Silvia Duhau - Academia.edu (original) (raw)
Papers by Silvia Duhau
Los modelos del geodinamo suponen que el campo magnetico terrestre crece de un campo "semill... more Los modelos del geodinamo suponen que el campo magnetico terrestre crece de un campo "semilla" debido a la conveccion en el nucleo exterior, liquido, generada por una fuente de calor radial ubicada en la interfase entre el nucleo solido y el liquido. Sin embargo, recientemente se han encontrado evidencias de que las fluctuaciones de largo plazo en la actividad solar controlan las variaciones en la longitud del dia. Estas junto con las variaciones geomagneticas seculares estan vinculadas a movimientos en el nucleo. Para profundizar en el estudio de estas relaciones analizamos las series temporales del promedio anual de la longitud del dia y del numero de manchas solares desde 1657, y del indice geomagnetico aa desde 1844, respectivamente, mediante un analisis multi-resuelto basado en las ondeletas de Morlet. Encontramos que para escalas de tiempo mayores que los 40 anos ciclos en la intensidad del campo dipolar solar excitan ciclos en la longitud del dia cuando su longitud ...
Global Warming - Impacts and Future Perspectives, 2012
Physics & Astronomy International Journal, 2018
In the first years of this century the International World Data Center (WDCJ–SILSO) proposed to i... more In the first years of this century the International World Data Center (WDCJ–SILSO) proposed to improve the current Zürich sunspot numbering system, introduced by Wolf, developed further by Waldmeier and successors: the Wolf Sunspot Numbers, generally called International Sunspot Number; ISN. It was proposed to replace it by a new system of sunspot counting (the Modified International Sunspot Numbers (MISN).1,2 Around the same time another proposed counting system was introduced; it is called the Group Sunspot Numbers (GSN).3–5
We analyze the variation of the solar-dynamo magnetic-field components during the last millennium... more We analyze the variation of the solar-dynamo magnetic-field components during the last millennium through a study of their proxy data. We introduce a phase diagram with as abscissa and ordinate the proxies of the values of the toroidal and poloidal magnetic field components. In this diagram the dynamo system appears to regularly cross a well-defined point, which we call the Transition Point. Such crossings occurred five times during the past millennium. Each of these crossings preceded a Grand Episode, either a Minimum or a Maximum one. In addition to these two types of quasiperiodic behavior, a third type consisting of weaker quasiregular oscillations (R) around the Transition Point’s coordinates is identified. These periods appear to last one or two times the Gleissberg cycle length. Between the various types of episodes there are brief phase transitions. We identify two types of such phase transitions.
La actividad solar afecta la temperatura atmosferica. Lo que esta en disputa en algunos circulos ... more La actividad solar afecta la temperatura atmosferica. Lo que esta en disputa en algunos circulos cientificos es la magnitud del impacto. ?Seguira el calentamiento de la Tierra inexorablemente un camino ascendente o comenzara una pequena edad de hielo?
ABSTRACT Solar variability is controlled by the internal dynamo which is a nonlinear system. It i... more ABSTRACT Solar variability is controlled by the internal dynamo which is a nonlinear system. It is therefore unpredictable in principle (Tobias, 2004). Yet we have found that the system shows regularities, in line with what can be expected from chaos theory (Duhau ad de Jager, 2008). It is dominated by an attractor state to which the system returns more or less regularly. In addition we distinguish between Grand Maxima, Grand Minima and periods of a more regular oscillation around the attractor state level. Here, we show that the dynamo system is presently undergoing a transition from the recent Grand Maximum to another regime. This transition started in 2000 and is expected to end around the maximum of cycle #24, that we foresee for 2012 - 2013. At that time the maximum sunspot number Rmax will be 70 ± 17, where the 'error' is the largest conceivable deviation from the expected value. At that time a period of lower solar activity will start. That period will most probably be a regular quasiperiodic episode, as occurred between 1730 and 1925. It is characterized by the superposition of weak 'regular' Gleissberg cycle and decadal oscillations. These last will be negative and might turn out to be very strong, as around 1810, in which case a Dalton-type Grand Minimum would develop. This moderate to low-activity episode is expected to last for an integer number of Gleissberg cycles.
