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等离子体层嘶声是引起辐射带电子投掷角散射进而沉降到地球大气层的重要物理机理,也被认为是导致地球内、外辐射带之间槽区形成的主因,因此研究空间等离子体层嘶声的全球分布特性具有重要科学意义.本文利用范阿伦探测双星中的A星从2012年9月到2015年5月长达33个月的高质量波动观测数据,详细计算了等离子体层嘶声的平均波幅和发生率,建立了等离子体层嘶声的全球分布数据库,并细致分析了其场强幅度随地磁活动水平、磁壳值L、地磁纬度、磁地方时的统计变化规律.结果表明,等离子体层嘶声的平均波幅与地磁活动剧烈程度具有很强的相关性,并表现出明显的昼夜不对称性.随着地磁活动的增强,日侧等离子体层嘶声的平均波幅相应增大,增强的区域集中在2.5 L 4,但是夜侧等离子体层嘶声的平均波幅反而下降.另外,不同幅度的等离子体层嘶声随地磁活动的变化表现出不同的响应特性.随着地磁活动水平的增强,较小幅度(530 pT)的等离子体层嘶声的日侧发生率减小,夜侧发生率增大;更强幅度(30 pT)的等离子体层嘶声的变化特性正好相反,日侧发生率增大,夜侧发生率减小.在各种地磁活动条件下,磁赤道面附近及中纬地区等离子体层嘶声都广泛存在,波动幅度位于530 pT范围的嘶声发生概率最大.以上统计观测结果为现有的等离子体层嘶声全球分布模型提供了合理、可靠的补充,充分说明不同场强幅度的等离子体层嘶声在2 L 6的内磁层空间经常性地存在,为定量分析、模拟不同能量、不同投掷角的地球辐射带电子在不同太阳风与磁层背景条件下的动态时空变化过程提供了重要参数支持.Plasmaspheric hiss plays an important role in driving the precipitation loss of radiation belt electrons via pitch angle scattering, which is also known as the major cause of the formation of the slot region between the inner and outer radiation belt. Therefore, it is of scientific importance to acquire a complete picture of the global distribution of plasmaspheric hiss. Using the thirty-three month high-quality wave data of the Van Allen Probes from September 2012 to May 2015, which provide excellent coverage in the entire inner magnetosphere, we investigate in detail the characteristics of the global distribution of plasmaspheric hiss bin-averaged wave amplitude and occurrence rate with respect to the geomagnetic activity level, L-shell, geomagnetic latitude, and magnetic local time. It is demonstrated that the bin-averaged hiss amplitude strongly depends on the level of geomagnetic activity and exhibits a pronounced day-night asymmetry. Dayside hiss shows a tendency intensifying with the disturbed geomagnetic condition, which is primarily confined to L=2.5-4.0. In contrast, the average hiss amplitude on the nightside tends to decrease. It should also be noted that plasmaspheric hiss at different amplitude levels varies distinctly with geomagnetic condition. As the geomagnetic disturbance increases, the occurrence rate of hiss wave at a smaller amplitude level (i.e., 5-30 pT) increases on the nightside but decreases on the dayside, while the occurrence pattern of higher amplitude ( 30 pT) hiss wave is opposite. For high amplitude hiss wave, the occurrence rate increases on the dayside during intense geomagnetic activities while decreases on the nightside. This is probably because during active times, suprathermal electron fluxes are larger on the nightside, which causes stronger Landau damping of whistler mode waves and thus limits the ability of chorus waves to propagate into the plasmasphere and evolve into plasmaspheric hiss. In addition, plasmaspheric hiss waves with the amplitudes ranging from 5 to 30 pT have the highest occurrence probability both around the geomagnetic equator and at higher latitudes. Our statistical results can provide a reasonable and accurate cognition complementary to the current knowledge of the global features of plasmaspheric hiss, especially in the inner magnetosphere of L=2-6, thereby offering essential input parameters of hiss wave distribution for future simulations of the dynamic spatiotemporal variations of radiation belt electrons at different energies and pitch angles under the influence of diverse solar wind and magentospheric circumstances. Therefore, we suggest that these new properties of hiss wave should be incorporated into the future modeling of radiation belt electron dynamics.
