Готові списки джерел за темами / Magnetosphere-ionosphere current systems

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Автор: Grafiati

Опубліковано: 6 вересня 2023

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Статті в журналах з теми "Magnetosphere-ionosphere current systems"

Cowley, S. W. H., A. J. Deason, and E. J. Bunce. "Axi-symmetric models of auroral current systems in Jupiter's magnetosphere with predictions for the Juno mission." Annales Geophysicae 26, no. 12 (December 12, 2008): 4051–74. http://dx.doi.org/10.5194/angeo-26-4051-2008.

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Abstract. We develop two related models of magnetosphere-ionosphere coupling in the jovian system by combining previous models defined at ionospheric heights with magnetospheric magnetic models that allow system parameters to be extended appropriately into the magnetosphere. The key feature of the combined models is thus that they allow direct connection to be made between observations in the magnetosphere, particularly of the azimuthal field produced by the magnetosphere-ionosphere coupling currents and the plasma angular velocity, and the auroral response in the ionosphere. The two models are intended to reflect typical steady-state sub-corotation conditions in the jovian magnetosphere, and transient super-corotation produced by sudden major solar wind-induced compressions, respectively. The key simplification of the models is that of axi-symmetry of the field, flow, and currents about the magnetic axis, limiting their validity to radial distances within ~30 RJ of the planet, though the magnetic axis is appropriately tilted relative to the planetary spin axis and rotates with the planet. The first exploration of the jovian polar magnetosphere is planned to be undertaken in 2016–2017 during the NASA New Frontiers Juno mission, with observations of the polar field, plasma, and UV emissions as a major goal. Evaluation of the models along Juno planning orbits thus produces predictive results that may aid in science mission planning. It is shown in particular that the low-altitude near-periapsis polar passes will generally occur underneath the corresponding auroral acceleration regions, thus allowing brief examination of the auroral primaries over intervals of ~1–3 min for the main oval and ~10 s for narrower polar arc structures, while the "lagging" field deflections produced by the auroral current systems on these passes will be ~0.1°, associated with azimuthal fields above the ionosphere of a few hundred nT.

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Rostoker, G., and F. Pascal. "Dependence of the response of the magnetosphere–ionosphere current systems on the preconditioning of the auroral oval and on the level of the solar–terrestrial interaction." Canadian Journal of Physics 68, no. 1 (January 1, 1990): 74–80. http://dx.doi.org/10.1139/p90-011.

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It is now well accepted that the impulse response time of the magnetosphere to sudden changes in the interplanetary medium is of the order of 2 h with the shape of the impulse response function approximating a Rayleigh function with a peak near 50 min. In a recent study, Bargatze et al. (J. Geophys. Res. 90, 6387 (1985)) examined the response of the magnetosphere for varying activity levels and found that the impulse response function has two well-defined peaks for moderate activity and a single broad peak for low and high activity levels. They explain the two peaks in the response function as the sequential contributions of the directly driven process and the unloading of stored magnetotail energy. In this paper, we ascribe to the magnetosphere–ionosphere system the bulk properties of self-inductance, capacitance, and resistance. We then proceed to construct an equivalent current system for the magnetosphere–ionosphere coupling process and study its response to changes in the cross polar cap potential drop. In particular, we permit the bulk electrical parameters to change in the manner expected as the input of energy from the solar wind modifies the magnetosphere–ionosphere system. We find that the double peak in the impulse response function identified by Bargatze et al. can be understood purely in terms of changes in the directly driven system without the need to introduce the effects of the unloading of stored energy in the magnetotail.

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Cowley, S. W. H., and E. J. Bunce. "Corotation-driven magnetosphere-ionosphere coupling currents in Saturn’s magnetosphere and their relation to the auroras." Annales Geophysicae 21, no. 8 (August 31, 2003): 1691–707. http://dx.doi.org/10.5194/angeo-21-1691-2003.

