Upward electrical discharges observed above Tropical Depression Dorian

Area of Science:

• Atmospheric science
• Electromagnetism
• Thunderstorm phenomena

Background:

• Upward electrical discharges from thunderstorms, classified as starters, jets, and gigantic jets, are rare and unpredictable.
• Previous knowledge is based on limited observations, often recording only one type of discharge.
• These phenomena significantly impact atmospheric regions and couple different atmospheric layers.

Purpose of the Study:

• To report a unique, close-distance observation of multiple upward electrical discharge types from a single event.
• To analyze the characteristics and origins of starters, jets, and gigantic jets.
• To investigate the electrical properties and electromagnetic emissions of these discharges.

Main Methods:

• Close-distance optical and electromagnetic data collection during Tropical Depression Dorian.
• Classification of observed upward discharges based on terminal altitudes.
• Analysis of discharge polarity and electromagnetic radiation patterns.

Main Results:

• Observation of seven upward discharges: one starter, two jets, and four gigantic jets.
• All discharges exhibited negative polarity, indicating a common origin in the thundercloud's charge region.
• Discharge channels extended up to 30 km above the thundercloud.
• Discharges did not emit low-frequency electromagnetic radiation typical of normal lightning.

Conclusions:

• The simultaneous occurrence of multiple upward discharge types suggests a shared initiation mechanism within a single thundercloud.
• The negative polarity indicates a connection to the cloud's main negative charge region.
• The extended channel and lack of low-frequency radiation differentiate these events from conventional lightning, requiring further investigation into their physics.