sentences:  Where blue jets are believed to initiate between the upper positive charge region and a negative screening layer directly above this region, gigantic jets appear to initiate between the upper positive and lower negative charge regions in the thundercloud.In a similar process to how blue jets form, the higher charge region is discharged by the leader network before the same occurs in the lower charge region, and one end of the leader network propagates upward from the cloud toward the ionosphere.Gigantic jets reach higher altitudes than blue jets, and the upper portion of the jet changes color from blue to red.