A Cyclotron Theory for the Beaming Pattern of Jupiter’s Decametric Radio Emission

1981 ◽  
Vol 4 (2) ◽  
pp. 221-226 ◽  
Author(s):  
R. G. Hewitt ◽  
D. B. Melrose ◽  
K. G. Rönnmark
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Observational Data ◽  
Theoretical Interpretation ◽  
Theoretical Interest ◽  
Hollow Cone ◽  
The Past ◽  
Jovian Magnetosphere ◽  
Half Angle ◽  
Occurrence Pattern

Ground-based observations of Jupiter’s decametric radio emission (DAM) have been reviewed by Ellis (1965), Warwick (1967, 1970) and Carr and Gulkis (1969). A startling feature of DAM is the modulating effect of Io, and interpretation of the Io effect has dominated theoretical discussions of DAM until quite recently, specifically until the fly-by s of Voyagers 1 and 2. The Voyager data showed that the DAM appears as nested arcs in the frequency-Jovian longitude plane (Warwick et al. 1979, Boischot et al. 1981). The interpretation of this arc structure has been of primary theoretical interest over the past two years. The most widely adopted explanation is that the emission from each point is confined to the surface of a hollow cone (Goldstein and Thieman 1981). This idea is not new: emission on the surface of a cone was discussed by Ellis and McCulloch (1963); Dulk (1967) derived detailed parameters for the cone (half angle 79° width 1°) from the occurrence pattern of DAM; and Goldreich and Lynden-Bell (1969) presented a theoretical interpretation of it. More recently Goldstein et al. (1979) used observational data on the Jovian magnetic field in deriving properties of the required emission cone. It seems that one requires the properties of the emission cone to vary with position in the Jovian magnetosphere to account for the nested arc pattern (Goldstein and Thieman 1981; Gurnett and Goertz 1981).

scholarly journals Evolution of the Radio Emission from Young SNRs according to Observational Data

1979 ◽  
Vol 32 (2) ◽  
pp. 95 ◽  
Author(s):  
KS Stankevich
Keyword(s):  
Experimental Data ◽  
Radio Emission ◽  
Flux Density ◽  
Observational Data ◽  
Spectral Index ◽  
Density Measurements ◽  
The Past ◽  
Absolute Flux ◽  
Density Decrease ◽  
Frequency Variations

Results are given from a still-continuing series of absolute flux density measurements for the SNR CasA. The measurements have been taken regularly over the past 16 years at 24 wavelengths in the range 3-60 cm. New data are presented for the rate of flux density decrease, and for time and frequency variations in the spectral index. Intensity increases that are localized in frequency are described. The results are generalized in a model for the radio emission from a young SNR, and this is used to analyse experimental data for flux density decreases in the emission from 3C 10 and 58.

Open Localization in Micro LeadFrame Package Using Space Domain Reflectometry

2013 ◽  
Author(s):  
J. Gaudestad ◽  
V. Talanov ◽  
A. Orozco ◽  
M. Marchetti
Keyword(s):  
Magnetic Field ◽  
Radio Frequency ◽  
Standing Wave ◽  
High Resistance ◽  
Space Domain ◽  
The Past ◽  
Open Defects ◽  
Rf Electronics ◽  
Rf Signal ◽  
The Magnetic Field

Abstract In the past couple years, Space Domain Reflectometry (SDR) has become a mainstream method to locate open defects among the major semiconductor manufacturers. SDR injects a radio frequency (RF) signal into the open trace creating a standing wave with a node at the open location. The magnetic field generated by the standing wave is imaged with a SQUID sensor using RF electronics. In this paper, we show that SDR can be used to non-destructively locate high resistance failures in Micro LeadFrame Packages (MLP).

scholarly journals Can the Local Bubble explain the radio background?

