Polarity and energetics of inner core lightning in 2005 intense North Atlantic hurricanes

The World Wide Lightning Location Network (WWLLN; http://wwlln.net/) and low frequency magnetic fields measured at Duke University are used to examine the polarity and energetics of lightning within 100 km of the centers (inner core regions) of North Atlantic Hurricanes Emily, Katrina, and Rita (2005). WWLLN provides the lightning locations. Polarities, peak currents, and impulse vertical charge moment changes are derived from the Duke magnetic field measurements. In agreement with past studies, the episodic inner core lightning outbreaks occurred prior to and during most changes in storm intensity (winds and central pressure). A new result indicates an increase in the relative number of positive cloud-to-ground lightning in the inner core prior to and during periods of storm weakening, which is potentially important for hurricane intensity change forecasting. Additionally, the majority of inner core lightning located by WWLLN had peak currents that surpassed the threshold needed to produce optical emissions (ELVES) and drive electron density perturbations in the lower ionosphere (80-105 km). Since these high peak current lightning occurred in short duration outbreaks, there was an accumulated effect on the ionospheric electron density, as shown by recent modeling studies. Thus, inner core lightning in intense hurricanes might be significant drivers of perturbations in the lower ionosphere during these inner core lightning outbreaks. Additionally, in order to classify the type of lightning (cloud-to-ground, intra-cloud, or narrow bipolar) located by WWLLN in these hurricanes, comparisons with other lightning networks will be presented.