哨声模合声波与地球同步轨道高能电子通量增强事件事例研究
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摘要
局部加速机制是磁暴期间地球外辐射带高能电子通量增强事件发生的重要原因.此加速机制需要两个基本条件,一是存在种子电子,二是存在能与种子电子产生共振的加速波动,包括哨声模合声波.通过对2004—2006年Pi1地磁脉动持续时间与种子电子通量的相关性分析,更明确提出Pi1地磁脉动的持续时间可以作为种子电子通量的指示剂.通过对三个磁暴事例地球同步轨道的种子电子通量、高能电子通量及哨声模合声波变化情况的分析,发现在高能电子通量较强的事例中,均观测到较高的种子电子通量和较强的哨声模合声波,这在一定程度上验证了哨声模合声波对种子电子的回旋加速机制,且合声波强度与高能电子通量有正的相关性.
The local acceleration mechanism is one of the crucial factors for the high energy electron flux enhancement events in the outer radiation belt.There are two substantial preconditions for this acceleration mechanism.The first and the most important one is the presence of enough low energy electron(on the order of tens to hundreds of keV),so-called seed electron;the other is the enhancement of plasma waves including whistler chorus waves which can contribute to the electron acceleration by wave-particle interaction.Geomagnetic field data observed by Memambetsu(L = 1.57) observatory are used to extract Pi1 pulsation during 2004—2006.The linear correlation between Pil pulsation duration and seed electron flux(LANL 50～225keV) is greater than 0.7,which indicates that the Pil pulsation duration is a good indicator of seed electron flux.After the investigation of three magnetic storms events in 2005,the evidence had been found for acceleration of seed electrons to high energies by whistler chorus waves and the positive correlation between the chorus waves' spectral density and high energy electron flux.
The local acceleration mechanism is one of the crucial factors for the high energy electron flux enhancement events in the outer radiation belt.There are two substantial preconditions for this acceleration mechanism.The first and the most important one is the presence of enough low energy electron(on the order of tens to hundreds of keV),so-called seed electron;the other is the enhancement of plasma waves including whistler chorus waves which can contribute to the electron acceleration by wave-particle interaction.Geomagnetic field data observed by Memambetsu(L = 1.57) observatory are used to extract Pi1 pulsation during 2004—2006.The linear correlation between Pil pulsation duration and seed electron flux(LANL 50～225keV) is greater than 0.7,which indicates that the Pil pulsation duration is a good indicator of seed electron flux.After the investigation of three magnetic storms events in 2005,the evidence had been found for acceleration of seed electrons to high energies by whistler chorus waves and the positive correlation between the chorus waves' spectral density and high energy electron flux.
引文
http://wdc.kugi.kyoto-u.ac.jp/wdc/Sec3.html
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[1]O'BrienTP,LorentzenKR,Mann I R,et al.Energization of relativistic electrons in the presence of ULF power and MeV microbursts:Evidence for dual ULF and VLF acceleration[J].J.Geophys.Res.,2002,108(8),DOI: 10.1029/2002JA009784
[2]Ukhorskiy A Y,Takahashi K,Anderson B J,et al. Impact of toroidal ULF waves on the outer radiation belt electrons[J].J.Geophys.Res.:Space Phys.,2005, 110:19 782012
[3]Li Liuyuan,Cao Jinbin,Zhou Guocheng,et al.Electron acceleration by compressional ULF turbulence in the geomagnetosphere [J].Chin.J.Space Sci.,2005,25(1):1-5. In Chinese(李柳元,曹晋滨,周国成,等.磁层压缩ULF湍流对电子的加速[J].空间科学学报,2005,25(1):1-5)
[4]He T,Liu S Q,Xue B S,et al.Study on a forecasting method of the relativistic electron flux at geostationary orbit using geomagnetic pulsation data[J].Chinese J. Geophys.,2009,52(10):2419-2427.In Chinese(何甜,刘四清,薛炳森,等.利用地磁脉动预报地球同步轨道相对论电子通量方法的研究[J].地球物理学报,2009,52(10):2419-2427)
[5]Degtyarev V I,Kharchenko I P,Potapov A S,et al.Qualitative estimation of magnetic storm efficiency in producing relativistic electron flux in the Earth's outer radiation belt using geomagnetic pulsations data[J].J.Adv.Space Res.,2009,43(5):829-836
[6]Degtyarev V I,Kharchenko I P,Potapov A S,et al. The relation between geomagnetic pulsations and an increase in the fluxes of geosynchronous relativistic electrons during geomagnetic storms[J].Geomag.Aeron.,2010, 50(7):885-893
[7]Li Liuyuan,Cao Jinbin,Zhou Guocheng.Acceleration of "Seed Electrons" by whistler turbulence near the geosynchronous orbit[J].Chin.J.Geophys.,2004,47(5):756- 761.In Chinese(李柳元,曹晋滨,周国成.地球同步轨道附近哨声湍流对“种子电子”的加速[J].地球物理学报,2004, 47(5):756-761)
[8]Meredith N P,Home R B,Iles R H A,et al.Outer zone relativistic electron acceleration associated with substorm-enhanced whistler mode chorus[J].J.Geophys. Res.,2002,107:1-29
[9]Meredith N P,Home R B,Summers D,et al.Evidence for acceleration of outer zone electrons to relativistic energies by whistler mode chorus[J].Ann.Geophys.,2002, 20:967-979
[10]Xiao Fuliang,Su Zhenpeng,Zheng Huinan,et al.Modeling of outer radiation belt electrons by multidimensional diffusion process[J].J.Geophys.Res.,2009, 114:19 782012
[11]Ni B B,Zhao Z Y,Gu X D,et al.Resonant diffusion of radiation belt energetic electrons by field-aligned propagation whistler-mode chorus waves[J].J.Acta Phys.Sin., 2008,57(12):7937-7949.In Chinese(倪彬彬,赵正予,顾旭东,等.场向传播的内磁场哨声波对辐射带高能电子的共振扩散[J].物理学报,2008,57(12):7937-7949)
[12]Paulikas G,Blake J.Effects of the solar wind on magnetospheric dynamics:energetic electrons at the synchronous orbit,in Quantitative Modeling of the Magnetospheric Processes[J].Geophys.Monog.,1979,21:180-202
[13]Baker D N,McPherronRL,Cayton T E,et al.Linear prediction filter analysis of relativistic electron properties at 6.6 R_e[J].J.Geophys.Res.,1990,95:15133-15140
[14]Li Xinlin,Baker D N,Temerin M D,et al.Are energetic electrons in the solar wind the source of the outer radiation belt[J].Geophys.Res.Lett.,1997,24(8):923-926