http://hdl.handle.net/2122/99 Search the Channel search http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/3983 Title: Long period geomagnetic field fluctuations at Terra Nova Bay (Antarctica) <br/> <br/>Authors: Villante, U.; Dipartimento di Fisica, Università dell'Aquila, L’Aquila, Italy; Lepidi, S.; Dipartimento di Fisica, Università dell'Aquila, L’Aquila, Italy; Francia, P.; Dipartimento di Fisica, Università dell'Aquila, L’Aquila, Italy; Meloni, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Palangio, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia <br/> <br/>Abstract: A statistical analysis of the power spectra (0.7 - 5 mHz) of the geomagnetic field components H and D recorded at Terra Nova Bay (Antarctica) during three austral summers close to the maximum of solar activity reveals power enhancements in the H componenta t = 3.3, 3.9 and 4.5 mHz, which become more evident during daytime intervals. During intervals characterized by higher solar wind speeds these spectral features more clearly emerge and are also accompanied by other enhancements at lower frequencies (= 1.2, 1.9 and 2.7 mHz). The observed frequencies are close to the ones detected both at auroral and low latitudes. http://hdl.handle.net/2122/3892 Title: Geomagnetic and ionospheric data analysis over Antarctica: a contribution to the long term trends investigation <br/> <br/>Authors: Alfonsi, Lu.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; De Franceschi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; De Santis, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia <br/> <br/>Abstract: The analysis of the f oF2 ionosonde data acquired at mid and high latitudes reveals a general decreasing of the F2 plasma frequency over more than two solar cycles, showing steeper trends over the high latitude stations and, in particular, over Antarctica. A careful analysis of the f oF2 hourly data, opportunely catalogued in different levels of magneto-ionospheric conditions, highlights the role of the geomagnetic activity in the secular change of the ionosphere and confirms the latitudinal dependence of the trends. These results suggest interesting relations with some recent findings on the rapid decrease of some important physical and statistical quantities related to the geomagnetic field over the whole globe and mainly in Antarctica. In this paper we discuss the possibility of a connection between the ionospheric trends and a possible imminent geomagnetic reversal or excursion. http://hdl.handle.net/2122/3763 Title: Dynamics of high-latitude patches and associated small-scale irregularities during the October and November 2003 storms <br/> <br/>Authors: De Franceschi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Alfonsi, Lu.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Romano, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Aquino, M.; University of Nottingham; Dodson, A.; University of Nottingham; Mitchell, C. N.; University of Bath; Spencer, P.; University of Bath; Wernik, A. W.; SRC-PAS <br/> <br/>Abstract: Observations from a network of specially equipped GPS scintillation receivers in Northern Europe are used to investigate the dynamics of ionospheric plasma during the storm events of 30 October and 20 November 2003. The total electron content (TEC) and scintillation data, combined with ionospheric tomography produced by the multi-instrument data analysis system (MIDAS), reveal strong enhancements and steep gradients in TEC during nighttime under a prevailing negative Bz component of the interplanetary magnetic field (IMF). Amplitude and phase scintillation maxima are often co-located with the TEC gradients at the edge of plasma patches, revealing the presence of small-scale irregularities and suggesting association with a tongue of ionization (TOI) convecting in an anti-sunward direction from the American sector across the polar cap. Similarities and differences between the ionospheric response to the two storms are investigated. The 30 October event reveals a quite complex scenario showing two phases of plasma dynamics: the former reflects the expected convection pattern for IMF Bz southward and the latter possibly indicates a sort of TEC plasma stagnation signature of the more complex convection patterns during several positive/negative excursions of IMF Bz. http://hdl.handle.net/2122/3529 Title: GPS TEC and scintillation measurements from the polar ionosphere during the October 2003 storm <br/> <br/>Authors: Mitchell, C. N.; Electronic and Electrical Engineering, University of Bath, Bath, UK; Alfonsi, Lu.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; De Franceschi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Lester, M.; Department of Physics and Astronomy, University of Leicester, Leicester, UK; Romano, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Wernik, A. W.; Space Research Center, Polish Academy of Sciences, Warsaw, Poland <br/> <br/>Abstract: Severe ionospheric storms occurred at the end of October 2003. During the evening of 30 October a narrow stream of high electron concentration plasma crossed the polar cap in the antisunward ionospheric convection. A GPS scintillation receiver in the European high arctic, operating at 1.575 GHz, experienced both phase and amplitude scintillation on several satellite-to-ground links during this period. Close examination of the GPS signals revealed the scintillation to be co-located with strong gradients in Total Electron Content (TEC) at the edge of the plasma stream. The gradient-drift instability is a likely mechanism for the generation of the irregularities causing some of the scintillation at L band frequencies during this storm. The origin of the high TEC is explored and the possible implications of the work for scintillation forecasting are noted. The results indicate that the GPS scintillation over Svalbard can originate from traceable ionospheric plasma structures convecting from the American sector.