Magnetohydrodynamic Turbulent Evolution of a Magnetic Cloud in the Outer Heliosphere

TELLONI, DANIELE; LIANG, HAOMING; CARBONE, FRANCESCO; BRUNO, ROBERTO; ZHAO, LINGLING; NAKANOTANI, MASARU; D?AMICIS, RAFFAELLA; DASSO, SERGIO; ZANK, GARY P.; ADHIKARI, LAXMAN; PERRONE, DENISE

The Astrophysical Journal

The American Astronomical Society

Año: 2020 vol. 905

This Letter exploits joint observations of the same interplanetary coronal mass ejection by widely separatedspacecraft to study, for the first time, the turbulent evolution of the magnetohydrodynamic (MHD) properties of theembedded magnetic cloud, during its propagation throughout interplanetary space. Specifically, the event wasobserved by Wind at 1 au on 1998 March 4?6 and tracked to the location of Ulysses at 5.4 au 18 days later, whenthe two spacecraft were radially aligned with the Sun. The analysis of the MHD invariants within the magneticcloud, along with its energy budget, provides compelling evidence of magnetic erosion of the structure thanks to itsinteraction with a trailing magnetic cloud. The helical configuration is thus largely deformed and degraded, and theinitial dominance of magnetic over kinetic energy is observed to evolve toward a less imbalanced condition. This isconsistent with the expected conversion of magnetic energy into kinetic energy due to magnetic reconnectionprocesses. Local interaction of the magnetic cloud?s (MC) outer layers with the solar wind acts to generate largeramplitude Alfvénic fluctuations in the downstream region, leading the MC to turbulently evolve toward a morecomplex cross-helicity configuration in the outer heliosphere. Finally, evidence of a flux rope locally generated bymagnetic reconnection events at 1 au that likely decays by the time it reaches Ulysses is also reported.