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arXiv 2407.09684astro-ph.SRphysics.plasm-phphysics.space-ph
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帕克太阳探测器观测到的慢阿尔文太阳风的特征与源区

Characteristics and Source Regions of Slow Alfvenic Solar Wind Observed by Parker Solar Probe

Tamar Ervin, Kai Jaffarove, Samuel T. Badman, Jia Huang, Yeimy J. Rivera, Stuart D. Bale

AI总结:

本研究利用帕克太阳探测器第4至14次近日点观测数据,结合PFSS建模与弹道映射,揭示慢阿尔文太阳风的两类源区及相关特征,并量化映射误差、提出多点观测的改进方向。

摘要:

我们采用基于观测日心距离的太阳风类型分类方案,研究帕克太阳探测器第4至14次近日点附近的观测数据,以探究慢阿尔文太阳风(SASW)的来源。通过势场源表面(PFSS)建模与弹道映射,我们将太阳风流与其太阳源区关联,发现主要的SASW族群来自低磁场强度区域(低-B₀),大概率是小型冕洞(CHs)及其过度膨胀的边界;而第二支高磁场强度(高-B₀)的SASW族群似乎源自非冕洞结构,可能通过与附近开放磁力线的交换重联产生。这类低-B₀的SASW比快太阳风(FSW)膨胀程度更大,但质量通量相近,这可能表明临界点下方存在额外加热,且其源自温度更低的结构,进而导致类冕洞结构喷出的太阳风速度更慢。我们发现,低-B₀的SASW比高-B₀的SASW表现出更强的α粒子优先加速效应(与快太阳风类似),且如既往研究所示,这是一种与速度相关的现象。为进一步提升映射结果的可信度,我们量化了PFSS模型与弹道映射的误差,并讨论了更多等离子体参数与成分的多点观测将如何帮助我们更好地约束模型,建立太阳风与其源区的关联。

英文摘要:

Using a classification scheme for solar wind type based on the heliocentric distance of the observation, we look at near perihelion observations from Parker Solar Probe Encounters Four to Fourteen to study the sources of the slow Alfv$é$nic solar wind (SASW). Through Potential Field Source Surface (PFSS) modeling and ballistic mapping, we connect streams to their solar source and find that a primary population of SASW comes from low magnetic field strength regions (low-$B_0$), likely small coronal holes (CHs) and their over-expanded boundaries, while a second population of high field strength (high-$B_0$) seems to emerge from non-CH structures potentially through interchange reconnection with nearby open field lines. This low-$B_0$ SASW shows larger expansion than the fast solar wind (FSW) but similar mass flux, potentially indicating additional heating below the critical point, and emergence from a cooler structure, which could lead to slower wind emerging from CH-like structures. We show that this low-$B_0$ SASW shows stronger preferential acceleration of alpha particles (similar to the FSW) than the high-$B_0$ SASW, and that this is a velocity dependent phenomenon as found in previous studies. To have additional confidence in our mapping results, we quantify the error on both the PFSS model and ballistic mapping and discuss how additional multi-point observations of plasma parameters and composition would allow us to better constrain our models and connect the solar wind to its source.

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