1,721,071 research outputs found
Studio di strutture multigrid rinforzate con compositi polimerici avanzati per applicazioni spaziali
No full textPc5 geomagnetic fluctuations in response to solar wind excitation and their relationship with relativistic electron fluxes in the outer radiation belt
Full text linkThis study is focused to investigate the Pc5 geomagnetic pulsations in response to the solar wind forcing and their relationship with the relativistic electron flux at geostationary orbit. We analyzed the correlation of the Pc5 power in the magnetosphere and on the ground, at low and high latitude, with the solar wind speed and fluctuation power of the interplanetary magnetic field and solar wind dynamic pressure through the years 2006-2010, also examining the relative timing between pulsations and solar wind parameters. We found a very significant correlation of the Pc5 power with simultaneous solar wind pressure fluctuations and with the solar wind speed lagged by several hours, the relative amplitude of the two correlation peaks depending on the solar cycle phase and on the latitude.
We also found a strong relationship between the Pc5 power and the >600 keV and >2 MeV electron flux at geosynchronous orbit. Clear evidence emerges that the electron flux follows the Pc5 power by about 2 days; the time delay is a bit longer for the higher energy electrons
Materiali compositi nanoparticellati e strutture avanzate per applicazioni automobilistiche
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Analisi dei processi ad arco voltaico (Arc Discharge) per incrementare la sintesi dei nanotubi in carbonio
No full textThe occurrence of upstream waves in relation with the solar wind parameters: a statistical approach to estimate the size of the foreshock region
No full textWe studied the occurrence of upstream waves in the foreshock region and their relationship with the solar wind and interplanetary magnetic field parameters. To this purpose, we developed a method for a careful identification of the upstream wave events. The results of the statistical analysis based on Cluster data (2003-2010 years) confirm that the angle between the bow shock normal direction and the interplanetary magnetic field is the key element for the wave generation; they also show the relationship between the wave occurrence and the solar wind speed and density. We focused our attention on the occurrence of wave events as a function of the distance from the bow shock. The results show that the foreshock region, where we can observe upstream waves, is characterized by an effective size that decreases with the increase of both the solar wind speed and the wave frequency. Due to the relationship between the solar wind speed and the wave frequency, we suggest that such distance is simply a function of the solar wind speed, becoming smaller when the solar wind speed increases, and then the occurring higher frequency upstream waves are confined in a more restricted region
ULF fluctuations observed along the SEGMA array during very low solar wind density conditions
No full text"We examined several events of geomagnetic field fluctuations related to upstream waves, focusing the attention on the role of the solar wind density in the control of the wave activity. Recently, it was suggested that, when the solar wind density is lower than 2 cm-3, ULF wave activity on the ground dramatically drops. Based on geomagnetic field measurements conducted at low latitude along the SEGMA array, our analysis shows that, for extremely low solar wind densities (below 1 cm-3), the wave activity on the ground disappears, regardless of cone angle conditions favourable to the transmission of upstream waves through the subsolar magnetopause and independently on the solar wind speed; conversely, for solar wind densities in the range ~1-2 cm-3, ULF fluctuations can be still observed, during favourable cone angle conditions, if the solar wind speed is higher than ~600 km\/s. Such results are confirmed by the analysis of simultaneous measurements on the ground and from Cluster spacecraft when moving in the upstream region and in the magnetosheath, during one of the examined events. We suggest that, for extremely low SW densities, the wave generation mechanism is not operating efficiently, since very few ions are reflected by a very weak bow shock.
Development of nanostructured materials for reinforced carbon fiber by means of CVD methods
No full textNanostructured material
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