I. Alexeff et M. Rader, POSSIBLE PRECURSORS OF BALL-LIGHTNING - OBSERVATION OF CLOSED LOOPS IN HIGH-VOLTAGE DISCHARGES, Fusion technology, 27(3), 1995, pp. 271-273
Several hundred photographs of ultrahigh voltage discharges have been
obtained that show closed current loops. These closed current loops ma
y be precursors of ball lightning. One feature of these discharges may
explain why observations of ball lightning may be infrequent; that is
, there is a distinct threshold in voltage and/or current below which
the closed loops do not occur. This threshold current fits other exper
imental data but is well above the usually observed currents in natura
l lightning.