2021 ◽  
Vol 502 (2) ◽  
pp. 2807-2814
Author(s):  
Martin G H Krause ◽  
Martin J Hardcastle
Keyword(s):  
Magnetic Field ◽  
Energy Density ◽  
Radio Emission ◽  
Magnetic Energy ◽  
Cosmic Ray ◽  
Observational Constraints ◽  
Local Bubble ◽  
Magnetic Energy Density ◽  
Magnetic Field Model ◽  
Radio Background

ABSTRACT The ARCADE 2 balloon bolometer along with a number of other instruments have detected what appears to be a radio synchrotron background at frequencies below about 3 GHz. Neither extragalactic radio sources nor diffuse Galactic emission can currently account for this finding. We use the locally measured cosmic ray electron population, demodulated for effects of the Solar wind, and other observational constraints combined with a turbulent magnetic field model to predict the radio synchrotron emission for the Local Bubble. We find that the spectral index of the modelled radio emission is roughly consistent with the radio background. Our model can approximately reproduce the observed antenna temperatures for a mean magnetic field strength B between 3 and 5 nT. We argue that this would not violate observational constraints from pulsar measurements. However, the curvature in the predicted spectrum would mean that other, so far unknown sources would have to contribute below 100 MHz. Also, the magnetic energy density would then dominate over thermal and cosmic ray electron energy density, likely causing an inverse magnetic cascade with large variations of the radio emission in different sky directions as well as high polarization. We argue that this disagrees with several observations and thus that the magnetic field is probably much lower, quite possibly limited by equipartition with the energy density in relativistic or thermal particles (B = 0.2−0.6 nT). In the latter case, we predict a contribution of the Local Bubble to the unexplained radio background at most at the per cent level.

scholarly journals The Magnetic Be Star Sigma Orionis E

1987 ◽  
Vol 92 ◽  
pp. 82-83 ◽  
Author(s):  
C. T. Bolton ◽  
A. W. Fullerton ◽  
D. Bohlender ◽  
J. D. Landstreet ◽  
D. R. Gies
Keyword(s):  
Magnetic Field ◽  
Field Structure ◽  
High Signal ◽  
Rotational Period ◽  
Magnetic Field Structure ◽  
The Past ◽  
Distribution Of Elements ◽  
Be Star ◽  
Hα Emission ◽  
The Magnetic Field

Over the past two years, we have obtained high resolution high signal/noise (S/N) spectra of the magnetic Be star σ Ori E at the Canada-France-Hawaii Telescope and McDonald Observatory. These spectra, which cover the spectral regions 399-417.5 and 440-458.5 nm and the Hα line and have typical S/N>200 and spectral resolution ≃0.02 nm, were obtained at a variety of rotational phases in order to study the magnetic field structure, the distribution of elements in the photosphere, and the effects of the magnetic field on the emission envelope. Our analysis of these spectra confirms, refines and extends the results obtained by Landstreet & Borra (1978), Groote & Hunger (1982 and references therein), and Nakajima (1985).The Hα emission is usually double-peaked, but it undergoes remarkable variations with the 1.19081 d rotational period of the star, which show that the emitting gas is localized into two regions which co-rotate with the star.

scholarly journals An overview of the structure and kinematics of the Magellanic Clouds

1991 ◽  
Vol 148 ◽  
pp. 15-23 ◽  
Author(s):  
B. E. Westerlund
Keyword(s):  
Star Formation ◽  
Observational Data ◽  
Spiral Structure ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Line Of Sight ◽  
Small Magellanic Cloud ◽  
Complex Velocity ◽  
The Past

A vast amount of observational data concerning the structure and kinematics of the Magellanic Clouds is now available. Many basic quantities (e.g. distances and geometry) are, however, not yet sufficiently well determined. Interactions between the Small Magellanic Cloud (SMC), the Large Magellanic Cloud (LMC) and our Galaxy have dominated the evolution of the Clouds, causing bursts of star formation which, together with stochastic self-propagating star formation, produced the observed structures. In the youngest generation in the LMC it is seen as an intricate pattern imitating a fragmented spiral structure. In the SMC much of the fragmentation is along the line of sight complicating the reconstruction of its history. The violent events in the past are also recognizable in complex velocity patterns which make the analysis of the kinematics of the Clouds difficult.

Magnetic Field Draping of the Heliopause and Its Consequences for Radio Emission in the Very Local Interstellar Medium

2021 ◽  
Vol 917 (2) ◽  
pp. L20
Author(s):  
N. V. Pogorelov ◽  
F. Fraternale ◽  
T. K. Kim ◽  
L. F. Burlaga ◽  
D. A. Gurnett
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Interstellar Medium ◽  
Local Interstellar Medium

scholarly journals Long-term evolution of the heliospheric magnetic field inferred from cosmogenic 44Ti activity in meteorites

2018 ◽  
Vol 610 ◽  
pp. A28 ◽  
Author(s):  
S. Mancuso ◽  
C. Taricco ◽  
P. Colombetti ◽  
S. Rubinetti ◽  
N. Sinha ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Ice Cores ◽  
Long Term Evolution ◽  
Galactic Cosmic Rays ◽  
Sunspot Activity ◽  
Cosmogenic Isotopes ◽  
Heliospheric Magnetic Field ◽  
The Past ◽  
Term Evolution