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Abstract. We calculate the latitude profile of the equatorward-directed ionospheric Pedersen currents that are driven in Saturn’s ionosphere by partial corotation of the magnetospheric plasma. The calculation incorporates the flattened figure of the planet, a model of Saturn’s magnetic field derived from spacecraft flyby data, and angular velocity models derived from Voyager plasma data. We also employ an effective height-integrated ionospheric Pedersen conductivity of 1 mho, suggested by a related analysis of Voyager magnetic field data. The Voyager plasma data suggest that on the largest spatial scales, the plasma angular velocity declines from near-rigid corotation with the planet in the inner magnetosphere, to values of about half of rigid corotation at the outer boundary of the region considered. The latter extends to ~ 15–20 Saturn radii (RS) in the equatorial plane, mapping along magnetic field lines to ~ 15° co-latitude in the ionosphere. We find in this case that the ionospheric Pedersen current peaks near the poleward (outer) boundary of this region, and falls toward zero over ~ 5°–10° equator-ward of the boundary as the plasma approaches rigid corotation. The peak current near the poleward boundary, integrated in azimuth, is ~ 6 MA. The field-aligned current required for continuity is directed out of the ionosphere into the magnetosphere essentially throughout the region, with the current density peaking at ~ 10 nA m-2 at ~ 20° co-latitude. We estimate that such current densities are well below the limit requiring field-aligned acceleration of magnetospheric electrons in Saturn’s environment ( ~ 70 nAm-2), so that no significant auroral features associated with this ring of upward current is anticipated. The observed ultraviolet auroras at Saturn are also found to occur significantly closer to the pole (at ~ 10°–15° co-latitude), and show considerable temporal and local time variability, contrary to expectations for corotation-related currents. We thus conclude that Saturn’s ‘main oval’ auroras are not associated with corotation-enforcing currents as they are at Jupiter, but instead are most probably associated with coupling to the solar wind as at Earth. At the same time, the Voyager flow observations also suggest the presence of radially localized ‘dips’ in the plasma angular velocity associated with the moons Dione and Rhea, which are ~ 1–2 RS in radial extent in the equatorial plane. The presence of such small-scale flow features, assumed to be azimuthally extended, results in localized several-MA enhancements in the ionospheric Pedersen current, and narrow bi-polar signatures in the field-aligned currents which peak at values an order of magnitude larger than those associated with the large-scale currents. Narrow auroral rings (or partial rings) ~ 0.25° co-latitude wide with intensities ~ 1 kiloRayleigh may be formed in the regions of upward field-aligned current under favourable circumstances, located at co-latitudes between ~ 17° and ~ 20° in the north, and ~ 19° and ~22° in the south.Key words. Magnetospheric physics (current systems; magnetosphere-ionosphere interactions; planetary magnetospheres)

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Tsunomura, S. "Numerical analysis of global ionospheric current system including the effect of equatorial enhancement." Annales Geophysicae 17, no. 5 (May 31, 1999): 692–706. http://dx.doi.org/10.1007/s00585-999-0692-2.

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Abstract. A modeling method is proposed to derive a two-dimensional ionospheric layer conductivity, which is appropriate to obtain a realistic solution of the polar-originating ionospheric current system including equatorial enhancement. The model can be obtained by modifying the conventional, thin shell conductivity model. It is shown that the modification for one of the non-diagonal terms (Σθφ) in the conductivity tensor near the equatorial region is very important; the term influences the profile of the ionospheric electric field around the equator drastically. The proposed model can reproduce well the results representing the observed electric and magnetic field signatures of geomagnetic sudden commencement. The new model is applied to two factors concerning polar-originating ionospheric current systems. First, the latitudinal profile of the DP2 amplitude in the daytime is examined, changing the canceling rate for the dawn-to-dusk electric field by the region 2 field-aligned current. It is shown that the equatorial enhancement would not appear when the ratio of the total amount of the region 2 field-aligned current to that of region 1 exceeds 0.5. Second, the north-south asymmetry of the magnetic fields in the summer solstice condition of the ionospheric conductivity is examined by calculating the global ionospheric current system covering both hemispheres simultaneously. It is shown that the positive relationship between the magnitudes of high latitude magnetic fields and the conductivity is clearly seen if a voltage generator is given as the source, while the relationship is vague or even reversed for a current generator. The new model, based on the International Reference Ionosphere (IRI) model, can be applied to further investigations in the quantitative analysis of the magnetosphere-ionosphere coupling problems.Key words. Ionosphere (electric fields and currents; equatorial ionosphere; ionosphere-magnetosphere interactions)

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Tanaka, T. "Generation mechanisms for magnetosphere-ionosphere current systems deduced from a three-dimensional MHD simulation of the solar wind-magnetosphere-ionosphere coupling processes." Journal of Geophysical Research 100, A7 (1995): 12057. http://dx.doi.org/10.1029/95ja00419.

