Analysis of ionospheric electrodynamic parameters on mesoscales – a review of selected techniques using data from ground-based observation networks and satellites

Vanhamäki, Heikki; Amm, O.

doi:10.5194/angeo-29-467-2011

Cited by 21 publications

(24 citation statements)

References 70 publications

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“…These magnetic field components are then fitted with the one-dimensional (1-D) and two-dimensional (2-D) SECS (Vanhamäki & Amm, 2011). The geographic locations of the satellite's magnetic footpoints at 110-km altitude are calculated and then converted to SPH-AACGM coordinates.…”

Section: Magnetic Field Analysismentioning

confidence: 99%

Field‐Aligned and Horizontal Currents in the Northern and Southern Hemispheres From the Swarm Satellite

2019

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We present statistical investigation of the high‐latitude ionospheric current systems in the Northern Hemisphere (NH) and Southern Hemisphere (SH) during low (Kp < 2) and high (Kp ≥ 2) geomagnetic activity levels. Nearly 4 years of vector magnetic field measurements are analyzed from the two parallel flying Swarm A and C satellites using the spherical elementary current system method. The ionospheric horizontal and field‐aligned currents (FACs) for each auroral oval crossing are calculated. The distributions of the mean values of FACs as well as the horizontal curl‐free and divergence‐free currents in magnetic latitude and magnetic local time for each hemisphere and activity level are presented. To estimate the NH/SH current ratios for the two activity levels, we remove seasonal bias in the number of samples and in the Kp distribution by bootstrap resampling. This is done in such a manner that there are equal number of samples from each season in each Kp bin. We find that for the low activity level, the currents in the NH are stronger than in the SH by 12±4% for FAC, 9±2% for the horizontal curl‐free current, and 8±2% for the horizontal divergence‐free current. During the high activity level, the hemispheric differences are not statistically significant. This suggests that the local ionospheric conditions, such as magnetic field strength or daily variations in insolation, may be important and play a larger role during quiet than disturbed periods. This issue must be studied further.

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Section: Magnetic Field Analysismentioning

confidence: 99%

Field‐Aligned and Horizontal Currents in the Northern and Southern Hemispheres From the Swarm Satellite

2019

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“…The multiple arcs system is observed often rather than one auroral arc. Various observations have shown that in bright areas, Hall conductivity has maximum values; while in the dark areas, there is very low Hall conductivity [ Vanhamäki and Amm , ]. Since the asymptotically path‐connected set with d f ≥1 and θ <0 occurs in the ionosphere, Hall conductivity appears to be associated with “channeling” of particle motion.…”

Section: Comparison With Experimental Datamentioning

confidence: 99%

Use of fractal approach to investigate ionospheric conductivity in the auroral zone

2013

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[1] Fractal geometry is used to describe the spatial structure of the ionospheric conductivity. Topological values of fractal dimension and connectivity index, characterizing the structure of the Pedersen and Hall conductivities on the nightside of the auroral zone, are analytically obtained. Restrictions imposed on fractal structure of the ionospheric conductivity are analyzed in terms of the percolation of the ionospheric Pedersen and Hall currents. It is shown that the observed scaling for the fluctuations of electric field and for the auroral glow in the auroral region is well within the limitations imposed by the critical condition for percolation of Pedersen currents. The dimension of multiple arc structures corresponds well to fractal estimates of Hall conductivity. Correspondence of theoretical estimates and experimental results indicates validity of the fractal approach to describe processes in the auroral region.

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“…This means that we get the curl‐free current vector by rotating the magnetic field of FAC by 90°. On the other hand, ground‐based magnetic measurements give the divergence‐free part of the ionospheric current [e.g., Vanhamäki and Amm , 2011, and references therein]. Thus, if we combine satellite‐ and ground‐based magnetic measurements, we get the total ionospheric current at each foot point of the satellite path.…”

Section: Discussionmentioning

confidence: 99%

Ionospheric Joule heating and Poynting flux in quasi‐static approximation

et al. 2012

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[1] Energy flow is an important aspect of magnetosphere-ionosphere coupling. Electromagnetic energy is transported as Poynting flux from the magnetosphere to the ionosphere, where it is dissipated as Joule heating. Recently Richmond derived an "Equipotential Boundary Poynting Flux (EBPF) theorem", that the Poynting flux within a flux tube whose boundary is an equipotential curve is dissipated inside the ionospheric foot point of the flux tube. In this article we study Richmond's EBPF theorem more closely by considering the curl-free and divergence-free parts as well as the Hall and Pedersen parts of the ionospheric current system separately. Our main findings are that i) divergence-free currents are on average dissipationless, ii) the curl-free Pedersen current is responsible for the whole ionospheric Joule heating and iii) pointwise match between vertical Poynting flux and ionospheric Joule heating is broken by gradients of Hall and Pedersen conductances. Results i) and ii) hold when integrated over the whole ionosphere or any area bounded by an equipotential curve. The present study is limited to quasi-static phenomena. The more general topic of electrodynamic Joule heating and Poynting flux, including inductive effects, will be addressed in a future study.

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Analysis of ionospheric electrodynamic parameters on mesoscales – a review of selected techniques using data from ground-based observation networks and satellites

Cited by 21 publications

References 70 publications

Field‐Aligned and Horizontal Currents in the Northern and Southern Hemispheres From the Swarm Satellite

Field‐Aligned and Horizontal Currents in the Northern and Southern Hemispheres From the Swarm Satellite

Use of fractal approach to investigate ionospheric conductivity in the auroral zone

Ionospheric Joule heating and Poynting flux in quasi‐static approximation

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