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The Cluster mission of the European Space Agency (ESA) will allow, for the first time three-dimensional measurements in key regions of the Earth's magnetosphere to be carried out. The European Numerical Simulation Network (ENSN) aims at providing a theoretical support to the mission. We describe the achievements of the ENSN during its first period of activity 1991–1994, during which the network was funded by the European Union. In particular, the ENSN has set up (i) thematic Working Groups on the prime scientific goals of the mission, (ii) a code development Working Group to develop numerical simulation codes specifically adapted to studying magnetospheric boundaries and the corresponding scale mixing, and (iii) software models of Cluster instruments to test in a numerical simulation what the set of four instruments will measure. 相似文献
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G.P. Wu G.L. Huang Y. Huang D.Y. Wang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(6):984-987
Based upon the most efficient electron acceleration near the midplane of 3D non-neutral driven reconnecting current sheet (RCS) and the electrostatic wave excitation by the drift Maxwellian distribution of electrons in Vlasov simulation, we assume that the electrostatic waves mainly propagate opposite to the reconnecting electric field and investigated how these waves affect the electron acceleration. The main results are: (1) when the electron’s velocity equals to the phase speed of the waves, they will be trapped and have the different accelerating characteristics from the untrapped electrons through solving the momentum equations of electrons analytically; (2) the test particle simulations further prove that the number of the energetic electrons decreases with the increasing intensity of unstable waves, and the distribution of the energetic electrons takes on the double power-law. 相似文献
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P. Rafanelli S. Ciroi V. Cracco F. Di Mille D. Ilić G. La Mura L.Č. Popović 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
It is becoming clear that we can define two different types of nearby AGN belonging to the Seyfert 1 class (S1), on the basis of the match of the intensities of their Broad Balmer Lines (BBL) with the Boltzmann Plots (BP). These two types of S1 galaxies, that we call BP-S1 and NoBP-S1, are characterized, in first approximation, by Broad Line Regions (BLR) with different structural and physical properties. In this communication, we show that these features can be well pointed out by a multi-wavelength analysis of the continuum and of the broad recombination Hydrogen lines, that we carry out on a sample of objects detected at optical and X-ray frequencies. The investigation is addressed to verify whether BP-S1 are the ideal candidates for the study of the kinematical and structural properties of the BLR, in order to derive reliable estimates of the mass of their central engine and to constrain the properties of their nuclear continuum spectrum. 相似文献
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K.-I. Nishikawa J. Niemiec M. Medvedev B. Zhang P. Hardee A. Nordlund J. Frederiksen Y. Mizuno H. Sol M. Pohl D.H. Hartmann M. Oka G.J. Fishman 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Using our new 3-D relativistic particle-in-cell (PIC) code parallelized with MPI, we investigated long-term particle acceleration associated with a relativistic electron–positron jet propagating in an unmagnetized ambient electron–positron plasma. The simulations were performed using a much longer simulation system than our previous simulations in order to investigate the full nonlinear stage of the Weibel instability and its particle acceleration mechanism. Cold jet electrons are thermalized and ambient electrons are accelerated in the resulting shocks. Acceleration of ambient electrons leads to a maximum ambient electron density three times larger than the original value as predicted by hydrodynamic shock compression. In the jet (reverse) shock behind the bow (forward) shock the strongest electromagnetic fields are generated. These fields may lead to time dependent afterglow emission. In order to calculate radiation from first principles that goes beyond the standard synchrotron model used in astrophysical objects we have used PIC simulations. Initially we calculated radiation from electrons propagating in a uniform parallel magnetic field to verify the technique. We then used the technique to calculate emission from electrons in a small simulation system. From these simulations we obtained spectra which are consistent with those generated from electrons propagating in turbulent magnetic fields with red noise. This turbulent magnetic field is similar to the magnetic field generated at an early nonlinear stage of the Weibel instability. A fully developed shock within a larger simulation system may generate a jitter/synchrotron spectrum. 相似文献
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Abraham C.-L. Chian Maoan Han Rodrigo A. Miranda Chenggang Shu Juan A. Valdivia 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
A review of the fundamental physical processes in the planetary–exoplanetary environment is presented, with emphasis on nonlinear phenomena. First, we discuss briefly the detection of exoplanets and search for radio emissions from exoplanets. Next, we give an overview of the concepts of waves, instabilities, chaos and turbulence in the planetary–exoplanetary environment based on our present knowledge of the solar-terrestrial environment. We conclude by discussing cyclotron masers and chaos in nonthermal radio emissions in the planetary–exoplanetary environment. 相似文献
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