Form the end of substorm growth phase till the first 1-2 minutes of onset: Evidence of a transitional stage in optical auroral and in-situ observations

Jun Liang1, Ping Zhu2,3, Eric Donovan1 and Miho Saito4, (1)University of Calgary, Physics and Astronomy, Calgary, AB, Canada, (2)University of Science and Technology of China, Key Laboratory of Geospace Environment, Chinese Academy of Sciences, Hefei, China, (3)Univ Wisconsin-Madison, Madison, United States, (4)Tokyo Institute of Technology, Earth and Planetary Sciences, Tokyo, Japan