Recent observations suggest that magnetic flux cancellation may play a crucial role in heating the Sun's upper atmosphere (chromosphere, transition region, corona). Here, we intended to validate an analytic model for magnetic reconnection and consequent coronal heating, driven by a pair of converging and cancelling magnetic flux sources of opposite polarities. For this test, we analyzed photospheric magnetic field and multi-wavelength UV/EUV observations of a small-scale flux cancellation event in a quiet-Sun internetwork region over a target interval of 5.2 hr. The observed cancellation event exhibits a converging motion of two opposite-polarity magnetic patches on the photosphere and red-shifted Doppler velocities (downflows) therein consistently over the target interval, with a decrease in magnetic flux of both polarities at a rate of 10$^{15}$ Mx s$^{-1}$. Several impulsive EUV brightenings, with differential emission measure values peaked at 1.6-2.0 MK, are also observed in the shape of arcades with their two footpoints anchored in the two patches. The rate of magnetic energy released as heat at the flux cancellation region is estimated to be in the range of (0.2-1)$\times$10$^{24}$ erg s$^{-1}$ over the target interval, which can satisfy the requirement of previously reported heating rates for the quiet-Sun corona. Finally, both short-term (a few to several tens of minutes) variations and long-term (a few hours) trends in the magnetic energy release rate are clearly shown in the estimated rate of radiative energy loss of electrons at temperatures above 2.0 MK. All these observational findings support the validity of the investigated reconnection model for plasma heating in the upper solar atmosphere by flux cancellation.

中文翻译：

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磁通量抵消太阳等离子体加热的观测试验

最近的观察表明，磁通量抵消可能在加热太阳的高层大气（色球层、过渡区、日冕）方面起着至关重要的作用。在这里，我们打算验证由一对相反极性的会聚和抵消磁通量源驱动的磁重联和随之而来的日冕加热的分析模型。在此测试中，我们分析了光球磁场和多波长 UV/EUV 观测结果，该观测结果是在 5.2 小时的目标间隔内，在一个安静的太阳互联网络区域中发生的小规模通量抵消事件。观察到的抵消事件表现出光球上两个相反极性磁块的会聚运动，并且在目标间隔内始终如一地红移多普勒速度（下流），两个极性的磁通量以 10$^{15}$ Mx s$^{-1}$ 的速率减少。几个脉冲 EUV 增亮，其差分发射测量值在 1.6-2.0 MK 处达到峰值，在拱廊形状中也观察到，它们的两个脚点固定在两个补丁中。在磁通抵消区域以热量形式释放的磁能率估计在目标区间内的 (0.2-1)$\times$10$^{24}$ erg s$^{-1}$ 范围内，这可以满足先前报告的安静太阳日冕加热速率的要求。最后，磁能释放率的短期（几到几十分钟）变化和长期（几小时）趋势都清楚地显示在 2.0 MK 以上温度下电子辐射能量损失的估计率中.