Abstract:
We use the World Wide Lightning Location Network (WWLLN), low-frequency magnetic fields measured at Duke University, and storm intensity data (winds and central pressure) 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 vertical impulse charge moment changes are derived from the Duke magnetic field measurements. In agreement with past studies, we find episodic inner core lightning outbreaks prior to and during most changes in storm intensity. A new result of our analysis 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, we find that 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, they had an accumulated effect on the ionospheric electron density, as shown by recent modeling studies. Our results suggest that the inner core lightning in intense hurricanes might be significant drivers of perturbations in the lower ionosphere during these inner core lightning outbreaks.
