arXiv subjects

Andres R. R. Papa

Publications and source records attributed to Andres R. R. Papa.

10 recordsLinked to original sources

arXiv2015

Rayleigh and acoustic gravity waves detection on magnetograms during the Japanese Tsunami, 2011

The continuous geomagnetic field survey holds an important potential in future prevention of tsunami damages, and also, it could be used in tsunami forecast. In this work, we were able to detected for the first time Rayleigh and ionospheric acoustic gravity wave propagation in the Z-component of the geomagnetic field due to the Japanese tsunami, 2011 prior to the tsunami arrival. The geomagnetic measurements were obtained in the epicentral near and far-field. Also, these waves were detected within minutes to few hours of the tsunami arrival. For these reasons, these results are very encouraging, and confirmed that the geomagnetic field monitoring could play an important role in the tsunami warning systems, and also, it could provide additional information in the induced ionospheric wave propagation models due to tsunamis.

physics.space-ph↗

arXiv2012

Characteristics of solar diurnal variations: a case study based on records from the ground magnetic observatory at Vassouras, Brazil

The horizontal component amplitudes of magnetograms recorded by ground-based observatories of the INTERMAGNET network have been used to analyze the global pattern variance of the solar diurnal variations. Those kinds of data present gaps in records and consequently we explore them via a time-frequency gapped wavelet algorithm. We propose a new approach to analyze magnetograms based on scale correlation. The results show that the magnetic records have a latitudinal dependence affected by the season of year and by the level of solar activity. We have found a disparity on the latitudinal response at Southern and Northern Hemispheres during solstices, which is expected due to the asymmetry of the Sq field. On the other hand at equinoxes, records from stations located at approximately the same latitude but at different longitudes presented peculiar dissimilarities. The achieved results suggest that quiet day patterns and the physical processes involved in their formation are strongly affected by: the conductivity of the E-region, the geomagnetic field intensity and its configuration, and the thermospheric winds.

physics.space-ph↗

arXiv2011

Tsunami effects on the Z component of the geomagnetic field

The vertical component (Z) of the geomagnetic field observed by ground-based observatories of the INTERMAGNET network has been used to analyze the effects of the movement of electrically conducting sea water through the geomagnetic field due to a propagation of a tsumani. The purpose of this work is to study the geomagnetic variations induced by the tsunamis occurred at 26 December, 2004, 27 February, 2010 and 11 March, 2011. For each case study, we selected four magnetic stations belonging to the INTERMAGNET programme that were influenced or more direct affected by the tsumani. To detect these disturbances in the geomagnetic data, the discrete wavelet technique have been used in four levels of decomposition. We were able to detect the localized behavior of the geomagnetic variations induced by the movement of electrically conducting sea-water through the geomagnetic field, i. e., the identification of transients related to the tsunamis. As well, using the minutely magnetogram data, it was able to localize the initial phase and time of the tsunami maximum height. The first interpretation of the results suggests that discrete wavelet transform can be used to characterize the tsumani effects on the geomagnetic field, but need further study.

physics.space-ph↗

arXiv2011

A generalized Bak-Sneppen model for Earth's magnetic field reversals

We introduce a simple model for Earth's magnetic field reversals. The model consists in random nodes simulating vortices in the liquid part of the core which through a simple updating algorithm converge to a self organized critical state, with inter-reversal time probability distributions functions in the form of power laws (as supposed to be in actual reversals). It should not be expected a detailed description of reversals. However, we hope to reach a profounder knowledge of reversals through some of the basic characteristic that are well reproduced.

physics.geo-ph↗

arXiv2006

Statistical properties of geomagnetic measurements as possible precursors for magnetic storms

Records of geomagnetic measurements have been analyzed looking for evidences of possible precursors for magnetic storms. With this objective, the main magnetic storms in the period 1998-2002 have been located in Dst index record. Periods immediately before storms and periods well before them were studied by applying a method recently introduced in the literature. Statistical properties of both types of periods have been compared. One of the compared quantities was the slope of the power laws that have been found for some relevant distributions. A systematic deviation between slope distributions was found. This might be the fingerprint of a non self-organized component in records. There has also been found a correlation between slope values and the corresponding storm intensities, which could serve as a probabilistic approach to magnetic storms forecasting. Data is from the low latitude Vassouras Magnetic Observatory.

