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Littérature scientifique sur le sujet « Magnetosphere electromagnetic phenomenon »

Auteur : Grafiati

Publié le 6 septembre 2023

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Articles de revues sur le sujet "Magnetosphere electromagnetic phenomenon"

Gurevich, A. V., et Yu N. Istomin. « Nonstationary Processes in the Pulsar Magnetosphere ». International Astronomical Union Colloquium 128 (1992) : 228–31. http://dx.doi.org/10.1017/s0002731600155210.

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AbstractWe investigate several instabilities which give different characteristic times for nonstationary processes. Several instabilities are connected with the mechanism of plasma generation in the polar cap gap region. Another nonstationary process is due to the nonlinear phenomenon arising in the magnetosphere during the propagation of the flux of electromagnetic radiation.

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Savina, O. N., et P. A. Bespalov. « The Response of a Plasma Magnetospheric Maser to Atmospheric Perturbations ». Geomagnetism and Aeronomy 62, n^o 5 (28 septembre 2022) : 555–62. http://dx.doi.org/10.1134/s0016793222050115.

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Abstract The effect of weak external influences associated with infrasonic waves in the ionosphere on the operation of a plasma magnetospheric maser (PMM) is considered. It is shown that if the frequency of infrasonic waves is close to the eigen frequency oscillations of the PMM, then quasi-periodic (QP) electromagnetic VLF emissions with repetition periods of spectral forms of 10–300 s can be excited in radiation belts. It has been found that one of the possible reasons for this phenomenon may be the Q-switching of the magnetospheric resonator due to a change in the coefficient of reflection of whistler waves from the ionosphere from above by atmospheric infrasonic waves. For natural atmospheric sources of infrasonic disturbances with horizontal scales of approximately 100 km, model calculations of the depth of modulation of the energy density of electromagnetic waves in a magnetic field tube were carried out. It has been found that in the morning and daytime subauroral magnetosphere, even weak external influences lead to the appearance of signals with a sufficiently large modulation depth (tens of percent).

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Hakobyan, Hayk, Alexander Philippov et Anatoly Spitkovsky. « Magnetic Energy Dissipation and γ-Ray Emission in Energetic Pulsars ». Astrophysical Journal 943, n^o 2 (31 janvier 2023) : 105. http://dx.doi.org/10.3847/1538-4357/acab05.

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Abstract Some of the most energetic pulsars exhibit rotation-modulated γ-ray emission in the 0.1–100 GeV band. The luminosity of this emission is typically 0.1%–10% of the pulsar spin-down power (γ-ray efficiency), implying that a significant fraction of the available electromagnetic energy is dissipated in the magnetosphere and reradiated as high-energy photons. To investigate this phenomenon we model a pulsar magnetosphere using 3D particle-in-cell simulations with strong synchrotron cooling. We particularly focus on the dynamics of the equatorial current sheet where magnetic reconnection and energy dissipation take place. Our simulations demonstrate that a fraction of the spin-down power dissipated in the magnetospheric current sheet is controlled by the rate of magnetic reconnection at microphysical plasma scales and only depends on the pulsar inclination angle. We demonstrate that the maximum energy and the distribution function of accelerated pairs is controlled by the available magnetic energy per particle near the current sheet, the magnetization parameter. The shape and the extent of the plasma distribution is imprinted in the observed synchrotron emission, in particular, in the peak and the cutoff of the observed spectrum. We study how the strength of synchrotron cooling affects the observed variety of spectral shapes. Our conclusions naturally explain why pulsars with higher spin-down power have wider spectral shapes and, as a result, lower γ-ray efficiency.

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Lin, Jyh-Woei. « Space Radiation of Solar Storm : A Meeting Report in Taiwan ». European Journal of Environment and Earth Sciences 2, n^o 6 (11 novembre 2021) : 10–11. http://dx.doi.org/10.24018/ejgeo.2021.2.6.202.

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Solar storm was an effect when Sun was active. Solar flares flame released a large amount of energy and caused a large-scale explosion. A large amount of coronal matter was ejected into space by plasma composed of electrons and protons. Their shock waves or magnetic clouds and the earth Magnetic storms generated by the interaction of magnetic fields caused disturbances and squeezing of the earth’s magnetosphere. A solar flare was a phenomenon of solar storm. It had huge eruptions of electromagnetic radiation. The sudden electromagnetic energy traveled with the speed of light. Large solar flare might affect the effects of reliability of electronic components in satellites and could cause economic losses by soft error and could affect human health through the space radiation, especially causing cancer.

