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Artykuły w czasopismach na temat „Earth's Magnetosheath”

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Data publikacji: 6 września 2023

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1

Artemyev, A. V., C. Shi, Y. Lin, Y. Nishimura, C. Gonzalez, J. Verniero, X. Wang, M. Velli, A. Tenerani i N. Sioulas. "Ion Kinetics of Plasma Flows: Earth's Magnetosheath versus Solar Wind". Astrophysical Journal 939, nr 2 (1.11.2022): 85. http://dx.doi.org/10.3847/1538-4357/ac96e4.

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Abstract Revealing the formation, dynamics, and contribution to plasma heating of magnetic field fluctuations in the solar wind is an important task for heliospheric physics and for a general plasma turbulence theory. Spacecraft observations in the solar wind are limited to spatially localized measurements, so that the evolution of fluctuation properties with solar wind propagation is mostly studied via statistical analyses of data sets collected by different spacecraft at various radial distances from the Sun. In this study we investigate the evolution of turbulence in the Earth’s magnetosheath, a plasma system sharing many properties with the solar wind. The near-Earth space environment is being explored by multiple spacecraft missions, which may allow us to trace the evolution of magnetosheath fluctuations with simultaneous measurements at different distances from their origin, the Earth’s bow shock. We compare ARTEMIS and Magnetospheric Multiscale (MMS) Mission measurements in the Earth magnetosheath and Parker Solar Probe measurements of the solar wind at different radial distances. The comparison is supported by three numerical simulations of the magnetosheath magnetic and plasma fluctuations: global hybrid simulation resolving ion kinetic and including effects of Earth’s dipole field and realistic bow shock, hybrid and Hall-MHD simulations in expanding boxes that mimic the magnetosheath volume expansion with the radial distance from the dayside bow shock. The comparison shows that the magnetosheath can be considered as a miniaturized version of the solar wind system with much stronger plasma thermal anisotropy and an almost equal amount of forward and backward propagating Alfvén waves. Thus, many processes, such as turbulence development and kinetic instability contributions to plasma heating, occurring on slow timescales and over large distances in the solar wind, occur more rapidly in the magnetosheath and can be investigated in detail by multiple near-Earth spacecraft.

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Turc, Lucile, Vertti Tarvus, Andrew P. Dimmock, Markus Battarbee, Urs Ganse, Andreas Johlander, Maxime Grandin, Yann Pfau-Kempf, Maxime Dubart i Minna Palmroth. "Asymmetries in the Earth's dayside magnetosheath: results from global hybrid-Vlasov simulations". Annales Geophysicae 38, nr 5 (6.10.2020): 1045–62. http://dx.doi.org/10.5194/angeo-38-1045-2020.

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Abstract. Bounded by the bow shock and the magnetopause, the magnetosheath forms the interface between solar wind and magnetospheric plasmas and regulates solar wind–magnetosphere coupling. Previous works have revealed pronounced dawn–dusk asymmetries in the magnetosheath properties. The dependence of these asymmetries on the upstream parameters remains however largely unknown. One of the main sources of these asymmetries is the bow shock configuration, which is typically quasi-parallel on the dawn side and quasi-perpendicular on the dusk side of the terrestrial magnetosheath because of the Parker spiral orientation of the interplanetary magnetic field (IMF) at Earth. Most of these previous studies rely on collections of spacecraft measurements associated with a wide range of upstream conditions which are processed in order to obtain average values of the magnetosheath parameters. In this work, we use a different approach and quantify the magnetosheath asymmetries in global hybrid-Vlasov simulations performed with the Vlasiator model. We concentrate on three parameters: the magnetic field strength, the plasma density, and the flow velocity. We find that the Vlasiator model reproduces the polarity of the asymmetries accurately but that their level tends to be higher than in spacecraft measurements, probably because the magnetosheath parameters are obtained from a single set of upstream conditions in the simulation, making the asymmetries more prominent. A set of three runs with different upstream conditions allows us to investigate for the first time how the asymmetries change when the angle between the IMF and the Sun–Earth line is reduced and when the Alfvén Mach number decreases. We find that a more radial IMF results in a stronger magnetic field asymmetry and a larger variability of the magnetosheath density. In contrast, a lower Alfvén Mach number leads to a reduced magnetic field asymmetry and a decrease in the variability of the magnetosheath density, the latter likely due to weaker foreshock processes. Our results highlight the strong impact of the quasi-parallel shock and its associated foreshock on global magnetosheath properties, in particular on the magnetosheath density, which is extremely sensitive to transient quasi-parallel shock processes, even with the perfectly steady upstream conditions in our simulations. This could explain the large variability of the density asymmetry levels obtained from spacecraft measurements in previous studies.

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3

Longmore, M., S. J. Schwartz i E. A. Lucek. "Rotation of the magnetic field in Earth's magnetosheath by bulk magnetosheath plasma flow". Annales Geophysicae 24, nr 1 (7.03.2006): 339–54. http://dx.doi.org/10.5194/angeo-24-339-2006.

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Abstract. Orientations of the observed magnetic field in Earth's dayside magnetosheath are compared with the predicted field line-draping pattern from the Kobel and Flückiger static magnetic field model. A rotation of the overall magnetosheath draping pattern with respect to the model prediction is observed. For an earthward Parker spiral, the sense of the rotation is typically clockwise for northward IMF and anticlockwise for southward IMF. The rotation is consistent with an interpretation which considers the twisting of the magnetic field lines by the bulk plasma flow in the magnetosheath. Histogram distributions describing the differences between the observed and model magnetic field clock angles in the magnetosheath confirm the existence and sense of the rotation. A statistically significant mean value of the IMF rotation in the range 5°-30° is observed in all regions of the magnetosheath, for all IMF directions, although the associated standard deviation implies large uncertainty in the determination of an accurate value for the rotation. We discuss the role of field-flow coupling effects and dayside merging on field line draping in the magnetosheath in view of the evidence presented here and that which has previously been reported by Kaymaz et al. (1992).

