The ULF Magnetic Fields Generated by Thunderstorms: A Source of ULF Geomagnetic Pulsations?
Abstract
It has long been known that thunderstorms produce strong electric field fluctuations in their immediate vicinity but it has been little recognized that these storms are also a source of strong ULF magnetic field fluctuations. Some characteristics of the magnetic field fluctuations were documented for a thunderstorm occurring in 1990 [Fraser-Smith, Geophys. Res. Letts., 20, 467--470, 1993]. We now provide further measurements of these magnetic field changes for an intense isolated thunderstorm that passed over the San Francisco Bay area on 9 September 1999. The thunderstorm is characterized by NLDN measurements of its associated lightning and, as compared with the earlier measurements, the new measurements have much greater time resolution and more components of the magnetic field changes are measured. Given the possibility that the thunderstorm-related ULF magnetic field changes can stimulate ULF hydromagnetic waves in the ionosphere, these measurements suggest, once again, that thunderstorms may be a source of ULF energy in the magnetosphere that can contribute to the generation and amplification of some classes of ULF geomagnetic pulsations. In addition, it may also be significant that there are a large number of thunderstorms ( ~ 2000) in progress at any time at low (tropical) latitudes, and thus they are ideally located to inject ULF hydromagnetic waves into the radiation belt at frequencies corresponding to some of the ion gyrofrequences.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2001
- Bibcode:
- 2001AGUFMAE31A0067F
- Keywords:
-
- 1530 Rapid time variations