http://hdl.handle.net/2122/108 2013-05-21T17:02:45Z http://hdl.handle.net/2122/7310 Title: Relative ordering in the radial evolution of solar wind turbulence: the S-Theorem approach Authors: Consolini, G.; INAF – Istituto di Fisica dello Spazio Interplanetario, 00133 Roma, Italy; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Over the past few decades scientists have shown growing interest in space plasma complexity and in understanding the turbulence in magnetospheric and interplanetary media. At the beginning of the 1980s, Yu. L. Klimontovich introduced a criterion, named S-Theorem, to evaluate the degree of order in far-from-equilibrium open systems, which applied to hydrodynamic turbulence showed that turbulence flows were more organized than laminar ones. Using the same theorem we have evaluated the variation of the degree of self-organization in both Alfv´enic and non-Alfv´enic turbulent fluctuations with the radial evolution during a long time interval characterized by a slow solar wind. This analysis seems to show that the radial evolution of turbulent fluctuations is accompanied by a decrease in the degree of order, suggesting that, in the case of slow solar wind, the turbulence decays with radial distance. 2011-12-22T23:00:00Z http://hdl.handle.net/2122/5237 Title: Complexity in the sunspot cycle Authors: Consolini, G.; INAF – Istituto di Fisica dello Spazio Interplanetario, 00133 Roma, Italy; Tozzi, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia Abstract: The occurrence of complexity in the solar cycle, as monitored by the sunspot area butterfly diagram, is investigated by means of the natural orthogonal composition (NOC) technique and information theory approach. Although the butterfly diagram may be reconstructed using only two modes as already found in other papers for the Hale cycle, on deeper investigation it is possible to notice that the high variability, complexity, and stochasticity observed during the solar cycle are missing. A full description of the complex evolution of the solar cycle requires at least 30 modes. We show that these modes identify two different dynamical regimes, whose existence is also confirmed by the analysis of the Lyapunov exponents of the associated principal components. We suggest that the existence of these two physical dynamical regimes is at the origin of the dynamical complexity of the solar cycle. We attempt a discussion of these dynamical regimes also in terms of a nearly stable dynamo process described by the first two modes and a local superficial turbulent dynamo responsible for the more stochastic features observed in the solar cycle. 2009-11-02T23:00:00Z http://hdl.handle.net/2122/5031 Title: A probabilistic approach to heterogeneity in space plasmas: the case of magnetic field intensity in solar wind Authors: Consolini, G.; INAF-Istituto di Fisica dello Spazio Interplanetario, 00133 Roma, Italy; Bavassano, B.; INAF-Istituto di Fisica dello Spazio Interplanetario, 00133 Roma, Italy; De Michelis, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Since the early 90s it was shown that Probability Distribution Functions (PDFs) of small scale differences (fluctuations) of several quantities in space plasmas display significant departures from Gaussianity. The non-Gaussian shape of PDFs was ascribed to intermittency and discussed in the framework of intermittent MHD turbulence. Here, we put the attention to the PDF of magnetic field intensity instead of its differences showing how the PDF of such quantity in a quiet solar wind can be related with the occurrence of heterogeneity. In detail, we derive the shape of the PDFs by simple statistical considerations based on the concept of subordination in probability theory. An interpretation and a discussion in terms of existing coherent magnetic structures in a mechanical near-equilibrium state are also presented. 2009-04-06T22:00:00Z http://hdl.handle.net/2122/3668 Title: La variazione secolare del campo geomagnetico Authors: Meloni, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia 1992-12-31T23:00:00Z http://hdl.handle.net/2122/1684 Title: Probable values of rise and fall off time of solar cycles 23,24, and 25 Authors: Ortiz de Adler, N.; Laboratorio de Ionosfera, Instituto de Fisica, Facultad de Ciencias Exactas y Tecnologia, Universidad Nacional de Tucuman, Argentina; Elias, A. G.; Consejo Nacional de Investigaciones Cientificas y Técnicas, Buenos Aires, Argentina Abstract: From an analysis of the rise and fall off time of solar cycles 4 to 22, a recurrence tendency of 7 cycles is observed in the rise time and, apparently, of 9 cycles in the fall off time. The envelope of these times presents a decreasing amplitude of oscillation. According to this behaviour, the rise and fall length of future solar cycles until cycle 25 can be inferred qualitatively. These values are compared with those obtained with a multiple regression method showing a good agreement. 