May 2022, Volume 7 Issue 6
    

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  • Topic：Exploring the Solar System Boundary
    Scientific Objectives for the Exploration of the Boundary of Solar System
    WANG Chi, LI Hui, GUO Xiaocheng, XU Xinfeng
    2020, 7(6): 517-524,535. https://doi.org/10.15982/j.issn.2096-9287.2020.20200058
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    The edge of Solar system is the outermost fence of the heliosphere that protects the homeland of mankind. In recent years，Voyager 1 and Voyager 2 have reached the edge，leaving some major scientific mysteries in a unresolved state because of the limits of the payload function. Therefore，a specific mission for the edge of Solar system contains huge scientific value. Here we introduce the definition of the edge of Solar system and the main detection elements，summarizes the current status of the missions for the outer heliosphere，including the scientific targets and the scientific payload for the missions. Some major scientific issues in heliophysics，interstellar space physics and Solar system evolution，have been presented，as well as the prospects for the scientific goals for our future interstellar mission.
  • Topic：Exploring the Solar System Boundary
    Research Progress of Thermoelectric Materials and Devices for Radioisotope Thermoelectric Generators
    BAI Shengqiang, LIAO Jingchen, XIA Xugui, CHEN Lidong
    2020, 7(6): 525-535. https://doi.org/10.15982/j.issn.2096-9287.2020.20200062
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    Radioisotope Thermoelectric Generator (RTG) have been used in deep space exploration since 1960s. In this paper, the main characteristics and key technologies of the RTG battery are reviewed，and the current developments of high efficiency thermoelectric conversion materials and devices are introduced. Considering the requirements of the deep space exploration， the developments thoughts of the thermoelectric conversion and devices technologies for RTG are put forward.
  • Topic：Exploring the Solar System Boundary
    Target Selection of Multiple Gravity-Assist Trajectories for Solar Boundary Exploration
    CAO Zhiyuan, LI Xiangyu, QIAO Dong
    2020, 7(6): 536-544. https://doi.org/10.15982/j.issn.2096-9287.2020.20200068
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    Solar system boundary exploration will enhance our understanding of the formation and evolution of the Solar system，which is an important issue of future deep space exploration. As the boundary is far from Earth，the energy needed in the exploration is huge. Thus，gravity-assist technique is essential to carry out Solar system boundary exploration mission. This paper aims at multiple gravity-assist transfer design in Solar system boundary exploration missions. First，processing method of goals and constraints in Solar system boundary exploration are studied. And a progressive nested-loop optimization method combining two different kinds of multiple gravity-assist dynamics is provide，as well as the detailed steps. At last，taking the nose and the tail of Solar system boundary for example，the optimal fly-by sequences are provided，proofing the validity of the method. The simulations demonstrates that the optimal multiple gravity –assists trajectories is Earth-Venus-Earth-Earth-Jupiter-Saturn- nose of Solar system，and the optimal multiple gravity –assists trajectories is Earth-Venus-Earth-Earth-Neptune-tail of Solar system. The research will provide the reference for the target selection and mission planning for future Solar system exploration in China.
  • Topic：Exploring the Solar System Boundary
    Scientific Payloads Proposal for Chinese Solar System Boundary Exploration Mission
    ZHANG Aibing, LI Hui, KONG Linggao, ZHANG Shenyi, FU Liping, XUE Hongbo, YANG Jianfeng, HE Zhiping, WANG Linghua, LI Yanwei
    2020, 7(6): 545-553. https://doi.org/10.15982/j.issn.2096-9287.2020.20200060
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    In view of the scientific objectives of Chinese Solar System Boundary Exploration Mission which is being under discussion，10 scientific payloads for field，particle and optics are proposed. The payloads performance requirements and engineering requirements such as mass and power are given. The high performance and tight schedule are both taken into consideration for the payloads schemes taking the technical advantages from several Chinese institutions. The development of payloads has good technical basis and inheritability. For this super far away exploration，preliminary solutions to common key technologies such as miniaturization and low power，high reliability and long lifetime，science data processing and compression for payloads are given. The payloads are mainly developed domestically，well international cooperation according to the previous successful collaboration is to play a bigger role.
