The Properties and Origins of Corotating Plasmaspheric Irregularities as Revealed Through a New Tomographic Technique

This paper describes insights into the nature of corotating plasmaspheric irregularities (CPIs) enabled by a newly developed method for range- and time-resolved tomographic images of these structures. The method is based on high-precision measurements of total electron content gradients measure toward cosmic radio sources using an interferometric radio telescope, the Very Large Array (VLA). Exploiting hundreds of hours of data from the VLA Low-band Ionosphere and Transient Experiment, we confirm that CPIs are predominantly detected at night and at L shells ∼2-4. Combining this large data set with other ionospheric, atmospheric, and space weather databases, we have established that CPI detection rates are much higher when levels of solar and geomagnetic activity are low. We also demonstrate that higher detection rates coincide with drivers of perturbations in the ionospheric electric field, including sporadic E and gravity waves. The gravity wave sources most commonly associated with CPIs are jet stream bend/shear and substorm-triggered atmospheric disturbances. We also show that simulations of the plasmaspheric impact of both gravity wave-driven electric field perturbations and polarization electric fields associated with electrobuoyancy waves/sporadic E produce results that are very similar to what is observed with the VLA.