Authentication email has already been sent, please check your email box: and activate it as soon as possible.
You can login to My Profile and manage your email alerts.
If you haven’t received the email, please:
|
|
There are 11 papers published in subject: > since this site started. |
Select Subject |
Select/Unselect all | For Selected Papers |
Saved Papers
Please enter a name for this paper to be shown in your personalized Saved Papers list
|
1. Why is a flare-rich active region CME-poor? | |||
Lijuan Liu,Yuming Wang,Jingxiu Wang,Chenglong Shen,Pinzhong Ye,Quanhao Zhang,Rui Liu,Shui Wang | |||
Earth Science 16 November 2015 | |||
Show/Hide Abstract | Cite this paper︱Full-text: PDF (0 B) | |||
Abstract:Solar active regions (ARs) are the major sources of two kinds ofthe most violent solar eruptions, namely flares and coronal massejections (CMEs). The largest AR in the past 24 years, NOAA AR12192, crossed the visible disk from 2014October 17 to 30, unusually produced morethan one hundred flares, including 32 M-class and 6 X-class ones,but only one small CME. Flares and CMEs are believed to be twophenomena in the same eruptive process. Why is such a flare-rich ARso CME-poor? We compared this AR with other four ARs; two were productive in both and two were inert. The investigation of the parameters based on the SDO/HMI vector magnetogram reveals thatthe flare-rich AR 12192, as the other two productive ARs, has larger magnetic flux, current and free magnetic energy thanthe two inert ARs, but contrast to the two productive ARs, it has no strong, concentrated current helicity along both sidesof the flaring neutral line, indicating the absence of a matured magnetic structure consisting of sheared or twisted field lines.Furthermore, the decay index above the AR 12192 is relatively low, showing strong constraint.These results suggest that productive ARs are always large and have enough current and free energy to power flares, but whether or nota flare is accompanied by a CME is seemingly related to (1) if there is matured sheared or twisted core field serving as the seed of theCME, (2) if the constraint of the overlying arcades is weak enough. | |||
TO cite this article:Lijuan Liu,Yuming Wang,Jingxiu Wang, et al. Why is a flare-rich active region CME-poor?[OL].[16 November 2015] http://en.paper.edu.cn/en_releasepaper/content/4661519 |
2. Parametric instabilities of parallel propagating circularly polarized Alfvén waves: One-dimensional hybrid simulations | |||
HE Peng,GAO Xinliang,ZHAO Jinsong,LU Quanming | |||
Earth Science 03 August 2015 | |||
Show/Hide Abstract | Cite this paper︱Full-text: PDF (0 B) | |||
Abstract:The parametric decay of a monochromatic Alfvén wave in a low beta plasma is found to decay into a forward propagating density mode and a backward propagating daughter Alfvén wave mode. In this paper, by performing one-dimensional (1-D) hybrid simulations, we detailedly analyze the parametric instabilities of the Alfvén waves with a spectrum in a low beta plasma. The results show that the parametric instabilities have two stages. In the first stage, the density wave modes are excited due to the modulation of the pump Alfvén waves, and then magnetic fluctuations appear after these density modes interact with the pump Alfvén waves. In the second stage, each pump Alfvén wave will decay into a density mode and a daughter Alfvén wave mode, as in the parametric decay of a monochromatic Alfvén wave. | |||
TO cite this article:HE Peng,GAO Xinliang,ZHAO Jinsong, et al. Parametric instabilities of parallel propagating circularly polarized Alfvén waves: One-dimensional hybrid simulations[OL].[ 3 August 2015] http://en.paper.edu.cn/en_releasepaper/content/4651188 |
3. The effect of a guide field on the structures of magnetic islands formed during multiple X line reconnection: two-dimensional particle-in-cell simulations | |||
HUANG Can,LU Quanming,LU San,WANG Peiran,WANG Shui | |||
Earth Science 16 October 2013 | |||
Show/Hide Abstract | Cite this paper︱Full-text: PDF (0 B) | |||
