We have conducted a survey of 575 slow-to-fast stream interaction regions (SIRs) using Solar Terrestrial Relations Observatory (STEREO) A and B data, analyzing their properties while extending a Level-3 data product through 2016. Among 518 pristine SIRs, 54% are associated with heliospheric current sheet (HCS) crossings, and 34% are without any HCS crossing. The other 12% of the SIRs often occur in association with magnetic sectors shorter than three days. The SIRs with HCS crossings have slightly slower speeds but higher maximum number densities, magnetic-field strengths, dynamic pressures, and total pressures than the SIRs without an HCS. The iron charge state is higher throughout the SIRs with an HCS than the SIRs without an HCS, by about 1/3$1/3$ charge unit. In contrast with the comparable phases of Solar Cycle 23, slightly more SIRs and higher recurrence rates are observed in the years 2009 – 2016 of Cycle 24, with a lower HCS association rate, possibly attributed to persistent equatorial coronal holes and more pseudo-streamers in this recent cycle. The solar-wind speed, peak magnetic field, and peak pressures of SIRs are all lower in this cycle, but the weakening is less than for the comparable background solar-wind parameters. Before STEREO-B lost contact in October 2014, 151 SIR pairs were observed by the twin spacecraft. Of the dual observations, the maximum speed is the best correlated of the plasma parameters. We have obtained a sample of plasma-parameter differences analogous to those that would be observed by a mission at Lagrange points 4 or 5. By studying several cases with large discrepancies between the dual observations, we investigate the effects of HCS relative location, tilt of stream interface, and small transients on the SIR properties. To resolve the physical reasons for the variability of SIR structures, mesoscale multi-point observations and time-dependent solar-wind modeling are ultimately required.

中文翻译：

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日地关系观测站（STEREO）2007-2016年流相互作用区域的观测：与日光层电流片、太阳周期变化和双重观测的关系


我们使用日地关系观测站 (STEREO) A 和 B 数据对 575 个慢到快流相互作用区域 (SIR) 进行了调查，分析了它们的属性，同时将 3 级数据产品扩展到 2016 年。在 518 个原始 SIR 中， 54% 与日光层电流片 (HCS) 交叉有关，34% 与任何 HCS 交叉无关。另外 12% 的 SIR 通常与短于三天的磁区相关。与没有 HCS 的 SIR 相比，具有 HCS 交叉的 SIR 的速度稍慢，但最大数密度、磁场强度、动态压力和总压力更高。具有 HCS 的 SIR 中的铁电荷态比不具有 HCS 的 SIR 更高，约高 1/3$1/3$ 电荷单位。与第 23 太阳周期的可比较阶段相比，第 24 周期的 2009 年至 2016 年观察到的 SIR 略多，复发率较高，HCS 关联率较低，可能归因于持续的赤道日冕洞和更多的伪流光。最近的这个周期。此周期中太阳风速度、峰值磁场和峰值压力均较低，但减弱幅度小于可比较的背景太阳风参数。在 2014 年 10 月 STEREO-B 失去联系之前，这对双胞胎航天器观测到了 151 个 SIR 对。在双重观察中，最大速度是等离子体参数的最佳相关性。我们已经获得了等离子体参数差异的样本，类似于拉格朗日点 4 或 5 的任务所观察到的差异。通过研究双重观察之间存在较大差异的几个案例，我们研究了 HCS 相对位置、倾斜角的影响。流接口，以及 SIR 属性上的小瞬变。 为了解决 SIR 结构变化的物理原因，最终需要中尺度多点观测和瞬态太阳风建模。