Connor H K, Sibeck D G, Collier M R, Baliukin I I, Branduardi-Raymont G, Brandt P C, Buzulukova N Y, Collado-Vega Y M, Escoubet C P, Fok M-C, Hsieh S-Y, Jung J, Kameda S, Kuntz K D, Porter F S, Sembay S, Sun T, Walsh B M, Zoennchen J H
Geophysical Institute University of Alaska Fairbanks Fairbanks AK USA.
NASA Goddard Space Flight Center Greenbelt MD USA.
J Geophys Res Space Phys. 2021 Mar;126(3):e2020JA028816. doi: 10.1029/2020JA028816. Epub 2021 Mar 9.
The LEXI and SMILE missions will provide soft X-ray images of the Earth's magnetosheath and cusps after their anticipated launch in 2023 and 2024, respectively. The IBEX mission showed the potential of an Energetic Neutral Atom (ENA) instrument to image dayside magnetosheath and cusps, albeit over the long hours required to raster an image with a single pixel imager. Thus, it is timely to discuss the two imaging techniques and relevant science topics. We simulate soft X-ray and low-ENA images that might be observed by a virtual spacecraft during two interesting solar wind scenarios: a southward turning of the interplanetary magnetic field and a sudden enhancement of the solar wind dynamic pressure. We employ the OpenGGCM global magnetohydrodynamics model and a simple exospheric neutral density model for these calculations. Both the magnetosheath and the cusps generate strong soft X-rays and ENA signals that can be used to extract the locations and motions of the bow shock and magnetopause. Magnetopause erosion corresponds closely to the enhancement of dayside reconnection rate obtained from the OpenGGCM model, indicating that images can be used to understand global-scale magnetopause reconnection. When dayside imagers are installed with high-ENA inner-magnetosphere and FUV/UV aurora imagers, we can trace the solar wind energy flow from the bow shock to the magnetosphere and then to the ionosphere in a self-standing manner without relying upon other observatories. Soft X-ray and/or ENA imagers can also unveil the dayside exosphere density structure and its response to space weather.
LEXI和SMILE任务预计分别于2023年和2024年发射，之后将提供地球磁鞘和磁尖的软X射线图像。IBEX任务展示了高能中性原子（ENA）仪器对日间磁鞘和磁尖成像的潜力，尽管使用单像素成像仪绘制一幅图像需要很长时间。因此，适时讨论这两种成像技术及相关科学主题很有必要。我们模拟了虚拟航天器在两种有趣的太阳风情景下可能观测到的软X射线和低能中性原子图像：行星际磁场向南转向以及太阳风动压突然增强。我们使用OpenGGCM全球磁流体动力学模型和一个简单的高层大气中性密度模型进行这些计算。磁鞘和磁尖都会产生强烈的软X射线和ENA信号，可用于确定弓形激波和磁层顶的位置及运动。磁层顶侵蚀与从OpenGGCM模型获得的日间重联率增强密切相关，这表明图像可用于理解全球尺度的磁层顶重联。当在日间安装高能中性原子内磁层成像仪以及FUV/UV极光成像仪时，我们可以独立追踪太阳风能从弓形激波到磁层再到电离层的流动，而无需依赖其他观测站。软X射线和/或ENA成像仪还可以揭示日间高层大气密度结构及其对空间天气的响应。
