Viavattene Giorgio, Murabito Mariarita, Guglielmino Salvatore L, Ermolli Ilaria, Consolini Giuseppe, Giorgi Fabrizio, Jafarzadeh Shahin
INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00078 Monte Porzio Catone, Italy.
INAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95123 Catania, Italy.
Entropy (Basel). 2021 Mar 31;23(4):413. doi: 10.3390/e23040413.
The solar photosphere and the outer layer of the Sun's interior are characterized by convective motions, which display a chaotic and turbulent character. In this work, we evaluated the pseudo-Lyapunov exponents of the overshooting convective motions observed on the Sun's surface by using a method employed in the literature to estimate those exponents, as well as another technique deduced from their definition. We analyzed observations taken with state-of-the-art instruments at ground- and space-based telescopes, and we particularly benefited from the spectro-polarimetric data acquired with the Interferometric Bidimensional Spectrometer, the Crisp Imaging SpectroPolarimeter, and the Helioseismic and Magnetic Imager. Following previous studies in the literature, we computed maps of four quantities which were representative of the physical properties of solar plasma in each observation, and estimated the pseudo-Lyapunov exponents from the residuals between the values of the quantities computed at any point in the map and the mean of values over the whole map. In contrast to previous results reported in the literature, we found that the computed exponents hold negative values, which are typical of a dissipative regime, for all the quantities derived from our observations. The values of the estimated exponents increase with the spatial resolution of the data and are almost unaffected by small concentrations of magnetic field. Finally, we showed that similar results were also achieved by estimating the exponents from residuals between the values at each point in maps derived from observations taken at different times. The latter estimation technique better accounts for the definition of these exponents than the method employed in previous studies.
太阳光球层和太阳内部外层的特征是对流运动，这些运动呈现出混沌和湍流的特性。在这项工作中，我们使用文献中用于估计这些指数的一种方法以及从其定义推导出来的另一种技术，评估了在太阳表面观测到的过冲对流运动的伪李雅普诺夫指数。我们分析了使用地基和天基望远镜的最先进仪器获取的观测数据，特别受益于通过干涉二维光谱仪、清晰成像光谱偏振仪和日震与磁成像仪获取的光谱偏振数据。遵循文献中的先前研究，我们计算了在每次观测中代表太阳等离子体物理性质的四个量的图谱，并根据图谱中任意点计算的量值与整个图谱上量值的平均值之间的残差来估计伪李雅普诺夫指数。与文献中报道的先前结果相反，我们发现对于从我们的观测中得出的所有量，计算出的指数均为负值，这是耗散状态的典型特征。估计指数的值随数据的空间分辨率增加，并且几乎不受小磁场浓度的影响。最后，我们表明，通过从不同时间观测得到的图谱中各点的值之间的残差估计指数，也能得到类似的结果。后一种估计技术比先前研究中使用的方法更符合这些指数的定义。
