Validation and Interpretation of a Three-dimensional Configuration of a Magnetic Cloud Flux Rope

One strong magnetic cloud (MC) with a magnetic field magnitude reaching ∼40 nT at 1 au during 2012 June 16–17 is examined in association with a preexisting magnetic flux rope (MFR) identified on the Sun. The MC is characterized by a quasi-three-dimensional (3D) flux rope model based on in situ measurements from the Wind spacecraft. The contents of the magnetic flux and other parameters are quantified. In addition, a correlative study with the corresponding measurements of the same structure crossed by the Venus Express (VEX) spacecraft at a heliocentric distance of 0.7 au and with an angular separation of ∼6° in longitude is performed to validate the MC modeling results. The spatial variation between the Wind and VEX magnetic field measurements is attributed to the 3D configuration of the structure appearing as a knotted bundle of flux. A comparison of the magnetic flux contents between the MC and the preexisting MFR on the Sun indicates that the 3D reconnection process accompanying an M1.9 flare may correspond to the magnetic reconnection between the field lines of the preexisting MFR rooted in the opposite polarity footpoints. Such a process reduces the amount of the axial magnetic flux in the erupted flux rope, by approximately 50%, in this case.

在2012年6月16 - 17日期间，在1个天文单位处有一个强磁云（MC），其磁场强度达到约40纳特，本文结合在太阳上识别出的一个预先存在的磁通量绳（MFR）对其进行了研究。该磁云通过基于“风”号航天器原位测量的准三维（3D）磁通量绳模型来表征。磁通量及其他参数的含量被量化。此外，还与“金星快车”（VEX）航天器在日心距离为0.7个天文单位、经度角距约为6°处对同一结构的相应测量进行了相关研究，以验证磁云建模结果。“风”号和“金星快车”磁场测量值之间的空间差异归因于该结构呈现为打结的磁通量束的三维形态。对磁云与太阳上预先存在的磁通量绳之间磁通量含量的比较表明，伴随M1.9级耀斑的三维重联过程可能对应于扎根于相反极性足点的预先存在的磁通量绳的磁力线之间的磁重联。在这种情况下，这样一个过程使爆发的磁通量绳中的轴向磁通量减少了约50%。