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Гульельми, Анатолий, Anatol Guglielmi, Александр Потапов et Alexander Potapov. « Problems of the Pc1 magnetospheric wave theory. A review ». Solar-Terrestrial Physics 5, n^o 3 (30 septembre 2019) : 87–92. http://dx.doi.org/10.12737/stp-53201910.

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The Pc1 ultralow-frequency electromagnetic waves (frequency range 0.2–5 Hz), also known as pearl necklace, are a unique phenomenon in near-Earth space physics. Many properties of pearls remain a mystery, despite the research of prominent cosmophysicists for more than half a century. In the proposed review, we briefly outline the main points of the so-called standard model, which is widely used to interpret Pc1. Next, we focus on the criticism of the standard model and on the identification of open problems in the Pc1 theory. The general conclusion is that it is necessary to develop new ideas outside the framework of the standard model in order to understand the processes of excitation and propagation of Pc1 waves in Earth’s magnetosphere.

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Гульельми, Анатолий, Anatol Guglielmi, Александр Потапов et Alexander Potapov. « Problems of the Pc1 magnetospheric wave theory. A review ». Solnechno-Zemnaya Fizika 5, n^o 3 (30 septembre 2019) : 102–9. http://dx.doi.org/10.12737/szf-53201910.

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Leto, P., C. Trigilio, C. S. Buemi, F. Leone, I. Pillitteri, L. Fossati, F. Cavallaro et al. « The auroral radio emission of the magnetic B-type star ρ OphC ». Monthly Notices of the Royal Astronomical Society : Letters 499, n^o 1 (10 septembre 2020) : L72—L76. http://dx.doi.org/10.1093/mnrasl/slaa157.

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ABSTRACT The non-thermal radio emission of main-sequence early-type stars is a signature of stellar magnetism. We present multiwavelength (1.6–16.7 GHz) ATCA measurements of the early-type magnetic star ρ OphC, which is a flat-spectrum non-thermal radio source. The ρ OphC radio emission is partially circularly polarized with a steep spectral dependence: the fraction of polarized emission is about $60{{\ \rm per\ cent}}$ at the lowest frequency sub-band (1.6 GHz) while is undetected at 16.7 GHz. This is clear evidence of coherent Auroral Radio Emission (ARE) from the ρ OphC magnetosphere. Interestingly, the detection of the ρ OphC’s ARE is not related to a peculiar rotational phase. This is a consequence of the stellar geometry, which makes the strongly anisotropic radiation beam of the amplified radiation always pointed towards Earth. The circular polarization sign evidences mainly amplification of the ordinary mode of the electromagnetic wave, consistent with a maser amplification occurring within dense regions. This is indirect evidence of the plasma evaporation from the polar caps, a phenomenon responsible for the thermal X-ray aurorae. ρ OphC is not the first early-type magnetic star showing the O-mode dominated ARE but is the first star with the ARE always on view.

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Andrievsky, S. M. « AN ENIGMA OF THE PRZYBYLSKI STAR ». Odessa Astronomical Publications 35 (14 décembre 2022) : 13–17. http://dx.doi.org/10.18524/1810-4215.2022.35.268673.

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A new scenario to explain the Przybylski star phenomenon is proposed. It is based on the supposition that this star is a component of a binary system with a neutron star (similar to the hypothesis proposed earlier by Gopka, Ul’yanov & Andrievskii). The main difference with previous scenario is as following. The orbits of the stars of this system lie in the plane of the sky (or very close to this plane). Thus, we see this star (and its companion) nearly polar-on, and therefore we cannot detect the orbital motion (spectral line based) from the Przybylski star spectrum. In relation to the Przybylski star, the neutron star is a γ-ray pulsar for it. A neutron star is a source of relativistic particles and radiation emitted from the certain parts of its surface. The topology of this radiation strongly depends on the the magnetic field configuration of the neutron star. Existing models suppose that 1) high-energy electronpositron pairs and hard radiation are produced in the (magnetic) polar zones. Accelerated charge particles that move along magnetic lines emit electromagnetic quanta. In this model the radio-emission is genetically linked with the emission of the γ-quanta. 2) Another model of the outer gap is based on the assumption that there is a vacuum gap in the outer magnetosphere of the neutron star, which arises due to the constant escape of charged particles through the light cylinder along the open magnetic field lines. The direction of such escape may be roughly orthogonal to the rotation axis. If the rotational axes of the Przybylski star and the neutron star are close in direction (or even aligned), charged particles and hard radiation ejected in the approximately orthogonal direction at a large solid angle can enter the Przybylski star atmosphere, causing there different physical processes. As a possible source of the free neutrons could be the nuclear reactions between high-energy γ-quanta and nuclei of some atoms in the Przybylski star atmosphere gas. As a result, photoneutrons can be generated. Large enough neutron flux can be produced in the reactions with quite abundant element of the atmosphere gas (for example, helium). The photoneutrons produced in these reactions are rapidly thermalized and, as resonant neutrons, react with seed nuclei in the s-process. It should be also noted that together with s-process elements, the deuterium nuclei could be formed as a result of the interactions of the free resonant neutrons with the hydrogen atoms, but this issue has not yet been worked out.