Abstract:Magnetic island plays an important role in magnetic reconnection. In this paper, using a series of two-dimensional (2-D) particle-in-cell (PIC) simulations, we investigate the magnetic structures of a magnetic island formed during multiple X-line magnetic reconnection, considering the effects of the guide field in symmetric and asymmetric current sheets. In a symmetric current sheet, the current in the direction forms a tripolar structure inside a magnetic island during anti-parallel reconnection, which results in a quadrupole structure of the out-of-plane magnetic field. With the increase of the guide field, the symmetry of both the current system and out-of-plane magnetic field inside the magnetic island is distorted. When the guide field is sufficiently strong, the current forms a ring along the magnetic field lines inside magnetic island. At the same time, the current carried by the energetic electrons accelerated in the vicinity of the X lines forms another ring at the edge of the magnetic island. Such a dual-ring current system enhance the out-of-plane magnetic field inside the magnetic island with a dip in the center of the magnetic island. In an asymmetric current sheet, when there is no guide field, electrons flows toward the X lines along the separatrices from the side with a higher density, and are then directed away from the X lines along the separatrices to the side with a lower density. The formed current results in the enhancement of the out-of-plane magnetic field at one end of the magnetic island, and the attenuation at the other end. With the increase of the guide field, the structures of both the current system and the out-of-plane magnetic field are distorted. | |||
TO cite this article:HUANG Can,LU Quanming,LU San, et al. The effect of a guide field on the structures of magnetic islands formed during multiple X line reconnection: two-dimensional particle-in-cell simulations[OL].[16 October 2013] http://en.paper.edu.cn/en_releasepaper/content/4564369 |
4. Numerical simulations of magnetic reconnection in an asymmetric current sheet | |||
Wang Peiran,HuangCan,Lu Quanming,WangShui | |||
Earth Science 26 July 2013 | |||
Show/Hide Abstract | Cite this paper︱Full-text: PDF (0 B) | |||
Abstract:Magnetic reconnection in a symmetric current sheet has been thoroughly investigated in previous studies. The out-of-plane magnetic field is found to have a quadrupole structure in the diffusion region. The perpendicular electric field and the parallel electric field with a bipolar structure exist around the four separatrices. In this paper, by performing two-dimensional (2-D) particle-in-cell (PIC) simulations, we investigate the electric and magnetic structures of magnetic reconnection in an asymmetric current sheet. Compared with magnetic reconnection in a symmetric current sheet, the quadrupole structure of the out-of-plane magnetic field now disappears in the diffusion region, and both the parallel and perpendicular electric field only exist in the upper separatrices. The parallel electric field with a bipolar structure is considered to be the results of the nonlinear evolution of the Buneman instability, which is excited by the high-speed electron flow formed after their acceleration around the X line. The disappearance of the parallel electric field around the lower separatrices may be due to the transverse instability, which is unstable in a weak magnetized plasma. | |||
TO cite this article:Wang Peiran,HuangCan,Lu Quanming, et al. Numerical simulations of magnetic reconnection in an asymmetric current sheet[OL].[26 July 2013] http://en.paper.edu.cn/en_releasepaper/content/4553296 |
5. Out-of-plane electron currents in magnetic islands formed during collisionless magnetic reconnection | |||
HUANG Can,LU Quanming,WU Mingyu,LU San,WANG Shui | |||
Earth Science 01 March 2013 | |||
Show/Hide Abstract | Cite this paper︱Full-text: PDF (0 B) | |||
Abstract:Secondary islands are considered to play a crucial role in collisionless magnetic reconnection. Based on 2-D particle-in-cell simulations, we investigate the characteristics of the out-of-plane electron currents in magnetic islands formed during collisionless magnetic reconnection with an initial guide field. In a primary island (formed simultaneously with the appearance of the X lines), due to the acceleration of the trapped electrons, the direction of the formed out-of-plane electron current is reverse to the original one. In the secondary island (formed in the vicinity of the X-line), the out-of-plane electron current is generated due to the accelerated electrons by the reconnection electric field in the vicinity of the X line. In such a way, the direction of the out-of-plane electron current in a secondary island is found to be opposite to that in a primary island. Such characteristics are found to be related to the evolution of the magnetic islands and then electron dynamics in the islands, which are proposed in this paper to be a possible criterion to identify a secondary island formed during collisionless magnetic reconnection, especially in the magnetotail. | |||
