Introducing a new Disturbance Ionosphere Index (DIX)

Abstract

Although ionospheric perturbations such as Traveling Ionospheric Disturbances have a strong impact on Global Navigation Satellite Systems (GNSS) and other space based radio systems, the description of individual perturbations that might cause problems is difficult. This is due to the fact that our knowledge on the spatial and temporal variations of the ionosphere is still incomplete. A pragmatic solution to overcome this problem is the use of information that describes the perturbation degree of the ionosphere in a less specific form e.g. as an index. Although such an index does not describe the exact propagation conditions at the measurement site, the derived quantity, a scaled index number, indicates the probability of a possible impact on radio systems used in communication, navigation and remote sensing. The definition of a perturbation index that might be used in operational applications must take into account the following major requirements: relevance to practical needs, objective measure of ionospheric conditions, easy and reproducible computation and availability of a reliable data base. Following these criteria, we propose an index which is specified for its potential use by GNSS customers. Since the Total Electron Content (TEC) has been shown in many publications to act as an outstanding parameter for quantifying not only the range error but also the strength of ionospheric perturbations, we propose the definition of a Disturbance Ionosphere indeX (DIX) that is based on GNSS measurements. Following standard computational rules the proposed DIX may be defined on local, regional and global scale depending on user needs. To illustrate the use of the index, the Halloween storm is discussed. The proposed index does not require any calibration procedure and can easily be calculated. The index is applicable to radio systems which are impacted by a perturbed ionosphere characterized by a high variability in space and time. If accepted by a broad community, the index could efficiently be used in operational ionosphere data services.