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4

Song, P. "Forecasting Earth's magnetopause, magnetosheath, and bow shock". IEEE Transactions on Plasma Science 28, nr 6 (2000): 1966–75. http://dx.doi.org/10.1109/27.902225.

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5

Walsh, B. M., D. G. Sibeck, Y. Wang i D. H. Fairfield. "Dawn-dusk asymmetries in the Earth's magnetosheath". Journal of Geophysical Research: Space Physics 117, A12 (grudzień 2012): n/a. http://dx.doi.org/10.1029/2012ja018240.

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6

ONSAGER, T. G., i M. F. THOMSEN. "The Earth's Foreshock, Bow Shock, and Magnetosheath". Reviews of Geophysics 29, S2 (styczeń 1991): 998–1007. http://dx.doi.org/10.1002/rog.1991.29.s2.998.

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7

Guicking, L., K. H. Glassmeier, H. U. Auster, Y. Narita i G. Kleindienst. "Low-frequency magnetic field fluctuations in Earth's plasma environment observed by THEMIS". Annales Geophysicae 30, nr 8 (27.08.2012): 1271–83. http://dx.doi.org/10.5194/angeo-30-1271-2012.

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Abstract. Low-frequency magnetic wave activity in Earth's plasma environment was determined based on a statistical analysis of THEMIS magnetic field data. We observe that the spatial distribution of low-frequency magnetic field fluctuations reveals highest values in the magnetosheath, but the observations differ qualitatively from observations at Venus presented in a previous study since significant wave activity at Earth is also observed in the nightside magnetosheath. Outside the magnetosheath the low-frequency wave activity level is generally very low. By means of an analytical streamline model for the magnetosheath plasma flow, we are able to investigate the spatial and temporal evolution of wave intensity along particular streamlines in order to characterise possible wave generation mechanisms. We observe a decay of wave intensity along the streamlines, but contrary to the situation at Venus, we obtain good qualitative agreement with the theoretical concept of freely evolving/decaying turbulence. Differences between the dawn region and the dusk region can be observed only further away from the magnetopause. We conclude that wave generation mechanisms may be primarily attributed to processes at or in the vicinity of the bow shock. The difference with the observations of the Venusian magnetosheath we interpret to be the result of the different types of solar wind interaction processes since the Earth possesses a global magnetic field while Venus does not, and therefore the observed magnetic wave activities may be caused by diverse magnetic field controlled characteristics of wave generation processes.

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8

Turc, L., D. Fontaine, P. Savoini i E. K. J. Kilpua. "Magnetic clouds' structure in the magnetosheath as observed by Cluster and Geotail: four case studies". Annales Geophysicae 32, nr 10 (15.10.2014): 1247–61. http://dx.doi.org/10.5194/angeo-32-1247-2014.

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Abstract. Magnetic clouds (MCs) are large-scale magnetic flux ropes ejected from the Sun into the interplanetary space. They play a central role in solar–terrestrial relations as they can efficiently drive magnetic activity in the near-Earth environment. Their impact on the Earth's magnetosphere is often attributed to the presence of southward magnetic fields inside the MC, as observed in the upstream solar wind. However, when they arrive in the vicinity of the Earth, MCs first encounter the bow shock, which is expected to modify their properties, including their magnetic field strength and direction. If these changes are significant, they can in turn affect the interaction of the MC with the magnetosphere. In this paper, we use data from the Cluster and Geotail spacecraft inside the magnetosheath and from the Advanced Composition Explorer (ACE) upstream of the Earth's environment to investigate the impact of the bow shock's crossing on the magnetic structure of MCs. Through four example MCs, we show that the evolution of the MC's structure from the solar wind to the magnetosheath differs largely from one event to another. The smooth rotation of the MC can either be preserved inside the magnetosheath, be modified, i.e. the magnetic field still rotates slowly but at different angles, or even disappear. The alteration of the magnetic field orientation across the bow shock can vary with time during the MC's passage and with the location inside the magnetosheath. We examine the conditions encountered at the bow shock from direct observations, when Cluster or Geotail cross it, or indirectly by applying a magnetosheath model. We obtain a good agreement between the observed and modelled magnetic field direction and shock configuration, which varies from quasi-perpendicular to quasi-parallel in our study. We find that the variations in the angle between the magnetic fields in the solar wind and in the magnetosheath are anti-correlated with the variations in the shock obliquity. When the shock is in a quasi-parallel regime, the magnetic field direction varies significantly from the solar wind to the magnetosheath. In such cases, the magnetic field reaching the magnetopause cannot be approximated by the upstream magnetic field. Therefore, it is important to take into account the conditions at the bow shock when estimating the impact of an MC with the Earth's environment because these conditions are crucial in determining the magnetosheath magnetic field, which then interacts with the magnetosphere.

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9

Hou, Chuanpeng, Jiansen He, Die Duan, Xingyu Zhu, Wenya Li, Daniel Verscharen, Terry Liu i Tieyan Wang. "Efficient Energy Conversion through Vortex Arrays in the Turbulent Magnetosheath". Astrophysical Journal 946, nr 1 (1.03.2023): 13. http://dx.doi.org/10.3847/1538-4357/acb927.

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Abstract Turbulence is often enhanced when transmitted through a collisionless plasma shock. We investigate how the enhanced turbulent energy in the Earth's magnetosheath effectively dissipates via vortex arrays. This research topic is of great importance as it relates to particle energization at astrophysical shocks across the universe. Wave modes and intermittent coherent structures are the key candidate mechanisms for energy conversion in turbulent plasmas. Here, by comparing in-situ measurements in the Earth's magnetosheath with a theoretical model, we find the existence of vortex arrays at the transition between the downstream regions of the Earth's bow shock. Vortex arrays consist of quasi-orthogonal kinetic waves and exhibit both high volumetric filling factors and strong local energy conversion, thereby showing a greater dissipative energization than traditional waves and coherent structures. Therefore, we propose that vortex arrays are a promising mechanism for efficient energy conversion in the sheath regions downstream of astrophysical shocks.