  • Topic：Exploring the Solar System Boundary
    From Earth’s Magnetospheres to the Outer Heliosphere & Beyond
    ZONG Qiugang, REN Jie, HE Jiansen, WANG Linghua
    2020, 7(6): 554-559. https://doi.org/10.15982/j.issn.2096-9287.2020.20200063
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    In the Solar system，there are many astronomical objects owning the magnetosphere structure generated by the interaction between their intrinsic magnetic field and Solar wind，including Mercury，Earth，Jupiter，Saturn，Uranus，Neptune and some of their satellites. Heliosphere is the Sun’s magnetosphere，which is filled with Solar wind and surrounded by the interstellar medium. According to the data obtained by the existing detectors，the interaction between the Solar wind and the interstellar medium，the distribution of energy neutral atoms and the relative spatial density changes of picked-up particles，the formation mechanism of abnormal cosmic rays，and possible changes in the shape of the heliosphere are introduced. The marginal exploration plan of China’s Solar system exploration mission is given. Two detectors in opposite directions are designed. One will fly towards the nose tip of the heliosphere to conduct comprehensive exploration of the marginal Solar system and its adjacent space; and the other will fly in the opposite direction to fill the gap at the tail boundary of the spherical layer. The knowledge of the space environment of the heliosphere can provide reference for the design of the probe.
  • Topic：Exploring the Solar System Boundary
    One-Dimentional Numerical MHD Simulation of the Shock Events in the Outer Heliosphere
    GUO Xiaocheng, ZHOU Yucheng, WANG Chi, LI Hui
    2020, 7(6): 560-566,604. https://doi.org/10.15982/j.issn.2096-9287.2020.20200059
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    Voyager 1 occasionally detected the sudden jumps of the interstellar magnetic field strength since its heliopause crossing in August，2012. These events are believed to be the interstellar shocks，and associated with the product of the interaction between the large-scale solar wind structures and the heliopause. In this paper, this possibility is examined by means of a two-fluid magnetohydrodynamics（MHD）simulation consisting of the solar wind plasma and the interstellar neutrals. Three different solar wind observations from OMNI，STEREO A and B at a heliocentric distance of 1 au during the year 2010－2017 are used as input to the simulation，and the evolution of solar wind in the outer heliosphere is investigated after the charge-exchange between solar wind and interstellar neutrals.The numerical results are compared with the observation from the two Voyagers，showing that the shock events in the interstellar medium observed by Voyager 1 have direct linkage with the pressure pulses in the inner heliosheath detected by Voyager 2.
  • Topic：Exploring the Solar System Boundary
    Detection of Energetic Particles in the Outer Heliosphere and its Boundaries
    WANG Linghua, ZONG Qiugang, REN Jie
    2020, 7(6): 567-573. https://doi.org/10.15982/j.issn.2096-9287.2020.20200061
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    The origin，acceleration and propagation of energy particles in the heliosphere/solar system has always been one of key frontier topics in physics and space physics. An exploration of the outer heliosphere and local interstellar medium will provide crucial information to investigate this frontier topic. In its boundaries，the energy particles originating from the heliosphere are mainly divided into two groups: solar wind suprathermal particles and energy neutral atoms（ENAs）. These energy particles can strongly mediate the morphology and dynamics of the outer boundaries of heliosphere. However，key observations is still lacking，suah as in-situ detection of solar wind suprathermal particles and ENA imaging in the outer boundaries of heliosphere. Based on the high-resolution detection of solar wind suprathermal particles and high-resolution ENA imaging of the Earth’s magnetosphere by the STE instrument on the STEREO satellite，a new-generation semiconductor detectors with low energy thresholds is proposed，combined with the RHESSI’s imaging concept to achieve the ENA imaging and in situ observations of suprathermal particles with high time，energy and angle resolutions in the outer heliosphere. These observations will provide key information to understand the dynamic evolution of the interaction between the heliopshere and local interstellar medium，as well as the origin，acceleration，and propagation of energy particles in the heliosphere.