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Nichols, J. D., and S. W. H. Cowley. "Magnetosphere-ionosphere coupling currents in Jupiter’s middle magnetosphere: dependence on the effective ionospheric Pedersen conductivity and iogenic plasma mass outflow rate." Annales Geophysicae 21, no. 7 (July 31, 2003): 1419–41. http://dx.doi.org/10.5194/angeo-21-1419-2003.

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Abstract. The amplitude and spatial distribution of the coupling currents that flow between Jupiter’s ionosphere and middle magnetosphere, which enforce partial corotation on outward-flowing iogenic plasma, depend on the values of the effective Pedersen conductivity of the jovian ionosphere and the mass outflow rate of iogenic plasma. The values of these parameters are, however, very uncertain. Here we determine how the solutions for the plasma angular velocity and current components depend on these parameters over wide ranges. We consider two models of the poloidal magnetospheric magnetic field, namely the planetary dipole alone, and an empirical current sheet field based on Voyager data. Following work by Hill (2001), we obtain a complete normalized analytic solution for the dipole field, which shows in compact form how the plasma angular velocity and current components scale in space and in amplitude with the system parameters in this case. We then obtain an approximate analytic solution in similar form for a current sheet field in which the equatorial field strength varies with radial distance as a power law. A key feature of the model is that the current sheet field lines map to a narrow latitudinal strip in the ionosphere, at ≈ 15° co-latitude. The approximate current sheet solutions are compared with the results of numerical integrations using the full field model, for which a power law applies beyond ≈ 20 RJ, and are found to agree very well within their regime of applicability. A major distinction between the solutions for the dipole field and the current sheet concerns the behaviour of the field-aligned current. In the dipole model the direction of the current reverses at moderate equatorial distances, and the current system wholly closes if the model is extended to infinity in the equatorial plane and to the pole in the ionosphere. In the approximate current sheet model, however, the field-aligned current is unidirectional, flowing consistently from the ionosphere to the current sheet for the sense of the jovian magnetic field. Current closure must then occur at higher latitudes, on field lines outside the region described by the model. The amplitudes of the currents in the two models are found to scale with the system parameters in similar ways, though the scaling is with a somewhat higher power of the conductivity for the current sheet model than for the dipole, and with a somewhat lower power of the plasma mass outflow rate. The absolute values of the currents are also higher for the current sheet model than for the dipole for given parameters, by factors of approx 4 for the field-perpendicular current intensities, ≈ 10 for the total current flowing in the circuit, and ≈ 25 for the field-aligned current densities, factors which do not vary greatly with the system parameters. These results thus confirm that the conclusions drawn previously from a small number of numerical integrations using spot values of the system parameters are generally valid over wide ranges of the parameter values.Key words. Magnetospheric physics (current systems, magnetosphere-ionosphere interactions, planetary magnetospheres)

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Le, G., C. T. Russell, and K. Takahashi. "Morphology of the ring current derived from magnetic field observations." Annales Geophysicae 22, no. 4 (April 2, 2004): 1267–95. http://dx.doi.org/10.5194/angeo-22-1267-2004.

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Abstract. Our examination of the 20 years of magnetospheric magnetic field data from ISEE, AMPTE/CCE and Polar missions has allowed us to quantify how the ring current flows and closes in the magnetosphere at a variety of disturbance levels. Using intercalibrated magnetic field data from the three spacecraft, we are able to construct the statistical magnetic field maps and derive 3-dimensional current density by the simple device of taking the curl of the statistically determined magnetic field. The results show that there are two ring currents, an inner one that flows eastward at ~3 RE and a main westward ring current at ~4–7 RE for all levels of geomagnetic disturbances. In general, the in-situ observations show that the ring current varies as the Dst index decreases, as we would expect it to change. An unexpected result is how asymmetric it is in local time. Some current clearly circles the magnetosphere but much of the energetic plasma stays in the night hemisphere. These energetic particles appear not to be able to readily convect into the dayside magnetosphere. During quiet times, the symmetric and partial ring currents are similar in strength (~0.5MA) and the peak of the westward ring current is close to local midnight. It is the partial ring current that exhibits most drastic intensification as the level of disturbances increases. Under the condition of moderate magnetic storms, the total partial ring current reaches ~3MA, whereas the total symmetric ring current is ~1MA. Thus, the partial ring current contributes dominantly to the decrease in the Dst index. As the ring current strengthens the peak of the partial ring current shifts duskward to the pre-midnight sector. The partial ring current is closed by a meridional current system through the ionosphere, mainly the field-aligned current, which maximizes at local times near the dawn and dusk. The closure currents flow in the sense of region-2 field-aligned currents, downward into the ionosphere near the dusk and upward out of the ionosphere near the dawn. Key words. Magnetospheric physics (current systems; storms and substorms; magnetospheric configuration and dynamics)

