All You Need To Know About Lightning
Cloud-to-Air Lightning
Cloud-to-air lightning usually happens when the air around a positively charged cloud top reaches out to the negatively charged air around it. The discharge of this lightning is not as strong as cloud-to-ground lightning and generally does not need more than one stroke to reduce the differences in the charge. If the lightning is in the lower part of the cloud it is in combination with cloud-to-ground lightning. These appear as the fingers off the main bolt. This happens because the charge difference between the ground and the cloud is much grater than the difference between the cloud and the atmosphere.