1996-04-30T22:00:00Z http://hdl.handle.net/2122/1494 Title: Solar cycle 22 control on daily geomagnetic variation at Terra Nova Bay (Antarctica) Authors: Cafarella, L.; Istituto Nazionale di Geofisica, Roma, Italy; Meloni, A.; Istituto Nazionale di Geofisica, Roma, Italy; Palangio, P.; Istituto Nazionale di Geofisica, Roma, Italy Abstract: Nine summer geomagnetic observatory data (1986-1995) from Terra Nova Bay Base, Antarctica (Lat.74.690S, Long. 164.120E, 80.040S magnetic latitude) are used to investigate the behaviour of the daily variation of the geomagnetic field at polar latitude. The instrumentation includes a proton precession magnetometer for total intensity |F| digital recordings; DI magnetometers for absolute measuring of the angular elements D and I and a three axis flux-gate system for acquiring H,D Z time variation data. We find that the magnetic time variation amplitude follows the solar cycle evolution and that the ratio between minimum solar median and maximum solar median is between 2-3 for intensive elements (H and Z) and 1.7 for declination(D). The solar cycle effect on geomagnetic daily variation elements amplitude in Antarctica, in comparison with previous studies, is then probably larger than expected. As a consequence, the electric current system that causes the daily magnetic field variation reveals a quite large solar cycle effect at Terra Nova Bay. 1998-10-31T23:00:00Z http://hdl.handle.net/2122/1474 Title: The solar-cycle variation of M(3000)F2 and its correlation with that of f0F2 Authors: Kouris, S. S.; Electrical Engineering Department, Aristotelian University of Thessaloniki, Greece Abstract: Using hourly monthly-median measured values from nine long-standing ionospheric sounding stations with data sets extending over several decades, best-fit empirical relationships are established for M (3000)F2 with different solar and ionospheric indices representative of state of the solar cycle. The statistical analysis shows that there is no difference in the degree of correlation in using one index over another. Comparisons are also made with similar relationships for monthly median f0F2 determined from the corresponding measurement data sets and the degree of correlation between the two ionospheric parameters is established. 1998-09-30T22:00:00Z http://hdl.handle.net/2122/1435 Title: Forecast of solar maximum and minimum dates for solar cycles 23 to 29 Authors: Elias, A. G.; Laboratorio de Ionosfera, Instituto de Física, Facultad de Ciencias Exactas, Universidad Nacional de Tucumán, Argentina; Ortiz de Adler, N.; Laboratorio de Ionosfera, Instituto de Física, Facultad de Ciencias Exactas, Universidad Nacional de Tucumán, Argentina Abstract: The solar cycle length for cycles 23 to 29 are forecasted. Two methods are analysed. In the first one, the solar cycle length is separated into its two phases í the rise time and the fall off time í and a multiple regression method is applied to each phase using lagged values as independent variables. In the second method, the multiple regression is fitted directly to the solar cycle length. The minimum and maximum solar activity dates are listed for the cycles predicted with the latter method which proves to be more accurate. Two lagged values appear in the multiple regression adjusted to the solar cycle length. One is associated with the Gleissberg period, also observed in the maximum sunspot number, and the other is coincident with one of the periodicities in the C14 time record, which is associated with solar activity variation 1998-03-31T22:00:00Z http://hdl.handle.net/2122/1198 Title: On the relation between ionospheric winter anomalies and solar wind Authors: Rumi, G. C.; Lecco, Italy Abstract: There are two different winter anomalies. A small one that appears in connection with ionization at relatively low latitudes in the bottom of the D-region of the ionosphere. There, the electron densities in the winter happen to be less than should be expected. On the other hand, the classic winter anomaly is present when in the winter the upper D-region, again at relatively low latitudes, has more ionization than should be expected. Both these effects are due to the slant compression of the geomagnetic field produced by the solar wind in the winter season (which is, of course, the summer season when reference is made to events in the other hemisphere). It is shown that the small winter anomaly is a consequence of a hemispheric imbalance in the flux of galactic cosmic rays determined by the obliquely distorted geomagnetic field. It is shown that the standard winter anomaly can be ascribed to the influx of a super solar wind, which penetrates into the Earth’s polar atmosphere down to E-region heights and, duly concentrated through a funneling action at the winter pole of the distorted geomagnetic field, slows down the winter polar vortex. An equatorward motion of the polar air with its content of nitric oxide brings about the excess of ionization in the upper D-region at lower latitudes. The experimentally observed rhythmic recurrence of the upper winter anomaly is correlated to a possible rhythmic recurrence of the super solar wind. The actual detection of the upper winter anomaly could yield some information on the velocity of the basic solar wind. A by-product of the present analysis, the determination of à , the coefficient of collisional detachment of the electrons from the O2 ions, is presented in the Appendix. 2001-05-31T22:00:00Z http://hdl.handle.net/2122/654 Title: Magnetic and solar effects on ionospheric absorption at high latitude Authors: Romano, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cerrone, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Perrone, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Pietrella, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Some periods of intense solar events and of strong magnetic storms have been selected and their effects on the ionospheric D region have been investigated on the basis of ionospheric absorption data derived from riometer measurements made at the Italian Antarctic Base of Terra Nova Bay (geographic coordinates: 74.69 S, 164.12 E; geomagnetic coordinates: 77.34 S, 279.41 E). It was found that sharp increases in ionospheric absorption are mainly due to solar protons emission with an energy greater than 10 MeV. Moreover, the day to night ratios of the ionospheric absorption are greater than 2 in the case of strong events of energetic protons emitted by the Sun, while during magnetic storms, these ratios range between 1 and 2. 2001-12-31T23:00:00Z