Esta ampliamente aceptado que la actividad solar en cada maximo esta relacionada con la actividad... more Esta ampliamente aceptado que la actividad solar en cada maximo esta relacionada con la actividad geomagnetica en el minimo precedente. Eso implica que debe existir una relacion a largo plazo entre los indices que las miden. En el presente trabajo se estudia esta relacion mediante la aplicacion de un analisis multi-resuelto basado en la transformada de ondeletas, a la serie temporal del indice geomagnetico aa y del numero de manchas solares desde el ano 1844 al presente. A diferencia de la transformada de Fourier, la metodologia empleada permite describir tanto fenomenos periodicos como transitorios y por lo tanto detectar ciclos cuya longitud varia en el tiempo. Se encuentra que las variaciones temporales de Rz y de aa pueden separase en tres escalas distintas: la escala mas corta corresponde para Rz al bien conocido ciclo de 11 anos - ciclo de Schwabe - y las variaciones temporales en las otras dos escalas tienen propiedades que permiten identificarlas con el ciclo de Hale y el de...
Space Science Reviews, 2016
We summarize the major aspects of the remarkable, fairly long lasting period (∼ 2005 to ∼ 2010) o... more We summarize the major aspects of the remarkable, fairly long lasting period (∼ 2005 to ∼ 2010) of low solar activity, that we will call the Transition. It is the transitional stage between the Grand Maximum of the 20th century and a forthcoming (most probably Regular) episode of solar activity. The various kinds of activity in the functioning of the equatorial components of the solar dynamo before and during the Transition are summarized. While the behavior of unipolar magnetic regions and their rest-latitudes already gave very early indications-mid 20th century-of the forthcoming Transition, more such indications became available around 1995 and the main part of it occurred between 2005 and 2010. Some of the inferences are discussed. We submit the hypothesis that the solar tachocline undergoes pulsations and we present some helioseismic evidences. In that scenario we find that its equatorial part has moved downward over a fairly small semi-amplitude (∼ 0.03 solar radii) during the time of the Transition. There are several indications, apart from this 'pulsation', that the tachocline may even be pulsating with still smaller amplitudes in more modes. We speculate about the physical mechanism(s).
We analyse the variation of the polar and toroidal components of the solar dynamo magnetic field ... more We analyse the variation of the polar and toroidal components of the solar dynamo magnetic field during the last millennium through a study of their proxy data. We identify one well defined attractor level of the solar dynamo. Besides, there are three types of oscillations around it, the Grand Minima (M), the Grand Maxima (H) and a weaker type of quasi-regular oscillations (R), also around the attractor level's coordinates. These episodes last for one or two Gleissberg cycles. The system returns to the various types of episodes by brief phase transitions. We identify two types of such phase transitions. The origin of this behavior, that constrain solar dynamo models, is discussed.
By a Morlet wavelet analysis in sub harmonics of the 11 year fundamental frequency of sunspot num... more By a Morlet wavelet analysis in sub harmonics of the 11 year fundamental frequency of sunspot number as a proxy for the toroidal component of solar dynamo magnetic field the evolution for the last 400 years of four well defined cycles- a decadal, a semi-secular, the Gleissberg and the Suess ones - in the modulation of this component of the solar dynamo field is found. The properties of these cycles as seen in geomagnetic index aa and Si as proxy data for polar dynamo field and CME's frequency and intensity, respectively, are described . From this procedure and by analyzing longer proxy time series in the light of the known non-linear properties of solar dynamo system, the meaning of the four cycles and its variability are discussed.
Solar variability is controlled by the internal dynamo which is a nonlinear system. It is therefo... more Solar variability is controlled by the internal dynamo which is a nonlinear system. It is therefore unpredictable in principle (Tobias, 2004). Yet we have found that the system shows regularities, in line with what can be expected from chaos theory (Duhau ad de Jager, 2008). It is dominated by an attractor state to which the system returns more or less regularly. In addition we distinguish between Grand Maxima, Grand Minima and periods of a more regular oscillation around the attractor state level. Here, we show that the dynamo system is presently undergoing a transition from the recent Grand Maximum to another regime. This transition started in 2000 and is expected to end around the maximum of cycle #24, that we foresee for 2012 - 2013. At that time the maximum sunspot number Rmax will be 70 ± 17, where the 'error' is the largest conceivable deviation from the expected value. At that time a period of lower solar activity will start. That period will most probably be a regul...
