2005), which conforms to the contribution of the finite-gyroradius inflow across MP. A linkage through the TCS between different plasmas results from the momentum conservation of the higher-energy ions. If the finite-gyroradius penetration occurs along the MP over similar to 1.5 R-E from the observation site, then it can completely account for the formation of the jet under the MP. To provide the downstream acceleration of the flow near the MP via the cross-field drift, the weak magnetic field is suggested to rotate from its nearly parallel direction to the unperturbed flow toward being almost perpendicular to the accelerated flow near the MP. We discuss a deceleration of the higher-energy ions in the MP normal direction due to the interaction with finite-scale electric field bursts in the magnetosheath flow frame, equivalent to collisions, providing a charge separation. These effective collisions, with a nonlinear frequency proxy of the order of the proton cyclotron one, in extended turbulent zones are a promising alternative in place of the usual parallel electric fields invoked in the macro-reconnection scenarios. Further cascading towards electron scales is supposed to be due to unstable parallel electron currents, which neutralize the potential differences, either resulted from the ion-burst interactions or from the inertial drift. The complicated MP shape suggests its systematic velocity departure from the local normal towards the average one, inferring domination for the MP movement of the non-local processes over the small-scale local ones. The measured Poynting vector indicates energy transmission from the MP into the upstream region with the waves triggering impulsive downstream flows, providing an input into the local flow balance and the outward movement of the MP. Equating the transverse electric field inside the MP TCS by the Hall term in the Ohm's law implies a separation of the different plasmas primarily by the Hall current, driven by the respective part of the TCS surface charge. The Hall dynamics of TCS can operate either without or as a part of a macro-reconnection with the magnetic field annihilation.
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26.
  • Zhou, M., et al. (författare)
  • Observation of waves near lower hybrid frequency in the reconnection region with thin current sheet
  • 2009
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 114, s. A02216-
  • Tidskriftsartikel (refereegranskat)abstract
    • The role of waves and turbulence in the process of magnetic reconnection has been the subject of a great deal of studies and debates in the theoretical literature. Here we report the Cluster observations of electrostatic and electromagnetic waves near the lower hybrid frequency in the reconnection region with a thin current sheet. During the crossing of the separatrix with the reversal of plasma flow and Hall magnetic fields, strong electrostatic fluctuations near the lower hybrid frequency were observed, and the waves were polarized with a large angle to the ambient magnetic field. Strong electromagnetic fluctuations were observed in the center of the current sheet in the diffusion region. The dispersion properties of the electromagnetic wave are studied by using the interferometer method and are compared with the properties of lower hybrid drift instability. The role of the waves in reconnection is discussed.
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27.
  • Amata, E., et al. (författare)
  • Experimental study of nonlinear interaction of plasma flow with charged thin current sheets : 1. Boundary structure and motion
  • 2006
  • Ingår i: Nonlinear processes in geophysics. - 1023-5809 .- 1607-7946. ; 13:4, s. 365-376
  • Tidskriftsartikel (refereegranskat)abstract
    • We study plasma transport at a thin magnetopause (MP), described hereafter as a thin current sheet (TCS), observed by Cluster at the southern cusp on 13 February 2001 around 20:01 UT. The Cluster observations generally agree with the predictions of the Gas Dynamic Convection Field (GDCF) model in the magnetosheath (MSH) up to the MSH boundary layer, where significant differences are seen. We find for the MP a normal roughly along the GSE x-axis, which implies a clear departure from the local average MP normal, a similar to 90 km thickness and an outward speed of 35 km/s. Two populations are identified in the MSH boundary layer: the first one roughly perpendicular to the MSH magnetic field, which we interpret as the "incident" MSH plasma, the second one mostly parallel to B. Just after the MP crossing a velocity jet is observed with a peak speed of 240 km/s, perpendicular to B, with M-A=3 and beta> 10 (peak value 23). The magnetic field clock angle rotates by 70 degrees across the MP. E-x is the main electric field component on both sides of the MP, displaying a bipolar signature, positive on the MSH side and negative on the opposite side, corresponding to a similar to 300 V electric potential jump across the TCS. The E x B velocity generally coincides with the perpendicular velocity measured by CIS; however, in the speed jet a difference between the two is observed, which suggests the need for an extra flow source. We propose that the MP TCS can act locally as an obstacle for low-energy ions (<350 eV), being transparent for ions with larger gyroradius. As a result, the penetration of plasma by finite gyroradius is considered as a possible source for the jet. The role of reconnection is briefly discussed. The electrodynamics of the TCS along with mass and momentum transfer across it are further discussed in the companion paper by Savin et al. (2006).
