Institute of Geophysics and Astronomy

IGA, Cuba

Institute of Geophysics and Astronomy

IGA, Cuba
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Ojeda-Gonzalez A.,University of Paraíba Valley | Ojeda-Gonzalez A.,National Institute for Space Research | Ojeda-Gonzalez A.,Brazilian National Council for Scientific and Technological Development | Mendes O.,National Institute for Space Research | And 4 more authors.
Astrophysical Journal | Year: 2017

Spatio-temporal entropy (STE) analysis is used as an alternative mathematical tool to identify possible magnetic cloud (MC) candidates. We analyze Interplanetary Magnetic Field (IMF) data using a time interval of only 10 days. We select a convenient data interval of 2500 records moving forward by 200 record steps until the end of the time series. For every data segment, the STE is calculated at each step. During an MC event, the STE reaches values close to zero. This extremely low value of STE is due to MC structure features. However, not all of the magnetic components in MCs have STE values close to zero at the same time. For this reason, we create a standardization index (the so-called Interplanetary Entropy, IE, index). This index is a worthwhile effort to develop new tools to help diagnose ICME structures. The IE was calculated using a time window of one year (1999), and it has a success rate of 70% over other identifiers of MCs. The unsuccessful cases (30%) are caused by small and weak MCs. The results show that the IE methodology identified 9 of 13 MCs, and emitted nine false alarm cases. In 1999, a total of 788 windows of 2500 values existed, meaning that the percentage of false alarms was 1.14%, which can be considered a good result. In addition, four time windows, each of 10 days, are studied, where the IE method was effective in finding MC candidates. As a novel result, two new MCs are identified in these time windows. © 2017. The American Astronomical Society. All rights reserved.

Ojeda Gonzalez A.,National Institute for Space Research | Mendes Junior O.,National Institute for Space Research | Oliveira Domingues M.,Institute of Geophysics and Astronomy | Menconi V.E.,National Institute for Space Research
Geofisica Internacional | Year: 2014

We have studied a set of 41 magnetic clouds (MCs) measured by the ACE spacecraft, using the discrete orthogonal wavelet transform (Daubechies wavelet of order two) in three regions: Pre-MC (plasma sheath), MC and Post-MC. We have used data from the IMF GSM-components with time resolution of 16 s. The mathematical property chosen was the statistical mean of the wavelet coefficients (〈Dd1〉). The Daubechies wavelet coefficients have been used because they represent the local regularity present in the signal being studied. The results reproduced the wellknown fact that the dynamics of the sheath region is more than that of the MC region. This technique could be useful to help a specialist to find events boundaries when working with IMF datasets, i.e., a best form to visualize the data. The wavelet coefficients have the advantage of helping to find some shocks that are not easy to see in the IMF data by simple visual inspection. We can learn that fluctuations are not low in all MCs, in some cases waves can penetrate from the sheath to the MC. This methodology has not yet been tested to identify some specific fluctuation patterns at IMF for any other geoeffective interplanetary events, such as Co-rotating Interaction Regions (CIRs), Heliospheric Current Sheet (HCS) or ICMEs without MC signatures. In our opinion, as is the first time that this technique is applied to the IMF data with this purpose, the presentation of this approach for the Space Physics Community is one of the contributions of this work.

Gonzalez A.O.,National Institute for Space Research | Gonzalez A.O.,Institute of Geophysics and Astronomy | Mendes O.,National Institute for Space Research | Calzadilla M.A.,Institute of Geophysics and Astronomy | Domingues M.O.,National Institute for Space Research
Journal of Geophysical Research: Space Physics | Year: 2013

The aim of this work is to create a methodology to characterize the dynamics of magnetic clouds (MCs) from signals measured by satellites in the interplanetary medium. We have tested spatio-temporal entropy (STE) technique to study 41 MCs identified by other authors, where the plasma sheath region has been identified. The STE was implemented in Visual Recurrence Analysis software to quantify the order in the recurrence plot. Some tests using synthetic time series were performed to validate the method. In particular, we worked with interplanetary magnetic field (IMF) components Bx, By, Bz of 16 s. Time windows from March 1998 to December 2003 for some MCs were selected. We found higher STE values in the sheaths and 0 STE values in some of the three components in most of the MCs (30 among 41 events). The trend is the principal cause of the lower STE values in the MCs. Also, MCs have magnetic field more structured than sheath and quiet solar wind. We have done a test considering the magnetic components of a cylindrically symmetric force-free field constructed analytically, with the result of 0 STE value. It agrees with the physical assumption of finding 0 STE values when studying experimental data in MC periods. The new feature just examined here adds to the usual features, as described in Burlaga et al. (1981), for the characterization of MCs. The STE calculation can be an auxiliary objective tool to identify flux ropes associated with MCs, mainly during events with no available plasma data but only with IMF. Key PointsSTE values for MCs are lower than the ones for sheath region and quiet SWForce-free field constructed analytically results zero STE valueSTE could be an auxiliary tool to identify flux-ropes associated with MCs ©2013. American Geophysical Union. All Rights Reserved.

Mendez Berhondo A.L.,Institute of Geophysics and Astronomy | Rodriguez Taboada R.E.,Institute of Geophysics and Astronomy | Zlobec P.,National institute for astrophysics | Diaz Rodriguez A.K.,Institute of Geophysics and Astronomy
Advances in Space Research | Year: 2013

Source length scales are estimated for the September 14, 2005 solar noise storm from the spectral and temporal observed characteristics of the background continuum fluctuations and clusters of Type I bursts. The characteristic height of the magnetic structure where the noise storm source is located and the size of the source where Type I bursts clustering takes place were calculated. A lower limit for the height of the magnetic structure supporting the noise storm at 237 MHz was estimated too.© 2012 COSPAR. Published by Elsevier Ltd. All rights reserved.

Berhondo A.L.M.,Institute of Geophysics and Astronomy | Rodriguez A.K.D.,Institute of Geophysics and Astronomy | Zlobec P.,National institute for astrophysics | Perez L.C.,Institute of Geophysics and Astronomy
Astrophysics and Space Science | Year: 2013

The dynamic characteristics of solar metric radio bursts with intermediate drifting patterns (fiber bursts) as they evolve at fixed frequency are examined. The data were recorded using the radio polarimeter of the Trieste Astronomical Observatory. The aim is to determine if the underlying process can be described as a deterministic chaos. Correlation dimensions and Hurst exponent are estimated showing deterministic chaotic system of low dimension. © 2013 Springer Science+Business Media Dordrecht.

Mendez Berhondo A.L.,Institute of Geophysics and Astronomy
Revista Cubana de Fisica | Year: 2011

SClimatic changes are not an exclusively terrestrial phenomenon. Evidences of changes exist in climatic patterns in other planets of the Solar System. The complexity of global climate changes on Earth requires a multidisciplinary approach due to different factors and concomitant contributing phenomenology. In particular, purely astronomical phenomena have had an incidence in the variability of the Earth climate and weather. This paper resumes some of the evidences that point toward a relationship between solar activity and climatic changes occurred on our planet.

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