On the 2015 St. Patrick's Storm Turbulent State of the Ionosphere: Hints From the Swarm Mission. Issue 8 (12th August 2020) - De Michelis, P.
Abstract: The scaling features of electron density fluctuations during the St. Patrick's magnetic storm (17 March 2015) are analyzed to try to characterize the possible turbulent nature of the ionosphere during the development of the geomagnetic storm. The electron density values recorded by two of the three satellites of Swarm constellation during a period of 7 days (16–22 March 2015) around the storm peak are analyzed at middle‐ and high‐latitude regions in both hemispheres. The analysis reveals interesting patterns in the scaling properties of electron density fluctuations and a possible explanation for the occurrence of high values of the Rate of change Of the electron Density Index (RODI). Indeed, the obtained results seem to suggest that very high values of RODI, which describes the structuring of the plasma within a fixed time and is used as an ionospheric disturbance index, are correlated with the antipersistent character of electron density fluctuations and with the values around 5/3 of the power spectral density scaling exponent. These features are independent of the different phases of the analyzed geomagnetic storm and seem to support the idea of a fluid and/or magnetohydrodynamic turbulence as the main responsible of the high values of RODI recorded at high latitudes in the auroral and polar cap regions. Plain Language Summary: Electron density fluctuations characterizing the ionospheric plasma during the St. Patrick's geomagnetic storm occurred on 17 March 2015 are analyzed to investigate their possible turbulent nature. To perform this study, electron density values recorded by two of the three satellites of the Swarm constellation are considered at middle and high latitudes of both hemispheres between 16 and 22 March 2015. Results show that electron density fluctuations present interesting patterns and that high values of the Rate Of change of electron Density Index (RODI), which is used as an ionospheric disturbance index, may be related to a turbulent dynamics of the ionosphere. Specifically, independently of the different phases of the analyzed geomagnetic storm, the observed features seem to support the idea of a fluid and/or magnetohydrodynamic turbulence as the main cause of the high values of RODI recorded at high latitudes in the auroral and polar cap regions. Key Points: Self‐similarity/affinity nature of the plasma density fluctuations in the F region of middle‐ and high‐latitude ionosphere Plasma density fluctuations at high latitudes in the auroral and polar cap regions seem to be related to a turbulent ionospheric dynamics High values of RODI can be a proxy of the occurrence of ionospheric turbulence