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10

Paschalidis, N. P., S. M. Krimigis, E. T. Sarris, D. G. Sibeck, R. W. McEntire, S. P. Christon i L. J. Zanetti. "Ion burst event in the Earth's dayside magnetosheath". Geophysical Research Letters 18, nr 3 (marzec 1991): 377–80. http://dx.doi.org/10.1029/91gl00140.

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11

Paularena, K. I., J. D. Richardson, M. A. Kolpak, C. R. Jackson i G. L. Siscoe. "A dawn-dusk density asymmetry in Earth's magnetosheath". Journal of Geophysical Research: Space Physics 106, A11 (1.11.2001): 25377–94. http://dx.doi.org/10.1029/2000ja000177.

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12

Gallagher, D. L. "Short-wavelength electrostatic waves in the Earth's magnetosheath". Journal of Geophysical Research 90, A2 (1985): 1435. http://dx.doi.org/10.1029/ja090ia02p01435.

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13

Lacombe, C., i G. Belmont. "Waves in the Earth's magnetosheath: Observations and interpretations". Advances in Space Research 15, nr 8-9 (styczeń 1995): 329–40. http://dx.doi.org/10.1016/0273-1177(94)00113-f.

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14

Pokhotelov, D., S. von Alfthan, Y. Kempf, R. Vainio, H. E. J. Koskinen i M. Palmroth. "Ion distributions upstream and downstream of the Earth's bow shock: first results from Vlasiator". Annales Geophysicae 31, nr 12 (17.12.2013): 2207–12. http://dx.doi.org/10.5194/angeo-31-2207-2013.

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Abstract. A novel hybrid-Vlasov code, Vlasiator, is developed for global simulations of magnetospheric plasma kinetics. The code is applied to model the collisionless bow shock on scales of the Earth's magnetosphere in two spatial dimensions and three dimensions in velocity space retrieving ion distribution functions over the entire foreshock and magnetosheath regions with unprecedented detail. The hybrid-Vlasov approach produces noise-free uniformly discretized ion distribution functions comparable to those measured in situ by spacecraft. Vlasiator can reproduce features of the ion foreshock and magnetosheath well known from spacecraft observations, such as compressional magnetosonic waves generated by backstreaming ion populations in the foreshock and mirror modes in the magnetosheath. An overview of ion distributions from various regions of the bow shock is presented, demonstrating the great opportunities for comparison with multi-spacecraft observations.

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15

Turc, L., D. Fontaine, P. Savoini i E. K. J. Kilpua. "A model of the magnetosheath magnetic field during magnetic clouds". Annales Geophysicae 32, nr 2 (21.02.2014): 157–73. http://dx.doi.org/10.5194/angeo-32-157-2014.

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Abstract. Magnetic clouds (MCs) are huge interplanetary structures which originate from the Sun and have a paramount importance in driving magnetospheric storms. Before reaching the magnetosphere, MCs interact with the Earth's bow shock. This may alter their structure and therefore modify their expected geoeffectivity. We develop a simple 3-D model of the magnetosheath adapted to MCs conditions. This model is the first to describe the interaction of MCs with the bow shock and their propagation inside the magnetosheath. We find that when the MC encounters the Earth centrally and with its axis perpendicular to the Sun–Earth line, the MC's magnetic structure remains mostly unchanged from the solar wind to the magnetosheath. In this case, the entire dayside magnetosheath is located downstream of a quasi-perpendicular bow shock. When the MC is encountered far from its centre, or when its axis has a large tilt towards the ecliptic plane, the MC's structure downstream of the bow shock differs significantly from that upstream. Moreover, the MC's structure also differs from one region of the magnetosheath to another and these differences vary with time and space as the MC passes by. In these cases, the bow shock configuration is mainly quasi-parallel. Strong magnetic field asymmetries arise in the magnetosheath; the sign of the magnetic field north–south component may change from the solar wind to some parts of the magnetosheath. We stress the importance of the Bx component. We estimate the regions where the magnetosheath and magnetospheric magnetic fields are anti-parallel at the magnetopause (i.e. favourable to reconnection). We find that the location of anti-parallel fields varies with time as the MCs move past Earth's environment, and that they may be situated near the subsolar region even for an initially northward magnetic field upstream of the bow shock. Our results point out the major role played by the bow shock configuration in modifying or keeping the structure of the MCs unchanged. Note that this model is not restricted to MCs, it can be used to describe the magnetosheath magnetic field under an arbitrary slowly varying interplanetary magnetic field.

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16

Mitchell, J. J., S. J. Schwartz i U. Auster. "Electron cross talk and asymmetric electron distributions near the Earth's bowshock". Annales Geophysicae 30, nr 3 (6.03.2012): 503–13. http://dx.doi.org/10.5194/angeo-30-503-2012.

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Abstract. Electron distributions in the magnetosheath display a number of far from equilibrium features. It has been suggested that one factor influencing these distributions may be the large distances separating locations at which electrons with different energies and pitch angles must cross the bowshock in order to reach a given point in the magnetosheath. The overall heating requirements at these distant locations depends strongly on the shock geometry. In the absence of collisions or other isotropization processes this suggests that the convolution of electrons arriving from different locations should give rise to asymmetries in the distribution functions. Moreover, such cross-talk could influence the relative electron to ion heating, rendering the shock heating problem intrinsically non-local in contrast to classic shock physics. Here, we study electron distributions measured simultaneously by the Plasma Electron and Current Experiment (PEACE) on board the Cluster spacecraft and the Electrostatic Analyser (ESA) on board THEMIS b during a time interval in which both the Cluster spacecraft and THEMIS b are in the magnetosheath, close to the bowshock, and during which the local magnetic field orientation makes it likely that electron trajectories may connect both spacecraft. We find that the relevant portions of the velocity distributions of such electrons measured by each spacecraft display remarkable similarities. We map trajectories of electrons arriving at each spacecraft back to the locations at which they crossed the bowshock, as a function of pitch angle and energy. We then use the Rankine-Hugoniot relations to estimate the heating of electrons and compare this with temperature asymmetries actually observed. We conclude that the electron distributions and temperatures in the magnetosheath depend heavily on non-local shock properties.

