Evolving outer heliosphere: Large-scale stability and time variations observed by the Interstellar Boundary Explorer
Evolving outer heliosphere: Large-scale stability and time variations observed by the Interstellar Boundary Explorer
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不断演化的外日光层：星际边界探测器观测到的大规模稳定性和时间变化
DOI：
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发表时间：
2010
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通讯作者：
N. Schwadron
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作者：
D. McComas;M. Bzowski;P. Frisch;G. Crew;M. Dayeh;R. DeMajistre;H. Funsten;S. Fuselier;M. Gruntman;P. Janzen;M. Kubiak;G. Livadiotis;E. Möbius;D. Reisenfeld;N. Schwadron
来自星际边界探测器（IBEX）的第一张高能中性原子（ENAs）的全天图显示出平滑变化的、全球分布的通量和一个狭窄的“带状”增强的ENA发射。在这项研究中，我们将第二组天空图与第一组进行比较，以评估在6个月的时间内，每个部分天空的视图之间的时间变化的可能性。虽然两组地图之间的大尺度结构总体上是稳定的，但有一些显著的变化表明，日球层也在这个短时间尺度上发生了演变。特别是，我们发现：(1)与第一组相比，第二组图中来自外日层的总ENA排放量似乎略低，(2)在0.5至6 keV的能量范围内，第二组图中南北两极的ENA排放量都明显低于第一组（~ 10-15%）。(3)在第一张地图中，条带北部的“结”不太亮，似乎在第二组地图获得时已经扩散和/或消散。最后，该带最南端通量的空间分布略有变化，可能平均向赤道方向移动了6°（一个地图像素）。观测到的大尺度稳定性和这些在较小空间尺度上的系统变化提供了关于外层日球层及其与星系的整体相互作用的重要新信息，并有助于了解产生IBEX带的可能机制。
[1] The first all-sky maps of Energetic Neutral Atoms (ENAs) from the Interstellar Boundary Explorer (IBEX) exhibited smoothly varying, globally distributed flux and a narrow “ribbon” of enhanced ENA emissions. In this study we compare the second set of sky maps to the first in order to assess the possibility of temporal changes over the 6 months between views of each portion of the sky. While the large-scale structure is generally stable between the two sets of maps, there are some remarkable changes that show that the heliosphere is also evolving over this short timescale. In particular, we find that (1) the overall ENA emissions coming from the outer heliosphere appear to be slightly lower in the second set of maps compared to the first, (2) both the north and south poles have significantly lower (∼10–15%) ENA emissions in the second set of maps compared to the first across the energy range from 0.5 to 6 keV, and (3) the “knot” in the northern portion of the ribbon in the first maps is less bright and appears to have spread and/or dissipated by the time the second set was acquired. Finally, the spatial distribution of fluxes in the southernmost portion of the ribbon has evolved slightly, perhaps moving as much as 6° (one map pixel) equatorward on average. The observed large-scale stability and these systematic changes at smaller spatial scales provide important new information about the outer heliosphere and its global interaction with the galaxy and help inform possible mechanisms for producing the IBEX ribbon.