| Περίληψη: |
• A toroidal ring current model is developed to assess the ring current characteristics. • The model successfully replicates Dst index variations for G5-class geomagnetic storms with error 1–4 nT. • For G5-class storms, the peak intensity and closest inner boundary of the ring current are found to be 11.9–12.2 MA and 1.5–2.6 R E , respectively. Several current systems operate within the Earth's ionosphere-magnetosphere system, intensified during severe space weather events. Among these, the ring current plays a crucial role in determining the intensity of geomagnetic storms. Each storm exhibits distinct characteristics, largely influenced by the topology of the interplanetary magnetic field, the convection electric field, and solar wind conditions at the magnetopause. An enhanced interplanetary convection electric field enables plasma penetration into lower L-shells. In particular, the intensity, location, and spatial extent of the ring current control the reduction in the horizontal magnetic field recorded at low-latitude ground stations during a storm's main phase. However, these characteristics of the ring current are not well quantified yet. To investigate the influence of the ring current system on the geomagnetic field, we developed a model considering a three-dimensional torus-shaped current loop positioned over the magnetic equator. In the model, the current torus is defined using parameters such as intensity, azimuthal tilt, radial and latitudinal extent. The quiet-time magnetic field is described using the International Geomagnetic Reference Field model, while disturbed-time conditions are simulated by taking nonzero current intensity. We modelled ten G5-class geomagnetic storms from solar cycles 19–25 and compared the model output with the Dst index. The analysis establishes a relationship between the Dst index and ring current characteristics. The study suggests that during G5-class geomagnetic storms, the peak ring current is extremely strong, reaching 11.9–12.2 MA, and is formed close to the Earth. [ABSTRACT FROM AUTHOR] |