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17

Kessel, R. L., I. R. Mann, S. F. Fung, D. K. Milling i N. O'Connell. "Correlation of Pc5 wave power inside and outside themagnetosphere during high speed streams". Annales Geophysicae 22, nr 2 (1.01.2004): 629–41. http://dx.doi.org/10.5194/angeo-22-629-2004.

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Abstract. We show a clear correlation between the ULF wave power (Pc5 range) inside and outside the Earth's magnetosphere during high speed streams in 1995. We trace fluctuations beginning 200RE upstream using Wind data, to fluctuations just upstream from Earth's bow shock and in the magnetosheath using Geotail data and compare to pulsations on the ground at the Kilpisjarvi ground station. With our 5-month data set we draw the following conclusions. ULF fluctuations in the Pc5 range are found in high speed streams; they are non-Alfvénic at the leading edge and Alfvénic in the central region. Compressional and Alfvénic fluctuations are modulated at the bow shock, some features of the waveforms are preserved in the magnetosheath, but overall turbulence and wave power is enhanced by about a factor of 10. Parallel (compressional) and perpendicular (transverse) power are at comparable levels in the solar wind and magnetosheath, both in the compression region and in the central region of high speed streams. Both the total parallel and perpendicular Pc5 power in the solar wind (and to a lesser extent in the magnetosheath) correlate well with the total Pc5 power of the ground-based H-component magnetic field. ULF fluctuations in the magnetosheath during high speed streams are common at frequencies from 1–4mHz and can coincide with the cavity eigenfrequencies of 1.3, 1.9, 2.6, and 3.4mHz, though other discrete frequencies are also often seen. Key words. Interplanetary physics (MHD waves and turbulence) – Magnetospheric physics (solar wind-magnetosphere interactions; MHD waves and instabilities)

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Schwartz, S. J., D. Burgess i J. J. Moses. "Low-frequency waves in the Earth's magnetosheath: present status". Annales Geophysicae 14, nr 11 (30.11.1996): 1134–50. http://dx.doi.org/10.1007/s00585-996-1134-z.

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Abstract. The terrestrial magnetosheath contains a rich variety of low-frequency (≲ proton gyrofrequency) fluctuations. Kinetic and fluid-like processes at the bow shock, within the magnetosheath plasma, and at the magnetopause all provide sources of wave energy. The dominance of kinetic features such as temperature anisotropies, coupled with the high-β conditions, complicates the wave dispersion and variety of instabilities to the point where mode identification is difficult. We review here the observed fluctuations and attempts to identify the dominant modes, along with the identification tools. Alfvén/ion-cyclotron and mirror modes are generated by T^/T∥>1 temperature anisotropies and dominate when the plasma β is low or high, respectively. Slow modes may also be present within a transition layer close to the subsolar magnetopause, although they are expected to suffer strong damping. All mode identifications are based on linearized theory in a homogeneous plasma and there are clear indications, in both the data and in numerical simulations, that nonlinearity and/or inhomogeneity modify even the most basic aspects of some modes. Additionally, the determination of the wave vector remains an outstanding observational issue which, perhaps, the Cluster mission will overcome.

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Volwerk, M., J. Berchem, Y. V. Bogdanova, O. D. Constantinescu, M. W. Dunlop, J. P. Eastwood, P. Escoubet i in. "Interplanetary magnetic field rotations followed from L1 to the ground: the response of the Earth's magnetosphere as seen by multi-spacecraft and ground-based observations". Annales Geophysicae 29, nr 9 (8.09.2011): 1549–69. http://dx.doi.org/10.5194/angeo-29-1549-2011.

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Abstract. A study of the interaction of solar wind magnetic field rotations with the Earth's magnetosphere is performed. For this event there is, for the first time, a full coverage over the dayside magnetosphere with multiple (multi)spacecraft missions from dawn to dusk, combined with ground magnetometers, radar and an auroral camera, this gives a unique coverage of the response of the Earth's magnetosphere. After a long period of southward IMF Bz and high dynamic pressure of the solar wind, the Earth's magnetosphere is eroded and compressed and reacts quickly to the turning of the magnetic field. We use data from the solar wind monitors ACE and Wind and from magnetospheric missions Cluster, THEMIS, DoubleStar and Geotail to investigate the behaviour of the magnetic rotations as they move through the bow shock and magnetosheath. The response of the magnetosphere is investigated through ground magnetometers and auroral keograms. It is found that the solar wind magnetic field drapes over the magnetopause, while still co-moving with the plasma flow at the flanks. The magnetopause reacts quickly to IMF Bz changes, setting up field aligned currents, poleward moving aurorae and strong ionospheric convection. Timing of the structures between the solar wind, magnetosheath and the ground shows that the advection time of the structures, using the solar wind velocity, correlates well with the timing differences between the spacecraft. The reaction time of the magnetopause and the ionospheric current systems to changes in the magnetosheath Bz seem to be almost immediate, allowing for the advection of the structure measured by the spacecraft closest to the magnetopause.

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20

Karanikola, I., G. C. Anagnostopoulos i A. Rigas. "Characteristics of <u>></u> 290 keV magnetosheath ions". Annales Geophysicae 17, nr 5 (31.05.1999): 650–58. http://dx.doi.org/10.1007/s00585-999-0650-z.

