They look strange to us because they are rare, but they are just a different variety of plasma discharge. Depending on the temperature and energy level of the plasma, electrical discharges will take different forms. Actually, the plasma itself will undergo several “phases” as well, and one of these, the “glow” phase is manifested in the atmosphere in the form of the aurora.
People had been reporting these for years, but no scientist believed it until the phenomenon had been captured with high-speed cameras. A few very skilled amateurs knowing where to look with good SLR’s have recorded them. Another thing that was thought to be impossible were flashes on the moon reported visually by observers for years. These have now been recorded be camera and I believe that new craters have been found.