The coupling of the ionosphere to processes in the troposphere remains an elusive and difficult problem. The interaction between lightning and E-region ionization enhancements, specifically sporadic-E, has yet to be fully understood.
Previous research has indicated that interactions between thunderstorms and the middle and upper atmospheres do occur. Current thinking suggests that there are two primary mechanisms that transport energy from the troposphere to the lower ionosphere: the first is mechanical wave activity, and the second is electrical effects associated with lightning, including electromagnetic pulses and relativistic electrons. The mechanical coupling of waves may increase the peak plasma densities of sporadic-E layers before propagating into the F-region. Discharges from lightning couple electromagnetically and may potentially increase the peak plasma densities by creating more long-lived metal ions from the ambient population found at these altitudes. However, very little is known about the electromagnetic coupling between lightning and the ionosphere.
We hope to answer the following questions in the field of ionosphere-troposphere coupling:
- What is the coupling mechanism between lightning and sporadic E?
- What is the relationship between lightning and conductances in the ionosphere?
- Can we use measured lightning and ionospheric data to simultaneously model and analyze the physical characteristics of lightning emission and the detailed structuring of the ionospheric response?
In order to fully characterize the effect of lightning on ionospheric density structures, the TALIS (Tomographic Array for Lightning and Ionosphere Studies) project will deploy co-located ionosphere and lightning RF arrays at HF (1-30 MHz) for D- and E-region imaging, and VLF (0-500 kHz) and VHF (120-150 MHz) for lightning studies. In addition, we will utilize the IDA4D (Ionospheric Data Assimilation Four-Dimensional) model to perform tomographic reconstruction of the ionosphere for heights extending from the E-region and above using these data as well as other opportunistic E-region data sources.