IMAGE/LENA Observations of Neutral Atoms from the Solar Wind
IMAGE/LENA Observations of Neutral Atoms from the Solar Wind
复制标题
IMAGE/LENA 对太阳风中性原子的观测
DOI：
10.1029/2000ja000382
复制
发表时间：
2001
影响因子：
3.1
通讯作者：
M. Collier
中科院分区：
文献类型：
--
作者：
M. Collier
我们报告了用磁层-极光全球探测（IMAGE）航天器上的低能中性原子（LENA）成像仪对地球附近太阳风中性原子的观测。这台仪器被设计成能够观察太阳的方向。在太阳方向上氢计数率的增强与太阳紫外线发射或过热离子无关，并推断是由太阳风中的中性粒子引起的。即使太阳不在LENA的90°视场范围内，LENA也会从最接近太阳的方向观察这些粒子。模拟结果表明，这些中性物质是太阳风离子在磁鞘中的冲击波后流中与外逸层中性氢原子交换电荷的结果。根据模拟结果和飞行时间光谱中转换面溅射的氧离子的观测，推断其能量超过300 eV，与太阳风的能量一致。此外，溅射的氧丰度跟踪太阳风的速度，即使当图像在磁层深处。这些结果表明，低能中性原子成像提供了从磁层内部直接监测太阳风在磁鞘中的流动的能力，因为渗透磁层的太阳风产生了连续和显著的中性原子通量。
We report observations of neutral atoms from the solar wind in the Earth's vicinity with the low-energy neutral atom (LENA) imager on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) spacecraft. This instrument was designed to be capable of looking at and in the direction of the Sun. Enhancements in the hydrogen count rate in the solar direction are not correlated with either solar ultraviolet emission or suprathermal ions and are deduced to be due to neutral particles from the solar wind. LENA observes these particles from the direction closest to that of the Sun even when the Sun is not directly in LENA's 90° field of view. Simulations show that these neutrals are the result of solar wind ions charge exchanging with exospheric neutral hydrogen atoms in the postshock flow of the solar wind in the magnetosheath. Their energy is inferred to exceed 300 eV, consistent with solar wind energies, based on simulation results and on the observation of oxygen ions, sputtered from the conversion surface in the time-of-flight spectra. In addition, the sputtered oxygen abundance tracks the solar wind speed, even when IMAGE is deep inside the magnetosphere. These results show that low-energy neutral atom imaging provides the capability to directly monitor the solar wind flow in the magnetosheath from inside the magnetosphere because there is a continuous and significant flux of neutral atoms originating from the solar wind that permeates the magnetosphere.