  • Topic：Exploring the Solar System Boundary
    Broad Energy-Band Ions in the Ourter Heliosphere and Their Coupling with Turbulence
    HE Jiansen, LIN Rong, CUI Bo, WANG Linghua, ZONG Qiugang
    2020, 7(6): 574-583. https://doi.org/10.15982/j.issn.2096-9287.2020.20200064
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    This paper focuses on the theme of “solar wind in the heliosphere and its interaction with the invading interstellar wind”，and discusses it from three aspects：current cognition，frontier problems，and exploration suggestions. The ions in the heliosphere include primary solar wind ions，pick-up ions converted partially from interstellar wind，and super-thermal ions. Among them，pick-up ions and super-thermal ions have their contribution from the local interstellar medium flow. The deep-space spacecraft have detected the prevalence of two modes in the heliosphere：the inner boundary of the heliosphere，the solar wind，the interplanetary turbulence，and the energy spectrum of the super-thermal ions. There are three types of cutting-edge issues：① the territory never reached，that is，the tail of the heliosphere in the ecliptic plane and the outer heliosphere at high latitudes；② the territory that has been reached，but some key variables have not been detected，such as the picked-up ions in the outer heliosphere；③ the territory and variables that have been reached and detected，but the formation mechanism is unknown，such as the power-law spectrum and dual-mode of the super-thermal ions. To address these problems，we put forward the following suggestions：① to design different flight paths and detect in different directions；② to carry ion spectra instruments with wide energy band，covering the primary solar wind plasma，the pick-up ions，and the super-thermal ions；③ to carry high sensitivity magnetometer to measure the compressible magnetic turbulence in the outer heliosphere.
  • Topic：Exploring the Solar System Boundary
    The Exploration of Neptune：A Noble Gas and Volatile Perspective
    Thomas SMITH, ?Huaiyu HE, Ranran LIU
    2020, 7(6): 584-604. https://doi.org/10.15982/j.issn.2096-9287.2020.20200057
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    Most of the probes visiting other bodies in our Solar system only focused，due to technical shortcomings，on the exploration of the closer planets and planetary bodies and/or their natural satellites，i.e. Mercury，Venus，the Moon，Mars，and Jupiter，the comet 67P/Churyumov-Gerasimenko，or the 25143 Itokawa near-Earth asteroid. At present time，no specific missions to one of the two ice giants of our Solar System，Uranus and Neptune，has been planned. Our knowledge of Uranus and Neptune is，therefore，so far restricted to the data which have been collected during the flyby of the Voyager 2 mission，in January 1986 and August 1989，respectively，and to observations with the Hubble Space Telescope and the Keck Telescope. Ice giants are，in our galaxy，thought to be much more abundant than gas giant planets such as Jupiter or Saturn，therefore a better knowledge of ice giants is essential for our understanding of exoplanet candidates. Among other scientific goals，the atmospheric composition of ice giants，with a particular emphasis on their noble gas and volatile distribution，is of great significance，and can constrain models about their formation and evolution. In this review，we report，in a first part，the volatile inventories and the measurements in the planetary bodies of our Solar System；in a second part，we will discuss the scientific background about the concentration，distribution，and evolution of noble gases and volatiles in Uranus and Neptune，and finally describe a possible scenario of a future interstellar probe visiting one of the two ice giants as well as the feasibility of such a space mission，in term of payloads selection and mission profile. We will as well briefly evoke the possibility of using an ion trap mass spectrometer，a potential payload for the ice giant atmospheric exploration，onboard a Chinese interstellar mission to the outer Solar system.