Whistler‐Mode Waves in Magnetic Ducts

Abstract

AbstractObservations from the NASA Magnetospheric Multiscale (MMS) satellites show packages of extremely low frequency (ELF) whistler‐mode waves localized inside the small‐scale irregularities of the magnetic field. These irregularities are formed by the narrow field‐aligned channels where the magnitude of the background magnetic field inside the channel is greater or less than outside. By analogy with the classical density ducts, we introduce the high‐B duct, where the magnitude of the field inside the channel is greater than the outside, and the low‐B duct, where the magnitude of the field inside the channel is less than the outside. We investigate the guiding of the ELF whistler‐mode waves by high‐B and low‐B ducts. We derive the analytical criteria for the wave ducting by these ducts and confirm them with two‐dimension, time‐dependent simulations of the electron‐MHD model. Also, we model ELF whistler‐mode waves observed inside the high‐B and low‐B ducts by MMS satellites.