Efectos de la precipitación de partículas energéticas de origen solar en la atmosfera de la tierra

La Tierra es continuamente “bombardeada” por partículas energéticas cargadas procedentes del espacio exterior que penetran en la atmósfera y pueden influir en una variedad de procesos atmosféricos. El Sol emite ondas de radio, rayos X y partículas energéticas, además de la luz visible. El transporte de energía desde el Sol hacia la Tierra se produce de dos formas: (1) radiación electromagnética, que emite alrededor de 4 x 1033 erg/s irradiando la Tierra con 1,37x 10 3 W m-2 y (2) radiación corpuscular (el viento solar con el campo magnético interplanetario “congelado” en él y cualquier partícula solar energética que puede estar presente). El ingreso de partículas energéticas solares a la magnetosfera de la Tierra produce efectos sobre las especies químicas de la atmosfera alta y media cuando precipitan en las zonas aurorales de ambos hemisferios guiadas por el campo geomagnético. La ionosfera, como parte del entorno meteorológico espacial, juega un papel crucial a través de la modulación del circuito electrodinámico global, su acoplamiento a la magnetosfera y como medio clave para la comunicación, el sondeo y la navegación. Por tanto, una comprensión profunda de su variabilidad en todas las escalas de tiempo es un importante aporte al estudio de la meteorología espacial. Como consecuencia de la intensificación de la precipitación de partículas durante periodos de tormenta geomagnética, se produce un aumento de la ionización, la creación de nitrógeno impar (NOx) y de hidrógeno impar (HOx) en la atmósfera superior, afectando la química del ozono estratosférico. Por otro lado, los campos eléctricos de origen magnetosférico, las perturbaciones atmosféricas viajeras, la circulación termosférica, y los cambios de composición química, explican las características ionosféricas de la densidad electrónica durante las distintas fases de tormentas geomagnéticas y en diferentes latitudes.The Earth is continuously "bombarded" by energetic charged particles from outer space that penetrate the atmosphere and can influence a variety of atmospheric processes. The Sun emits radio waves, X-rays and energetic particles in addition to visible light. The energy transport from the Sun to the Earth occurs in two forms: (1) electromagnetic radiation, which emits about 4 x 1033 erg/s irradiating the Earth with 1.37x 10 3 W m-2 and (2) corpuscular radiation (the solar wind with the interplanetary magnetic field "frozen" into it and any energetic solar particles that may be present). The inflow of solar energetic particles into the Earth's magnetosphere produces effects on chemical species in the high and middle atmosphere as they precipitate into the auroral zones of the two hemispheres guided by the geomagnetic field. The ionosphere, as part of the space weather environment, plays a crucial role through modulation of the global electrodynamic circuitry, its coupling to the magnetosphere, and as a key medium for communication, sounding, and navigation. Therefore, a deep understanding of its variability on all time scales is an important contribution to the study of space weather. As a consequence of intensified particle precipitation during periods of geomagnetic storms, there is an increase in ionization, the creation of odd nitrogen (NOx) and odd hydrogen (HOx) in the upper atmosphere, affecting the chemistry of stratospheric ozone. Also, electric fields of magnetospheric origin, circulating atmospheric disturbances, thermospheric circulation, and chemical composition changes explain the ionospheric characteristics of the electron density during different phases of geomagnetic storms and at different latitudes.Asociación Argentina de Geofísicos y Geodesta

Comportamiento geomagnético e ionosférico durante las subtormentas del día 9 de enero de 1975

La disponibilidad de un número significativo de magnetómetros cubriendo los anillos aurorales norte y sur, y cadenas longitudinales nos permite un amplio análisis del comportamiento del campo geomagnético durante las subtormentas producidas el día 9 de enero de 1975. Los resultados confirman los modelos que establecen que las mismas son generadas en la cola nocturna magnética terrestre por ruptura del sistema de corriente que atraviesa la lengua de plasma desde alba a crepúsculo y aparición de corrientes de Birkeland alineadas con las líneas magnéticas de campo con pie u origen en las zonas aurorales. Se observa también que el proceso no se propaga a bajas latitudes. El análisis del comportamiento ionosférico muestra contradicciones con algunas ideas presentes.The abundance of information from magnetometers covering north and south auroral zones and meridional chains, makes it possible to analize the geomagnetic field behaviour during January, the 9th, 1975, substorms. The results confirm previous models establishing that the substorms are generated at the nocturnal magnetic tail, as a consequence of the break of the current system crossing the plasmasheet from dawn to dusk and to the presence of the field - aligned Birkeland currents with origin or foot at the auroral zones. Propagation of the process to lower latitudes has not been observed. The ionospheric behaviour shows contradictions with some present ideas.Asociación Argentina de Geofísicos y Geodesta