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28.
  • Backrud, M., et al. (författare)
  • Cluster observations and theoretical explanations of broadband waves in the auroral region
  • 2005
  • Ingår i: Annales Geophysicae. - : Copernicus Publications. - 1432-0576. ; 23, s. 3739-3752
  • Tidskriftsartikel (refereegranskat)abstract
    •  Broadband waves are common on auroral field lines. We use two different methods to study the polarization of the waves at 10 to 180 Hz observed by the Cluster spacecraft at altitudes of about 4 Earth radii in the nightside auroral region. Observations of electric and magnetic wave fields, together with electron and ion data, are used as input to the methods. We find that much of the wave emissions are consistent with linear waves in homogeneous plasma. Observed waves with a large electric field perpendicular to the geomagnetic field are more common (electrostatic ion cyclotron waves), while ion acoustic waves with a large parallel electric field appear in smaller regions without suprathermal (tens of eV) plasma. The regions void of suprathermal plasma are interpreted as parallel potential drops of a few hundred volts.
  •  
29.
  • Bavassano Cattaneo, M. Bice, et al. (författare)
  • Kinetic signatures during a quasi-continuous lobe reconnection event : Cluster Ion Spectrometer (CIS) observations
  • 2006
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 111:A9, s. A09212-
  • Tidskriftsartikel (refereegranskat)abstract
    • On 3 December 2001 the Cluster spacecraft observed a long-lasting lobe reconnection event in the southern high-latitude dusk magnetopause (MP) tailward of the cusp, during a 4 hour interval of mainly northward interplanetary magnetic field ( IMF) and of sub-Alfvenic magnetosheath flow. Almost all the MP encounters have accelerated flows ( for which the Walen test has been successfully verified by Retino et al. ( 2005)) as well as a large number of secondary populations related to reconnection, that is, ions of magnetosheath or magnetospheric origin which cross the MP either way. The detailed analysis of the distribution functions shows that the reconnection site frequently moves relative to the spacecraft, but simultaneous measurements by two spacecraft on opposite sides of the reconnection site indicate that the spacecraft's distance from the X line is small, i.e., below 3200 km. The vicinity to the X line throughout the event is probably the reason why the distribution functions characteristics agree with theoretical expectations on both sides of the reconnection site throughout this long event. Moreover, the detailed analysis of the distribution functions shows evidence, during a few time intervals, of dual reconnection, i.e., of reconnection simultaneously going on also in the northern hemisphere.
  •  
30.
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31.
  • Duan, Suping, et al. (författare)
  • Oxygen Ions O+ Energized by Kinetic Alfven Eigenmode During Dipolarizations of Intense Substorms
  • 2017
  • Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 122:11, s. 11256-11273
  • Tidskriftsartikel (refereegranskat)abstract
    • Singly charged oxygen ions, O+, energized by kinetic Alfven wave eigenmode (KAWE) in the plasma sheet boundary layer during dipolarizations of two intense substorms, 10: 07 UT on 31 August 2004 and 18: 24 UT on 14 September 2004, are investigated by Cluster spacecraft in the magnetotail. It is found that after the beginning of the expansion phase of substorms, O+ ions are clearly energized in the direction perpendicular to the magnetic field with energy larger than 1 keV in the near-Earth plasma sheet during magnetic dipolarizations. The pitch angle distribution of these energetic O+ ions is significantly different from that of O+ ions with energy less than 1 keV before substorm onset that is in the quasi-parallel direction along the magnetic field. The KAWE with the large perpendicular unipolar electric field, E-z similar to -20 mV/m, significantly accelerates O+ ions in the direction perpendicular to the background magnetic field. We present good evidences that O+ ion origin from the ionosphere along the magnetic field line in the northward lobe can be accelerated in the perpendicular direction during substorm dipolarizations. The change of the move direction of O+ ions is useful for O+ transferring from the lobe into the central plasma sheet in the magnetotail. Thus, KAWE can play an important role in O+ ion transfer process from the lobe into the plasma sheet during intense substorms.
  •  
32.
