One fundamental question about pulsars concerns the mechanism of their pulsed electromagnetic emission. Measuring the high-end region of a pulsar's spectrum would shed light on this question. By ...developing a new electronic trigger, we lowered the threshold of the Major Atmospheric γ-ray Imaging Cherenkov (MAGIC) telescope to 25 giga--electron volts. In this configuration, we detected pulsed γ-rays from the Crab pulsar that were greater than 25 giga--electron volts, revealing a relatively high cutoff energy in the phase-averaged spectrum. This indicates that the emission occurs far out in the magnetosphere, hence excluding the polar-cap scenario as a possible explanation of our measurement. The high cutoff energy also challenges the slot-gap scenario.
The inner magnetosphere plasma is a very unique composition of different plasma particles and waves. It covers a huge energy plasma range with spatial and time variations of many orders of magnitude. ...In such a situation, the kinetic approach is the key element, and the starting point of the theoretical description of this plasma phenomena which requires a dedicated book to this particular area of research.
Radiação quilométrica auroral Costa Junior, Edio da; Alves, Maria Virgínia
Revista Brasileira de Ensino de Física,
12/2015, Letnik:
37, Številka:
4
Journal Article
Odprti dostop
Vários fenômenos puderam ser mais bem estudados ou até mesmo só foram descobertos depois do desenvolvimento dos satélites e espaçonaves. Dentre esses fenômenos podemos destacar a radiação ...quilométrica auroral (AKR, do inglês auroral kilometric radiation). O fenômeno foi descoberto apenas há pouco mais de 40 anos; as frequências típicas são muito baixas para penetrar na ionosfera em direção à Terra. Sua geração se dá através de interações onda-partícula na região noturna do planeta, acima da ionosfera auroral, sendo a energia necessária proveniente dos feixes de elétrons que se precipitam nessas regiões. É gerada principalmente no modo extraordinário (modo-X), no intervalo de frequências de 20-800 kHz, próximo à frequência local ciclotrônica de elétrons. Sabe-se muito bem que a AKR é intensificada durante subtempestades magnéticas, sendo bem correlacionada com o índice AE. Entretanto, estudos recentes têm mostrado que a radiação desaparece nas fases inicial e principal de algumas tempestades magnéticas, apesar do grande aumento do índice AE e de correntes alinhadas ao campo. Nesses casos, a radiação volta a ser emitida durante a fase de recuperação. Esse comportamento sugere que o campo elétrico alinhado ao campo magnético que acelera os elétrons que se precipitam e induz correntes alinhadas não é formado nas fases inicial e principal de algumas tempestades magnéticas. O intuito desse artigo é apresentar aos leitores a AKR e suas características, tornando esse importante fenômeno mais conhecido entre estudantes e professores de física.
Several phenomena could be better studied and even disclosed after the development of the satellites and spacecrafts. Auroral kilometric radiation (AKR) is one of these phenomena. AKR was first detected only about forty years ago; its typical frequencies are too low to penetrate earthward across the ionosphere. This radiation is generated through wave-particle interactions, in the nightside region above the auroral ionosphere. It grows at the expense of free energy from the precipitating auroral electron beam. It is generated mainly in the extraordinary (X) mode, in the frequency range of 20-800 kHz, near the local electron cyclotron frequency. Nowadays, it is well known that AKR is intensified during magnetic substorms and has a good correlation with the AE magnetic index. However, recent studies showed that the radiation disappears in the initial and main phases of some magnetic storms, in spite of the large enhancement of the AE index and field aligned currents. The radiation activates strongly in the recovery phase. This behavior suggests that the field-aligned electric field, which accelerates precipitating electrons and drives field-aligned currents, is not formed in the initial and main phases of some magnetic storms. The purpose of this article is introduce readers to AKR and its features, making this important phenomenon best known among students and teachers of physics.
The Handbook of the Solar-Terrestrial Environment is a unique compendium. Recognized international leaders in their field contribute chapters on basic topics of solar physics, space plasmas and the ...Earth`s magnetosphere, and on applied topics like the aurora, magnetospheric storms, space weather, space climatology and planetary science. This book will be of highest value as a reference for researchers working in the area of planetary and space science. However, it is also written in a style accessible to graduate students majoring in those fields.