TO cite this article:HUANG Can,LU Quanming,WU Mingyu, et al. Out-of-plane electron currents in magnetic islands formed during collisionless magnetic reconnection[J]. |
6. Waiting times of Quasi-homologous Coronal Mass Ejections from Super Active Regions | |||
Yuming Wang,Lijuan Liu,Chenglong Shen,Rui Liu,S.Wang | |||
Earth Science 28 February 2013 | |||
Show/Hide Abstract | Cite this paper︱Full-text: PDF (0 B) | |||
Abstract:Why and how may some active regions (ARs) frequently produce coronal mass ejections (CMEs)? It is one of the key questions to deepen our understanding of the mechanisms and processes of energy accumulation and sudden release in ARs and to improve our capability of space weather prediction. Although some case studies have been made, the question is still far from fully answered. This issue is now being tried to address statistically through an investigation of waiting times of quasi-homologous CMEs from super ARs in solar cycle 23. It is found that the waiting times of quasi-homologous CMEs have a two-component distribution with a separation at about 18 hours, the peak waiting time of the first component is at about 7 hours, and the likelihood of occurrences of two or more CMEs faster than 1200 km /s within 18 hours is about 20%. Furthermore, the correlation analysis among CME waiting times, CME speeds and CME occurrence rates reveals that these quantities are independent to each other, suggesting that the perturbation by preceding CMEs rather than free energy input be the direct cause of quasi-homologous CMEs. The peak waiting time of 7 hours probably characterize the time scale of the growth of instabilities triggered by preceding CMEs. This study uncovers more clues for us to understand quasi-homologous CMEs as well as CME-rich ARs. | |||
TO cite this article:Yuming Wang,Lijuan Liu,Chenglong Shen, et al. Waiting times of Quasi-homologous Coronal Mass Ejections from Super Active Regions[J]. |
7. Double layers and ion-acoustic waves: a fully particle-in-cell simulation | |||
GUO Jun,LI Bo | |||
Earth Science 26 February 2013 | |||
Show/Hide Abstract | Cite this paper︱Full-text: PDF (0 B) | |||
Abstract:Double layers and ion-acoustic waves are investigated by using a one-dimensional electrostatic particle-in-cell simulation code. Our results show that double layers can be formed even when the drift velocity between electrons and ions is less than the electron thermal velocity. The electron and ion density depressions are clearly seen. Electrons gradually develop a distribution comprising both background and beam components. In fact, as the initial electron-ion drift velocity is less than the electron thermal velocity, intense ion-acoustic waves can be found only where the electron beam is located, suggesting that they are excited by the self-consistently developed electron beam. Besides the Langmuir waves and ion-acoustic waves, the beam mode excited by electron beam produced in our simulation has been found clearly. | |||
TO cite this article:GUO Jun,LI Bo. Double layers and ion-acoustic waves: a fully particle-in-cell simulation[OL].[26 February 2013] http://en.paper.edu.cn/en_releasepaper/content/4522566 |
8. Sodium lidar observed quasi-two-day wave in sodium density and temperature | |||
Tao Li,Chiao-Yao She | |||
Earth Science 22 December 2012 | |||
Show/Hide Abstract | Cite this paper︱Full-text: PDF (0 B) | |||
