http://hdl.handle.net/2122/103 Search the Channel search http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/4135 Title: Daily variation at three Antarctic geomagnetic observatories within the polar cap <br/> <br/>Authors: Pietrolungo, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Lepidi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cafarella, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Santarelli, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Di Mauro, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia <br/> <br/>Abstract: In this work we present a statistical analysis of the diurnal variation as observed at three Antarctic observatories located at different positions within the polar cap during the year 2006. Data used for the analysis are from the Italian geomagnetic observatory at Mario Zucchelli Station (formerly Terra Nova Bay, geographic latitude 74.7° S, corrected geomagnetic latitude 80.0° S), from the French-Italian observatory at Concordia Station (75.1° S, 88.9° S) and from the French observatory at Dumont D’Urville (66.7° S, 80.4° S), which are located in pairs at the same geographic and corrected geomagnetic latitude; such a position allows to distinguish whether the geographic or the geomagnetic reference system is better suitable to describe the observed phenomena at so high latitudes. The peculiarities of the daily variation as observed during this year and its relation with the observatory location and magnetospheric and interplanetary conditions were analysed. Data were also studied taking into account different Lloyd seasons. The results indicate that the 24-h variation is quite persistent, but its amplitude strongly depends on season and global geomagnetic activity: indeed, it almost vanishes during local winter for quiet geomagnetic conditions; this reduction is more evident at the stations closer to the geographic pole, where the solar radiation reduction during winter is more dramatic. The Interplanetary Magnetic Field orientation has been found to be important in that the north-south and the east-west components control the amplitude and the diurnal pattern of the variation, respectively. http://hdl.handle.net/2122/4010 Title: Pc3-Pc4 pulsations at Terra Nova Bay (Antarctica): seasonal dependence of the power and its relationship with solar wind parameters <br/> <br/>Authors: Santarelli, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Lepidi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Palangio, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cafarella, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia <br/> <br/>Abstract: We conducted a statistical analysis of the pulsation activity detected during 1998 at the Antarctic Italian geomagnetic observatory at Terra Nova Bay (corrected geomagnetic latitude: -80°). In particular, the availability of high resolution (1 Hz) data for an entire year allowed us to extend also to the local winter, for the first time, the analysis of the daily variation of the Pc3-Pc4 pulsation power and of its relationship with the solar wind parameters and to investigate possible seasonal dependences. Our results suggest that the location of the station with respect to the polar cusp (which strongly depends on local time and season) plays an important role in determining the local Pc3-Pc4 power level and its dependence on the global magnetospheric activity and interplanetary parameters. http://hdl.handle.net/2122/3934 Title: The Earth's passage of the April 11, 1997 coronal ejecta: geomagnetic field fluctuations at high and low latitude during northward interplanetary magnetic field conditions <br/> <br/>Authors: Lepidi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Francia, P.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Villante, U.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Meloni, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Lazarus, A. J.; Center for Space Research, MIT, Cambridge, USA; Lepping, R. P.; Laboratory for Extraterrestrial Physics, NASA/GSFC, Greenbelt, USA <br/> <br/>Abstract: An analysis of the low frequency geomagnetic field fluctuations at an Antarctic (Terra Nova Bay) and a low latitude (L'Aquila, Italy) station during the Earth's passage of a coronal ejecta on April 11, 1997 shows that major solar wind pressure variations were followed at both stations by a high fluctuation level. During northward interplanetary magnetic field conditions and when Terra Nova Bay is close to the local geomagnetic noon, coherent fluctuations, at the same frequency (3.6 mHz) and with polarization characteristics indicating an antisunward propagation, were observed simultaneously at the two stations. An analysis of simultaneous measurements from geosynchronous satellites shows evidence for pulsations at approximately the same frequencies also in the magnetospheric field. The observed waves might then be interpreted as oscillation modes, triggered by an external stimulation, extending to a major portion of the Earth's magnetosphere. http://hdl.handle.net/2122/3933 Title: Polarization pattern of low-frequency geomagnetic field fluctuations (0.8-3.6 mHz) at high and low latitude <br/> <br/>Authors: Lepidi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Francia, P.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Villante, U.; Dipartimento di Fisica, Università dell'Aquila, L'Aquila, Italy; Lanzerotti, L. J.; Bell Laboratories, Lucent Technologies, Murray Hill, New Jersy; Meloni, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia <br/> <br/>Abstract: A statistical analysis of the polarization pattern of low-frequency geomagnetic field fluctuations (0.8-3.6 mHz) covering the entire 24-hour interval has been performed at an Antarctic station (Terra Nova Bay) and a low-latitude station (L'Aquila, Italy) during the entire 1995. The results show a complex pattern in which, in agreement with predictions, four polarization reversals occur at high latitude during the local day. A comparison with another Antarctic station, McMurdo, during a shorter interval in 1994 confirms these results. At low latitude the polarization sense in the afternoon reverses with respect to the morning, but the reversal is delayed by a few hours after the expected local noon. In Antarctica the polarization pattern does not show any dependence on frequency and season, while at L'Aquila it is better defined for frequencies below ≈2 mHz and during local summer.