Plasma irregularities in the high‐latitude ionospheric F‐region and their diamagnetic signatures as observed by CHAMP

Abstract

[1] Diamagnetic effects of ionospheric irregularities have been investigated at low-latitudes before, but no corresponding effort has been made at high latitudes.In this study we demonstrate clear diamagnetic signatures of high-latitude ionospheric irregularities as observed by the CHAMP satellite. We also present the climatology of these diamagnetic signatures for the years 2001-2010 and compare it with a previous study based on Global Positioning System (GPS) scintillation measurements. The climatology of the diamagnetic signatures is in reasonable agreement with that of the scintillations. The occurrence rate of the ionospheric irregularities generally peaks along the auroral latitudes around the pole, but it is not uniform zonally. The occurrence rate exhibits a maximum at the dayside cusp and in the pre-midnight ionosphere. The occurrence rate increases with solar and/or auroral activity. The region of high occurrence rate expands equatorward with increasing auroral activity. Occurrence probabilities are higher in local winter than in local summer. The overall occurrence rate is smallest around June solstice and largest around December solstice. The ionospheric irregularities are generally accompanied by bursts of small-scale field-aligned currents (FACs), and they are related to Region 1 FACs.Citation: Park, J., R. Ehrlich, H. Lühr, and P. Ritter (2012), Plasma irregularities in the high-latitude ionospheric F-region and their diamagnetic signatures as observed by CHAMP,

Magnetic Effects of Plasma Pressure Gradients in the Upper F Region

“…Park et al () also reported higher occurrence rates in winter than summer, opposite of what we find. The contradicting results may be related to the rather complex seasonal variation of polar cap patches, discussed by, for example, Chartier et al ().…”

“…In the second row we combine data from the two hemispheres but divide the data according to seasons, in 90‐day bins centered at the solstices. The maps show significantly higher probabilities in summer than winter, the opposite of what was reported by Park et al (). In the bottom set of maps we divide the data according to geomagnetic activity via the Ap index.…”

“…This may be explained by the higher sensitivity of the Swarm instruments but could also be related to methodological differences: Park et al (2012) based their analysis on high-pass-filtered magnetic field and density measurements directly, and not estimates of their spatial gradients, as we have done here. It is therefore more significant that the distribution of events is also very different: Park et al (2012) reported highest occurrence rates in the auroral oval, while we have a clear peak in the polar cap. It is possible that this is because their study only included very strong perturbations, while our Swarm-based analysis resolves finer variations.…”

“…To our knowledge, the only previous report of diamagnetic effects at high latitudes was presented by Park et al (). They showed that magnetic field perturbations in the auroral zone, measured with the CHAMP satellite, occasionally were anticorrelated with electron density.…”

Morphology of high‐latitude plasma density perturbations as deduced from the total electron content measurements onboard the Swarm constellation

“…It was attributed to possible contribution of E ‐layer disturbances which are located between the LEO satellite and ground: hence, only signals received at the ground are affected by the E ‐layer disturbances. Our Swarm results exhibit annual variations with the maximum during December solstice (see Figures and ), which agrees with earlier in situ observations of the CHAMP satellite [ Park et al , ].…”