Magnetic Flux Rope with a Complicated Core Field by a Cluster Case
-
摘要: 2002年8月28日09:50UT-10:50UT,Cluster卫星在地球磁尾观测到一次导向场磁场重联事件.卫星观测到磁场重联扩散区附近清晰的霍尔(Hall)四极型磁结构.由于导向场的存在,该四极型结构被扭曲变形.在该磁场重联事件中,卫星观测到多个磁通量绳,大部分磁通量绳的核心场极性与导向场极性一致.但是,其中一例磁通量绳的核心场结构极性较复杂.该例磁通量绳中心区域核心场强度出现峰值,核心场极性和导向场极性一致;中心以外区域的核心场极性和导向场极性相反.这种复杂核心场结构以前未见报道.通过最小方向导数法,发现该磁通量绳的轴向是弯曲的.C1和C3卫星穿越了磁通量绳弯曲部分,探测到核心场极性变化;C2和C4卫星位于C1和C3卫星的北侧,仅穿越了磁通量绳弯曲处的一部分,故核心场具有单极性.Abstract: The Cluster spacecraft observed a magnetic reconnection event at the Earth magnetotail during 09:50 UT-10:50 UT on 28 August 2002. Cluster observed an evident quadrupole structure of the Hall magnetic field near the magnetic reconnection diffusion region. Due to the existence of the guide field, this quadrupole structure was distorted. During this reconnection event, Cluster observed a few magnetic flux ropes, and the polarity of the core field of most magnetic flux ropes is consistent with the polarity of the guiding field. However, one particular magnetic flux rope has a more complex structure of the core field than the others. In the core region of the flux ropes, the intensity peaks of the core field appeared there and its polarity is agreement with the guide field. Outside the core region, the polarity of the core field is opposite to that of the guide field. This complex structure of the core field within a flux rope has not been reported until now. Using the method of Minimum Directional Derivative (MDD), it is found that the flux rope was curved at the place where Cluster passed through. C1 and C3 satellites crossed the curved flux rope and detected the core field contrary to the guide field. C2 and C4 satellites situated on northward of C1 and C3 satellites, only crossed one part of the curved flux rope and thus detected the core field with a polarity consistent with the ambient magnetic field.
-
Key words:
- Magnetotail /
- Magnetic flux rope /
- Core field /
- Guide field
-
[1] DUNGEY J W. Interplanetary magnetic field and the auroral zones[J]. Phys. Rev. Lett., 1961, 6:47-48 [2] PARKER E N. Sweet's mechanism for merging fields in conducting fluids[J]. J. Geophys. Res. Atmos., 1957, 62:509-520 [3] PETSCHEK H E. Magnetic field annihilation[J]. NASA Special Pub., 1963, 50:425 [4] YOKOYAMA T, TANUMA S, KUDOH T, et al. Magnetic reconnection model of X-ray plasmas in the galactic center[J]. Adv. Space Res., 2000, 25:505-508 [5] FU X R, LU Q M, WANG S. The process of electron acceleration during collisionless magnetic reconnection[J]. Phys. Plasmas, 2006, 13:423-430 [6] EASTWOOD J P, PHAN T, OIEROSET M, et al. Average properties of magnetic reconnection ion diffusion regions in the Earth's magnetotail:2001-2005 Cluster observations and comparison with simulations[C]//Agu Fall Meeting. AGU Fall Meeting Abstracts, 2009 [7] WANG R, LU Q, DU A, et al. In situ observations of a secondary magnetic island in an ion diffusion region and associated energetic electrons[J]. Phys. Rev. Lett., 2010, 104:175003 [8] SONNERUP B U. Magnetic field reconnection[J]. Sol. Syst. Plasma Phys., 1979, 50:45-108 [9] HUBA J D. Hall magnetic reconnection:guide field dependence[J]. Phys. Plasmas, 2005, 12:012322-012322-012326 [10] WANG R, NAKAMURA R, LU Q, et al. Electron-scale quadrants of the hall magnetic field observed by the magnetospheric multiscale spacecraft during asymmetric reconnection[J]. Phys. Rev. Lett., 2017, 118:DOI: 10.1103/PhysRevLett.118.175101 [11] COWLEY S W H. Magnetospheric asymmetries associated with the y-component of the IMF[J]. Planet. Space Sci., 1981, 29:79-96 [12] OTTO A. 3d resistive mhd computations of magnetospheric physics[J]. Comput. Phys. Commun., 1990, 59:185-195 [13] SLAVIN J A, LEPPING R P, GJERLOEV J, et al. Geotail observations of magnetic flux ropes in the plasma sheet[J]. J. Geophys. Res. Space Phys., 2003, 108:SMP 10-11-SMP 10-18 [14] DING D Q, LEE L C, MA Z W. Different FTE signatures generated by the bursty single X line reconnection and the multiple X line