First comparison of composite 0.52-55 keV ENA spectra observed by IBEX and Cassini/INCA with simulated ENAs inferred by proton hybrid simulations downstream of the termination shock

理解IBEX带状结构：基于无散射极限下拾取质子输运的动力学模型

Understanding the IBEX ribbon using the kinetic model of pickup proton transport in a scatter-free limit

本文提出动力学模型模拟IBEX带状结构，基于无散射极限拾取质子输运，考虑IHS的ENA，定性再现观测并在低日纬定量一致，高日纬低估归因于忽略太阳风非稳态。

Variations in the pickup ion density structure in response to the growth of the Kelvin--Helmholtz instability along the heliopause

Features of the response of pickup ions (PUIs) to the Kelvin--Helmholtz instability (KHI) on the heliopause (HP) are examined by means of two-dimensional hybrid simulations. We assume the supersonic neutral solar wind as the source of PUIs gyrating about the magnetic field in the outer heliosheath. These PUIs become energetic neutral atoms (ENAs) via charge exchange with interstellar hydrogen, and a portion of these ENAs are detected by spacecraft such as the Interstellar Boundary Explorer (IBEX}. To evaluate the possibility of identifying the KHI on HP from ENA observations, we assume that an…

An empirical model of Energetic Neutral Atom imaging of the heliosphere and its implications for future heliospheric missions at great heliocentric distances

Several concepts for heliospheric missions operating at heliocentric distances far beyond Earth orbit are currently investigated by the scientific community. The mission concept of the Interstellar Probe (McNutt et al. 2018), e.g., aims at reaching a distance of 1000 au away from the Sun within this century. This would allow the coming generation to obtain a global view of our heliosphere from an outside vantage point by measuring the Energetic Neutral Atoms (ENAs) originating from the various plasma regions. It would also allow for direct sampling of unperturbed interstellar medium, and for m…

Asymmetries in Mars' Exosphere: Implications for X-ray and ENA Imaging

Observations and simulations show that Mars' atmosphere has large seasonal variations. Total atmospheric density can have an order of magnitude latitudinal variation at exobase heights. By numerical simulations we show that these latitude variations in exobase parameters induce asymmetries in the hydrogen exosphere that propagate to large distances from the planet. We show that these asymmetries in the exosphere produce asymmetries in the fluxes of energetic neutral atoms (ENAs) and soft X-rays produced by charge exchange between the solar wind and exospheric hydrogen. This could be an explana…

日球层中5 eV至500 keV能量中性氢原子的产生与损失过程

Production and Loss Processes of Hydrogen Energetic Neutral Atoms in the Heliosphere from 5 eV to 500 keV

本研究考察了日球层中5 eV至500 keV宽能量范围内能量中性原子的多种产生与损失过程，发现除质子-氢电荷交换外，高能ENA还显著来自与氦原子的电荷交换，且高能下剥离电离取代电荷交换成为主要损失机制。

The Sub-keV Atom Reflecting Analyzer (SARA) Experiment Aboard Chandrayaan-1 Mission: Instrument and Observations

SARA experiment aboard the first Indian lunar mission Chandrayaan-1 had the objective to explore the solar wind-lunar interaction using energetic neutral atoms (ENA) from the lunar surface as diagnostic tool. SARA consisted of an ENA imaging mass analyzer CENA (Chandrayaan-1 Energetic Neutral Analyzer) and an ion mass analyser SWIM (Solar Wind Monitor), along with a digital processing unit (DPU) which commands and controls the sensors and provides the interface to the spacecraft. Both sensors have provided excellent observational data. CENA has observed ENAs from the lunar surface and found th…

The downwind hemisphere of the heliosphere: Eight years of IBEX-Lo observations

We present a comprehensive study of energetic neutral atoms (ENAs) of 10 eV to 2.5 keV from the downwind hemisphere of the heliosphere. These ENAs are believed to originate mostly from pickup protons and solar wind protons in the inner heliosheath. This study includes all low-energy observations made with the Interstellar Boundary Explorer over the first 8 years. Since the protons around 0.1 keV dominate the plasma pressure in the inner heliosheath in downwind direction, these ENA observations offer the unique opportunity to constrain the plasma properties and dimensions of the heliosheath whe…

The Confinement of the Heliosheath Plasma by the Solar Magnetic Field as Revealed by Energetic Neutral Atom Simulations

Traditionally, the solar magnetic field has been considered to have a negligible effect in the outer regions of the heliosphere. Recent works have shown that the solar magnetic field may play a crucial role in collimating the plasma in the heliosheath. Interstellar Boundary Explorer (IBEX) observations of the heliotail indicated a latitudinal structure varying with energy in the energetic neutral atom (ENA) fluxes. At energies ~1 keV, the ENA fluxes show an enhancement at low latitudes and a deficit of ENAs near the poles. At energies >2.7 keV, ENA fluxes had a deficit within low latitudes, an…

Seven Years of Imaging the Global Heliosphere with IBEX

The Interstellar Boundary Explorer (IBEX) has now operated in space for 7 years and returned nearly continuous observations that have led to scientific discoveries and reshaped our entire understanding of the outer heliosphere and its interaction with the local interstellar medium. Here we extend prior work, adding the 2014-2015 data for the first time, and examine, validate, initially analyze, and provide a complete 7-year set of Energetic Neutral Atom (ENA) observations from ~0.1 to 6 keV. The data, maps, and documentation provided here represent the 10th major release of IBEX data and inclu…

Plasma pressures in the heliosheath from Cassini ENA and Voyager 2 measurements: Validation by the Voyager 2 heliopause crossing

We report "ground truth", 28-3500 keV in-situ ion and 5.2-55 keV remotely sensed ENA measurements from Voyager 2/Low Energy Charged Particle (LECP) detector and Cassini/Ion and Neutral Camera (INCA), respectively, that assess the components of the ion pressure in the heliosheath. In this process, we predict an interstellar neutral hydrogen density of ~0.12 cm-3 and an interstellar magnetic field strength of ~0.5 nT upstream of the heliopause in the direction of V2, i.e. consistent with the measured magnetic field and neutral density measurements at Voyager 1 from August 2012, when the spacecra…

内日鞘层中的绝热能量变化：它如何影响拾取质子的分布与高能中性原子通量？

Adiabatic energy change in the inner heliosheath: How does it affect the distribution of pickup protons and energetic neutral atom fluxes?

本研究聚焦内日鞘层中常被忽略的绝热能量变化过程，借助结合太阳风-星际介质相互作用动力学-磁流体模拟结果的动力学模型，量化其对拾取质子和高能中性原子分布的影响，发现其可显著提升ENA通量，为解释观测与模拟的差异提供了新思路。

IBEX观测到的高能中性原子通量分量的球谐表示

Spherical Harmonic Representation of Energetic Neutral Atom Flux Components Observed by IBEX

本文提出用球谐函数表示IBEX全天ENA通量图，从而在不依赖像素网格的情况下分离GDF与IBEX ribbon，并据此分析二者在太阳周期中的演化及空间尺度差异。