论文标题
非球面冠状质量弹出及其驱动冲击的三维分析
Three-dimensional analyses of an aspherical coronal mass ejection and its driven shock
论文作者
论文摘要
语境。观察结果表明，冲击可以由快速的冠状质量弹出（CME）驱动，并在粒子加速度中起重要作用。临界比率为$δ$，它来自CME的曲率半径（ROC）标准化的冲击对峙距离，使我们能够估算电击和环境冠状参数。但是，由于观察到的投影效应，CME的真实ROC很难衡量。 目标。我们研究了由非球面CME驱动的没有明显横向膨胀的冲击的形成机理。通过没有先验假设对象形态的三维（3D）重建，我们估算了CME表面的两个主要ROC，并证明了CME的两个主要ROC之间的差异如何影响冠状物理参数的估计。 方法。 CME通过Sun Earth Connection Coronal和Heliosperic Revention（SECCHI）仪器以及大角度和光谱冠状动脉（LASCO）观察到CME。我们使用蒙版拟合方法获得了CME的不规则3D形状，并使用弓箭模型重建了冲击表面。通过具有五阶多项式函数和蒙特卡洛模拟的平滑度，我们计算了CME鼻子的ROC。 结果。我们发现（1）最大ROC是CME最小ROC的2-4倍。 CME ROC之间的显着差异意味着，一个非球体CME的ROC的假设可能会导致电击和冠状参数的过度估计。 （2）休克鼻子遵守弓形造型机构，考虑到恒定的隔离距离以及鼻子周围的冲击和CME之间的相似速度。 （3）使用更精确的$δ$通过太空中的3D ROC计算出来，我们以大约-50 $^{\ Circ} $的高纬度来得出电晕参数，包括Alfv {é} N速度和冠状磁场强度。
Context. Observations reveal that shocks can be driven by fast coronal mass ejections (CMEs) and play essential roles in particle accelerations. A critical ratio, $δ$, derived from a shock standoff distance normalized by the radius of curvature (ROC) of a CME, allows us to estimate shock and ambient coronal parameters. However, true ROCs of CMEs are difficult to measure due to observed projection effects. Aims. We investigate the formation mechanism of a shock driven by an aspherical CME without evident lateral expansion. Through three-dimensional (3D) reconstructions without a priori assumptions of the object morphology, we estimate two principal ROCs of the CME surface and demonstrate how the difference between two principal ROCs of the CME affects the estimate of the coronal physical parameters. Methods. The CME was observed by the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instruments and the Large Angle and Spectrometric Coronagraph (LASCO). We used the mask-fitting method to obtain the irregular 3D shape of the CME and reconstructed the shock surface using the bow-shock model. Through smoothings with fifth-order polynomial functions and Monte Carlo simulations, we calculated the ROCs at the CME nose. Results. We find that (1) the maximal ROC is 2-4 times the minimal ROC of the CME. A significant difference between the CME ROCs implies that the assumption of one ROC of an aspherical CME could cause over-/under- estimations of the shock and coronal parameters. (2) The shock nose obeys the bow-shock formation mechanism, considering the constant standoff distance and the similar speed between the shock and CME around the nose. (3) With a more precise $δ$ calculated via 3D ROCs in space, we derive corona parameters at high latitudes of about -50$^{\circ}$, including the Alfv{é}n speed and the coronal magnetic field strength.
