Voyager 2 Hourly Averaged Plasma Data

The plasma investigation made use of two Faraday-cup detectors, one pointed along the earth-spacecraft line and one at right angles to this line. The earth-pointing detector determined the macroscopic properties of the plasma ions, obtaining accurate values of their velocity, density, and pressure. Three sequential energy scans were employed with (delta E)/E equal to 20, 7.2, and 1.8%, allowing a coverage from subsonic to highly supersonic flow. The side-looking Faraday cup measured electrons in the energy range from 5 eV to 1 keV. The plasma parameters are obtained by finding the best fit of a convected isotropic Maxwellian distribution to the data. One sigma errors are typically less than 0.5% in the speed and VR, less than 5% for the density and thermal speed, and vary greatly for VT and VN. Sampling times range from 12 to 192 sec., with sampling generally more frequent early in the mission. One hour averages were produced from these samples. The velocity components are given in the RTN coordinate system, where R is radially outward, T is in a plane parallel to the solar equatorial plane and positive in the direction of solar rotation, and N completes a right-handed system.

本次等离子体探测采用两台法拉第杯（Faraday-cup）探测器，一台沿地球-航天器连线指向，另一台与该连线呈直角布置。指向地球的探测器用于测定等离子体离子的宏观特性，可精准获取其速度、密度与压强的数值。本次探测采用三次连续能量扫描，其(ΔE)/E分别为20%、7.2%与1.8%，覆盖了从亚声速到高超声速的流场范围。侧视法拉第杯用于测量能量区间为5 eV至1 keV的电子。等离子体参数通过将对流各向同性麦克斯韦（Maxwellian）分布与实测数据进行最优拟合得到。速度与VR分量的单σ误差通常小于0.5%，密度与热速度的误差小于5%，而VT与VN分量的误差则存在较大波动。采样时长区间为12秒至192秒，任务初期的采样频率通常更高。基于上述采样数据可生成1小时的平均观测结果。速度分量采用RTN坐标系表示，其中R轴沿径向向外，T轴位于平行于太阳赤道平面的平面内，正方向与太阳自转方向一致，N轴与二者构成右手坐标系。