Inflow direction of interstellar neutrals deduced from pickup ion measurements at 1 AU
Inflow direction of interstellar neutrals deduced from pickup ion measurements at 1 AU
复制标题
DOI：
10.1029/2012ja017746
复制
发表时间：
2012-09
影响因子：
--
通讯作者：
C. Drews;L. Berger;R. Wimmer–Schweingruber;P. Bochsler;A. Galvin;B. Klecker;E. Möbius
中科院分区：
文献类型：
--
作者：
C. Drews;L. Berger;R. Wimmer–Schweingruber;P. Bochsler;A. Galvin;B. Klecker;E. Möbius
对日球层内星际拾取离子的观测提供了一种间接获取周围星际介质信息的方法。所谓的拾取离子聚焦锥和拾取离子新月，在太阳的逆风面和逆风面表现出两种过剩形式，显示出星际中性物质相关的纵向分布的印记，它们都被认为是沿着星际介质的流入矢量排列的。通过确定它们的纵向位置，我们可以给出星际物质流入方向λISM的精确值。为此，我们利用日地关系观测任务（STEREO）上的等离子体和超热离子组成仪（PLASTIC）对星际拾取离子进行了历元分析，并能够在1天文单位的黄道平面上原位揭示星际He+， O+和Ne+拾取离子的纵向分布。先前通过Ulysses/GAS （λ = 75.4°±0.5°）、Prognoz 6 （λ = 74.5°±1°）和ACE/SWICS （λ = 74.43°±0.33°）获得的黄道经度星际物质流入方向的接受值目前正在争论中，特别是考虑到星际边界探索者（IBEX）任务最近的结果显示星际中性氦的流入方向为λ = 79°+ 3.0°（−3.5°）。在STEREO A上用PLASTIC收集了四年的数据，提供了足够的统计数据，不仅可以得到星际氦的流入方向值（λCone = 77.4°±1.9°，λCrescent = 80.4°±5.4°，分别由He+聚焦锥和新月的分析得出），还可以得到星际氖的流入方向值（λCone = 77.4°±5.0°，λCrescent = 79.7°±2.6°）和氧的流入方向值（λCrescent = 78.9°±3.1°）。虽然我们的He+， O+和Ne+的值与ACE， Ulysses和Prognoz 6的结果一致，但考虑到统计和系统的不确定性（除了λNe，Crescent），它们比之前接受的74.99±0.55°的值系统地大，并且与IBEX的值显示出更好的一致性。
[1] Observations of interstellar pickup ions inside the heliosphere provide an indirect method to access information on the surrounding interstellar medium. The so-called pickup ion focusing cone and pickup ion crescent, which show an imprint of the related longitudinal distribution of interstellar neutrals in form of two overabundances on the down- and upwind side of the sun, are both believed to be aligned along the inflow vector of the interstellar medium. By finding their longitudinal positions, we can give an accurate value for the inflow direction λISM of interstellar matter. For that we performed an epoch analysis of interstellar pickup ions measured by the PLAsma and SupraThermal Ion Composition instrument (PLASTIC) on the Solar TErrestrial RElations Observatory mission (STEREO) and were able to reveal in situ the longitudinal distribution of interstellar He+, O+, and Ne+ pickup ions in the ecliptic plane at 1 AU. The previously accepted values for the inflow direction of interstellar matter in ecliptic longitude, as obtained with Ulysses/GAS (λ = 75.4° ± 0.5°), Prognoz 6 (λ = 74.5° ± 1°), and ACE/SWICS (λ = 74.43° ± 0.33°), are currently debated, especially in view of recent results from the Interstellar Boundary Explorer (IBEX) mission that show an inflow direction of interstellar neutral helium of λ = 79° + 3.0°(−3.5°). Four years of data collected with PLASTIC aboard STEREO A provided statistics sufficient not only to obtain values for the inflow direction of interstellar helium (λCone = 77.4° ± 1.9° and λCrescent = 80.4° ± 5.4°, deduced from an analysis of the He+ focusing cone and crescent, respectively) but also to derive values for the inflow direction of interstellar neon (λCone = 77.4° ± 5.0° and λCrescent = 79.7° ± 2.6°) and oxygen (λCrescent = 78.9° ± 3.1°). Although our values for He+, O+, and Ne+ are consistent with results from ACE, Ulysses, and Prognoz 6, considering the statistical and systematic uncertainties (except λNe,Crescent), they are systematically larger than the previously accepted values of 74.99 ± 0.55° and show a better agreement with the values from IBEX.