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Abstract. We performed a statistical analysis of 290-500 keV ion data obtained by IMP-8 during the years 1982-1988 within the earth's magnetosheath and analysed in detail some time periods withdistinct ion bursts. These studies reveal the following characteristics for magnetosheath 290-500 keV energetic ions: (a) the occurrence frequency and the flux of ions increase with increasing geomagnetic activity as indicated by the Kp index; the occurrence frequency was found to be as high as P > 42% for Kp > 2, (b) the occurrence frequency in the dusk magnetosheath was found to be slightly dependent on the local time and ranged between ~30% and ~46% for all Kp values; the highest occurrence frequency was detected near the dusk magnetopause (21 LT), (c) the high energy ion bursts display a dawn-dusk asymmetry in their maximum fluxes, with higher fluxes appearing in the dusk magnetosheath, and (d) the observations in the dusk magnetosheath suggest that there exist intensity gradients of energetic ions from the bow shock toward the magnetopause. The statistical results are consistent with the concept that leakage of magnetospheric ions from the dusk magnetopause is a semi-permanent physical process often providing the magnetosheath with high energy (290-500 keV) ions.Key words. Magnetospheric physics (magnetosheath; planetary magnetospheres). Space plasma physics (shock waves).

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Grabbe, Crockett L. "MHD theory of Earth's magnetosheath for an axisymmetric model". Geophysical Research Letters 23, nr 7 (1.04.1996): 777–80. http://dx.doi.org/10.1029/96gl00847.

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Gleaves, D. G., i D. J. Southwood. "Phase delays in transverse disturbances in the Earth's magnetosheath". Geophysical Research Letters 17, nr 12 (listopad 1990): 2249–52. http://dx.doi.org/10.1029/gl017i012p02249.

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Kozak, L. V., A. T. Y. Lui, E. A. Kronberg i A. S. Prokhorenkov. "Turbulent processes in Earth's magnetosheath by Cluster mission measurements". Journal of Atmospheric and Solar-Terrestrial Physics 154 (luty 2017): 115–26. http://dx.doi.org/10.1016/j.jastp.2016.12.016.

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Shoji, Masafumi, Yoshiharu Omura i Lou-Chuang Lee. "Multidimensional nonlinear mirror-mode structures in the Earth's magnetosheath". Journal of Geophysical Research: Space Physics 117, A8 (sierpień 2012): n/a. http://dx.doi.org/10.1029/2011ja017420.

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Chen, C. H. K., i S. Boldyrev. "Nature of Kinetic Scale Turbulence in the Earth's Magnetosheath". Astrophysical Journal 842, nr 2 (22.06.2017): 122. http://dx.doi.org/10.3847/1538-4357/aa74e0.

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Sarafopoulos, D. V., M. A. Athanasiu, E. T. Sarris, T. Yamamoto i S. Kokubun. "Properties and origin of energetic particles at the duskside of the Earth's magnetosheath throughout a great storm". Annales Geophysicae 17, nr 9 (30.09.1999): 1121–33. http://dx.doi.org/10.1007/s00585-999-1121-2.

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Abstract. We study an interval of 56 h on January 16 to 18, 1995, during which the GEOTAIL spacecraft traversed the duskside magnetosheath from X @ -15 to -40 RE and the EPIC/ICS and EPIC/STICS sensors sporadically detected tens of energetic particle bursts. This interval coincides with the expansion and growth of a great geomagnetic storm. The flux bursts are strongly dependent on the magnetic field orientation. They switch on whenever the Bz component approaches zero (Bz @ 0 nT). We strongly suggest a magnetospheric origin for the energetic ions and electrons streaming along these "exodus channels". The time profiles for energetic protons and "tracer" O+ ions are nearly identical, which suggests a common source. We suggest that the particles leak out of the magnetosphere all the time and that when the magnetosheath magnetic field connects the spacecraft to the magnetotail, they stream away to be observed by the GEOTAIL sensors. The energetic electron fluxes are not observed as commonly as the ions, indicating that their source is more limited in extent. In one case study the magnetosheath magnetic field lines are draped around the magnetopause within the YZ plane and a dispersed structure for peak fluxes of different species is detected and interpreted as evidence for energetic electrons leaking out from the dawn LLBL and then being channelled along the draped magnetic field lines over the magnetopause. Protons leak from the equatorial dusk LLBL and this spatial differentiation between electron and proton sources results in the observed dispersion. A gradient of energetic proton intensities toward the ZGSM = 0 plane is inferred. There is a permanent layer of energetic particles adjacent to the magnetosheath during this interval in which the dominant component of the magnetic field was Bz.Key words. Magnetospheric physics (magnetosheath; magnetotail boundary layers; storms and substorms)

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27

Palmroth, Minna, Heli Hietala, Ferdinand Plaschke, Martin Archer, Tomas Karlsson, Xóchitl Blanco-Cano, David Sibeck i in. "Magnetosheath jet properties and evolution as determined by a global hybrid-Vlasov simulation". Annales Geophysicae 36, nr 5 (7.09.2018): 1171–82. http://dx.doi.org/10.5194/angeo-36-1171-2018.

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Abstract. We use a global hybrid-Vlasov simulation for the magnetosphere, Vlasiator, to investigate magnetosheath high-speed jets. Unlike many other hybrid-kinetic simulations, Vlasiator includes an unscaled geomagnetic dipole, indicating that the simulation spatial and temporal dimensions can be given in SI units without scaling. Thus, for the first time, this allows investigating the magnetosheath jet properties and comparing them directly with the observed jets within the Earth's magnetosheath. In the run shown in this paper, the interplanetary magnetic field (IMF) cone angle is 30∘, and a foreshock develops upstream of the quasi-parallel magnetosheath. We visually detect a structure with high dynamic pressure propagating from the bow shock through the magnetosheath. The structure is confirmed as a jet using three different criteria, which have been adopted in previous observational studies. We compare these criteria against the simulation results. We find that the magnetosheath jet is an elongated structure extending earthward from the bow shock by ∼2.6 RE, while its size perpendicular to the direction of propagation is ∼0.5 RE. We also investigate the jet evolution and find that the jet originates due to the interaction of the bow shock with a high-dynamic-pressure structure that reproduces observational features associated with a short, large-amplitude magnetic structure (SLAMS). The simulation shows that magnetosheath jets can develop also under steady IMF, as inferred by observational studies. To our knowledge, this paper therefore shows the first global kinetic simulation of a magnetosheath jet, which is in accordance with three observational jet criteria and is caused by a SLAMS advecting towards the bow shock.