Typical reconstructions of historic heliospheric magnetic field (HMF) BHMF are based on the analysis of the sunspot activity, geomagnetic data or on measurement of cosmogenic isotopes stored in terrestrial reservoirs like trees (14C) and ice cores (10Be). The various reconstructions of BHMF are however discordant both in strength and trend. Cosmogenic isotopes, which are produced by galactic cosmic rays impacting on meteoroids and whose production rate is modulated by the varying HMF convected outward by the solar wind, may offer an alternative tool for the investigation of the HMF in the past centuries. In this work, we aim to evaluate the long-term evolution of BHMF over a period covering the past twenty-two solar cycles by using measurements of the cosmogenic 44Ti activity (τ1∕2 = 59.2 ± 0.6 yr) measured in 20 meteorites which fell between 1766 and 2001. Within the given uncertainties, our result is compatible with a HMF increase from 4.87-0.30+0.24 nT in 1766 to 6.83-0.11+0.13 nT in 2001, thus implying an overall average increment of 1.96-0.35+0.43 nT over 235 years since 1766 reflecting the modern Grand maximum. The BHMF trend thus obtained is then compared with the most recent reconstructions of the near-Earth HMF strength based on geomagnetic, sunspot number, and cosmogenic isotope data.

Social Theory and the Study of Christian Missions in Africa

Africa ◽  
1974 ◽  
Vol 44 (3) ◽  
pp. 235-249 ◽  
Author(s):  
T. O. Beidelman
Keyword(s):  
Social Theory ◽  
Pacific Islanders ◽  
Theoretical Interest ◽  
Relevant Research ◽  
Broad Area ◽  
Christian Missions ◽  
The Past ◽  
Native Populations ◽  
Opening Paragraph ◽  
The Impact

Opening ParagraphIn the past anthropology was concerned with alien, exotic societies such as Indians, Africans, and Pacific Islanders. Today it is in vogue to do the anthropology of modern societies. Abroad this is termed the study of nation-building and development; at home it becomes the study of various sub-cultures with attention towards ethnic minorities and deviant groups rather than upon the more powerful and prominent segments of our society. Anthropologists tend to neglect those groups nearest themselves, and in the scurry to conduct relevant research, a broad area of great theoretical interest has been passed by. Almost no attention was ever paid by anthropologists to the study of colonial groups such as administrators, missionaries, or traders. Today we can read anthropological studies of the impact of such groups upon native populations, but the focus of such work dims with the colour line. Thus, an anthropologist has studied the machinations of the members of a Nigerian emirate but not the tactics of the British Resident and his staff. Another applied potted Weberian bureaucratic theory to Soga local government but neglected to discuss the British district officers in the same chiefdom. Another asked how Christian Tswana behaved, but not about those missionaries who had converted them. Anthropologists may have spoken about studying total societies, but they did not seem to consider their compatriots as subjects for wonder and analysis.* In the studies of Christianity in Africa, consideration was mainly in terms of the relations of the convert to his traditional society, to the process of social change, or sometimes to the development of native separatist churches. It never included the missionaries who had made the conversions or described everyday affairs at the mission station, clinic, or school.

scholarly journals Polarization VLBI Observations of a Complete Sample of Northern BL Lacertae Objects

1998 ◽  
Vol 164 ◽  
pp. 165-166
Author(s):  
A. B. Pushkarev ◽  
D. C. Gabuzda
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Synchrotron Emission ◽  
Complete Sample ◽  
Bl Lacertae Objects ◽  
Bl Lacertae ◽  
Vlbi Observations ◽  
Core Components ◽  
Jet Structure ◽  
The Magnetic Field

AbstractThe polarization electric vectors in the VLBI jets of BL Lacertae objects are typically aligned with the jet structure. If the jet radio emission is optically thin synchrotron emission, this implies that the magnetic field is perpendicular to the jet, usually interpreted as a signature of shocks. The distribution of polarization position angles in the VLBI core components appears to be bimodal, with the polarization angles either aligned with or perpendicular to the jet direction. In order to study the origin of this characteristic polarization structure, we have made VLBI polarization observations of all 34 sources in the Kühr and Schmidt sample of BL Lacertae objects.

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