Comparative analysis of extreme ultraviolet solar radiation proxies during minimum activity levels

Four extreme ultraviolet (EUV) solar radiation proxies (Magnesium II core-to-wing ratio (MgII), Lyman α flux (Fα), 10.7-cm solar radio flux (F10.7), and sunspot number (Rz)) were analyzed during the last four consecutive solar activity minima to investigate how they differ during minimum periods and how well they represent solar EUV radiation. Their variability within each minimum and between minima was compared by considering monthly means. A comparison was also made of their role in filtering the effect of solar activity from the critical frequency of the ionospheric F2 layer, foF2, which at mid to low latitudes depends mainly on EUV solar radiation. The last two solar cycles showed unusually low EUV radiation levels according to the four proxies. Regarding the connection between the EUV “true” variation and that of solar proxies, according to the foF2 filtering analysis, MgII and Fα behaved in a more stable and suitable way, whereas Rz and F10.7 could be overestimating EUV levels during the last two minima, implying they would both underestimate the inter-minima difference of EUV when compared with the first two minima

Another way of deriving the ring current decay time during disturbed periods

Coupling parameter, E, and the total energy dissipated by the magnetosphere, UT, are determined for six disturbed periods, following three known criteria for UT computation. It is observed that UT exceeds E for Dst < -90 nT, for alI models. Differences between models reside on the estimated valnes for the particles' life time il1 the equatorial ring current. The values of TR, used in the models, are small during the main phase of the di."turbance, in disagreement with the charge exchange life time of the majority species, H+ and O'-. Based on this conclusion, a different criterion to calculate TR is proposed, differentiating the different stages of the perturbation. TR is calculated, for the main phase of the storm, from the rate of energy deposition estimation, Q, in the ring current. For Dst recovery phase, the vallles are obtained from a ring current decay law computation. The UTvu calculated, physically more coherent with the processes occurring during the event, is now smaller than expected. In this sense, it is understood that the power generated by the solar wind-magnetosphere dy- namo, should also be distributed in the inner magnetosphere, auroral zones and equatorial ring current, as in the outer magnetosphere, plasmoids in the tail shot in antisolar direction. A further adjustment of E, with the Chapman-Ferraro distance, 10' variable, has been made. Although the reslllts, improve the estimation of E, they are sti!l smaller than UT, except UTNU, for some disturbed periods. This result indicates the uncertainty in the computation of the input energy, by using the many expressions proposed in the literature, which are always presented as laws proportional to a given group of parameters, with an unknown factor of proportionality, which deserves more detailed physical analysis

Austral electrojet indices derived for the great storm of March 1989 1177

Available magnetic records from eight stations in the Antarctica, for the March 1989 geomagnetic storm, are used to construct the southern hemisphere auroral indices, analogous to the boreal ones. The results show a diurnal variation depending on the distribution of the stations. An acceptable correlation between the northern and southern hemisphere indices are found except for the index indicating the presence of the eastward auroral electrojet. However, differences in the amplitudes of both auroral electrojet indices were observed

Análisis de la variabilidad del índice PC usando wavelets

Los índices geomagnéticos proveen un control permanente de los procesos que ocurren en la alta atmósfera y la magnetosfera, representando datos fundamentales en el estudio del clima espacial. En este trabajo se analizan periodicidades y tendencia del índice PC (Polar Cap) usando la transformada wavelet (ondeletas). Este índice registra la actividad magnética llamada DP2, asociada con el sistema de corriente equivalente en el casquete polar. Se analizan valores promedios mensuales del índice, correspondientes al observatorio de Thule, durante el período 1975-2000. Entre las periodicidades, se destaca una de 8,7 años, observada en la aproximación con un aporte del 44% a la varianza total de la serie. Además se distinguen en los distintos detalles oscilaciones alrededor de los 3 meses, 6 meses, 1 año, la cuasibienal y una alrededor de 5,2 años. En la búsqueda de las posibles causas de los ciclos detectados se consideran promedios mensuales de la velocidad del viento solar y de la intensidad del campo magnético interplanetario en el período estudiado. La periodicidad de 8,7 años se observa con gran significancia en los valores correspondientes a la intensidad del campo magnético interplanetario, que correspondería al período más corto del ciclo solar de 11 años Los resultados se comparan con los obtenidos anteriormente para otros índices geomagnéticos usando distintas técnicas de análisis. Las causas de las periodicidades detectadas en el índice PC, podrían estar vinculadas con variaciones en el sol.The geomagnetic indices provide a permanent control of the processes that take place in the upper atmosphere and the magnetosfere, being an important data set in the study of space weather. In the present work, periodicities and trends of the Polar Cap index, PC, are analyzed using the Wavelet transformed. This index registers the magnetic activity DP2, associated with the equivalent current system ofthe polar cap. Monthly mean values ofthe index are analyzed, corresponding to the observatory ofThule, during the period 1975 -2000. Among the periodicities, one of 8.7 years stands out, with a 44% contribution to the total variance of the series. Oscillations around 3 months, 6 months, 1 year, quasi-biennial and around 5.2 years are distinguished. In the search ofpossible causes ofthe detected cycles, monthly averages ofthe solar wind velocity and ofthe intensity ofthe interplanetary magnetic field are considered. The 8.7 years periodicity is observed with great significance in the values corresponding to the intensity ofthe interplanetary magnetic field that it would correspond to the shortest period in the 11 years solar cycle. The results are compared with those obtained previously for other geomagnetic indices. The causes ofthe periodicities detected in PC index, could be linked with variations in the sun.Material digitalizado en SEDICI gracias a la colaboración de la Facultad de Ciencias Astronómicas y Geofísicas (UNLP).Asociación Argentina de Geofísicos y Geodesta

