Observations of quiet-time moderate midlatitude L-band scintillation in association with plasma bubbles

Observations of moderate night time amplitude scintillation on the GPS L1C/A signal were recorded at the midlatitude station of Nicosia, corresponding geographic latitude and longitude of 35.18˚N and 33.38˚E respectively, on a geomagnetically quiet day. The variations of slant total electron content (STEC) and amplitude scintillation index (S4) on the night of June 12, 2014, indicate the presence of electron density depletions accompanying scintillation occurrence. The estimated apparent horizontal drift velocity and propagation direction of the plasma depletions are consistent with those observed for the equatorial plasma bubbles, thus suggesting that the moderate amplitude L-band scintillation observed over Nicosia may be associated with the extension of such plasma bubbles. The L-band scintillation occurrence was concurrent with the observations of range spread F on the ionograms recorded by the digisonde at Nicosia. The height–time–intensity plot generated using the ionogram data also showed features which can be attributed to off-angle reflections from electron density depletions, thus corroborating the STEC observations. This observation suggests that the midlatitude ionosphere is more active even during geomagnetically quiet days than previously thought and that further studies are necessary. This is particularly relevant for the GNSS user community and related applications

Observations of high-latitude geomagnetic field fluctuations during St. Patrick’s Day storm: Swarm and SuperDARN measurements

The aim of this work is to study the properties of the magnetic field’s fluctuations produced by ionospheric and magnetospheric electric currents during the St. Patrick’s Day geomagnetic storm (17 March 2015). We analyse the scaling features of the external contribution to the horizontal geomagnetic field recorded simultaneously by thethree satellites of the Swarm constellation during a period of 13 days (13–25 March 2015). We examine the different latitudinal structure of the geomagnetic field fluctuations and analyse the dynamical changes in the magnetic field scaling features during the development of the geomagnetic storm. Analysis reveals consistent patterns in the scaling properties of magnetic fluctuations and striking changes between the situation before the storm, during the main phase and recovery phase. We discuss these dynamical changes in relation to those of the overall ionospheric polar convection and potential structures as reconstructed using SuperDARN data. Our findings suggest that distinct turbulent regimes characterised the mesoscale magnetic field’s fluctuations and that some factors, which are known to influence large-scale fluctuations, have also an influence on mesoscale fluctuations. The obtained results are an example of the capability of geomagnetic field fluctuations data to provide new insights about ionospheric dynamics and ionosphere–magnetosphere coupling. At the same time, these results could open doors for development of new applications where the dynamical changes in the scaling features of the magnetic fluctuations are used as local indicators of magnetospheric conditions.Published1051A. Geomagnetismo e PaleomagnetismoJCR Journa

Reduced-dynamic and kinematic baseline determination for the Swarm mission

The Swarm mission of the European Space Agency was launched in November 2013 with the objective of performing measurements of the earth’s magnetic field with unprecedented accuracy. At the beginning of data collection, two satellites started to fly in orbits with a separation in ascending nodes of 1�–1.5� at an altitude of about 480 km, and a third satellite has been placed in a higher orbit with an altitude of 530 km. The three spacecraft are equipped with dual-frequency eight-channel GPS receivers for the generation of precise orbits. Although such orbits support the fulfillment of the primary objectives of the mission, precise space baselines may be helpful for studying the earth’s gravity field, a spin-off application of the Swarm mission. Hitherto, a particular challenge for the computation of precise baselines from Swarm has been the presence of half-cycle ambiguities in GPS carrier phase observations, which complicate the implementation of integer ambiguity resolution methods. The present study shows the feasibility of generating carrier phase observations with full-cycle ambiguities, which in turn has been used to improve the performance of reduced-dynamic and kinematic precise baseline determination schemes. The implemented strategies have been tested in a period of 90 days in 2016. The obtained reduced-dynamic and kinematic baseline products were evaluated by inter-product and inter-agency comparisons using two independent software tools