What is the shortest possible x-line extent for 3D magnetic reconnection?

Yi-Hsin Liu, Dartmouth College, Physics and Astronomy, Hanover, NH, United States, Kai Huang, University of Science and Technology of China, Hefei, China; Dartmouth College, Hanover, United States, Tak Chu Li, Dartmouth College, Hanover, NH, United States, Michael Hesse, University of Bergen, Bergen, Norway, Wei-Jie Sun, University of Michigan Ann Arbor, Climate and Space Sciences and Engineering, Ann Arbor, MI, United States, Jiang Liu, University of California Los Angeles, Department of Earth, Planetary, and Space Sciences and Institute of Geophysics and Planetary Physics, Los Angeles, CA, United States, James Burch, Southwest Research Institute, San Antonio, TX, United States, James A Slavin, University of Michigan Ann Arbor, Department of Climate and Space Sciences and Engineering, Ann Arbor, MI, United States and Quanming Lu, Univ. Sci. & Tech. of China, Hefei, China