Troposphere-Ionosphere Interactions

The coupling of the ionosphere to processes in the troposphere remains a complex and outstanding problem. Specifically, the mechanism by which lightning causes E region ionization enhancements (i.e. sporadic-E) has yet to be fully understood. These enhancements disrupt ground-to-satellite communication and cause loss of lock on satellite (e.g. GPS) signals. 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 higher regions. 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.


Representation of atmospheric layers with coupling between lightning and the E region of the ionosphere

In order to fully characterize the effect of lightning on ionospheric density structures, we have deployed ground-based lightning and ionospheric receivers in New Mexico, which is an area of high-lightning activity. In addition, we have modified the Ionospheric Data Assimilation Three-Dimensional (IDA4D) 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, most notably from the Los Alamos Portable Pulser (LAPP) and the FORTE satellite. By merging knowledge in these areas, we hope to achieve significant progress in the field of ionosphere-troposphere coupling and to answer the following outstanding questions:

  1. What is the coupling mechanism between lightning and sporadic E?
  2. What is the relationship between lightning and conductances in the ionosphere?
  3. 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?