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28

Lacombe, C., J. L. Steinberg, C. C. Harvey, D. Hubert, A. Mangeney i M. Moncuquet. "Density fluctuations measured by ISEE 1-2 in the Earth's magnetosheath and the resultant scattering of radio waves". Annales Geophysicae 15, nr 4 (30.04.1997): 387–96. http://dx.doi.org/10.1007/s00585-997-0387-5.

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Abstract. Radio waves undergo angular scattering when they propagate through a plasma with fluctuating density. We show how the angular scattering coefficient can be calculated as a function of the frequency spectrum of the local density fluctuations. In the Earth's magnetosheath, the ISEE 1-2 propagation experiment measured the spectral power of the density fluctuations for periods in the range 300 to 1 s, which produce most of the scattering. The resultant local angular scattering coefficient can then be calculated for the first time with realistic density fluctuation spectra, which are neither Gaussian nor power laws. We present results on the variation of the local angular scattering coefficient during two crossings of the dayside magnetosheath, from the quasi-perpendicular bow shock to the magnetopause. For a radio wave at twice the local electron plasma frequency, the scattering coefficient in the major part of the magnetosheath is b(2fp) ≃ 0.5 – 4 × 10–9 rad2/m. The scattering coefficient is about ten times stronger in a thin sheet (0.1 to1RE) just downstream of the shock ramp, and close to the magnetopause.

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29

Karlsson, Tomas, Henriette Trollvik, Savvas Raptis, Hans Nilsson i Hadi Madanian. "Solar wind magnetic holes can cross the bow shock and enter the magnetosheath". Annales Geophysicae 40, nr 6 (15.12.2022): 687–99. http://dx.doi.org/10.5194/angeo-40-687-2022.

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Abstract. Solar wind magnetic holes are localized depressions of the magnetic field strength, on timescales of seconds to minutes. We use Cluster multipoint measurements to identify 26 magnetic holes which are observed just upstream of the bow shock and, a short time later, downstream in the magnetosheath, thus showing that they can penetrate the bow shock and enter the magnetosheath. For two magnetic holes, we show that the relation between upstream and downstream properties of the magnetic holes are well described by the MHD (magnetohydrodynamic) Rankine–Hugoniot (RH) jump conditions. We also present a small statistical investigation of the correlation between upstream and downstream observations of some properties of the magnetic holes. The temporal scale size and magnetic field rotation across the magnetic holes are very similar for the upstream and downstream observations, while the depth of the magnetic holes varies more. The results are consistent with the interpretation that magnetic holes in Earth's and Mercury's magnetosheath are of solar wind origin, as has previously been suggested. Since the solar wind magnetic holes can enter the magnetosheath, they may also interact with the magnetopause, representing a new type of localized solar wind–magnetosphere interaction.

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30

Lakhina, G. S., S. V. Singh, A. P. Kakad, M. L. Goldstein, A. F. Viñas i J. S. Pickett. "A mechanism for electrostatic solitary structures in the Earth's magnetosheath". Journal of Geophysical Research: Space Physics 114, A9 (wrzesień 2009): n/a. http://dx.doi.org/10.1029/2009ja014306.

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31

Price, Channon P., Daniel W. Swift i Lou-Chuang Lee. "Numerical simulation of nonoscillatory mirror waves at the Earth's magnetosheath". Journal of Geophysical Research 91, A1 (1986): 101. http://dx.doi.org/10.1029/ja091ia01p00101.

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32

Li, Xinlin, H. R. Lewis, J. LaBelle, T. D. Phan i R. A. Treumann. "Characteristics of the ion pressure tensor in the Earth's magnetosheath". Geophysical Research Letters 22, nr 6 (15.03.1995): 667–70. http://dx.doi.org/10.1029/95gl00005.

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33

Leckband, J. A., D. Burgess, F. G. E. Pantellini i S. J. Schwartz. "Ion distributions associated with mirror waves in the Earth's magnetosheath". Advances in Space Research 15, nr 8-9 (styczeń 1995): 345–48. http://dx.doi.org/10.1016/0273-1177(94)00115-h.

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34

Osmane, A., A. P. Dimmock i T. I. Pulkkinen. "Universal properties of mirror mode turbulence in the Earth's magnetosheath". Geophysical Research Letters 42, nr 9 (4.05.2015): 3085–92. http://dx.doi.org/10.1002/2015gl063771.

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35

Génot, V., L. Broussillou, E. Budnik, P. Hellinger, P. M. Trávníček, E. Lucek i I. Dandouras. "Timing mirror structures observed by Cluster with a magnetosheath flow model". Annales Geophysicae 29, nr 10 (24.10.2011): 1849–60. http://dx.doi.org/10.5194/angeo-29-1849-2011.

