多车道II型射电暴：对日冕中激波传播的洞察
Multi-lane type II radio bursts: Insights into shock propagation in the corona
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中文总结 AI 辅助
本研究分析2024年5月29日观测到的异常多车道II型太阳射电暴，结合频谱与成像数据发现CME前沿激波的不均匀动力学及几何、等离子体不均匀性对II型射电暴产生的重要作用。
中文摘要 AI 辅助
II型太阳射电暴被认为是日冕激波的标志，这类射电暴由磁流体动力学（MHD）激波激发的等离子体波产生，随后在局部等离子体频率及其谐波处转换为射电波，因此这类射电暴常具有基频-谐频（FH）和谱线分裂（SB）结构，可为日冕中激波的产生与传播乃至对应的日冕条件提供洞察。本研究分析了2024年5月29日世界时14:24至14:43期间，地基太阳射电频谱仪观测到的一次异常的多车道II型射电暴，该射电暴的起始频率为450 MHz，终止频率为25 MHz。通过结合频谱信息与射电成像数据，研究发现射电波通过不同激波区域的辐射从日冕逃逸；除了传统的FH和SB结构外，该II型射电暴还存在多车道结构。分析结果表明，日冕物质抛射（CME）前沿（LE）附近存在复杂、不均匀的激波动力学，这意味着前沿区域的等离子体物质压缩更强烈，该结论得到射电成像观测的证实——观测显示高频辐射的高度高于低频辐射。研究结果表明，激波几何与等离子体不均匀性在II型射电暴的产生中发挥重要作用，导致传统的基频-谐频分裂带（FH-SB）对出现，且II型射电带中存在额外的分裂。
英文摘要
Type II solar radio bursts are considered as the signatures of the coronal shocks. These bursts are generated from plasma waves excited by magnetohydrodynamic (MHD) shocks, and then converted into radio waves at the local plasma frequency and/or its harmonics. Hence, these bursts often have fundamental-harmonic (FH) and band-splitting (SB) structures, which provide insights into shock generation and propagation in the corona, hence, in turn, the corresponding coronal conditions. In the present study, we analysed an unusual multi-lane type II burst observed with ground-based solar radio spectrographs on May 29, 2024, between 14:24 and 14:43 UT. The start and end frequencies of the type II burst were 450 MHz and 25 MHz, respectively. By combining spectral information with radio imaging data, we found that radio waves were escaping from the corona via emissions from distinct shock regions. In addition, along with the traditional FH and SB, there were multi-lane structures in the type II bursts. Our analysis suggests complex, inhomogeneous shock dynamics near the leading edge (LE) of the coronal mass ejection (CME). This indicates that the plasma material compresses more strongly in these forefront regions. This was confirmed by radio imaging observations, which showed that the higher-frequency emission occurred at a higher altitude than the lower-frequency emission. Our results suggest that the shock geometry and plasma inhomogeneity play an important role in the generation of type II bursts, leading to traditional fundamental-harmonic split-band (FH-SB) pairs with additional splitting in the type II bands.
