Papers by Massimo Materassi
Journal of Aeronautics and Aerospace Engineering, Aug 2, 2016
Chaos Solitons & Fractals, Apr 1, 2019
Nonlinear Processes in Geophysics, Aug 27, 2008
Acta Geophysica Polonica, 2004
An essential component of the ionosphere is a small-scale electron density structure that causes ... more An essential component of the ionosphere is a small-scale electron density structure that causes scintillation of radio waves on transionospheric links. We briefly review the morphology of irregularities and physical mechanisms of their formation. Results of the scintillation theory relating statistical characteristics of irregularities and scintillation are also outlined. Examples of the scintillation effect on the system performance are given. Finally, we will present recent attempts to model the scintillation.
Journal of Atmospheric and Solar-Terrestrial Physics, Aug 1, 2005
... The inversion algorithm used here, which is referred to as Multi Instrument Data Analysis Sys... more ... The inversion algorithm used here, which is referred to as Multi Instrument Data Analysis System (MIDAS) can integrate different data sources obtaining ionospheric images of the electron distribution (Mitchell and Spencer, 2003). ...
AGUFM, Dec 1, 2006
ABSTRACT One of the most intriguing processes occurring in space plasmas is the magnetic field re... more ABSTRACT One of the most intriguing processes occurring in space plasmas is the magnetic field reconnection/reconfiguration process, the comprehension of which is still under debate. The classical reconnection models do not take account of the inherent stocasticity displayed by many space plasma properties. For example in the recent past it has been widely documented that turbulence, scale-invariance and multifractal properties are common features of space-plasmas. In this work, moving by the simple argument of flux conservation, we approach the problem of magnetic reconnection assuming a multifractal topology of the reconnection/diffusion region. A simple relationship between the magnetic Reynolds' number and the reconnection rate can be estimated in the case of a simple fractal geometry. The evaluation of the rate in the full multifractal case is more complex. Anyway, in the monofractal case it is possible to find a close expression of the reconnection rate, which directly depends on the fractal dimension of the reconnection/diffusion region, and results to be more efficient than those predicted by Sweet/Parker and Petschek-like theories in a limited interval of magnetic Reynolds' numbers. The results are discussed in connection with recent estimation of reconnection rate by in-situ satellite magnetospheric observations.
Annals of Geophysics, Dec 18, 2009
arXiv (Cornell University), Apr 8, 2020
Some ideas are presented about the physical motivation of the apparent capacity of generalized lo... more Some ideas are presented about the physical motivation of the apparent capacity of generalized logistic equations to describe the outbreak of the COVID-19 infection, and in general of quite many other epidemics. The main focuses here are: the complex, possibly fractal, structure of the locus describing the "contagion event set"; what can be learnt from the models of trophic webs with "herd behaviour".
International Journal of Modern Physics, Aug 20, 1999
Chaos Solitons & Fractals, Nov 1, 2020
Radio Science, Feb 1, 2007
arXiv (Cornell University), Mar 27, 2018
A dynamical system defined by a metriplectic structure is a dissipative model characterized by a ... more A dynamical system defined by a metriplectic structure is a dissipative model characterized by a specific pair of tensors, which defines the Leibniz brackets. Generally, these tensors are Poisson brackets tensor and a symmetric metric tensor that models purely dissipative dynamics. In this paper, the metriplectic system describing a simplified two-photon absorption by a two-level atom is disclosed. The Hamiltonian component describes the free electromagnetic radiation. The metric component encodes the radiation-matter coupling, driving the system to an asymptotically stable state in which the excited level of the atom is populated due to absorption. This work is intended as a first result to pave the way to apply the metriplectic formalism to many other irreversible processes in nonlinear optics.
arXiv (Cornell University), Jun 4, 2017
arXiv (Cornell University), May 7, 1999
Two Italian non-profit organizations (Set and Galea) are working together to realize a center (Cd... more Two Italian non-profit organizations (Set and Galea) are working together to realize a center (Cdcs) supported by the town administration of Sesto Fiorentino (a little town not far from Florence, Italy), for the divulgation of the scientific culture in the schools and among people. This is their project: the key idea is to let the non-profit organizations intervent in the public school system by creating cooperative structures in which young scientists can work.
arXiv (Cornell University), May 5, 1999
EGU General Assembly Conference Abstracts, May 1, 2010
Uploads
Papers by Massimo Materassi
Abstract The fluid dynamical picture of the ionosphere is the most classical and conceptually simple one, and this makes it extremely widespread in terms of theoretical models and applications. On the other hand, this representation has differential equations whose solutions are fields smooth almost everywhere, preventing it to represent irregular regimes, e.g. turbulence.