Return stroke in Positive 30-90 60x103 3-5 pulses per flash negative ground time) flashes Stepped leader in Positive 1-2 15-25 Within 200 µs just negative ground prior to a return flashes stroke Dart-stepped leader Positive 1-2 6-8 Within 200 µs just in negative ground to a return stroke flashes Initial breakdown in Positive 20-40 70-130 Some milliseconds to negative ground some tens of flashes milliseconds before the first return stroke Initial breakdown in Negative 50-80 600-800 The largest pulses in a cloud flashes Regular pulse burst Both polarities are 1-2 5-7 Occur later in a flash; in both cloud and about equally 20-40 pulses per burst negative ground probable flashes Compact intracloud Both polarities 10-30 - Typically not discharge (narrow with negative being preceded or followed bipolar event) more frequent by any other lightning process within hundreds of milliseconds Notes: 1. The polarity of the initial half cycle in the case of bipolar pulses. 2. According to the atmospheric electricity sign convention, a downward directed electric field vector is assumed to be positive.
Return stroke in negative ground flashes Positive 30-90 time) 60x103 3-5 pulses per flash Stepped leader in negative ground flashes Positive 1-2 15-25 Within 200 µs just prior to a return stroke Dart-stepped leader in negative ground flashes Positive 1-2 6-8 Within 200 µs just to a return stroke Initial breakdown in negative ground flashes Positive 20-40 70-130 Some milliseconds to some tens of milliseconds before the first return stroke Initial breakdown in cloud flashes Negative 50-80 600-800 The largest pulses in a Regular pulse burst in both cloud and negative ground flashes Both polarities are about equally probable 1-2 5-7 Occur later in a flash; 20-40 pulses per burst Compact intracloud discharge (narrow bipolar event) Both polarities with negative being more frequent 10-30 - Typically not preceded or followed by any other lightning process within hundreds of milliseconds Notes: 1. The polarity of the initial half cycle in the case of bipolar pulses. 2. According to the atmospheric electricity sign convention, a downward directed electric field vector is assumed to be positive.
EdBd-2_P-II_Ch-7.docx