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33.
  • Hamrin, Maria, et al. (författare)
  • Observations of concentrated generator regions in the nightside magnetosphere by Cluster/FAST conjunctions
  • 2006
  • Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 24, s. 637-49
  • Tidskriftsartikel (refereegranskat)abstract
    • Here and in the companion paper, Marghitu et al. (2006), we investigate plausible auroral generator regions in the nightside auroral magnetosphere. In this article we use magnetically conjugate data from the Cluster and the FAST satellites during a 3.5-h long event from 19-20 September 2001. Cluster is in the Southern Hemisphere close to apogee, where it probes the plasma sheet and lobe at an altitude of about 18 RE. FAST is below the acceleration region at approximately 0.6 RE. Searching for clear signatures of negative power densities, E(.)J < O, in the Cluster data we can identify three concentrated generator regions (CGRs) during our event. From the magnetically conjugate FAST data we see that the observed generator regions in the Cluster data correlate with auroral precipitation. The downward Poynting flux observed by Cluster, as well as the scale size of the CGRs, are consistent with the electron energy flux and the size of the inverted-V regions observed by FAST. To our knowledge, these are the first in-situ observations of the crossing of an auroral generator region. The main contribution to E(.)J < O comes from the GSE E(y)J(y). The electric field E-y is weakly negative during most of our entire event and we conclude that the CGRs occur when the duskward current J(y) grows large and positive. We find that our observations are consistent with a local southward expansion of the plasma sheet and/or rather complicated, 3-D wavy structures propagating over the Cluster satellites. We find that the plasma is working against the magnetic field, and that kinetic energy is being converted into electromagnetic energy. Some of the energy is transported away as Poynting flux.
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34.
  • Hobara, Y., et al. (författare)
  • Cluster observations of electrostatic solitary waves near the Earth's bow shock
  • 2008
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 113:A5, s. A05211-
  • Tidskriftsartikel (refereegranskat)abstract
    • Using a period of internal burst mode data from the Cluster Electric Field and Wave instrument a number of electrostatic solitary structures have been identified in the foot region of Earth's quasi-perpendicular bow shock. The four individual probe potential measurements are utilized to investigate the fundamental characteristics of the solitary wave structures such as wave propagation vector, propagation velocity, scale-size and potential amplitude. Two classes of waves are observed. Bipolar solitary waves typically propagate in the solar wind direction toward the shock but at a significant angle from the ambient magnetic field. Unipolar/tripolar solitary waves tend to propagate along the ambient magnetic field. The wave amplitude-scale size relation is similar to that obtained for similar structures observed in the auroral zone. The structures lie in the theoretically allowed region in width-amplitude space to be consistent with the BGK ion holes. Using a period of internal burst mode data from the Cluster Electric Field and Wave instrument a number of electrostatic solitary structures have been identified in the foot region of Earth's quasi-perpendicular bow shock. The four individual probe potential measurements are utilized to investigate the fundamental characteristics of the solitary wave structures such as wave propagation vector, propagation velocity, scale-size and potential amplitude. Two classes of waves are observed. Bipolar solitary waves typically propagate in the solar wind direction toward the shock but at a significant angle to the ambient magnetic field in contrast to most previous studies which assume parallel propagation to the ambient magnetic field. In contrast, unipolar/tripolar solitary waves tend to propagate along the ambient magnetic field. The wave amplitude-scale size relation is similar to that obtained for structures observed in the auroral zone. The structures lie in the theoretically allowed region in width-amplitude space to be consistent with the BGK (Bernstein-Greene-Kruskal) ion holes. The two classes of observed solitary waves may greatly influence the ambient plasma dynamics around the shock. The bipolar solitary waves do not exhibit a large net potential difference but may still play an important role in plasma thermalisation by particle scattering. Unipolar/tripolar solitary waves exhibit a remarkable net potential difference that may be responsible for the plasma energisation along the ambient magnetic field.
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35.
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36.
