A likely detection of a local interplanetary dust cloud passing near the Earth in the AKARI mid-infrared all-sky map
A likely detection of a local interplanetary dust cloud passing near the Earth in the AKARI mid-infrared all-sky map
复制标题
AKARI 中红外全天地图中可能检测到局部行星际尘埃云经过地球附近
DOI：
10.1051/0004-6361/201628954
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发表时间：
2017
影响因子：
6.5
通讯作者：
Onaka T.
中科院分区：
文献类型：
--
作者：
Ishihara D.;Kondo T.;Kaneda H.;Suzuki T.;Nakamichi K.;Takaba S.;Kobayashi H.;Masuda S.;Ootsubo T.;Pyo J.;Onaka T.
我们正在创建AKARI中红外全天空漫反射地图。通过对黄道带发射的前景去除，我们偶然发现了一个明亮的残余分量，其角大小约为50° × 20°，波长为9μm，目的是研究残余分量的来源和物理性质。方法在AKARI中红外全天空图上测量残余分量的表面亮度。结果残余分量仅在2007年1月被显著检测到，尽管在2006年7月和2007年7月观察到了同一区域，这表明它不是由于银河系的排放。我们认为，这可能是一个小的云通过地球附近。通过将观测到的I9 μm/I18μ m的强度比与假设不同尘埃成分和大小的尘埃颗粒在1 Au处热平衡的预期强度比进行比较，我们发现移动云中的尘埃颗粒可能比产生大部分黄道光的典型颗粒小得多。它很可能起源于2007年1月25日发生的太阳日冕物质抛射（CME）。
ContextWe are creating the AKARI mid-infrared all-sky diffuse maps. Through a foreground removal of the zodiacal emission, we serendipitously detected a bright residual component whose angular size is about 50° × 20° at a wavelength of 9μm.AimsWe investigate the origin and the physical properties of the residual component.MethodsWe measured the surface brightness of the residual component in the AKARI mid-infrared all-sky maps.ResultsThe residual component was significantly detected only in 2007 January, even though the same region was observed in 2006 July and 2007 July, which shows that it is not due to the Galactic emission. We suggest that this may be a small cloud passing near the Earth. By comparing the observed intensity ratio ofI9μm/I18μmwith the expected intensity ratio assuming thermal equilibrium of dust grains at 1 AU for various dust compositions and sizes, we find that dust grains in the moving cloud are likely to be much smaller than typical grains that produce the bulk of the zodiacal light.ConclusionsConsidering the observed date and position, it is likely that it originates in the solar coronal mass ejection (CME) which took place on 2007 January 25.