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Keywords:
- Van Allen Probes /
- plasmaspheric hiss /
- global distribution /
- averaged wave amplitude
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[18] Li W, Thorne R M, Bortnik J, Kletzing C A, Kurth W S, Hospodarsky G B, Nishimura Y 2015 J. Geophys. Res. Space Phys. 120 3394
[19] Spasojevic M, Shprits Y Y, Orlova K 2015 J. Geophys. Res. Space Phys. 120 10370
[20] Mauk B H, Fox N J, Kanekal S G, Kessel R L, Sibeck D G, Ukhorskiy A 2013 Space Sci. Rev. 179 3
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[1] Thorne R M, Smith E J, Burton R K, Holzer R E 1973 J. Geophys. Res. 78 1581
[2] Meredith N P, Horne R B, Thorne R M, Summers D, Anderson R R 2004 J. Geophys. Res. A 109 06209
[3] Summers D, Ni B, Meredith N P, Horne R B, Thorne R M, Moldwin M B, Anderson R R 2008 J. Geophys. Res. A 113 04219
[4] Lyons L R, Thorne R M 1973 J. Geophys. Res. 78 2142
[5] Summers D, Ni B, Meredith N P 2007 J. Geophys. Res. A 112 04207
[6] Reeves G D, Friedel H W, Larsen B A, Skoug R M, Funsten H O, Claudepierre S G, Fennell J F, Turener D L, Denton M H, Spence H E, Blake J B, Baker D N 2016 J. Geophys. Res. Space Phys. 121 397
[7] Ripoll J F, Reeves G D, Loridan V, Denton M, Santolik O, Kurth W S, Kletzing C A, Turner D L, Henderson M G, Ukhorskiy A Y 2016 Geophys. Res. Lett. 43 5616
[8] Thorne R M, Li W, Ni B, Ma Q, Bortnik J, Baker D N, Spence H E, Reeves G D, Henderson M G, Kletzing C A, Kurth W S, Hospodarsky G B, Turener D, Angelopoulos V 2013 Geophys. Res. Lett. 40 3507
[9] Ni B, Bortnik J, Thorne R M, Ma Q, Chen L 2013 J. Geophys. Res. Space Phys. 118 7740
[10] Thorne R M, Church S R, Gorney D J 1979 J. Geophys. Res. 84 5241
[11] Bortnik J, Thorne R M, Meredith N P 2008 Nature 452 62
[12] Bortnik J, Li W, Thorne R M, Angelopouslos V, Cully C, Bonnell J, Contel O L, Roux A 2009 Science 324 775
[13] Chen L, Bortnik J, Li W, Thorne R M, Horne R B 2012 J. Geophys. Res. A 117 05201
[14] Chen L, Bortnik J, Li W, Thorne R M, Horne R B 2012 J. Geophys. Res. A 117 05202
[15] Tsurutani B T, Falkowski B J, Pickett J S, Santolik O, Lakhina G S 2015 J. Geophys. Res. Space Phys. 120 414
[16] Li W, Thorne R M, Bortnik J, Reeves G D, Kletzing C A, Kurth W S, Hospodarsky G B, Spence H E, Blake J B, Fennell J F, Claudepierre S G, Wygant J R, Thaller S A 2013 Geophys. Res. Lett. 40 3798
[17] Ni B, Li W, Thorne R M, Jacob B, Ma Q, Chen L, Kletzing C A, Kurth W S, Hospodarsky G B, Reeves G D, Spence H E, Blake J B, Fennell J F, Claudepierre S G 2014 Geophys. Res. Lett. 41 1854
[18] Li W, Thorne R M, Bortnik J, Kletzing C A, Kurth W S, Hospodarsky G B, Nishimura Y 2015 J. Geophys. Res. Space Phys. 120 3394
[19] Spasojevic M, Shprits Y Y, Orlova K 2015 J. Geophys. Res. Space Phys. 120 10370
[20] Mauk B H, Fox N J, Kanekal S G, Kessel R L, Sibeck D G, Ukhorskiy A 2013 Space Sci. Rev. 179 3
[21] Kletzing C A 2013 Space Sci. Rev. 179 127
[22] Santolík O, Parrot M, Lefeuvre F 2003 Radio Sci. 38 1010
[23] Kurth W S, de Pascuale S, Faden J B, Kletzing C A, Hospodarsky G B, Thaller S, Wygant J R 2015 J. Geophys. Res. Space Phys. 120 904
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