There are some evidences that support the occurrence of total ozone content changes by high energ... more There are some evidences that support the occurrence of total ozone content changes by high energetic particle flux intensity variations. In turn, these last are strongly linked to sudden commencement storms (SSC´s). Therefore, an analysis of total ozone content in selected ground stations, radiative input and SSC index yearly means time series, the last defined as the product of the amplitude by the duration time of each storm, is performed. It is found that long-term ozone variations are mostly related to SSC index long-term variations in all the stations, with different behaviours that depend on geographical location. In particular, the strong decrease of total ozone content during cycle 22 is related to the very high SSC values that occurred during that sunspot cycle and is remarkably strong in Faraday and Halley Bay stations. In all the stations the minimum in total ozone content long term variation is reached around 1993 and is followed by an steady increase, that would contin...
It has been suggested that length of the Day in the decadal time scale is related to solar activi... more It has been suggested that length of the Day in the decadal time scale is related to solar activity. Here, the non-linear relationship between time changes in the involved variables is analyzed by a Morlet wavelet base function by the methodology introduced in a previous paper (ST1. XX, EGU 2009). It is found that for the purpose of the present study, it is convenient to split the amplitude modulation of the two components of the magnetic 11-year cycle in four oscillations, VIZ.: Hale, semi-secular, Gleissberg and millennial. The same procedure is then applied to split the length of the day, the westward drift and the time derivative of the geomagnetic dipolar field time series. The amplitudes and phases of each of the four oscillations in the five time series are then compared. The most relevant result is that the millennial and the semi-secular oscillations in the solar dynamo magnetic field components are also visible in the variations of the length of the day, where they appear ...
The solar Gleissberg cycle is not restricted to one single periodicity, as was assumed by its dis... more The solar Gleissberg cycle is not restricted to one single periodicity, as was assumed by its discoverer. Later, it was shown that there are at least two components, each of which dominating in another period of time. We connect this observation to an earlier finding, viz. that the occurrence of the Grand Episodes is related to the behaviour of the solar dynamo in connection to its so-called Transition Point: another Grand Episode starts when the curve defined by the proxies of the poloidal and toroidal magnetic field components has crossed or passed along the Transition Point's coordinates. Here, we present evidence that each Grand Episode is related to one or more specific components of the Gleissberg cycle; each of them with its own period length. This finding must have implications for our understanding of the dynamo mechanism
Eos Transactions American Geophysical Union, 1993
Los modelos del geodinamo suponen que el campo magnetico terrestre crece de un campo "semill... more Los modelos del geodinamo suponen que el campo magnetico terrestre crece de un campo "semilla" debido a la conveccion en el nucleo exterior, liquido, generada por una fuente de calor radial ubicada en la interfase entre el nucleo solido y el liquido. Sin embargo, recientemente se han encontrado evidencias de que las fluctuaciones de largo plazo en la actividad solar controlan las variaciones en la longitud del dia. Estas junto con las variaciones geomagneticas seculares estan vinculadas a movimientos en el nucleo. Para profundizar en el estudio de estas relaciones analizamos las series temporales del promedio anual de la longitud del dia y del numero de manchas solares desde 1657, y del indice geomagnetico aa desde 1844, respectivamente, mediante un analisis multi-resuelto basado en las ondeletas de Morlet. Encontramos que para escalas de tiempo mayores que los 40 anos ciclos en la intensidad del campo dipolar solar excitan ciclos en la longitud del dia cuando su longitud ...
Global Warming - Impacts and Future Perspectives, 2012
Physics & Astronomy International Journal, 2018
In the first years of this century the International World Data Center (WDCJ–SILSO) proposed to i... more In the first years of this century the International World Data Center (WDCJ–SILSO) proposed to improve the current Zürich sunspot numbering system, introduced by Wolf, developed further by Waldmeier and successors: the Wolf Sunspot Numbers, generally called International Sunspot Number; ISN. It was proposed to replace it by a new system of sunspot counting (the Modified International Sunspot Numbers (MISN).1,2 Around the same time another proposed counting system was introduced; it is called the Group Sunspot Numbers (GSN).3–5
We analyze the variation of the solar-dynamo magnetic-field components during the last millennium... more We analyze the variation of the solar-dynamo magnetic-field components during the last millennium through a study of their proxy data. We introduce a phase diagram with as abscissa and ordinate the proxies of the values of the toroidal and poloidal magnetic field components. In this diagram the dynamo system appears to regularly cross a well-defined point, which we call the Transition Point. Such crossings occurred five times during the past millennium. Each of these crossings preceded a Grand Episode, either a Minimum or a Maximum one. In addition to these two types of quasiperiodic behavior, a third type consisting of weaker quasiregular oscillations (R) around the Transition Point’s coordinates is identified. These periods appear to last one or two times the Gleissberg cycle length. Between the various types of episodes there are brief phase transitions. We identify two types of such phase transitions.