physics.geo-ph↗

arXiv2006

Changes in fractal properties of geomagnetic indexes as possible magnetic storms precursors

Records of Dst, Kp and Sym-H indexes are analyzed looking for evidences of possible precursors for magnetic storms. To accomplish this task the main magnetic storms were located and some periods immediately before storms and some periods well before them studied. Statistical properties of both types of periods were then compared. In particular, were compared the slopes of the power laws that have been found for the distributions of indexes values. A systematic deviation was found between both distributions for the Kp index. It was no so for Dst and Sym-H indexes. For the three indexes it was found a correlation between slopes and the corresponding storm intensity, which could serve as a probabilistic approach to magnetic storms forecasting. The data for the analysis was obtained at the World Data Centre for Geomagnetism at Kyoto.

physics.geo-ph↗

arXiv2006

On the time distribution of reversals in Earth's magnetic field

This paper presents an analysis on the distribution of periods between consecutive reversals of the Earth's magnetic field. The analysis includes the randomness of polarities, whether the data corresponding to different periods belong to a unique distribution and finally, the type of distribution that data obey. It was found that the distribution is a power law (which could be the fingerprint of a critical system as the cause of geomagnetic reversions). For the distribution function a slope value of -1.42 was found. This value differs about 15% from results obtained when the present considerations are not taken into account and it is considered the main finding.

physics.geo-ph↗

arXiv2006

Simulating geomagnetic reversals through 2D Ising systems

In this work 2D Ising systems were used to simulate the reversals of the Earth's magnetic field. Each spin was supposed to be a ring current in the Earth dynamo and the magnetization to be proportional to the field intensity. Given the relative success of some physical few-discs modeling of this system all the simulations were implemented in small systems. The temperature T was used as a tunning parameter. It plays the role of external perturbations. Power laws were obtained for the distribution of times between reversals. When the system size was increased the exponent of the power law asymptotically tended towards values very near -1.5, generally accepted as the right value for this phenomenon. Depending on the proximity of T and Tc the average duration of reversal period changes. In this way it is possible to establish a parallel between the model and more or less well defined periods of the reversal record. Some possible trends for future works are advanced.

physics.geo-ph↗

arXiv2005

Evidences of a threshold system as the source for magnetic storms detected on Earth s surface

Threshold systems appear to underlie the global behaviour of physical phenomena very unlike at a first look. The usual experimental fingerprint of threshold system grounded phenomena is the presence of power laws. Experimental evidence has been found, for example, in superconductor vortex avalanches, sand piles, the brain, 4He superfluidity and earthquakes. Double power-laws have been found in social networks, in the luminosity of some galactic nuclei and, very recently, in solar flares, among others. Here we show evidences that point to a threshold system as the source for magnetic storms detected on the Earth. We based our analysis on series of data acquired during many years in the network of magnetic observatories of the National Observatory (Brazil). In particular we focused our attention on October 2000 month of the Vassouras Observatory (RJ, Brazil), which have been active since 1915. We have found both power laws and double power laws for some relevant distributions.

physics.geo-ph↗

arXiv2005

Gravity is indeed the driving force for fault pattern formation and westward displacement of the lithosphere

Gravity influence of the Sun and the Moon on the Earth is the cause of the fault pattern on Earth's surface we observe nowadays and also of the westward displacement of the lithosphere. A somewhat related hypotheses advanced in the past have been that tidal torque of the Moon may be significant. However, it has been argued that it is untenable essentially on the grounds that the viscosity of the Earth's mantle is far too high in comparison with the forces involved. To state this it was assumed that the Earth's relevant characteristic is that of two spherical shells separated by a viscous liquid, the external shell rotating at a constant angular velocity with respect to the inner shell. Here I show that this picture is not quite right and that a more careful look leads us to one in which both shells rotates at different mean angular velocities and with a forward-backward sequence of movements relative to each other. In this way what was supposed to be the principal factor against gravity influence becomes the main favourable one.

physics.geo-ph↗