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Xiao F.,Changsha University of Science and Technology | Zong Q.,Peking University | Pu Z.,Peking University | Su Z.,Hefei University of Technology | And 4 more authors.
Plasma Physics and Controlled Fusion | Year: 2010

The magnetic field configuration around a magnetic null pair and its associated electron behavior during 3D magnetic reconnection have recently been reported from in situ observations. Electrons are suggested to be temporarily trapped in the central reconnection region as indicated by an electron density peak observed near the magnetic null (He J-S et al 2008 Geophys. Res. Lett. 35 L14104). It is highly interesting that energetic electron beams of a few kiloelectronvolts are found to be related to the magnetic null structure. However, the acceleration mechanism is still not fully understood. In this paper, we show that strong whistler-mode electromagnetic waves are indeed found around the magnetic null. Further we propose a new electron acceleration scenario of trapped electrons near the magnetic null points driven by the whistler-mode waves, which is confirmed by numerical results. It is demonstrated that whistler waves can enhance the phase space density (PSD) of electrons for energies of ∼2 keV by a factor of 100 at lower pitch angles very rapidly, typically within 2 s. The accelerated electrons may escape from the loss cone of the magnetic cusp mirrors around the magnetic null, leading to the observed energetic beams. © 2010 IOP Publishing Ltd.

Yan Y.,CAS National Astronomical Observatories | Yan Y.,State Key Laboratory of Space Weather | Huang J.,CAS National Astronomical Observatories | Chen B.,CAS National Astronomical Observatories | And 2 more authors.
Advances in Space Research | Year: 2010

Radio bursts with fine structures in decimetric-centimetric wave range are generally believed to manifest the primary energy release process during flare/CME events. By spectropolarimeters in 1-2 GHz, 2.6-3.8 GHz, and 5.2-7.6 GHz at NAOC/Huairou with very high temporal (1.25-8 ms) and spectral (4-20 MHz) resolutions, the zebra patterns, spikes, and new types of radio fine structures with mixed frequency drift features are observed during several significant flare/CME events. In this paper we will discuss the occurrence of radio fine structures during the impulsive phase of flares and/or CME initiations, which may be connected to the magnetic reconnection processes. © 2010 COSPAR. Published by Elsevier Ltd.

Xu D.,State Key Laboratory of Space Weather | Xu D.,University of Chinese Academy of Sciences | Chen T.,State Key Laboratory of Space Weather
Planetary and Space Science | Year: 2012

A statistical study of electron data observed within magnetosheath regions after interplanetary (IP) shocks driven by magnetic clouds has been performed to understand the constraints on temperature anisotropies of suprathermal electron component due to collective effects of electron wave-particle interactions with plasma micro-instabilities. Results show that although shock heating and acceleration, downstream selective reflection and leakage into upstream region, and wave-particle scattering all can contribute to suprathermal electron temperature anisotropy in downstream sheath regions of IP shocks, the consequent whistler anisotropy instabilities triggered by the sufficiently large temperature anisotropies can constrain temperature anisotropy increase to a more nearly isotropic distribution as plasma beta increases. © 2011 Elsevier Ltd. All rights reserved.

Yao Z.,Hainan Normal University | Gong S.,Hainan Normal University | Gong S.,State Key Laboratory of Space Weather | Fu J.,Hainan Normal University | And 2 more authors.
Solid State Communications | Year: 2010

The electronic and magnetic properties of the full-Heusler compound Co 2MnP were studied using the full-potential augmented plane wave plus the local orbitals method within the density functional theory. Spin-polarized calculations predicted that the full-Heusler compound Co2MnP is a half-metallic ferromagnet with a magnetic moment of 6.00μB per formula unit and a spin-flip gap of 0.60 eV at its equilibrium lattice constant. The half-metallic ferromagnetism of the full-Heusler compound Co2MnP can be retained even when the lattice constant is changed by 1.2%. © 2010 Elsevier B.V. All rights reserved.

Wang C.,CAS Center for Space Science and Applied Research | Wang C.,State Key Laboratory of Space Weather | Wang C.,Meridian
Space Weather | Year: 2010

To develop an understanding of near-Earth space's response to solar activities and to eventually enhance the success of space weather predictions, it is crucial to make synergetic observations of the entire environment from the Sun to the Earth as a system. Since the beginning of the space era, direct observations by satellites have become a much needed means toward this end. However, ground-based observations also have advantages and serve as a counterpart to those made in space. For example, instruments on the ground are much less expensive and easier to repair than those on satellites. Ground-based observations provide continuous high-resolution data not subject to the limitation of the downlink data rate from satellites to ground receiving stations. Also, because some observations have been made from Earth for hundreds of years, society has long and continuous records of quantities such as geomagnetic field variations, measurements of relative ionospheric opacity, and sunspot observations. Data from spacecraft, on the other hand, go back only a few decades. Copyright © 2010 by the American Geophysical Union.

Yihua H.,Changsha University of Science and Technology | Chang Y.,Changsha University of Science and Technology | Chang Y.,State Key Laboratory of Space Weather | Zhaoguo H.,Changsha University of Science and Technology | And 3 more authors.
Plasma Science and Technology | Year: 2013

We provide correlated observations of enhanced dayside whistler-mode waves and energetic electron acceleration collected by the CLUSTER and GOES satellites during the 23~24 September 2001 storm. Energetic (>0.6 MeV) electron fluxes are found to increase significantly during the recovery phase and the main phase, by a factor of ~50 higher than the prestorm level. These high electron fluxes occur when strong dayside whistler-mode waves are present. Two-dimensional (2D) numerical simulations are carried out and the results demonstrate that the dayside whistler-mode wave can contribute to such enhancements in electron fluux within 24 h, consistent with the observation.

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