La actividad solar afecta la temperatura atmosferica. Lo que esta en disputa en algunos circulos ... more La actividad solar afecta la temperatura atmosferica. Lo que esta en disputa en algunos circulos cientificos es la magnitud del impacto. ?Seguira el calentamiento de la Tierra inexorablemente un camino ascendente o comenzara una pequena edad de hielo?
ABSTRACT Solar variability is controlled by the internal dynamo which is a nonlinear system. It i... more ABSTRACT Solar variability is controlled by the internal dynamo which is a nonlinear system. It is therefore unpredictable in principle (Tobias, 2004). Yet we have found that the system shows regularities, in line with what can be expected from chaos theory (Duhau ad de Jager, 2008). It is dominated by an attractor state to which the system returns more or less regularly. In addition we distinguish between Grand Maxima, Grand Minima and periods of a more regular oscillation around the attractor state level. Here, we show that the dynamo system is presently undergoing a transition from the recent Grand Maximum to another regime. This transition started in 2000 and is expected to end around the maximum of cycle #24, that we foresee for 2012 - 2013. At that time the maximum sunspot number Rmax will be 70 ± 17, where the 'error' is the largest conceivable deviation from the expected value. At that time a period of lower solar activity will start. That period will most probably be a regular quasiperiodic episode, as occurred between 1730 and 1925. It is characterized by the superposition of weak 'regular' Gleissberg cycle and decadal oscillations. These last will be negative and might turn out to be very strong, as around 1810, in which case a Dalton-type Grand Minimum would develop. This moderate to low-activity episode is expected to last for an integer number of Gleissberg cycles.
Esta ampliamente aceptado que la actividad solar en cada maximo esta relacionada con la actividad... more Esta ampliamente aceptado que la actividad solar en cada maximo esta relacionada con la actividad geomagnetica en el minimo precedente. Eso implica que debe existir una relacion a largo plazo entre los indices que las miden. En el presente trabajo se estudia esta relacion mediante la aplicacion de un analisis multi-resuelto basado en la transformada de ondeletas, a la serie temporal del indice geomagnetico aa y del numero de manchas solares desde el ano 1844 al presente. A diferencia de la transformada de Fourier, la metodologia empleada permite describir tanto fenomenos periodicos como transitorios y por lo tanto detectar ciclos cuya longitud varia en el tiempo. Se encuentra que las variaciones temporales de Rz y de aa pueden separase en tres escalas distintas: la escala mas corta corresponde para Rz al bien conocido ciclo de 11 anos - ciclo de Schwabe - y las variaciones temporales en las otras dos escalas tienen propiedades que permiten identificarlas con el ciclo de Hale y el de...
Space Science Reviews, 2016
We summarize the major aspects of the remarkable, fairly long lasting period (∼ 2005 to ∼ 2010) o... more We summarize the major aspects of the remarkable, fairly long lasting period (∼ 2005 to ∼ 2010) of low solar activity, that we will call the Transition. It is the transitional stage between the Grand Maximum of the 20th century and a forthcoming (most probably Regular) episode of solar activity. The various kinds of activity in the functioning of the equatorial components of the solar dynamo before and during the Transition are summarized. While the behavior of unipolar magnetic regions and their rest-latitudes already gave very early indications-mid 20th century-of the forthcoming Transition, more such indications became available around 1995 and the main part of it occurred between 2005 and 2010. Some of the inferences are discussed. We submit the hypothesis that the solar tachocline undergoes pulsations and we present some helioseismic evidences. In that scenario we find that its equatorial part has moved downward over a fairly small semi-amplitude (∼ 0.03 solar radii) during the time of the Transition. There are several indications, apart from this 'pulsation', that the tachocline may even be pulsating with still smaller amplitudes in more modes. We speculate about the physical mechanism(s).