Abstract:Three 80-90 hour sodium lidar campaigns during the month of August in three consecutive years, 2002, 2003, and 2004 were analyzed to investigate the correlations of the response of sodium density to quasi-two day (QTD) wave with temperature perturbations. We found that the QTD wave amplitudes of sodium density and temperature are correlated remarkably well in most of altitudes from 80-100km. However, the sodium density QTD wave perturbation is in phase with temperature QTD wave perturbation below the height of mean sodium density peak, and out of phase above. The maximum wave amplitudes of sodium density and temperature are correlated very well with the peaks of the vertical gradient of mean sodium density mixing ratio. These observations may suggest, for the first time, that the response of sodium density to tides and QTD wave perturbation is likely not just dominated by dynamic effects of vertical advection. | |||
TO cite this article:Tao Li,Chiao-Yao She. Sodium lidar observed quasi-two-day wave in sodium density and temperature[OL].[22 December 2012] http://en.paper.edu.cn/en_releasepaper/content/4501560 |
9. Controlling of merging electric field and IMF magnitude on storm-time changes in thermospheric mass density | |||
MA Shuying,ZHOU Yunliang,LIU Ruosi,LUEHR H.,DOORNBOS E. | |||
Earth Science 09 June 2012 | |||
Show/Hide Abstract | Cite this paper︱Full-text: PDF (0 B) | |||
Abstract:The controls of merging electrical field, Em, and IMF magnitude, B, on the storm-time changes in upper thermospheric mass density are statistically investigated using GRACE accelerometer observations and the OMNI data of solar wind and IMF for 35 great storms during 2002-2006 years. It reveals that: (1) The correlation coefficients between the air mass density changes and the parameters of Em and B are larger at lower latitudes than at higher latitudes generally, and larger in noon and midnight sectors than in dawn and dusk. (2) As a whole, the delay times of mass density changes behind Em and B range 1.5-9h and 1.5-12h respectively. The most likely delay time (MLDT) is about 4.5h for both parameters at low/middle latitudes when taking statistics for all local time sectors. The MLDT is in fact local time dependent with about 1.5h in noon sector and ranging from 6 to 7.5h for other sectors. (3) The linear control factor of B on the density changes increases for large B, in contrast to somewhat saturation trend for larger Em. (4) The influence of B and Em on the mass densities shows different behaviour for different type storm. In general, the influence is stronger for CIR-driven than for CME-deiven storm, which seems more remarkable for parameter Em. Moreover, for CME-driven storms, both Em and B has largest influence at noon sector and smallest at dawn sector; while for CIR-diven storms, Em and B has larger influence at dawn/dusk sectors and smaller at noon/midnight sectors. | |||
TO cite this article:MA Shuying,ZHOU Yunliang,LIU Ruosi, et al. Controlling of merging electric field and IMF magnitude on storm-time changes in thermospheric mass density[OL].[ 9 June 2012] http://en.paper.edu.cn/en_releasepaper/content/4481687 |
10. Two Dimensional Simulation of Amplitude Modulated Electron Plasma Waves | |||
Zhou Meng,Deng Xiaohua,Y. Pang,S. Y. Li,R. X. Tang,J.F. Wang,Z.G. Yuan | |||
Earth Science 19 December 2007 | |||
Show/Hide Abstract | Cite this paper︱Full-text: PDF (0 B) | |||
Abstract:Highly modulated waves near electron plasma frequency with both parallel and perpendicular polarization have been observed near diffusion region at dayside and in the tail region. In this paper, two dimensional Particle-In-Cell (PIC) simulation was performed to study the possible generation mechanism of these modulated electron plasma waves. It is shown that weak beam instability could generate the modulated Langmuir wave and the ambient magnetic field plays an important role in the formation of modulation. When the weak beam has loss cone distribution, highly modulated upper hybrid waves are generated and propagate with large angle to the ambient magnetic field. The properties of these modulated waves are discussed and compared with observations. | |||
TO cite this article:Zhou Meng,Deng Xiaohua,Y. Pang, et al. Two Dimensional Simulation of Amplitude Modulated Electron Plasma Waves[OL].[19 December 2007] http://en.paper.edu.cn/en_releasepaper/content/17123 |
Select/Unselect all | For Selected Papers |
Saved Papers
Please enter a name for this paper to be shown in your personalized Saved Papers list
|
|
About Sciencepaper Online | Privacy Policy | Terms & Conditions | Contact Us
© 2003-2012 Sciencepaper Online. unless otherwise stated