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, Volume:
37, Issue:
4
Journal Article
Open access
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.
"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."
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.
The book deals with Ultra-Low-Frequency (ULF)-electromagnetic waves observed on the Earth and in Space. These are so-called geomagnetic variations or pulsations. Alfvén's discovery related to the ...influence of the strong magnetic field on the conducting fluids (magnetohydrodynamics) led to development of the concept that the ULF-waves are magnetospheric magnetohydrodynamic (MHD)-waves. MHD-waves at their propagation gather information about the magnetosphere, ionosphere, and the ground. There are two applied aspects based on using the ULF electromagnetic oscillations. The first one is the ground-based diagnostics of the magnetosphere. This is an attempt to monitor in the real time the magnetosphere size, distance to the last closed field-lines, distribution of the cold plasma, etc. The second one is the deep electromagnetic sounding of the Earth. The basis for these studies is the capability of any electromagnetic wave to penetrate a conductor to a finite depth. The ULF-waves can reach the depth of a few hundred kilometers. Thus, geophysicists now have a unique tool that can be applied to study the solid Earth as well as its gas-plasma shells - the ionosphere and magnetosphere. This book integrates topics pertaining to all scales of the MHD-waves, emphasizing the linkages between the ULF-waves below the ionosphere on the ground and magnetospheric MHD-waves. It will be most helpful to graduate and post-graduate students, familiar with advanced calculus, who study the science of MHD-waves in the magnetosphere and ionosphere.
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.
PDF
