Simulating coronas in color.
Simulating coronas in color.
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模拟颜色的电晕。
DOI：
10.1364/ao.42.000497
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发表时间：
2003
期刊：
影响因子：
1.9
通讯作者：
J. Lock
中科院分区：
文献类型：
--
作者：
S. Gedzelman;J. Lock
利用米氏散射理论，通过嵌入瑞利散射大气的有限光学厚度的云，小液滴对日冕进行了彩色模拟。影响日冕颜色、可见度和光环数量的主要因素是液滴的大小、尺寸分布的宽度和云光学厚度。当液滴半径小于约6微米时，日冕和虹彩的颜色序列会发生变化。当半径增加到大约3.5微米时，新的色带出现在日冕的中心，并随着它们向外移动而逐渐消失。当半径继续增加到大约6微米时，越来越多的内环按照经典衍射理论描述的方式固定下来，而外环继续向外迁移。波浪云或波纹云段产生最明亮和最生动的多环日冕和彩虹色，因为它们沿阳光的整体水滴大小分布比对流云或层状云窄得多。日冕的可见性和背景天空的外观随云光学深度的变化而变化。首先，当τ值约为0.001时，日冕在蓝天中以白色光环的形式出现。颜色纯度在0.05 <或= tau <或= 0.5范围内迅速增加到几乎平坦的最大值，然后下降，因此当tau >或= 4时，日冕几乎完全被明亮的灰色背景所淹没。
Coronas are simulated in color by use of the Mie scattering theory of light by small droplets through clouds of finite optical thickness embedded in a Rayleigh scattering atmosphere. The primary factors that affect color, visibility, and number of rings of coronas are droplet size, width of the size distribution, and cloud optical thickness. The color sequence of coronas and iridescence varies when the droplet radius is smaller than approximately 6-microm. As radius increases to approximately 3.5 microm, new color bands appear at the center of the corona and fade as they move outward. As the radius continues to increase to approximately 6 microm, successively more inner rings become fixed in the manner described by classical diffraction theory, while outer rings continue their outward migration. Wave clouds or rippled cloud segments produce the brightest and most vivid multiple ringed coronas and iridescence because their integrated dropsize distributions along sunbeams are much narrower than in convective or stratiform clouds. The visibility of coronas and the appearance of the background sky vary with cloud optical depth tau. First the corona becomes visible as a white aureole in a blue sky when tau approximately 0.001. Color purity then rapidly increases to an almost flat maximum in the range 0.05 < or = tau < or = 0.5 and then decreases, so coronas are almost completely washed out by a bright gray background when tau > or = 4.