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Abstract: We performed a systematic study of the Doppler shifts and electron densitiesmeasured in an EUV bright point hereafter BP observed in more than 10 EUVlines with formation temperatures from log T-K p 4.5 to 6.3. Those parts of aBP seen in transition region and coronal lines are defined as its cool and hotcomponents, respectively. We find that the transition from cool to hot occursat a temperature around log T-K p 5.7. The two components of the BP reveal atotally different orientation and Doppler-shift pattern, which might resultfrom a twist of the associated magnetic loop system. The analysis of magneticfield evolution and topology seems to favor a two-stage heating process, inwhich magnetic cancellation and separator reconnection are powering,respectively, the cool and hot components of the BP. We also found that theelectron densities of both components of the BP are higher than those of thesurrounding quiet Sun, and comparable to or smaller than active regiondensities.



Author: Hui Tian, Werner Curdt, Eckart Marsch, Jiansen He

Source: https://arxiv.org/







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