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Pulkkinen, A., M. Hesse, M. Kuznetsova et L. Rastätter. « First-principles modeling of geomagnetically induced electromagnetic fields and currents from upstream solar wind to the surface of the Earth ». Annales Geophysicae 25, n^o 4 (8 mai 2007) : 881–93. http://dx.doi.org/10.5194/angeo-25-881-2007.

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Abstract. Our capability to model the near-space physical phenomena has gradually reached a level enabling module-based first-principles modeling of geomagnetically induced electromagnetic fields and currents from upstream solar wind to the surface of the Earth. As geomagnetically induced currents (GIC) pose a real threat to the normal operation of long conductor systems on the ground, such as high-voltage power transmission systems, it is quite obvious that success in accurate predictive modeling of the phenomenon would open entirely new windows for operational space weather products. Here we introduce a process for obtaining geomagnetically induced electromagnetic fields and currents from the output of global magnetospheric MHD codes. We also present metrics that take into account both the complex nature of the signal and possible forecasting applications of the modeling process. The modeling process and the metrics are presented with the help of an actual example space weather event of 24–29 October 2003. Analysis of the event demonstrates that, despite some significant shortcomings, some central features of the overall ionospheric current fluctuations associated with GIC can be captured by the modeling process. More specifically, the basic spatiotemporal morphology of the modeled and "measured" GIC is quite similar. Furthermore, the presented user-relevant utility metrics demonstrate that MHD-based modeling can outperform simple GIC persistence models.

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Ganguli, Gurudas, Chris Crabtree, Alex Fletcher et Bill Amatucci. « Behavior of compressed plasmas in magnetic fields ». Reviews of Modern Plasma Physics 4, n^o 1 (26 novembre 2020). http://dx.doi.org/10.1007/s41614-020-00048-4.

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AbstractPlasma in the earth’s magnetosphere is subjected to compression during geomagnetically active periods and relaxation in subsequent quiet times. Repeated compression and relaxation is the origin of much of the plasma dynamics and intermittency in the near-earth environment. An observable manifestation of compression is the thinning of the plasma sheet resulting in magnetic reconnection when the solar wind mass, energy, and momentum floods into the magnetosphere culminating in the spectacular auroral display. This phenomenon is rich in physics at all scale sizes, which are causally interconnected. This poses a formidable challenge in accurately modeling the physics. The large-scale processes are fluid-like and are reasonably well captured in the global magnetohydrodynamic (MHD) models, but those in the smaller scales responsible for dissipation and relaxation that feed back to the larger scale dynamics are often in the kinetic regime. The self-consistent generation of the small-scale processes and their feedback to the global plasma dynamics remains to be fully explored. Plasma compression can lead to the generation of electromagnetic fields that distort the particle orbits and introduce new features beyond the purview of the MHD framework, such as ambipolar electric fields, unequal plasma drifts and currents among species, strong spatial and velocity gradients in gyroscale layers separating plasmas of different characteristics, etc. These boundary layers are regions of intense activity characterized by emissions that are measurable. We study the behavior of such compressed plasmas and discuss the relaxation mechanisms to understand their measurable signatures as well as their feedback to influence the global scale plasma evolution.

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Actes de conférences sur le sujet "Magnetosphere electromagnetic phenomenon"

TOJIEV, S. R., V. S. MOROZOVA, B. J. AHMEDOV et H. E. ESHKUVATOV. « ELECTROMAGNETIC STUDIES OF IONOSPHERIC AND MAGNETOSPHERIC PERTURBATIONS ASSOCIATED WITH THE EARTH, ATMOSPHERIC AND ASTROPHYSICAL PHENOMENA ». Dans Proceedings of the 13th Regional Conference. World Scientific Publishing Company, 2012. http://dx.doi.org/10.1142/9789814417532_0019.

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Rapports d'organisations sur le sujet "Magnetosphere electromagnetic phenomenon"

BARKHATOV, NIKOLAY, et 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, décembre 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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