  • Laitinen, T. V., et al. (författare)
  • Local influence of magnetosheath plasma beta fluctuations on magnetopause reconnection
  • 2010
  • Ingår i: Annales Geophysicae. - : Copernicus Publications. - 0992-7689 .- 1432-0576. ; 28:5, s. 1053-1063
  • Tidskriftsartikel (refereegranskat)abstract
    • We present observations from two subsolar Cluster magnetopause crossings under southward interplanetary magnetic field and strong mirror mode fluctuations in the magnetosheath. In both events the reconnection outflow jets show strong variations on the timescale of one minute. We show that at least some of the recorded variations are truly temporal, not spatial. On the same timescale, mirror mode fluctuations appear as strong magnetic fluctuations in the magnetosheath next to the magnetopause. This suggests that mirror modes can cause the variations either through modulation of continuous reconnection or through triggering of bursty reconnection. Using a theoretical scaling law for asymmetric reconnection we show that modulation of reconnection at a single x-line can explain the observations of the first event. The second event cannot be explained by a single modulated x-line: there the evidence points to patchy and bursty reconnection.
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37.
  • Lui, A. T. Y., et al. (författare)
  • Breakdown of the frozen-in condition in the Earth's magnetotail
  • 2007
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 112:A4, s. A04215-
  • Tidskriftsartikel (refereegranskat)abstract
    • [1] We investigate in detail the breakdown of the frozen-in condition detected by Cluster at the downstream distance of similar to 19 R-E in the midnight sector of the magnetotail during a substorm expansion on 22 August 2001. It is found that the breakdown occurred ( 1) in a low-density environment with moderate to large proton plasma flow and significant fluctuations in electric and magnetic fields, ( 2) in regions with predominantly dissipation but occasionally dynamo effect, and ( 3) at times simultaneously at two Cluster satellites separated by more than 1000 km in both X- and Z-directions. Evaluation of the terms in the generalized Ohm's law indicates that the anomalous resistivity contribution arising from field fluctuations during this event is the most significant, followed by the Hall, electron viscosity, and inertial contributions in descending order of importance. This result demonstrates for the first time from observations that anomalous resistivity from field fluctuations ( implying kinetic instabilities) can play a substantial role in the breakdown of the frozen-in condition in the magnetotail during substorm expansions. Consideration of several observed features in the breakdown regions indicates that the breakdown occurs in a turbulent site resembling observed features found in current disruption and dipolarization sites.
  •  
38.
  • Lui, A. T. Y., et al. (författare)
  • Cluster observation of plasma flow reversal in the magnetotail during a substorm
  • 2006
  • Ingår i: Annales Geophysicae. - 0992-7689 .- 1432-0576. ; 24:7, s. 2005-2013
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate in detail a reversal of plasma flow from tailward to earthward detected by Cluster at the downstream distance of similar to 19 RE in the midnight sector of the magnetotail on 22 August 2001. This flow reversal was accompanied by a sign reversal of the B-z component and occurred during the late substorm expansion phase as revealed by simultaneous global view of auroral activity from IMAGE. We examine the associated Hall current system signature, current density, electric field, Lorentz force, and current dissipation/dynamo term, the last two parameters being new features that have not been studied previously for plasma flow reversals. It is found that (1) there was no clear quadrupole Hall current system signature organized by the flow reversal time, (2) the x-component of the Lorentz force did not change sign while the other two did, (3) the timing sequence of flow reversal from the Cluster configuration did not match tailward motion of a single plasma flow source, (4) the electric field was occasionally dawnward, producing a dynamo effect, and (5) the electric field was occasionally larger at the high-latitude plasma sheet than near the neutral sheet. These observations are consistent with the current disruption model for substorms in which these disturbances are due to shifting dominance of multiple current disruption sites and turbulence at the observing location.
  •  
39.
  • Lui, A. T. Y., et al. (författare)
  • Evaluation of substorm models with Cluster observations of plasma flow reversal in the magnetotail
  • 2008
  • Ingår i: Advances in Space Research. - : Elsevier BV. - 0273-1177 .- 1879-1948. ; 41:10, s. 1611-1618
  • Tidskriftsartikel (refereegranskat)abstract
    • We evaluate two prevailing substorm, models with an event of plasma flow reversal from tailward to Earthward detected by Cluster at the downstream distance of similar to 19 R-E in the magnetotail during a substorm. oil August 22, 2001. We use the unique capability of Cluster measurements in determining gradients to examine the associated current density, Lorentz force, and current dissipation/dynamo term. In association with plasma flow reversal, it is found that (1) there was no clear quadrupole magnetic perturbation signature, (2) the x-component of the Lorentz force did not change sign, (3) the y-component of the product of the current density and the electric field was occasionally negative indicative of a dynamo effect, and (4) the timing sequence of flow reversal from the Cluster configuration did not match tailward motion of a single plasma flow source. These observations are consistent with the near-Earth initiation model for substorms with multiple current disruption sites moving progressively tailward near the late stage of substorm expansion.
