发表机构
University of Oulu（奥卢大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过偶极子通量输运模型模拟，发现活动区倾斜角控制赤道偶极子放大，纬度控制其寿命，低纬度活动区可产生强且持久的赤道偶极子，影响地磁活动。
AI 中文摘要
活动区参数对太阳轴向偶极子演化的影响已被充分理解。然而，它们对太阳赤道偶极子的影响尚未被详细研究。理解赤道偶极子的发展非常重要，因为它驱动着周期内时间尺度（约1年）的行星际磁场。我们研究了纬度、倾斜角和极性分离如何影响太阳赤道偶极子的演化。我们使用偶极子通量输运（DFT）模型，这是表面通量输运（SFT）模型的矩阵实现，来模拟具有广泛倾斜角和纬度的合成双极磁区（BMRs）的偶极子演化。我们还研究了HMI SHARP数据库中活动区的演化及其相关的BMRs。我们通过赤道偶极子的最大和平均放大以及增长和衰减时间来量化偶极子演化。倾斜角控制赤道偶极子的放大，较大的倾斜角导致更强的赤道偶极子。纬度控制赤道偶极子增长和衰减的时间尺度。低纬度区域产生寿命最长的赤道偶极子。我们发现，只有31%的反Joy活动区经历了赤道偶极子的放大，而规则倾斜的活动区这一比例为96%。活动区的纬度和倾斜角对太阳赤道偶极子有相当大的影响。它们性质的系统性变化可能增加或减少赤道偶极子相对于太阳活动的强度，这可能导致地磁活动的类似相对变化。我们建议，太阳活动周20下降阶段的大型低纬度冕洞和相对较高的地磁活动，可能与异常低纬度活动区的出现有关，这些活动区产生了强烈且持久的赤道偶极子。
英文摘要
The effect of active region parameters on the evolution of solar axial dipole is well understood. However, their effect on the solar equatorial dipole has not been studied in detail. Understanding the development of the equatorial dipole is important as it drives the interplanetary magnetic field on intracyclic timescales (~ 1yr). We study how the latitude, tilt angle, and the polarity separation affect the evolution of solar equatorial dipole. We use dipole flux transport (DFT), a matrix implementation of surface flux transport (SFT) model, to simulate the dipole evolution of synthetic bipolar magnetic regions (BMRs) with a wide range of tilt angles and latitudes. We also study the evolution of active regions in HMI SHARP database and their associated BMRs. We quantify the dipole evolution by means of the maximum and mean amplification and the growth and decay times of the equatorial dipole. Tilt angle controls the amplification of the equatorial dipole, with larger tilt angles leading to stronger equatorial dipole. Latitude controls the timescale at which the equatorial dipole grows and decays. Low-latitude regions produce the longest living equatorial dipole. We find that only 31% of anti-Joy regions experience amplification of equatorial dipole, compared with 96 of regularly tilted active regions. Latitudes and tilt angles of active regions can have considerable effect on the solar equatorial dipole. Systematic changes in their properties could increase/decrease the strength of the equatorial dipole relative to the solar activity, which could lead to similar relative change in geomagnetic activity. We suggest that large low-latitude coronal holes and relatively high geomagnetic activity in the declining phase of solar cycle 20, could be related to emergence of unusually low-latitude active regions that produced strong and persistent equatorial dipole.
Comments11 pages, 11 figures, under review at A&A
