标题： IBEX-Lo 对星际中性氦原子的相对飞行中响应 显示英文标题

标题： Relative In-flight Response of IBEX-Lo to Interstellar Neutral Helium Atoms

摘要： IBEX-Lo仪器是星际边界探测器（IBEX）任务的一部分，用于测量星际中性（ISN）氦原子。 通过氦原子从IBEX-Lo转换表面上溅射出的负氢（H$^-$）离子来检测氦原子。 由ISN氦原子溅射的离子的能量谱较宽，并与IBEX-Lo静电分析器（ESA）的四个最低能量步长重叠。 因此，氦原子的能量响应函数并不对应于标称能量步长的传输特性。 此外，实验室校准不完整，因为很难产生预期用于ISN氦原子的窄能量中性原子束。 在这里，我们分析ESA步骤1-4中的ISN氦观测数据，以推导IBEX-Lo对氦原子的相对在轨响应。 我们将观察到的计数率比值与使用华沙测试粒子模型（WTPM）估算的平均ISN氦原子能量进行比较。 WTPM利用全球日球层模型计算电荷交换增益和损失，以估计次级ISN氦原子种群。 我们发现，模拟的ISN氦原子平均能量，与其模拟通量不同，对非常局部的星际介质参数不太敏感。 获得的相对响应补充了实验室校准，并使得对ISN氦信号的更详细定量研究成为可能。 我们应用于IBEX-Lo观测的类似程序可用于补充即将开展的星际测绘与加速探测器（IMAP）任务上的下一代IMAP-Lo仪器的实验室校准。 显示英文摘要

摘要： The IBEX-Lo instrument on the Interstellar Boundary Explorer (IBEX) mission measures interstellar neutral (ISN) helium atoms. The detection of helium atoms is made through negative hydrogen (H$^-$) ions sputtered by the helium atoms from the IBEX-Lo conversion surface. The energy spectrum of ions sputtered by ISN helium atoms is broad and overlaps the four lowest IBEX-Lo electrostatic analyzer (ESA) steps. Consequently, the energy response function for helium atoms does not correspond to the nominal energy step transmission. Moreover, laboratory calibration is incomplete because it is difficult to produce narrow-energy neutral atom beams that are expected for ISN helium atoms. Here, we analyze the ISN helium observations in ESA steps 1-4 to derive the relative in-flight response of IBEX-Lo to helium atoms. We compare the ratios of the observed count rates as a function of the mean ISN helium atom energy estimated using the Warsaw Test Particle Model (WTPM). The WTPM uses a global heliosphere model to calculate charge exchange gains and losses to estimate the secondary ISN helium population. We find that the modeled mean energies of ISN helium atoms, unlike their modeled fluxes, are not very sensitive to the very local interstellar medium parameters. The obtained relative responses supplement the laboratory calibration and enable more detailed quantitative studies of the ISN helium signal. A similar procedure that we applied to the IBEX-Lo observations may be used to complement laboratory calibration of the next-generation IMAP-Lo instrument on the Interstellar Mapping and Acceleration Probe (IMAP) mission.