  •  
40.
  • Lui, A. T. Y., et al. (författare)
  • Internal structure of a magnetic flux rope from Cluster observations
  • 2007
  • Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 34:7, s. L07102-
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate a magnetic flux rope (MFR) observed by Cluster in the magnetotail during a substorm on 2001 August 22. The MFR was aligned with its principal axis closely along the dawn-dusk direction and had a small size of similar to 2 R-E with a total current of similar to 0.8 MA. The four spacecraft traversed the MFR at different distances from its center based on the magnetic field signature. This fortuitous situation reveals the irregular magnetic field structure in its inner core, which is a feature reported here for the first time. At the leading edge, the y-component of the electric field was dawnward against the current density direction ( dynamo action) and the x-component of the Lorentz force was Earthward. These parameters reversed in direction at its trailing edge (load).
  •  
41.
  • Lui, A. T. Y., et al. (författare)
  • Prelude to THEMIS tail conjunction study
  • 2007
  • Ingår i: Annales Geophysicae. - 0992-7689 .- 1432-0576. ; 25:4, s. 1001-1009
  • Tidskriftsartikel (refereegranskat)abstract
    • A close conjunction of several satellites (LANL, GOES. Polar. Geotail, and Cluster) distributed from the geostationary altitude to about 16 R-E downstream in the tail occurred during substorm activity as indicated by global auroral imaging and ground-based magnetometer data. This constellation of satellites resembles what is planned for the THEMIS (Time History of Events and Macroscopic Interactions during Substorms) mission to resolve the substorm controversy on the location of the substorm expansion onset region. In this article, we show in detail the dipolarization and dynamic changes seen by these satellites associated with two onsets of substorm intensification activity. In particular, we find that dipolarization at similar to 16 R-E downstream in the tail can occur with dawnward electric field and without plasma flow, just like some near-Earth dipolarization events reported previously. The spreading of substorm disturbances in the tail coupled with complementary ground observations indicates that the observed time sequence on the onsets of substorm disturbances favors initiation in the near-Earth region for this THEMIS-like conjunction.
  •  
42.
  • Marchaudon, A., et al. (författare)
  • Simultaneous double star and cluster ftes observations on the dawnside flank of the magnetosphere
  • 2006
  • Ingår i: Eur Space Agency Spec Publ ESA SP. - 929092909X - 9789290929093 ; , s. 163-170
  • Konferensbidrag (refereegranskat)abstract
    • We present Cluster and Double Star-1 (TC-1) observations from a close magnetic conjunction on May 8, 2004. The five spacecraft were on the dawnside flank of the magnetosphere, with TC-1 located near the equatorial plane and Cluster at higher geographic latitudes in the southern hemisphere. TC-1, at its apogee, skimmed the magnetopause for almost 8 hours (between 08:00-16:00 UT). Flux Transfer Events (FTEs), moving southward/tailward from the reconnection site, were observed by TC-1 throughout almost all of the period. Cluster, travelling on a mainly dawn-dusk trajectory, crossed the magnetopause at around 10:30 UT in the same Magnetic Local Time (MLT) sector as TC-1 and remained close to the magnetopause boundary layer in the southern hemisphere. The four Cluster spacecraft observed FTEs for a period of 6.5 hours between 07:30 and 14:00 UT. From the properties of these FTEs, the reconnection site was located northward of both TC-1 and Cluster on the dawn flank of the magnetosphere. Reconnection occurred between draped magnetosheath and closed magnetospheric field lines. Despite variable interplanetary magnetic field (IMF) conditions and IMF-B z turnings, the IMF clock-angle remained greater than 70° and the location site appeared to remain relatively stable in position during the whole period. This result is in agreement with previous studies which reported that the dayside reconnection remained active for an IMF clock-angle greater than 70°. The simultaneous observation of FTEs at both Cluster and TC-1, separated by 2 hours in MLT, implies that the reconnection site on the magnetopause must have been extended over several hours in MLT. This event has been already presented in more details in [1].
  •  
43.
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44.
