Erratum to “Assessment of the capabilities and applicability of ionospheric perturbation indices provided in Europe” [Adv. Space Res. 66 (2020) 546–562]

Perturbations in the ionosphere are of great interest not only for scientific research, but also for applications using transionospheric radiosignals (e.g. GNSS applications and HF communication), because the transmission of radiosignals is sensitive to the electron density in the ionosphere. However, ionospheric perturbations have manifold 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. All these perturbations have different physical background and different impact on applications. Many ionosphere perturbation indices that characterize the state of ionospheric perturbations have been introduced in the past (e.g. ROTI, S4, σPhi, AATR, Reff, W-index, SISTED, SOLERA, DIXSG, IBI, Dfu/Dfl, etc.). This manuscript is an assessment of a subset of diverse ionospheric indices developed and/or applied in Europe. It describes the objectives of the indices, demonstrates their character in a case study for September 2017, indicates their applicability for different use cases in science and industry and guides users to find the appropriate index for their purposes.