选址与日冕观测组知识库

太阳耀斑和微耀斑能量的幂律分布是太阳活动的一个典型特点。调查其统计特征和时变规律,对研究太阳能量的传输和耗散以及高层大气的加热机制有重要意义。研究太阳低层大气中能量释放的统计规律及其演化过程,使用二维区域标记算法,在日出（Hinode）卫星上的太阳光学望远镜（Solar Optical Telescope,SOT）对NOAA 10930活动区观测的低色球层Ca Ⅱ Hλ3 968.5单色像资料上,分析表征亮点能量分布的频数特征及其变化规律。在时间跨度为124 h、视场为202″.4×85″.3的时间序列中,共获得2.99×105个亮点,平均每帧图上每平方角分有24.15±6.34个亮点。主要分析结果如下:（1）亮点尺度(L=（LxLy）1/2)的瞬时分布基本符合幂律分布并满足自相似性;（2）亮点的产生率及其信噪比随着尺度的增加而减小。海量微小尺度亮点持续的发生可能是加热高层大气的一种稳定而可观的能量来源,例如,尺度小于4″的亮点产生的光通量在样本总光通量中占的比例达到53.23%;（3）小尺度亮点的瞬时数密度随着活动区的衰减而降低;（4）亮点集的尺度服从幂律分布,其离散系数σ（ζ）仅为4%。该实测样本尺度的幂指数γ为1.97,低噪声样本（L≤8″）的γ为2.12;（5）但是,在观测时段内,γ并没有收敛。样本集的γ是一个在观测积累中呈锯齿状变化的过程:在平静时段缓慢升高,在活动瞬间突然降低。（6）亮点瞬时子集的γ与其总光通量呈反比。在样本中剔除大尺度（L>8″）个体后,中小尺度亮点仍服从上述规律。太阳活动不仅产生中、大尺度的增亮区域,还对各尺度区间亮点的频数分布产生全局性的影响,引起瞬时γ的降低。

The power-law distribution of the energy of flares and microflares is an important character of solar activities. Investigating its attributes and temporal variations helps to study the transmission of energy and the heating of the solar corona. In this observation, we study the temporal variations of the frequency distribution of low-chromospheric bright points (BPs), and probe the pattern of energy release in low solar atmospheres. We utilize Ca II H λ3968.5 monograms of NOAA AR 10930 acquired by Hinode/SOT and recognize BPs with a two-dimensional region-labelling algorithm. On the time sequence with a time span of 124h and a field-of-view of 202″.4 × 85″. 3, a sample of 2. 99 × 10^5 BPs is identified, with a numerical density of 24.15 ± 6. 34 per square arcminute. The main results are summarized as follows: (1) The instantaneous frequency distribution of BP's scale (L = √LxLy ) virtually observes the power-law and self-similarity. (2) The value and signal-to-noise ratio of BP＇s production decrease with the increase of BP's scale. Numerous small- scale BPs could be a valid source of energy for the heating of upper atmosphere. For instance, BPs with a scale smaller than 4″ share approximately 53.23% of the sample＇s total light flux budget. (3) As the active region decays, the numerical density of small-scale BPs also decreases. (4) The distribution of the sample set＇s scale observes the power-law, with a dispersion index σ(ζ) of 4%. The power-law index T of the observed and low-noise (L ≤ 8″) samples are respectively 1.97 and 2. 12. (5) However, within the observation time, the overall power-law index y does not converge. The relationship between the power-law index and the time-span of observation is serrated： in quiet times T (6) gradual1 The instantaneous γ is reversely proportional to y increases, while in active moments T decreases sharply. the instantaneous total light flux. Even after filtering large- scale BPs (L >8″), the low-noise sample, which contains only middle- and small-scale BPs, still shows such correlation. This quashes our initial suspicion that the numerical calculation of γ is rigged by the injection of few large BPs into the sample pool; the observed relationship between large events and the dropping of γ is intrinsic. Solar activities not only produces middle and large scale BPs, but also changes the entire pattern of BP's distribution and hence lowers γ.