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Abstract. The evolution of structures associated with mirror modes during their flow in the Earth's magnetosheath is studied. The fact that the related magnetic fluctuations can take distinct shapes, from deep holes to high peaks, has been assessed in previous works on the observational, modeling and numerical points of view. In this paper we present an analytical model for the flow lines and velocity magnitude inside the magnetosheath. This model is used to interpret almost 10 years of Cluster observations of mirror structures: by back tracking each isolated observation to the shock, the "age", or flow time, of these structures is determined together with the geometry of the shock. Using this flow time the evolutionary path of the structures may be studied with respect to different quantities: the distance to mirror threshold, the amplitude of mirror fluctuations and the skewness of the magnetic amplitude distribution as a marker of the shape of the structures. These behaviours are confronted to numerical simulations which confirm the dynamical perspective gained from the association of the statistical analysis and the analytical model: magnetic peaks are mostly formed just behind the shock and are quickly overwhelmed by magnetic holes as the plasma conditions get more mirror stable. The amplitude of the fluctuations are found to saturate before the skewness vanishes, i.e. when both structures quantitatively balance each other, which typically occurs after a flow time of 100–200 s in the Earth's magnetosheath. Comparison with other astrophysical contexts is discussed.

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36

Gunell, H., G. Stenberg Wieser, M. Mella, R. Maggiolo, H. Nilsson, F. Darrouzet, M. Hamrin i in. "Waves in high-speed plasmoids in the magnetosheath and at the magnetopause". Annales Geophysicae 32, nr 8 (22.08.2014): 991–1009. http://dx.doi.org/10.5194/angeo-32-991-2014.

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Abstract. Plasmoids, defined here as plasma entities with a higher anti-sunward velocity component than the surrounding plasma, have been observed in the magnetosheath in recent years. During the month of March 2007 the Cluster spacecraft crossed the magnetopause near the subsolar point 13 times. Plasmoids with larger velocities than the surrounding magnetosheath were found on seven of these 13 occasions. The plasmoids approach the magnetopause and interact with it. Both whistler mode waves and waves in the lower hybrid frequency range appear in these plasmoids, and the energy density of the waves inside the plasmoids is higher than the average wave energy density in the magnetosheath. When the spacecraft are in the magnetosphere, Alfvénic waves are observed. Cold ions of ionospheric origin are seen in connection with these waves, when the wave electric and magnetic fields combine with the Earth's dc magnetic field to yield an E × B/B2 drift speed that is large enough to give the ions energies above the detection threshold.

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37

Pallocchia, G., A. A. Samsonov, M. B. Bavassano Cattaneo, M. F. Marcucci, H. Rème, C. M. Carr i J. B. Cao. "Interplanetary shock transmitted into the Earth's magnetosheath: Cluster and Double Star observations". Annales Geophysicae 28, nr 5 (20.05.2010): 1141–56. http://dx.doi.org/10.5194/angeo-28-1141-2010.

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Abstract. On day 7 May 2005, the plasma instruments on board Double Star TC1 and Cluster SC3 spacecraft register inside the magnetosheath, at 19:15:12 and 19:16:20 UT, respectively, a strong pressure pulse due to the impact of an interplanetary shock wave (IS) on the terrestrial bow shock. The analysis of this event provides clear and quantitative evidences confirming and strengthening some results given by past simulations and observational studies. In fact, here we show that the transmitted shock is slowed down with respect to the incident IS (in the Earth's reference frame) and that, besides the transmitted shock, the IS – bow shock interaction generates a second discontinuity. Moreover, supported also by a special set three-dimensional magnetohydrodynamic simulation, we discuss, as further effects of the interaction of the IS with the magnetosphere, other two interesting aspects of the present event, that is: the TC1 double crossing of the bow shock (observed few minutes after the impact of the IS) and the presence, only in the SC3 data, of a third discontinuity produced inside the magnetosheath.

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38

EL MEKKI, O. M. "Over-reflection of magnetoacoustic ion-cyclotron plasma waves". Journal of Plasma Physics 59, nr 1 (styczeń 1998): 1–14. http://dx.doi.org/10.1017/s0022377897006247.

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The over-reflection of magnetoacoustic ion-cyclotron waves in a warm Hall plasma is investigated. It is shown that the effect of the Hall term is to strongly support over-reflection, thereby destabilizing the flow. Its relevance to the current-vortex sheet of the magnetosheath resulting from the interaction of the solar wind and the Earth's magnetopause is pointed out.

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39

Tan, L. C., S. F. Fung, R. L. Kessel, S. H. Chen, J. L. Green i T. E. Eastman. "Ion temperature anisotropies in the Earth's high-latitude magnetosheath: Hawkeye observations". Geophysical Research Letters 25, nr 5 (1.03.1998): 587–90. http://dx.doi.org/10.1029/98gl00306.

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40

Masood, W., i S. J. Schwartz. "Observations of the development of electron temperature anisotropies in Earth's magnetosheath". Journal of Geophysical Research: Space Physics 113, A1 (styczeń 2008): n/a. http://dx.doi.org/10.1029/2007ja012715.

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41

Jun, Guo, Yang Zhongwei, Lu Quanming i Wang Shui. "The Nonlinear Evolution of Ion Cyclotron Waves in the Earth's Magnetosheath". Plasma Science and Technology 11, nr 3 (czerwiec 2009): 274–78. http://dx.doi.org/10.1088/1009-0630/11/3/05.

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42

Hubert, D., C. C. Harvey i C. T. Russell. "Observations of magnetohydrodynamic modes in the Earth's magnetosheath at 0600 LT". Journal of Geophysical Research 94, A12 (1989): 17305. http://dx.doi.org/10.1029/ja094ia12p17305.

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43

von Alfthan, S., D. Pokhotelov, Y. Kempf, S. Hoilijoki, I. Honkonen, A. Sandroos i M. Palmroth. "Vlasiator: First global hybrid-Vlasov simulations of Earth's foreshock and magnetosheath". Journal of Atmospheric and Solar-Terrestrial Physics 120 (grudzień 2014): 24–35. http://dx.doi.org/10.1016/j.jastp.2014.08.012.

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44

Fuselier, S. A., P. Hill, W. Baumjohann i J. T. Gosling. "Local time occurrence frequency of energetic ions in the Earth's magnetosheath". Geophysical Research Letters 20, nr 7 (9.04.1993): 551–54. http://dx.doi.org/10.1029/93gl00807.

