Equatorial ionospheric scintillation and spread F: Forecasting tools, responses to geomagnetic storms, and seasonal/longitudinal variations

Abstract

Equatorial spread F is a plasma irregularity phenomena occurring mostly at night in the equatorial F region ionosphere. Equatorial spread F is a manifestation of ionospheric interchange instabilities. It is a mode of feedback to the release of a free gravitational potential energy stored in the night-time equatorial F region due to sharp plasma density gradients. A broadband spectrum (few meters to kilometers) of field-aligned plasma density irregularities are produced by the interchange instabilities. Whenever the propagation path of an electromagnetic signal from communication and navigation satellites encounters equatorial spread F plasma irregularities, irregular fluctuations in the amplitude and phase of the signal (scintillation) are produced. Signal scintillations severely degrade the performance of trans-ionospheric communication and navigation systems. The major science objectives of this research proposal can be summarized as follow: 1. To develop scintillation forecasting tools using coherency and phase of spatial cross wavelet spectra of scintillation data from the SCINDA (Scintillation Network Decision Aid) signal receivers and the CERTO (Coherent Electromagnetic Radio Tomography) instrument on-board the C/NOFS (Communications/Navigation Outage Forecast Systems) satellite.2. To investigate the responses of equatorial spread F plasma instabilities to different levels of geomagnetic activity. The study also aims at investigating the variation with longitude and season of the responses of equatorial spread F to geomagnetic storms. We will utilize ion density, electric field and TEC data from the C/NOFS satellite, plasma density and cross polar cap potential data from the DMSP satellite, interplanetary magnetic field data from the ACE satellite, and SCINDA scintillation observations;3. To assess growth (or suppression) of the evening equatorial spread F plasma instabilities in the bottom-side equatorial F region using physics based model, empirical model, and vertical drift observations measured by an ionosonde thereby to address solstitial asymmetries and longitudinal variability of scintillation and equatorial spread F occurrences. The model calculation will utilize realistic ionospheric, geomagnetic, and atmospheric input parameters. (AU)