在11/22年的太阳活动周期中，太阳对流区的环形磁场的极性会周期性地反转。在有助于消除“旧极性”环形磁通量的各种过程中，出现了在太阳表面形成双极区的通量环。我们量化的损失，地下净环向通量通过这个过程。为此，我们确定了一个单独的新兴双极环的贡献，并表明它是不受表面通量运输后出现。与扩散过程的线性一起，这意味着可以通过将所有出现的双极磁性区域的贡献相加来获得总通量损失。由此产生的净环向通量的总损失率在活动最大值期间为1.3 X 10^{15} Mx/s，在活动最小值期间为6.1 X 10^{14} Mx/s，其中短暂区域分别贡献约90%和97%。这一速率与观测推断的进入行星际空间的环形通量损失率一致，对应于地下环形通量的衰减时间约为12年，也与基于湍流扩散率的简单估计一致。因此，通量出现的环向通量损失是太阳对流区净环向通量预算的相关贡献。由于通量出现的环形通量损失率与湍流扩散的预期一致，并且相应的衰减时间与太阳周期的长度相似，这是理解太阳周期和太阳内部动力学的重要限制。
英文摘要：
The polarity of the toroidal magnetic field in the solar convection zone periodically reverses in the course of the 11/22-year solar cycle. Among the various processes that contribute to the removal of `old-polarity' toroidal magnetic flux is the emergence of flux loops forming bipolar regions at the solar surface. We quantify the loss of subsurface net toroidal flux by this process. To this end, we determine the contribution of an individual emerging bipolar loop and show that it is unaffected by surface flux transport after emergence. Together with the linearity of the diffusion process this means that the total flux loss can be obtained by adding the contributions of all emerging bipolar magnetic regions. The resulting total loss rate of net toroidal flux amounts to 1.3 X 10^{15} Mx/s during activity maxima and 6.1 X 10^{14} Mx/s during activity minima, to which ephemeral regions contribute about 90% and 97%, respectively. This rate is consistent with the observationally inferred loss rate of toroidal flux into interplanetary space and corresponds to a decay time of the subsurface toroidal flux of about 12 years, also consistent with a simple estimate based on turbulent diffusivity. Consequently, toroidal flux loss by flux emergence is a relevant contribution to the budget of net toroidal flux in the solar convection zone. That the toroidal flux loss rate due to flux emergence is consistent with what is expected from turbulent diffusion, and that the corresponding decay time is similar to the length of the solar cycle are important constraints for understanding the solar cycle and the Sun's internal dynamics.
Besides their causal connection with long and short-term magnetic variability, solar bipolar magnetic regions are our chief source of insight into the location, size, and properties of large-scale toroidal magnetic structures in the solar interior. The great majority of these regions (~95%) follow a systematic east-west polarity orientation (Hale's law) that reverses in opposite hemispheres and across even and odd cycles. These regions also present a systematic north-south polarity orientation (Joy's law) that helps build the poloidal field that seeds the new cycle. Exceptions to Hale's law ar…
Magnetic flux ropes (MFRs) rising buoyantly through the Sun's convection zone are thought to be subject to viscous forces preventing them from rising coherently. Numerous studies have suggested that MFRs require a minimum twist in order to remain coherent during their rise. Furthermore, even MFRs that get to the photosphere may be unable to successfully emerge into the corona unless they are at least moderately twisted, since the magnetic pressure gradient needs to overcome the weight of the photospheric plasma. To date, however, no lower limit has been placed on the critical minimum twist req…
The sunspot cycle is the magnetic cycle of the Sun produced by the dynamo process. A central idea of the solar dynamo is that the toroidal and the poloidal magnetic fields of the Sun sustain each other. We discuss the relevant observational data both for sunspots (which are manifestations of the toroidal field) and for the poloidal field of the Sun. We point out how the differential rotation of the Sun stretches out the poloidal field to produce the toroidal field primarily at the bottom of the convection zone, from where parts of this toroidal field may rise due to magnetic buoyancy to produc…
Long observational series for bipolar active regions (ARs) provide significant information about the mutual transformation of the poloidal and toroidal components of the global solar magnetic field. The direction of the toroidal field determines the polarity of leading sunspots in ARs in accordance with the Hale's polarity law. The vast majority of bipolar ARs obey this regularity, whereas a few percent of ARs have the opposite sense of polarity (anti-Hale ARs). However, the study of these ARs is hampered by their poor statistics. The data for five 11-year cycles (16-18 and 23,24) were combine…
We explore a new, efficient mechanism that can power toroidally magnetized jets up to two to three times their original terminal velocity after they enter a self-similar phase of magnetic acceleration. Underneath the elongated outflow lobe formed by a magnetized bubble, a wide-angle free wind, through the interplay with its ambient toroid, is compressed and accelerated around its axial jet. The extremely magnetic bubble can inflate over its original size, depending on the initial Alfvén Mach number $M_A$ of the launched flow. The shape-independent slope $\partial{}v_r/\partial{}r=2/3t$ is a sa…
We investigate the effect of the surface bipolar magnetic regions (BMR) on the large-scale dynamo distributed in the bulk of the convection zone. The study employs the nonlinear 3D mean-field dynamo model. We model the emergence of the BMR on the surface through the nonaxisymmetric magnetic buoyancy effect, which acts on the large-scale toroidal magnetic field in the upper half of the convection zone. The nonaxisymmetric magnetic field which results from this mechanism is shallow. On the surface, the effect of the BMR on the magnetic field generation is dominant. {However, because of the shall…
