Scaling Features of High‐Latitude Geomagnetic Field Fluctuations at Swarm Altitude: Impact of IMF Orientation

Abstract

This paper attempts to explore the statistical scaling features of high‐latitude geomagnetic field fluctuations at Swarm altitude. Data for this study are low‐resolution (1 Hz) magnetic data recorded by the vector field magnetometer on board Swarm A satellite over 1 year (from 15 April 2014 to 15 April 2015). The first‐ and second‐order structure function scaling exponents and the degree of intermittency of the fluctuations of the intensity of the horizontal component of the magnetic field at high northern latitudes have been evaluated for different interplanetary magnetic field orientations in the GSM Y‐Z plane and seasons. In the case of the first‐order structure function scaling exponent, a comparison between the average spatial distributions of the obtained values and the statistical convection patterns obtained using a Super Dual Auroral Radar Network dynamic model (CS10 model) has been also considered. The obtained results support the idea that the knowledge of the scaling features of the geomagnetic field fluctuations can help in the characterization of the different ionospheric turbulence regimes of the medium crossed by Swarm A satellite. This study shows that different turbulent regimes of the geomagnetic field fluctuations exist in the regions characterized by a double‐cell convection pattern and in those regions near the border of the convective structures.

On the Multifractal Features of Low‐Frequency Magnetic Field Fluctuations in the Field‐Aligned Current Ionospheric Polar Regions: Swarm Observations

“…Indeed, according to 2D MHD calculations of the inertial Alfvenic fluid equations, the interacting coherent structures form nearly 2D static potential structures, and thus, as a satellite moves across these nearly static structures, they exhibit low‐frequency fluctuations due to Doppler shifts. Furthermore, the range of investigated timescales (from 0.1 up to 10 s) deals with time intervals where it can be reasonably assumed that the structures are mainly frozen, as also reported in other papers (e.g.,De Michelis et al, ; Gjerloev et al, ). Indeed, it has been clearly shown that in the dayside/nightside sectors, the FAC structures are nearly stable up to 60/160 s, respectively.…”

“…According to Kintner and Seyler (), the range of scales where turbulence plays a relevant role is from few meters up to ∼1000 km in the topside F region of the high‐latitude ionosphere, a range of spatial scales where large magnetic and electric field fluctuations have been observed. In recent years, an extensive literature has demonstrated that high‐latitude magnetic and electric field fluctuations, as well as plasma density variations, show scale‐invariance and intermittent turbulent features (De Michelis et al, ; ; Golovchanskaya et al, , Spicher et al, ; Tam Sunny et al, ). Furthermore, the scale‐invariance nature of magnetic field fluctuations has been shown to be a function of the different polar regions (polar cap, cusp, auroral oval), the magnetic local time, the interplanetary magnetic field conditions and the geomagnetic activity disturbance level (De Michelis et al, , , ).…”

On the 2015 St. Patrick's Storm Turbulent State of the Ionosphere: Hints From the Swarm Mission

“…For example, a great attention has been given to the turbulent properties of electric (see, e.g., Golovchanskaya & Kozelov, 2010; Heppner et al., 1993; Kozelov & Golovchanskaya, 2006; Tam et al., 2005; Weimer et al., 1985) and magnetic fluctuations (De Michelis et al., 2015; Golovchanskaya et al., 2006; Kozelov & Golovchanskaya, 2006) observed at different altitudes and latitudes by ground and space. The increased interest in the ionospheric turbulence phenomena (e.g., De Michelis et al., 2017; Dyrud et al., 2008; Grach et al., 2016; Pécseli, 2016; Spicher et al., 2015) demonstrates the need to better understand these processes and the different ways in which they can influence the ionospheric environment. For instance, the generation and dynamics of ionospheric inhomogeneities and irregularities (see, e.g., Basu et al., 1988; Earle et al., 1989; Giannattasio et al., 2019) can be affected by turbulence processes occurring in the plasma and this means that ionospheric turbulence may play a significant role in the framework of space weather.…”

Characterising the electron density fluctuations in the high-latitude ionosphere at Swarm altitude in response to the geomagnetic activity

“…In recent literature, the Hurst exponent has been successfully used to characterise the correlations and the persistent features inherent to magnetic field fluc− tuations observed from the ground [Balasis et al, 2006[Balasis et al, , 2008[Balasis et al, , 2009De Michelis et al, 2015a] and via in situ ionospheric measurements performed by the Swarm mission [De Michelis et al, 2015b;De Michelis et al, 2016;De Michelis et al, 2017]. In this work, we applied the Hurst exponent technique to the electron density fluctuations measured by Swarm in the ionospheric F− layer by performing the same approach of the detrended structure function analysis (DSFA) used by De Michelis et al [2015a] and consisting in the following steps.…”

“…This suggests that the internal stabilizing processes driving the antipersistence are less and less effective in bringing back the system to sta− tionary conditions in presence of stronger and stronger externally−induced disturbances that tend to more and more increase the electron density fluctuations. In pre− vious studies, the persistent character of the horizontal geomagnetic field fluctuations was associated with the onset of global convection patterns at high latitudes in different IMF orientations [De Michelis et al, 2017]. In the light of this, the reduced antipersistence during more disturbed periods could be associated with the en− hancement of the convection patterns driven by the electric field forcing the open geomagnetic field lines.…”