Magnetohydrodynamic Turbulent Evolution of a Magnetic Cloud in the Outer Heliosphere
Magnetohydrodynamic Turbulent Evolution of a Magnetic Cloud in the Outer Heliosphere
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DOI：
10.3847/2041-8213/abcb03
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发表时间：
2020-12
期刊：
影响因子：
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通讯作者：
D. Telloni;Lingling Zhao;G. Zank;Haoming Liang;M. Nakanotani;L. Adhikari;F. Carbone;R. D’Amicis
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文献类型：
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作者：
D. Telloni;Lingling Zhao;G. Zank;Haoming Liang;M. Nakanotani;L. Adhikari;F. Carbone;R. D’Amicis
这封信利用广泛分离的航天器对同一行星际日冕物质抛射的联合观测，首次研究嵌入磁云在整个行星际空间传播期间磁流体动力学（MHD）特性的湍流演化。具体地说，1998年3月4日至6日，Wind在1 Au观测到了这一事件，并在18天后的5.4 Au跟踪到了太阳的位置，当时两个航天器与太阳径向对齐。磁云内的MHD不变量的分析，沿着其能量预算，提供了令人信服的证据磁侵蚀的结构，由于其与尾随磁云的相互作用。因此，螺旋形的配置大大变形和退化，并观察到的初始优势的动能的磁场演变向一个不太不平衡的条件。这与由于磁重联过程而预期的磁能转化为动能是一致的。磁云（MC）外层与太阳风的局部相互作用在下游区域产生了更大幅度的阿尔夫文波动，导致MC在外部日光层中朝着更复杂的交叉螺旋度配置发展。最后，磁重联事件在1 Au，可能会衰变的时候，它达到1000万美元的磁通绳本地产生的证据也有报道。
This Letter exploits joint observations of the same interplanetary coronal mass ejection by widely separated spacecraft to study, for the first time, the turbulent evolution of the magnetohydrodynamic (MHD) properties of the embedded magnetic cloud, during its propagation throughout interplanetary space. Specifically, the event was observed by Wind at 1 au on 1998 March 4–6 and tracked to the location of Ulysses at 5.4 au 18 days later, when the two spacecraft were radially aligned with the Sun. The analysis of the MHD invariants within the magnetic cloud, along with its energy budget, provides compelling evidence of magnetic erosion of the structure thanks to its interaction with a trailing magnetic cloud. The helical configuration is thus largely deformed and degraded, and the initial dominance of magnetic over kinetic energy is observed to evolve toward a less imbalanced condition. This is consistent with the expected conversion of magnetic energy into kinetic energy due to magnetic reconnection processes. Local interaction of the magnetic cloud’s (MC) outer layers with the solar wind acts to generate larger amplitude Alfvénic fluctuations in the downstream region, leading the MC to turbulently evolve toward a more complex cross-helicity configuration in the outer heliosphere. Finally, evidence of a flux rope locally generated by magnetic reconnection events at 1 au that likely decays by the time it reaches Ulysses is also reported.