AI 中文总结
研究利用帕克太阳探测器观测低β流，通过反转质子引导中心方程测量扩散系数，计算加热率，以识别无碰撞等离子体中加热过程，为近太阳太阳风存在类似福克 - 普朗克扩散过程提供证据。
AI 中文摘要
无碰撞等离子体耗散中的开放性问题可通过不同天体物理环境中的天基观测来解决，这对天体物理和实验室等离子体系统都有影响。我们研究了帕克太阳探测器（PSP）观测到的低β、高度不平衡、亚阿尔文流，以识别和区分平行离子回旋波（ICW）引起的随机加热（SH）和共振加热（RH）的特征。先前研究该流的工作表明，考虑间歇性的SH率与局部能量转移（LET）率的幅度匹配，而RH率不匹配。这种比较依赖于关于扩散过程性质和LET率计算的一些假设。我们引入了一种新技术，通过反转质子引导中心方程，利用PSP上离子静电分析仪（SPANi）的三维质子速度分布函数（VDF）凭经验测量速度空间扩散系数。测量的扩散系数用于确定相空间加热率，从而计算出与先前工作中所做假设无关的完全动力学加热率。我们表明，通过非相干波动的SH的尺度相关解析表达式与PSP数据的经验测量结果相匹配，前提是我们在加热计算中考虑间歇性。相比之下，考虑螺旋度屏障效应的SH的推导加热率以及通过平行ICW的RH的加热率在速度空间的同一区域没有达到经验测量的峰值，也没有达到所需的幅度。我们的方法提供了一种新颖的方法来唯一识别和约束无碰撞等离子体中的加热过程，并显示了近太阳太阳风中类似福克 - 普朗克扩散过程的证据。
英文摘要
Open questions in collisionless plasma dissipation can be addressed using space-based observations in different astrophysical environments, with implications for both astrophysical and laboratory plasma systems. We study a low-$β$, highly imbalanced, sub-Alfvénic stream observed by Parker Solar Probe (PSP) to identify and distinguish between signatures of stochastic heating (SH) and resonant heating (RH) by parallel ion cyclotron waves (ICWs). Prior work studying this stream (Bowen et al., 2025) showed that the SH rate, accounting for intermittency, matched the amplitude of the local energy transfer (LET) rate while the RH rate did not. This comparison relied on a number of assumptions regarding the nature of the diffusive process, and the calculation of the LET rate. We introduce a novel technique of inverting the proton guiding center equation to empirically measure velocity-space diffusion coefficients using three-dimensional proton velocity distribution functions (VDFs), from the ion electrostatic analyzer (SPANi) on PSP. Measured diffusion coefficients are used to determine phase-space heating rates, leading to a calculation of a fully kinetic heating rate independent of assumptions made in prior work. We show that scale-dependent analytic expressions for SH via non-coherent fluctuations match the empirical measurements from PSP data, provided that we account for intermittency in the heating calculation. In contrast, the derived heating rates for SH that accounts for the effects of the helicity barrier, and heating rates for RH via $\parallel$-ICWs do not peak in the same region of velocity-space as the empirical measurements, nor reach the required magnitude. Our approach provides novel methodology to uniquely identify and constrain heating processes in collisionless plasmas, and shows evidence of a Fokker-Planck like diffusive process in the near-Sun solar wind.
CommentsAccepted in PRL, 10 pages, 5 figures
