arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1902.07294astro-ph.EP
收藏

从3- 37 GHz的VLA图导出木星的氨分布

Jupiter's Ammonia Distribution Derived from VLA Maps at 3--37 GHz

I. de Pater, R. J. Sault, M. H. Wong, L. N. Fletcher, D. DeBoer, B. Butler

摘要:

我们用升级后的卡尔G. Jansky甚大阵列(VLA),2013年12月至2014年12月。de Pater等人(2016)提供了4-17 GHz的初步结果;在本文中,我们提供了3 - 37 GHz频率的完整数据集。主要调查结果如下:(i)北赤道带(NEB)和赤道带(EZ)交界处北纬8.5- 11 $^\circ$的射电热带在所有频率(3- 37 GHz)上都很突出。它的位置与NEB的南纬(北纬7-$^{\circ}$ 17度)重合。(ii)经度模糊图显示了$\lesssim |20^\circ|$纬度上所有频率的带和带。最低亮温出现在4 $^\circ$ N附近的EZ,最高亮温出现在11 $^\circ$ N附近。NEB的明亮部分在纬度范围内增加(向北扩展),频率降低,即,深入大气层。在高分辨率的地图中,有几个带,特别是南半球的带,沿着纬度线并不连续,而是分成小段,好像是由底层波浪造成的。(iii)在每个纬度上获得了与去拖尾光谱的模型拟合。这些数据表明,在深层($P>8-10$条)大气中,NH $_3$丰度(体积混合比$\sim 4 \times 10^{-4}$)较高,在较高的高度由于云的形成而降低(例如,在区域),或动力学与云凝结(带)相结合。在NEB中,氨气被耗尽到至少20巴水平,具有丰富的$1.75 \times 10^{-4}$。(iv)使用整个VLA数据集,我们确认该行星在大气层的上层非常动态,在$P<$ 2- 3 bar,即,在云层形成的高度。[删节]

英文摘要:

We observed Jupiter four times over a full rotation (10 hrs) with the upgraded Karl G. Jansky Very Large Array (VLA) between December 2013 and December 2014. Preliminary results at 4-17 GHz were presented in de Pater et al. (2016); in the present paper we present the full data set at frequencies between 3 and 37 GHz. Major findings are: (i) the radio-hot belt at 8.5--11$^\circ$N latitude, near the interface between the North Equatorial Belt (NEB) and the Equatorial Zone (EZ) is prominent at all frequencies (3--37 GHz). Its location coincides with the southern latitudes of the NEB (7--17$^{\circ}$ N). (ii) Longitude-smeared maps reveal belts and zones at all frequencies at latitudes $\lesssim |20^\circ|$. The lowest brightness temperature is in the EZ near a latitude of 4$^\circ$N, and the NEB has the highest brightness temperature near 11$^\circ$N. The bright part of the NEB increases in latitudinal extent (spreads towards the north) with deceasing frequency, i.e., with depth into the atmosphere. In longitude-resolved maps, several belts, in particular in the southern hemisphere, are not continuous along the latitude line, but broken into small segments as if caused by an underlying wave. (iii) Model fits to longitude-smeared spectra are obtained at each latitude. These show a high NH$_3$ abundance (volume mixing ratio $\sim 4 \times 10^{-4}$) in the deep ($P>8-10$ bar) atmosphere, decreasing at higher altitudes due to cloud formation (e.g., in zones), or dynamics in combination with cloud condensation (belts). In the NEB ammonia gas is depleted down to at least the 20 bar level with an abundance of $1.75 \times 10^{-4}$. (iv) Using the entire VLA dataset, we confirm that the planet is extremely dynamic in the upper layers of the atmosphere, at $P<$2--3 bar, i.e., at the altitudes where clouds form. [Abridged]

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