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45

Anderson, Brian J., Stephen A. Fuselier, S. Peter Gary i Richard E. Denton. "Magnetic spectral signatures in the Earth's magnetosheath and plasma depletion layer". Journal of Geophysical Research 99, A4 (1994): 5877. http://dx.doi.org/10.1029/93ja02827.

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46

Fuselier, S. A., D. M. Klumpar i E. G. Shelley. "On the origins of energetic ions in the Earth's dayside magnetosheath". Journal of Geophysical Research 96, A1 (1991): 47. http://dx.doi.org/10.1029/90ja01751.

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47

Meister, C. V., B. Besser i V. Lebedeva. "Modeling of the Temperature-Anisotropy Relaxation Time of the Earth's Magnetosheath". Contributions to Plasma Physics 47, nr 4-5 (lipiec 2007): 381–87. http://dx.doi.org/10.1002/ctpp.200710051.

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48

Turc, L., D. Fontaine, P. Savoini, H. Hietala i E. K. J. Kilpua. "A comparison of bow shock models with Cluster observations during low Alfvén Mach number magnetic clouds". Annales Geophysicae 31, nr 6 (11.06.2013): 1011–19. http://dx.doi.org/10.5194/angeo-31-1011-2013.

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Abstract. Magnetic clouds (MCs) are very geoeffective solar wind structures. Their properties in the interplanetary medium have been extensively studied, yet little is known about their characteristics in the Earth's magnetosheath. The Cluster spacecraft offer the opportunity to observe MCs in the magnetosheath, but before MCs reach the magnetosphere, their structure is altered when they interact with the terrestrial bow shock (BS). The physics taking place at the BS strongly depends on ΘBn, the angle between the shock normal and the interplanetary magnetic field. However, in situ observations of the BS during an MC's crossing are seldom available. In order to relate magnetosheath observations to solar wind conditions, we need to rely on a model to determine the shock's position and normal direction. Yet during MCs, the models tend to be less accurate, because the Alfvén Mach number (MA) is often significantly lower than in regular solar wind. On the contrary, the models are generally optimised for high MA conditions. In this study, we compare the predictions of four widely used models available in the literature (Wu et al., 2000; Chapman and Cairns, 2003; Jeřáb et al., 2005; Měrka et al., 2005b) to Cluster's dayside BS crossings observed during five MC events. Our analysis shows that the ΘBn angle is well predicted by all four models. On the other hand, the Jeřáb et al. (2005) model yields the best estimates of the BS position during low MA MCs. The other models locate the BS either too far from or too close to Earth. The results of this paper can be directly used to estimate the BS parameters in all studies of MC interaction with Earth's magnetosphere.

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49

Coleman, I. J. "A multi-spacecraft survey of magnetic field line draping in the dayside magnetosheath". Annales Geophysicae 23, nr 3 (30.03.2005): 885–900. http://dx.doi.org/10.5194/angeo-23-885-2005.

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Abstract. When the interplanetary magnetic field (IMF) encounters the Earth's magnetosphere, it is compressed and distorted. This distortion is known as draping, and plays an important role in the interaction between the IMF and the geomagnetic field. This paper considers a particular aspect of draping, namely how the orientation of the IMF in a plane perpendicular to the Sun-Earth line (the clock angle) is altered by draping in the magnetosheath close to the dayside magnetopause. The clock angle of the magnetosheath field is commonly estimated from the interplanetary magnetic field (IMF) measured by upstream monitoring spacecraft either by assuming that the draping process does not significantly alter the clock angle ("perfect draping") or that the change in clock angle is reasonably approximated by a gas dynamic model. In this paper, the magnetosheath clock angles measured during 36 crossings of the magnetopause by the Geotail and Interball-Tail spacecraft are compared to the upstream IMF clock angles measured by the Wind spacecraft. Overall, about 30% of data points exhibit perfect draping within ±10°, and 70% are within 30°. The differences between the IMF and magnetosheath clock angles are not, in general, well-ordered in any systematic fashion which could be accounted for by hydrodynamic draping. The draping behaviour is asymmetric with respect to the y-component of the IMF, and the form of the draping distribution function is dependent on solar wind pressure. While the average clock angle observed in the magnetosheath does reflect the orientation of the IMF to within ~30° or less, the assumption that the magnetosheath field direction at any particular region of the magnetopause at any instant is approximately similar to the IMF direction is not justified. This study shows that reconnection models which assume laminar draping are unlikely to accurately reflect the distribution of reconnection sites across the dayside magnetopause.

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Plaschke, Ferdinand, i Yasuhito Narita. "On determining fluxgate magnetometer spin axis offsets from mirror mode observations". Annales Geophysicae 34, nr 9 (16.09.2016): 759–66. http://dx.doi.org/10.5194/angeo-34-759-2016.

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Abstract. In-flight calibration of fluxgate magnetometers that are mounted on spacecraft involves finding their outputs in vanishing ambient fields, the so-called magnetometer offsets. If the spacecraft is spin-stabilized, then the spin plane components of these offsets can be relatively easily determined, as they modify the spin tone content in the de-spun magnetic field data. The spin axis offset, however, is more difficult to determine. Therefore, usually Alfvénic fluctuations in the solar wind are used. We propose a novel method to determine the spin axis offset: the mirror mode method. The method is based on the assumption that mirror mode fluctuations are nearly compressible such that the maximum variance direction is aligned to the mean magnetic field. Mirror mode fluctuations are typically found in the Earth's magnetosheath region. We introduce the method and provide a first estimate of its accuracy based on magnetosheath observations by the THEMIS-C spacecraft. We find that 20 h of magnetosheath measurements may already be sufficient to obtain high-accuracy spin axis offsets with uncertainties on the order of a few tenths of a nanotesla, if offset stability can be assumed.

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