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Neudegg, D. A., B. J. Fraser, F. W. Menk, G. B. Burns, R. J. Morris, and M. J. Underwood. "Magnetospheric sources of Pc1-2 ULF waves observed in the polar ionospheric waveguide." Antarctic Science 14, no. 1 (March 2002): 93–103. http://dx.doi.org/10.1017/s0954102002000627.

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Energy from the outer regions of the magnetosphere may be transferred to the polar ionosphere by plasma waves. A magnetometer array operated during the Antarctic winter observed Ultra-Low-Frequency (ULF) plasma waves in the Pc 1–2 (0.1–10.0 Hz) frequency range, propagating parallel to the surface of the Earth in a waveguide or duct centred at ∼300 km altitude in the ionosphere. These compressional fast mode plasma waves most likely originated in the outer magnetosphere as shear mode plasma waves guided along the geomagnetic field. The region of origin in the magnetosphere for the waves is not certain as several widely spaced volumes map along geomagnetic field lines to a relatively close ensemble in the polar ionosphere. This paper compares the direction of propagation for the waves with signatures of magnetospheric regions geomagnetically projecting onto the ionosphere. Regions such as the polar cusp, low latitude boundary layer and mantle were observed by DMSP spacecraft and a SuperDARN high-frequency radar. The most likely region in the polar ionosphere for the fast mode waves to have originated from is equatorwards of the polar cusp, suggesting the field guided waves originated just inside the magnetopause. A case is made for association of the observed Pc1-2 ULF waves with post-noon, field-aligned-current systems driven by reconnection of the solar Interplanetary Magnetic Field (IMF) and the geomagnetic field near the magnetopause.

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Rostoker, G., D. Savoie, and T. D. Phan. "Response of magnetosphere-ionosphere current systems to changes in the interplanetary magnetic field." Journal of Geophysical Research 93, A8 (1988): 8633. http://dx.doi.org/10.1029/ja093ia08p08633.

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Kivelson, Margaret Galland. "The Current Systems of the Jovian Magnetosphere and Ionosphere and Predictions for Saturn." Space Science Reviews 116, no. 1-2 (January 2005): 299–318. http://dx.doi.org/10.1007/s11214-005-1959-x.

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Дисертації з теми "Magnetosphere-ionosphere current systems"

Mays, Mona Leila. "The study of interplanetary shocks, geomagnetic storms, and substorms with the WINDMI model." 2009. http://hdl.handle.net/2152/10703.

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WINDMI is a low dimensional plasma physics-based model of the coupled magnetosphere-ionosphere system. The nonlinear system of ordinary differential equations describes the energy balance between the basic nightside components of the system using the solar wind driving voltage as input. Of the eight dynamical variables determined by the model, the region 1 field aligned current and ring current energy is compared to the westward auroral electrojet AL index and equatorial geomagnetic disturbance storm time Dst index. The WINDMI model is used to analyze the magnetosphere-ionosphere system during major geomagnetic storms and substorms which are community campaign events. Numerical experiments using the WINDMI model are also used to assess the question of how much interplanetary shock events contribute to the geoeffectiveness of solar wind drivers. For two major geomagnetic storm intervals, it is found that the magnetic field compressional jump is important to producing the changes in the AL index. Further, the WINDMI model is implemented to compute model AL and Dst predictions every ten minutes using real-time solar wind data from the ACE satellite as input. Real-Time WINDMI has been capturing substorm and storm activity, as characterized by the AL and Dst indices, reliably since February 2006 and is validated by comparison with ground-based measurements of the indices. Model results are compared for three different candidate input solar wind driving voltage formulas. Modeling of the Dst index is further developed to include the additional physical processes of tail current increases and sudden commencement. A new model, based on WINDMI, is developed using the dayside magnetopause and magnetosphere current systems to model the magnetopause boundary motion and the dayside region 1 field aligned current which is comparable to the auroral upper AU index.
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Книги з теми "Magnetosphere-ionosphere current systems"

