Capabilities and applicability of ionospheric perturbation indices

Applications using transionospheric radiosignals (e.g. GNSS applications and HF communication) are impacted by ionosphere perturbations because the propagation of radiowaves is sensitive to the plasma density in the ionosphere. Ionospheric perturbations can have very different character. Their spatial range can vary between global and very local effects (a few hundreds of km range) and their temporal range varies between seconds and days. The source of these ionosphere perturbations can be very different dynamics in the ionosphere and upper atmosphere. Dependent on the charcter of the plasma perturbation, applications are impacted differently. Many ionosphere perturbation indices have been introduced in past (e.g. ROTI, S4, sigmaPhi, AATR, Reff, W-index, SISTED, SOLERA, DIXSG, IBI, Dfu/Dfl, etc.). They characterize the state of ionospheric perturbations considering different types of plasma perturbations. This is an assessment of a subset of diverse ionospheric indices. It describes the objectives of the indices, demonstrates their performance in a case study for September 2017 and indicates their applicability for different use cases in science and industry. This assessment will guide users to find the appropriate index for their purposes.