  • Motoba, T., et al. (författare)
  • In situ evidence for interplanetary magnetic field induced tail twisting associated with relative displacement of conjugate auroral features
  • 2011
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 116, s. A04209-
  • Tidskriftsartikel (refereegranskat)abstract
    • We provide in situ evidence for a twisted near-Earth tail configuration that is responsible for the time sequence of conjugate auroral features associated with relative interhemispheric displacement during a weak substorm, as reported by Motoba et al. (2010). We analyzed the magnetic field data observed using four Cluster satellites in the vicinity of 11-14 R-E central downtail, in close conjunction with the Iceland-Syowa conjugate optical auroral features. Interestingly, we found that the variations in the magnetic field y component (B-y) at all satellites correlated moderately well with the variations in the time-shifted interplanetary magnetic field (IMF) clock angle (theta(CA)). The correlation coefficients (0.56 similar to 0.61) between the B-y field at Cluster and IMF theta(CA) peaked at a time delay of 52 +/- 1 min from the dayside magnetopause, probably corresponding to the time scale for the reconfiguration of the IMF theta(CA) related B-y field in the near-Earth tail. The IMF theta(CA) related B-y variation at Cluster, regarded as a manifestation of the twisting magnetotail configuration, also roughly coincided with the relative magnetic local time displacement of nightside conjugate auroral forms. These results provide strong evidence that the reconfiguration (twisting) process of the near-Earth tail on a relatively longer time scale controls the nightside conjugate auroral locations in both ionospheres.
  •  
45.
  • Nakamura, R., et al. (författare)
  • Cluster observations of an ion-scale current sheet in the magnetotail under the presence of a guide field
  • 2008
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 113:A7, s. A07S16-
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on Cluster observations of a thin current sheet interval under the presence of a strong vertical bar B-Y vertical bar during a fast earthward flow interval between 1655 UT and 1703 UT on 17 August 2003. The strong vertical bar B-Y vertical bar in the tail could be associated with a strong IMF vertical bar B-Y vertical bar, but the large fluctuations in B-Y, not seen in the IMF, suggest that a varying reconnection rate causes a varying transport of B-Y-dominated magnetic flux and/or a change in B-Y due to the Hall-current system. During the encounter of the high-speed flow, an intense current layer was observed around 1655: 53 UT with a peak current density of 182 nA/m(2), the largest current density observed by the Cluster four-spacecraft magnetic field measurement in the magnetotail. The half width of this current layer was estimated to be similar to 290 km, which was comparable to the ion-inertia length. Its unique signature is that the strong current is mainly field-aligned current flowing close to the center of the plasma sheet. The event was associated with parallel heating of electrons with asymmetries, which suggests that electrons moving along the field lines can contribute to a strong dawn-to-dusk current when the magnetotail current sheet becomes sufficiently thin and active in a strong guide field case.
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46.
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47.
  • Pitout, F., Bosqueg, J.M., Alcayde, D., Denig, W. and Reme, H. (författare)
  • Observation of the cusp region under northward IMF.
  • 2001
  • Ingår i: Annales Geophysicae. ; 19, s. 11-15
  • Tidskriftsartikel (refereegranskat)abstract
    • Using EISCAT radar data, we find that electrons are strongly heated in the magnetic field-line direction during high electric field events. The remote site data show that the electron temperature increases in almost the same way in the field-perpendicular
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48.
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49.
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50.
  • Yordanova, Emiliya, et al. (författare)
  • Energy input from the exterior cusp into the ionosphere : Correlated ground-based and satellite observations
  • 2007
  • Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 34:4, s. L04102-
  • Tidskriftsartikel (refereegranskat)abstract
    • The energy transport from the exterior cusp into the ionosphere is investigated using coordinated ground-based (EISCAT and MIRACLE) and satellite ( Cluster) observations. EISCAT and MIRACLE data are used to estimate the plasma heating in the F-region and the Joule heating in the E-region. Cluster measurements are used to derive the electromagnetic and particle energy fluxes at the high altitudes. These fluxes are then compared with the energy deposition into the ionospheric cusp during a 30 minutes long time interval in which Cluster and EISCAT are nearly conjugated. It is shown that the particles seen at about 9 Re in the exterior cusp carry an earthward energy flux that corresponds to the observed heating of the F-region. The estimated earthward Poynting flux is more than enough to account for the Joule heating in the E-region.
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