With the awareness that the Earth has a magnetic field, its mathematical description, discovery of remanent magnetisation in rocks and discovery of the periodic reversals of the geomagnetic field ...polarity, geomagnetism within geophysics became an interesting field of study. This is primarily due to advances in measurement technology and improved understanding of the magnetic field and its fluctuations in the geospace. Several important aspects of solid Earth geomagnetism are elaborated in the book. The first six chapters cover the basics of magnetism, magnetic minerals, biomagnetics, instrumentation and the behavior of geomagnetic field, while the rest of the book is devoted to practical applications with carefully selected examples and illustrations. Well-written and easy to read, the book vividly describes modern techniques in the subject matter covered, adequately supported by graphical explanations for complex mathematical concepts.
Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 199.Dynamics of the Earth's Radiation Belts and Inner Magnetosphere draws together current knowledge of ...the radiation belts prior to the launch of Radiation Belt Storm Probes (RPSP) and other imminent space missions, making this volume timely and unique. The volume will serve as a useful benchmark at this exciting and pivotal period in radiation belt research in advance of the new discoveries that the RPSP mission will surely bring. Highlights include the following: a review of the current state of the art of radiation belt science; a complete and up-to-date account of the wave-particle interactions that control the dynamical acceleration and loss processes of particles in the Earth's radiation belts and inner magnetosphere; a discussion emphasizing the importance of the cross-energy coupling of the particle populations of the radiation belts, ring current, and plasmasphere in controlling the dynamics of the inner magnetosphere; an outline of the design and operation of future satellite missions whose objectives are to discover the dominant physical processes that control the dynamics of the Earth's radiation belts and to advance our level of understanding of radiation belt dynamics ideally to the point of predictability; and an examination of the current state of knowledge of Earth's radiation belts from past and current spacecraft missions to the inner magnetosphere. Dynamics of the Earth's Radiation Belts and Inner Magnetosphere will be a useful reference work for the specialist researcher, the student, and the general reader. In addition, the volume could be used as a supplementary text in any graduate-level course in space physics in which radiation belt physics is featured.
"Our planet exists within a space environment affected by constantly changing solar atmosphere producing cosmic particles and electromagnetic waves. This ""space weather"" profoundly influences the ...performance of our technology because we primarily use two means for transmitting information and energy, namely, electromagnetic waves and electricity. On an everyday basis, we have developed methods to cope with the normal conditions. However, the sun remains a fiery star whose 'angry' outbursts can potentially destroy spacecrafts, kill astronauts, melt electricity transformers, stop trains, and generally wreak havoc with human activities. Space Weather is the developing field within astronomy that aims at predicting the sun's violent activity and minimizing the impacts on our daily lives. Space Weather, Environment, and Societies explains why our technological societies are so dependent on solar activity and how the Sun disturbs the transmission of information and energy. Footnotes expand specific points and the appendices facilitate a more thorough command of the physics involved."
Hemos utilizado la Técnica de medición de intermitencia local (local Intermittency Measure Technique) basada en la técnica de la transformada de wavelet para estudiar las fluctuaciones de velocidad ...en el plasma, medidas por experimento de espectrómetro de iones de satélite CLUSTER, durante la tormenta geomagnética de 24–28 de agosto de 2005. Los resultados obtenidos mostraron un aumento significativo de nivel de turbulencia intermitente al final de la fase principal. Esto puede estar relacionado con un aumento significativo en la actividad de las subtormentas y estiramiento de las líneas del campo geomagnético observado en la fase principal. Este hecho es importante para la comprensión de la naturaleza de las tormentas geomagnéticas. doi: https://doi.org/10.22201/igeof.00167169p.2008.47.3.89
This volume fulfils the need for an overview of the field, rather than offering a topical focus. Its chapters, written by leading scientists, cover the latest results in many areas such as ...magnetospheric substorms and transport phenomena in the plasma sheet.
A collection of papers, which addresses the question "What is the Magnetospheric Cusp?" and its role in the coupling of the solar wind to the magnetosphere as well as its role in the processes of ...particle transport and energization within the magnetosphere. This book is useful to scientists as well as to those working in research organizations.
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