The Venus Express mission carries a magnetometer sampled at a rate of 128Hz and returned to Earth during its periapsis passage. These records contain many strong (up to 1nT peak to peak) short-lived (100-500ms) pulses of magnetic signals near 100Hz. Examination of the magnetic field orientation when bursts are present indicates that the magnetic field has a significant component radially into or out of the ionosphere. When there is no such radial component of the magnetic field there are not impulsive signals. This behavior is consistent with the well-known guidance of whistler mode waves by magnetic fields. Without a component of the magnetic field along wave normal the signal cannot escape from the atmosphere. Thus the rate of lightning signals beneath the ionosphere is much greater than it would first appear from the observations made within the ionosphere.
AAS/Division for Planetary Sciences Meeting Abstracts #39
- Pub Date:
- October 2007