reconnection at the dayside magnetopause[J]. J. Geophys. Res. Space Phys., 1991, 96:57-66 [15] SIBECK D G, KUZNETSOVA M, ANGELOPOULOS V, et al. Crater FTEs:simulation results and themis observations[J]. Geophys. Res. Lett., 2008, 35:148-161 [16] MA Z W, OTTO A, LEE L C. Core magnetic-field enhancement in single X-line, multiple X-line and patchy reconnection[J]. J. Geophys. Res. Space Phys., 1994, 99:6125-6136 [17] WANG R S, LU Q M, LI X, et al. Observations of energetic electrons up to 200keV associated with a secondary island near the center of an ion diffusion region:a Cluster case study[J]. J. Geophys. Res. Space Phys., 2010, 115:A11201 [18] DENG X H, MATSUMOTO H, KOJIMA H, et al. Geotail encounter with reconnection diffusion region in the Earth's magnetotail:evidence of multiple X lines collisionless reconnection[J]. J. Geophys. Res. Space Phys., 2004, 109:96-108 [19] LUI A T Y, DUNLOP M W, REME H, et al. Internal structure of a magnetic flux rope from Cluster observations[J]. Geophys. Res. Lett., 2007, 34.DOI: org/10.1029/2007GL029263 [20] BORG A L, TAYLOR M G G T, EASTWOOD J P. Observations of magnetic flux ropes during magnetic reconnection in the Earth's magnetotail[J]. Ann. Geophys., 2012, 30:761-773 [21] BALOGH A, DUNLOP M W. The cluster magnetic field investigation:FGM-specific multipoint analysis[J]. Space Sci. Rev., 2000, 449:65-91 [22] REME H, AOUSTIN C, BOSQUED M, et al. First multispacecraft ion measurements in and near the Earth's magnetosphere with the identical Cluster Ion Spectrometry (CIS) experiment[J]. Ann. Geophys., 2001, 19:1303-1354 [23] RUSSELL C T, MELLOTT M M, SMITH E J, et al. Multiple spacecraft observations of interplanetary shocks:four spacecraft determination of shock normals[J]. J. Geophys. Res. Space Phys., 1983, 88:4739-4748 [24] WANG R, LU Q, HUANG C, et al. Multispacecraft observation of electron pitch angle distributions in magnetotail reconnection[J]. J. Geophys. Res. Space Phys., 2010, 115:5 [25] WANG R S, NAKAMURA R, LU Q M, et al. Asymmetry in the current sheet and secondary magnetic flux ropes during guide field magnetic reconnection[J]. J. Geophys. Res. Space Phys., 2012, 117:A07223 [26] PRITCHETT P L, CORONITI F V. Three-dimensional collisionless magnetic reconnection in the presence of a guide field[J]. J. Geophys. Res., 2004, 109:379-384 [27] HUANG C, WANG R S, LU Q M, et al. Electron density hole and quadruple structure of by during collisionless magnetic reconnection[J]. Chin. Sci. Bull., 2010, 55:708-722 [28] ZONG Q G, FRITZ T A, PU Z Y, et al. Cluster observations of earthward flowing plasmoid in the tail[J]. Geophys. Res. Lett., 2004, 31:L18803 [29] HENDERSON P D, OWEN C J, ALEXEEV I V, et al. Cluster observations of flux rope structures in the near-tail[J]. Ann. Geophys., 2006, 24:651-666 [30] CHEN L J, BHATTACHARJEE A, PUHL-QUINN P A, et al. Observation of energetic electrons within magnetic islands[J]. Nat. Phys., 2008, 4:19-23 [31] HOFFMANN F D, TELLER E. Magneto-hydrodynamic shocks[J]. Phys. Rev., 1950, 80:692-703 [32] SHI Q Q, SHEN C, PU Z Y, et al. Dimensional analysis of observed structures using multipoint magnetic field measurements:application to cluster[J]. Geophys. Res. Lett., 2005, 32:273-280 [33] TAI D P, SONNERUP B U Ö, LIN R P. Fluid and kinetics signatures of reconnection at the dawn tail magnetopause:WIND observations[J]. J. Geophys. Res. Space Phys., 2001, 106:25489-25501 [34] HUANG C, LU Q, YANG Z, et al. The evolution of electron current sheet and formation of secondary islands in guide field reconnection[J]. Nonlin. Proces. Geophys., 2011, 18:727-733 [35] PASCHMANN G, DALY P W. Multi-spacecraft Analysis Methods Revisited[M]. Bern, Switzerland:International Space Science Institute, 2008 [36] KARIMABADI H, KRAUSS-VARBAN D, OMIDI N, et al. Magnetic structure of the reconnection layer and core field generation in plasmoids[J]. J. Geophys. Res. Space Phys., 1999, 104:12313-12326
点击查看大图
计量
- 文章访问数: 883
- HTML全文浏览量: 75
- PDF下载量: 49
- 被引次数: 0