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Balasis G.,National institute for astrophysics | Papadimitriou C.,National and Kapodistrian University of Athens | Daglis I.A.,National and Kapodistrian University of Athens | Pilipenko V.,Space Research Institute Moscow Russia
Geophysical Research Letters | Year: 2015

Recently developed automated methods for deriving the characteristics of ultra low frequency (ULF) waves are applied to the Swarm data sets in order to retrieve new information about the near-Earth electromagnetic environment. Here we present the first ULF wave observations by Swarm, analyzing 1 year data from the mission. We find evidence for the decay of the amplitude of the Pc3 (20-100 mHz) signal with altitude in the topside ionosphere as predicted by theoretical models of wave propagation. We show that the major characteristics of the Swarm ULF power maps generally agree with respect to the wave activity seen by the upper satellite and the lower pair of satellites when the power spectrum of the upper satellite is shifted by 1 h in magnetic local time. Moreover, a puzzling enhancement, not predicted by current ULF wave theories, of compressional Pc3 wave energy was revealed by Swarm in the region of South Atlantic Anomaly. © 2015. American Geophysical Union. All Rights Reserved. Source

Shalygin E.V.,Max Planck Institute for Solar System Research | Markiewicz W.J.,Max Planck Institute for Solar System Research | Basilevsky A.T.,University of Rhode Island | Titov D.V.,European Space Agency | And 2 more authors.
Geophysical Research Letters | Year: 2015

Venus is known to have been volcanically resurfaced in the last third of solar system history and to have undergone a significant decrease in volcanic activity a few hundred million years ago. However, fundamental questions remain: Is Venus still volcanically active today, and if so, where and in what geological and geodynamic environment? Here we show evidence from the Venus Express Venus Monitoring Camera for transient bright spots that are consistent with the extrusion of lava flows that locally cause significantly elevated surface temperatures. The very strong spatial correlation of the transient bright spots with the extremely young Ganiki Chasma, their similarity to locations of rift-associated volcanism on Earth, provide strong evidence for their volcanic origin and suggests that Venus is currently geodynamically active. ©2015. American Geophysical Union. Source

Surkov V.V.,National Research Nuclear University MEPhI | Pilipenko V.A.,Space Research Institute Moscow Russia
Journal of Geophysical Research A: Space Physics | Year: 2016

Interference of an incident and reflected Alfvén pulses propagating inside the ionospheric Alfvén resonator (IAR) is studied on the basis of a simple one-dimensional model. Particular emphasis has been placed on the analysis of spectral features of ultralow frequency (∼1-15 Hz) electric perturbations recently observed by Communications/Navigation Outage Forecasting System satellite. This "fingerprint" multiband spectral structure was observed when satellite descended in the terminator vicinity. Among factors affecting spectral structure the satellite position and distance from the IAR boundaries are most significant. It is concluded that the observed spectrograms exhibit modulation with "period" depending on propagation delay time of reflected Alfvén pulses in such a way that this effect can mask a spectral resonance structure resulted from excitation of IAR eigenmodes. The proposed interference effect is capable to produce a spectral pattern resembling a fingerprint which is compatible with the satellite observations. © 2016. American Geophysical Union. All Rights Reserved. Source

Sun T.R.,University of Chinese Academy of Sciences | Wang C.,CAS Center for Space Science and Applied Research | Zhang J.J.,CAS Center for Space Science and Applied Research | Pilipenko V.A.,Space Research Institute Moscow Russia | And 2 more authors.
Journal of Geophysical Research A: Space Physics | Year: 2015

In response to interplanetary (IP) shocks, magnetic field may decrease/increase (negative/positive response) in nightside magnetosphere, while at high latitudes on the ground it has two-phase bipolar variations: preliminary impulse and main impulse (MI). Using global MHD simulations, we investigate the linkage between the MI phase variation on the ground and the magnetospheric negative response to an IP shock. It is revealed that although the two phenomena occur at largely separated locations, they are physically related and form a response chain. The velocity disturbances near the flanks of the magnetopause cause the magnetic field to decrease, resulting in a dynamo which thus powers the transient field-aligned currents (FACs). These FACs further generate a pair of ionospheric current vortex, leading to MI variations on the ground. Therefore, we report here the intrinsic physically related chain response of the magnetospheric and ground magnetic field to IP shocks, and thus link the magnetospheric sudden impulse (SI) and ground SI together. © 2014. American Geophysical Union. All Rights Reserved. Source

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