The Babcock-Leighton (BL) flux-transport model is a widely-accepted dynamo model of the Sun. This dynamo model has been extensively studied in a two-dimensional (2D) mean-field framework in both kinematic and non-kinematic regimes. Recent three-dimensional (3D) models have been restricted to the kinematic regime. In these models, the surface poloidal flux is produced by the emergence of bipolar magnetic regions (BMRs) that are tilted according to Joy's law. We investigate the prescription for emergence of a BMR in 3D non-kinematic simulations. We also report initial results of cyclic BL dynamo…
A striking feature of the solar cycle is that at the beginning, sunspots appear around mid-latitudes, and over time the latitudes of emergences migrate towards the equator.The maximum level of activity (e.g., sunspot number) varies from cycle to cycle.For strong cycles, the activity begins early and at higher latitudes with wider sunspot distributions than for weak cycles. The activity and the width of sunspot belts increase rapidly and begin to decline when the belts are still at high latitudes. Surprisingly, it has been reported that in the late stages of the cycle the level of activity (sun…
Small-scale internetwork (IN) magnetic fields are considered to be the main building blocks of the quiet Sun magnetism. For this reason, it is crucial to understand how they appear on the solar surface. Here, we employ a high-resolution, high-sensitivity, long-duration Hinode/NFI magnetogram sequence to analyze the appearance modes and spatio-temporal evolution of individual IN magnetic elements inside a supergranular cell at the disk center. From identification of flux patches and magnetofrictional simulations, we show that there are two distinct populations of IN flux concentrations: unipola…
Observations of the solar magnetic cycle showed that the amplitude of the cycle did not grow all the time in the past. Thus, there must be a mechanism to halt the growth of the magnetic field in the Sun. We demonstrate a recently proposed mechanism for this under the Babcock--Leighton dynamo framework, which is believed to be the most promising paradigm for the generation of the solar magnetic field at present. This mechanism is based on the observational fact that the stronger solar cycles produce bipolar magnetic regions (BMRs) at higher latitudes and thus have higher mean latitudes than the…
We examine the cradle-to-grave magnetic evolution of 10 bipolar ephemeral active regions (BEARs) in solar coronal holes, especially aspects of the magnetic evolution leading to each of 43 obvious microflare events. The data are from Solar Dynamics Observatory: 211 A coronal EUV images and line-of-sight photospheric magnetograms. We find evidence that (1) each microflare event is a magnetic explosion that results in a miniature flare arcade astride the polarity inversion line (PIL) of the explosive lobe of the BEARs anemone magnetic field; (2) relative to the BEAR's emerged flux-rope omega loop…
Granular-Scale Elementary Flux Emergence Episodes in a Solar Active Region
我们分析了在AR 11024出现期间两个54分钟内拍摄的Hinode航天器的数据。我们专注于小规模的部分内观察到的太阳活动区，并发现非常独特的小规模和短暂的黑暗功能的Ca II H色球过滤图和斯托克斯我的图像的外观。这些特征出现在纵向磁场接近于零的区域，并且在它们最终消失之前观察到长度增加。当暗特征逐渐消失时，在低色球层谱线中检测到能量释放。在时间序列的磁图中，观测到一个发散的双极结构，伴随着暗特征和亮特征的出现。观测到的现象被解释为证明在太阳大气中的元素通量出现，即小规模的拱丝系统上升到较低的色球层与几个太阳颗粒的长度尺度。增亮被解释为色球加热的签名所引发的重新连接的上升环路（一旦他们达到色球高度）与预先存在的磁场，以及重新连接/取消事件中的U-环段出现的蛇形字段。我们研究的时间演化和动态的事件，并将它们与出现在安静的太阳区域和蛇形磁通出现签名检测到的活动区域的磁回路。阐述了本研究中提出的颗粒尺度通量出现的新特征，我们提出了蛇纹石通量出现的方案。
The relationship between bipolar magnetic regions (BMRs) and their sunspots is an important property of the solar magnetic field, but it is not well constrained. One consequence is that it is a challenge for surface flux transport models (SFTMs) based on sunspot observations to determine the details of BMR emergence, which they require as input, from such data. We aimed to establish the relationship between the amount of magnetic flux in newly emerged BMRs and the area of the enclosed sunspots. Earlier attempts to constrain BMR magnetic flux were hindered by the fact that there is no proper da…
The coronal magnetic field evolution of 20 bipolar active regions (ARs) is simulated from their emergence to decay using the time-dependent nonlinear force-free field method of Mackay et al. A time sequence of cleaned photospheric line-of-sight magnetograms, that covers the entire evolution of each AR, is used to drive the simulation. A comparison of the simulated coronal magnetic field with the 171 and 193 A observations obtained by the Solar Dynamics Observatory (SDO)/ Atmospheric Imaging Assembly (AIA), is made for each AR by manual inspection. The results show that it is possible to reprod…
A joint campaign of various space-borne and ground-based observatories, comprising the Japanese Hinode mission (HOP~338, 20\,--\,30~September 2017), the GREGOR solar telescope, and the \textit{Vacuum Tower Telescope} (VTT), investigated numerous targets such as pores, sunspots, and coronal holes. In this study, we focus on the coronal hole region target. On 24~September 2017, a very extended non-polar coronal hole developed patches of flux emergence, which contributed to the decrease of the overall area of the coronal hole. These flux emergence patches erode the coronal hole and transform the …
