标题： 自由传播的宽日冕物质抛射驱动激波边缘：建模与观测见解 显示英文标题

标题： Freely propagating flanks of wide coronal-mass-ejection-driven shocks: Modelling and observational insights

摘要： 广泛的太阳高能粒子（SEP）事件仍然是空间天气中的一个理解不足的现象。 这些事件通常与日冕物质抛射（CMEs）及其激波有关，但控制其全球粒子分布的机制仍存在争议。 2023年3月13日的事件尤其值得注意，因为它是一次与异常快速的行星际激波相关的广泛SEP事件。 其速度高达3000公里/秒，这是近年来观测到的最极端的激波之一。 我们旨在研究宽CME驱动激波的侧面是否可以与CME解耦，并继续作为自由传播的激波传播。 如果激波是主要的SEP源，这种机制可能有助于解释一些最广泛的SEP事件。 使用EUHFORIA，一种三维磁流体力学日球层模型，我们模拟了宽CME驱动激波的演化。 我们修改了模型，以允许在CME喷发物上游的内边界直接注入激波。 将这种方法应用于2023年3月13日的事件，我们模拟了两个同时发生的CME，其激波形成一个单一的、宽广的激波包络，跨越280{\deg}的经度。 然后我们将我们的结果与现场观测进行了比较。 我们的模拟表明，宽CME激波的侧面可以在超过2个天文单位的距离上作为自由传播的波持续存在。 对于2023年3月13日的事件，建模的激波到达时间和相关等离子体参数（如速度和密度）的幅度与来自不同径向距离和经度的各种航天器的观测结果有很好的一致性。 此外，当该复合激波结构向外传播时，会扩展成一个准环日波。 这些发现表明，快速CME的激波侧面可以长时间持续存在，支持了这种自由传播的激波侧面在广泛事件中的SEP全球分布中起关键作用的观点。 显示英文摘要

摘要： Widespread solar energetic particle (SEP) events remain poorly understood phenomena in space weather. These events are often linked to coronal mass ejections (CMEs) and their shocks, but the mechanisms governing their global particle distribution remain debated. The 13 March 2023 event is particularly notable as a widespread SEP event associated with an exceptionally fast interplanetary shock. With speeds of up to 3000 km/s, it is one of the most extreme shocks observed in recent years. We aim to investigate whether the flanks of a wide CME-driven shock can decouple from the CME and continue propagating as freely propagating shock waves. If shocks are the primary SEP source, such a mechanism could help explain some of the widest SEP events. Using EUHFORIA, a 3D magnetohydrodynamic heliospheric model, we simulated the evolution of wide CME-driven shocks. We modified the model to allow direct shock injection at the inner boundary, upstream of the CME ejecta. Applying this to the 13 March 2023 event, we modelled two simultaneous CMEs whose shocks form a single, wide shock envelope that spans 280{\deg} in longitude. We then compared our results to in situ observations. Our simulations show that the flanks of wide CME shocks can persist as freely propagating waves beyond 2 au. For the 13 March 2023 event, the modelled shock arrival times and amplitudes of associated plasma parameters (e.g. speed and density) show good agreement with observations from various spacecraft distributed across different radial distances and longitudes. Furthermore, the combined shock structure expands into a quasi-circumsolar wave as it propagates outwards. These findings indicate that the shock flanks of fast CMEs can persist for a long time, supporting the idea that such freely propagating shock flanks play a key role in the global distribution of SEPs in widespread events.