On Pitch-Angle Scattering Rates of Interstellar Pickup Ions as Determined by in Situ Measurement of Velocity Distributions
On Pitch-Angle Scattering Rates of Interstellar Pickup Ions as Determined by in Situ Measurement of Velocity Distributions
复制标题
速度分布原位测量确定星际拾取离子的俯仰角散射率
DOI：
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
P. Bochsler
中科院分区：
文献类型：
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作者：
L. Saul;E. Möbius;P. Isenberg;P. Bochsler
新电离的星际原子受到太阳风中电磁力的作用。这些皮卡离子的测量，使控制太阳风等离子体中带电粒子种群的演变的运输过程的研究。SOHO航天器上的CELIAS仪器提供的数据可以测量单电荷氦离子的速度分布。这些意见进行了比较，一个半球模型的俯仰角扩散的预测。为了证明半球模型的合理性，我们在这里证明了一个“共振间隙”，它阻碍了质子被阿尔文波跨半球散射，可以存在于被向外传播的波散射的拾取氦的情况下。我们发现所观察到的氦拾取离子速度分布的形状与半球模型的预测是一致的。发现平行平均自由程随波功率从0.1的值到超过1 Au而变化，在此呈现为平行平均自由程作为磁波功率的函数的第一测量。来自Wind航天器的磁场数据能够与重合磁场波功率进行比较。交叉半球的散射率被发现是单调的和指数依赖于波功率的动态范围内考虑。
Newly ionized interstellar atoms are acted upon by electromagnetic forces in the solar wind. Measurements of these pickup ions enable study of the transport processes controlling the evolution of charged particle populations in solar wind plasma. Data from the CELIAS instruments on board the SOHO spacecraft allow measurement of the velocity distribution of singly charged helium ions. These observations are compared to the predictions of a hemispheric model of pitch-angle diffusion. To justify the use of the hemispheric model we show here that a "resonance gap," which hinders cross-hemispheric scattering of protons by Alfvén waves, can exist for the case of pickup helium scattered by outward-propagating waves. We find that the observed shape of helium pickup ion velocity distributions is consistent with the hemispheric model prediction. The parallel mean free path is found to vary with wave power from values of 0.1 to over 1 AU, here presented as a first measurement of the parallel mean free path as a function of magnetic wave power. Magnetic field data from the Wind spacecraft enable comparison to the coincident magnetic field wave power. The cross-hemispheric scattering rate is found to be monotonic and exponentially dependent on wave power over the dynamic range considered.