Spitze Angle Changes during Rapid Geomagnetic Core Field Variation

International audienc

Another way of deriving the ring current decay time during disturbed periods

Coupling parameter, E, and the total energy dissipated by the magnetosphere, UT, are determined for six disturbed periods, following three known criteria for UT computation. It is observed that UT exceeds E for Dst < -90 nT, for alI models. Differences between models reside on the estimated valnes for the particles' life time il1 the equatorial ring current. The values of TR, used in the models, are small during the main phase of the di."turbance, in disagreement with the charge exchange life time of the majority species, H+ and O'-. Based on this conclusion, a different criterion to calculate TR is proposed, differentiating the different stages of the perturbation. TR is calculated, for the main phase of the storm, from the rate of energy deposition estimation, Q, in the ring current. For Dst recovery phase, the vallles are obtained from a ring current decay law computation. The UTvu calculated, physically more coherent with the processes occurring during the event, is now smaller than expected. In this sense, it is understood that the power generated by the solar wind-magnetosphere dy- namo, should also be distributed in the inner magnetosphere, auroral zones and equatorial ring current, as in the outer magnetosphere, plasmoids in the tail shot in antisolar direction. A further adjustment of E, with the Chapman-Ferraro distance, 10' variable, has been made. Although the reslllts, improve the estimation of E, they are sti!l smaller than UT, except UTNU, for some disturbed periods. This result indicates the uncertainty in the computation of the input energy, by using the many expressions proposed in the literature, which are always presented as laws proportional to a given group of parameters, with an unknown factor of proportionality, which deserves more detailed physical analysis

An Improved Stereoselective Synthesis of L-Alanosine

An improved, stereoselective synthesis of the natural, nonproteogenic amino acid L-alanosine has been developed, starting from the readily available and cheap substrate L-serine, in six steps and 49% overall yield. The process is very efficient, is suitable for large-scale production, and affords Lalanosine with properties comparable with those of the natural substance. In addition, the structural assignment concerning some previously reported synthetic alkylated derivatives of the natural amino acid has been definitively confirmed

Validación de una metodología para determinar el contenido de almidón en azúcar Validation of a methodology to determine starch in sugar

El almidón es un microcomponente indeseado en el proceso de fabricación de azúcar debido a los problemas que origina durante las distintas etapas de elaboración y en el producto final, cuando se emplea el azúcar como materia prima para la producción de otros alimentos. Por este motivo, es necesario contar con un método confiable para su determinación. En el marco del Sistema de Gestión de la Calidad de los laboratorios de la Sección Química de la Estación Experimental Agroindustrial "Obispo Colombres" (EEAOC), se validó la aplicación de la metodología COPERSUCAR para determinación de almidón en azúcar. Los parámetros determinados fueron: límite de detección, límite de cuantificación, linealidad e intervalo operativo, precisión, sesgo e incertidumbre relativa. Los resultados obtenidos demostraron que esta técnica es aceptable para determinar almidón en diferentes tipos de azúcares, en concentraciones comprendidas entre 25 y 600 mg/kg, con una incertidumbre de ±10,8%.<br>Starch is an undesirable microcomponent in sugar processing because of the problems it causes during this process and that of food production using sugar as raw material. For this reason, a reliable determination method is required. As the laboratory of Sección Química of Estación Experimental Agroindustrial "Obispo Colombres" (EEAOC) works under a quality system, a technique developed by Copersucar was validated. Detection and quantification limits, linearity, accuracy and uncertainty were determined. The results showed that this method is acceptable to determine starch concentrations in different sugar types at levels between 25 and 600 mg/kg. Uncertainty was ±10,8%