We analyse the variation of the polar and toroidal components of the solar dynamo magnetic field ... more We analyse the variation of the polar and toroidal components of the solar dynamo magnetic field during the last millennium through a study of their proxy data. We identify one well defined attractor level of the solar dynamo. Besides, there are three types of oscillations around it, the Grand Minima (M), the Grand Maxima (H) and a weaker type of quasi-regular oscillations (R), also around the attractor level's coordinates. These episodes last for one or two Gleissberg cycles. The system returns to the various types of episodes by brief phase transitions. We identify two types of such phase transitions. The origin of this behavior, that constrain solar dynamo models, is discussed.
By a Morlet wavelet analysis in sub harmonics of the 11 year fundamental frequency of sunspot num... more By a Morlet wavelet analysis in sub harmonics of the 11 year fundamental frequency of sunspot number as a proxy for the toroidal component of solar dynamo magnetic field the evolution for the last 400 years of four well defined cycles- a decadal, a semi-secular, the Gleissberg and the Suess ones - in the modulation of this component of the solar dynamo field is found. The properties of these cycles as seen in geomagnetic index aa and Si as proxy data for polar dynamo field and CME's frequency and intensity, respectively, are described . From this procedure and by analyzing longer proxy time series in the light of the known non-linear properties of solar dynamo system, the meaning of the four cycles and its variability are discussed.
Solar variability is controlled by the internal dynamo which is a nonlinear system. It is therefo... more Solar variability is controlled by the internal dynamo which is a nonlinear system. It is therefore unpredictable in principle (Tobias, 2004). Yet we have found that the system shows regularities, in line with what can be expected from chaos theory (Duhau ad de Jager, 2008). It is dominated by an attractor state to which the system returns more or less regularly. In addition we distinguish between Grand Maxima, Grand Minima and periods of a more regular oscillation around the attractor state level. Here, we show that the dynamo system is presently undergoing a transition from the recent Grand Maximum to another regime. This transition started in 2000 and is expected to end around the maximum of cycle #24, that we foresee for 2012 - 2013. At that time the maximum sunspot number Rmax will be 70 ± 17, where the 'error' is the largest conceivable deviation from the expected value. At that time a period of lower solar activity will start. That period will most probably be a regul...
There are some evidences that support the occurrence of total ozone content changes by high energ... more There are some evidences that support the occurrence of total ozone content changes by high energetic particle flux intensity variations. In turn, these last are strongly linked to sudden commencement storms (SSC´s). Therefore, an analysis of total ozone content in selected ground stations, radiative input and SSC index yearly means time series, the last defined as the product of the amplitude by the duration time of each storm, is performed. It is found that long-term ozone variations are mostly related to SSC index long-term variations in all the stations, with different behaviours that depend on geographical location. In particular, the strong decrease of total ozone content during cycle 22 is related to the very high SSC values that occurred during that sunspot cycle and is remarkably strong in Faraday and Halley Bay stations. In all the stations the minimum in total ozone content long term variation is reached around 1993 and is followed by an steady increase, that would contin...
It has been suggested that length of the Day in the decadal time scale is related to solar activi... more It has been suggested that length of the Day in the decadal time scale is related to solar activity. Here, the non-linear relationship between time changes in the involved variables is analyzed by a Morlet wavelet base function by the methodology introduced in a previous paper (ST1. XX, EGU 2009). It is found that for the purpose of the present study, it is convenient to split the amplitude modulation of the two components of the magnetic 11-year cycle in four oscillations, VIZ.: Hale, semi-secular, Gleissberg and millennial. The same procedure is then applied to split the length of the day, the westward drift and the time derivative of the geomagnetic dipolar field time series. The amplitudes and phases of each of the four oscillations in the five time series are then compared. The most relevant result is that the millennial and the semi-secular oscillations in the solar dynamo magnetic field components are also visible in the variations of the length of the day, where they appear ...
The solar Gleissberg cycle is not restricted to one single periodicity, as was assumed by its dis... more The solar Gleissberg cycle is not restricted to one single periodicity, as was assumed by its discoverer. Later, it was shown that there are at least two components, each of which dominating in another period of time. We connect this observation to an earlier finding, viz. that the occurrence of the Grand Episodes is related to the behaviour of the solar dynamo in connection to its so-called Transition Point: another Grand Episode starts when the curve defined by the proxies of the poloidal and toroidal magnetic field components has crossed or passed along the Transition Point's coordinates. Here, we present evidence that each Grand Episode is related to one or more specific components of the Gleissberg cycle; each of them with its own period length. This finding must have implications for our understanding of the dynamo mechanism
Eos Transactions American Geophysical Union, 1993