内日冕中的湍流动力学与流速：来自Akatsuki航天器无线电探测实验的结果
Turbulence dynamics and flow speeds in the inner solar corona: Results from radio-sounding experiments by the Akatsuki spacecraft
AI总结：
本研究利用Akatsuki航天器2021年金星-太阳会合期间的无线电探测数据，结合地面站X波段信号分析与EUV观测，探究内日冕太阳风湍流与流速，发现该区域太阳风速度高于预期，为内日冕研究提供新见解。
摘要：
太阳内日冕是在为太阳风供能并将其加速至超音速和超阿尔芬速度过程中发挥关键作用的区域。尽管其地位重要，但由于观测限制，该区域探索程度最低，人们对其的了解仍然十分有限。在这种背景下，日冕无线电探测技术颇具实用价值，因为它能为这一探索程度最低的区域的部分范围提供信息。为阐明内日冕中太阳风的动力学特性，我们利用Akatsuki航天器在2021年金星-太阳会合事件期间开展的日冕无线电探测实验所获取的数据开展了研究。通过分析两个地面站（班加罗尔的IDSN和日本的UDSC）记录的X波段无线电信号，我们研究了等离子体湍流特征，并基于各向同性准静态湍流模型估算了流速测量值。我们的分析显示，内日冕中（日心距为5至13个太阳半径的区域）的太阳风速度范围为220-550千米/秒，高于该区域的预期平均流速。通过将我们的无线电探测结果与太阳圆面的极紫外（EUV）图像相结合，我们对源自冕洞的高速等离子体流的性质与供能机制获得了独特的认知。我们追踪了从一个延伸冕洞发出的快速太阳风流在向更远日心距传播过程中的演化情况。我们的研究通过将无线电探测结果与日冕的EUV观测结果相互印证，为探索程度最低的内日冕区域提供了独特的见解。
英文摘要：
The solar inner corona is a region that plays a critical role in energizing the solar wind and propelling it to supersonic and supra-Alfvenic velocities. Despite its importance, this region remains poorly understood because of being least explored due to observational limitations. The coronal radio sounding technique in this context becomes useful as it helps in providing information in parts of this least explored region. To shed light on the dynamics of the solar wind in the inner corona, we conducted a study using data obtained from coronal radio-sounding experiments carried out by the Akatsuki spacecraft during the 2021 Venus-solar conjunction event. By analyzing X-band radio signals recorded at two ground stations (IDSN in Bangalore and UDSC in Japan), we investigated plasma turbulence characteristics and estimated flow speed measurements based on isotropic quasi-static turbulence models. Our analysis revealed that the speed of the solar wind in the inner corona (at heliocentric distances from 5 to 13 solar radii), ranging from 220-550 km/sec, was higher than the expected average flow speeds in this region. By integrating our radio-sounding results with EUV images of the solar disk, we gained a unique perspective on the properties and energization of high-velocity plasma streams originating from coronal holes. We tracked the evolution of fast solar wind streams emanating from an extended coronal hole as they propagated to increasing heliocentric distances. Our study provides unique insights into the least-explored inner coronal region by corroborating radio sounding results with EUV observations of the corona.
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