M, Raspopov O., Migulin V. V, Kovalevskai͡a︡ L. V, International Union of Geodesy and Geophysics., International Association of Geomagnetism and Aeronomy. та Poli͡a︡rnyĭ geofizicheskiĭ institut (Akademii͡a︡ nauk SSSR), ред. Poli͡a︡rnye geomagnitnye vozmushchenii͡a︡ i svi͡a︡zannye s nimi i͡a︡vlenii͡a︡: Materialy Mezhdunarodnogo simpoziuma "Poli͡a︡rnye geomagnitnye i͡a︡vlenii͡a︡," 25-31 mai͡a︡ 1986 g., Suzdalʹ, SSSR = Structure and dynamics of polar current systems : proceedings of International Symposium Polar Geomagnetic Phenomena, May 25-31, 1986, Souzdal, USSR. Apatity: Kolʹskiĭ nauch. t͡s︡entr AN SSSR, 1989.

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Assembly, COSPAR Scientific. The subauroral ionosphere, plasmasphere, ring current and inner magnetosphere system: Proceedings of the D0.5 symposium of COSPAR Scientific Commission D which was held during the thirty-first COSPAR scientific assembly, Birmingham, U.K., 14-21 July 1996. Kidlington, Oxford: Published for the Committee on Space Research [by] Pergamon, 1997.

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Cospar and M. W. Chen. The Subauroral Ionosphere, Plasmasphere, Ring Current and Inner Magnetosphere System. Elsevier Science Pub Co, 1997.

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Частини книг з теми "Magnetosphere-ionosphere current systems"

Cowley, S. W. H. "Magnetosphere-ionosphere interactions: A tutorial review." In Magnetospheric Current Systems, 91–106. Washington, D. C.: American Geophysical Union, 2000. http://dx.doi.org/10.1029/gm118p0091.

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Zesta, E., H. J. Singer, D. Lummerzheim, C. T. Russell, L. R. Lyons, and M. J. Brittnacher. "The Effect of the January 10, 1997, pressure pulse on the magnetosphere-ionosphere current system." In Magnetospheric Current Systems, 217–26. Washington, D. C.: American Geophysical Union, 2000. http://dx.doi.org/10.1029/gm118p0217.

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Lanzerotti, Louis J., and Andrew J. Gerrard. "Ring Current Ions Measured by the RBSPICE Instrument on the Van Allen Probes Mission." In Magnetosphere-Ionosphere Coupling in the Solar System, 145–54. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119066880.ch11.

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Tanaka, T. "Generation mechanism of the field-aligned current system deduced from a 3-D MHD simulation of the solar wind-magnetosphere-ionosphere coupling." In Magnetospheric Research with Advanced Techniques, Proceedings of the 9th COSPAR Colloquim, 133–42. Elsevier, 1998. http://dx.doi.org/10.1016/s0964-2749(98)80022-x.

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Звіти організацій з теми "Magnetosphere-ionosphere current systems"

BARKHATOV, NIKOLAY, and SERGEY REVUNOV. A software-computational neural network tool for predicting the electromagnetic state of the polar magnetosphere, taking into account the process that simulates its slow loading by the kinetic energy of the solar wind. SIB-Expertise, December 2021. http://dx.doi.org/10.12731/er0519.07122021.

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The auroral activity indices AU, AL, AE, introduced into geophysics at the beginning of the space era, although they have certain drawbacks, are still widely used to monitor geomagnetic activity at high latitudes. The AU index reflects the intensity of the eastern electric jet, while the AL index is determined by the intensity of the western electric jet. There are many regression relationships linking the indices of magnetic activity with a wide range of phenomena observed in the Earth's magnetosphere and atmosphere. These relationships determine the importance of monitoring and predicting geomagnetic activity for research in various areas of solar-terrestrial physics. The most dramatic phenomena in the magnetosphere and high-latitude ionosphere occur during periods of magnetospheric substorms, a sensitive indicator of which is the time variation and value of the AL index. Currently, AL index forecasting is carried out by various methods using both dynamic systems and artificial intelligence. Forecasting is based on the close relationship between the state of the magnetosphere and the parameters of the solar wind and the interplanetary magnetic field (IMF). This application proposes an algorithm for describing the process of substorm formation using an instrument in the form of an Elman-type ANN by reconstructing the AL index using the dynamics of the new integral parameter we introduced. The use of an integral parameter at the input of the ANN makes it possible to simulate the structure and intellectual properties of the biological nervous system, since in this way an additional realization of the memory of the prehistory of the modeled process is provided.

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