Traveling Ionospheric Disturbances (TIDs)

Traveling ionospheric disturbances are space weather in nature and cause fluctuations in electron density that can have impacts on HF propagation.  Two techniques, GNSS based total electron content (integrated density through the ionosphere and plasmasphere), and incoherent scatter radar (direct altitude profiles of temperature, density, velocity), can provide spatial structure information on these disturbances.

Solar Flare and Storm Effects

Solar flares cause D region based HF blackouts, but have effects through the ionosphere and neutral atmosphere.  September 2017 was characterized by multiple solar flares as well as large geomagnetic storm perturbations.  Studying these helps understand the system's response to forcing.

Small-Scale Mid Latitude Irregularities

At mid-latitudes over North America, we have known for more than a decade that HF radars (SuperDARN) see almost constant backscatter from small-scale irregularities moving at slow ionospheric speeds.  The causes of these irregularities are still under investigation, but they are very useful as a remote diagnostic.  This will give updates on progress toward understanding the irregularity origins.  Their presence may cause short time period HF propagation path changes.