Constraints to do realistic modeling of the electric field at the tip of a lightning leader

Alexander Broberg Skeltved1, Nikolai Ostgaard2, Brant Carlson3, Andrew Mezentsev4 and Nikolai G Lehtinen2, (1)University of Bergen, Bergen, Norway, (2)University of Bergen, Department of Physics and Technology, Bergen, Norway, (3)Carthage College, Kenosha, WI, United States, (4)University of Bergen, Birkeland Centre for Space Science, Bergen, Norway