Subionospheric VLF/LF phase perturbations produced by lightning‐whistler induced particle precipitation

Abstract

New evidence of phase perturbations of subionospheric VLF/LF signals, produced by lightning‐whistler‐induced precipitation of bursts of radiation belt electrons, is reported. Phase changes of 0.1–1.0 µs on a 12.9‐kHz signal arriving at Palmer, Antarctica (L ∼ 2.4), over a ∼2400‐km path are regularly observed with a characteristic signature of a rapid (≤ 1 s) onset followed by a relatively slow (10–30 s) recovery. Event occurrence peaks during equinoctial periods, with typical rates of 1–40 events per hour lasting for several hours per night. The observed phase perturbations can be interpreted to correspond to a rapid reduction of up to ∼0.1–1.0 km in the effective nighttime ionospheric reflection height (∼85 km) for the subionospheric VLF signals. The incident energetic particle fluxes that are required to produce the extra ionization are estimated to be ∼10−3‐10−2 ergs cm−2 s−1. Such flux levels are generally consistent with those estimated using theoretical models of whistler‐particle resonant scattering as well as direct satellite‐based observations of whistler‐induced precipitation. This phenomenon provides a sensitive means for detecting wave‐induced burst particle precipitation. The ionospheric perturbations resulting from such precipitation may cause significant errors in certain global navigation aids, such as the Differential Omega and LORAN‐C systems.

Long-term variations in tweek reflection height in the D and lowerEregions of the ionosphere

“…Energetic electrons trapped along magnetic field lines can precipitate into the lower ionosphere through pitch angle scattering in the magnetosphere. Electrons with energies of 30-300 keV can penetrate into the D region altitude [e.g., Helliwell et al, 1973;Inan et al, 1985]. At lower latitudes over Japan (L = 1.3), electron precipitation during a large geomagnetic storm was reported [Kikuchi and Evans, 1989].…”

Space weather effects on the low latitude D-region ionosphere during solar minimum

“…It is also well known that like solar flares, magnetic storms are accompanied by ionospheric disturbances which can occur up to the D and E regions (e.g., Antonova et al 1996). Communication and navigation systems such as VLF, LF, and GPS can be significantly affected by ionospheric perturbations associated with the auroral electrojet and high-energy particle precipitation during high geomagnetic activity and can extend to the mid-latitudes (Inan et al 1985). However, much of the focus of the impact of geomagnetic storms on the ionosphere has been at high latitudes (e.g., Kikuchi and Evans 1983).…”

Sub-ionospheric VLF signal anomaly due to geomagnetic storms: a statistical study

“…Various causes of disturbances have been identified mainly from space and tropospheric phenomena. Therefore VLF signals contain information about an evolution of the lower ionosphere (e.g., D-layer formation and disappearance time) (Chakrabarti et al, 2010), space weather effects such as geomagnetic storms (Kikuchi and Evans, 1983), effects of solar flares and solar energetic particles events (Mitra, 1974;Thomson and Clilverd, 2001;Todoroki et al, 2007), lightning-induced energetic particle precipitations and direct heating due to intensive lightning discharges and Transient Luminous Events (TLEs) (Inan et al, 1985(Inan et al, , 1988Hobara et al, 2001) and even effects of strong gamma ray bursts far away beyond the solar system (Tanaka et al, 2010).…”