Relevance of the magnetic field model for studying the beaming cone of the Jovian decameter emission

2020 ◽  
Author(s):  
Patrick Galopeau ◽  
Mohammed Boudjada
Keyword(s):  
Magnetic Field ◽  
Field Model ◽  
Source Region ◽  
Local Magnetic Field ◽  
Hollow Cone ◽  
The North ◽  
Cyclotron Maser ◽  
Specific Direction ◽  
Magnetic Field Model ◽  
The Magnetic Field

<p>We use five different Jupiter’s magnetic field models (O6, VIP4, VIT4, VIPAL and JRM09) to investigate the angular distribution of the Jovian decameter radiation occurrence probability, relatively to the local magnetic field<strong> B</strong> and its gradient <strong>∇</strong><em>B</em> in the source region. The most recent model JRM09, proposed by Connerney et al. [<em>Geophys. Res. Lett.</em>, <em>45</em>, 2590-2596, 2018], was derived from Juno’s first nine orbits observations. The JRM09 model confirms the results obtained several years ago using older models (O6, VIP4, VIT4 and VIPAL): the radio emission is beamed in a hollow cone presenting a flattening in a specific direction. The same assumptions were made as in the previous studies: the Jovian decameter radiation is supposed to be produced by the cyclotron maser instability (CMI) in a plasma where <strong>B</strong> and <strong>∇</strong><em>B</em> are not parallel. As a consequence, the emission cone does not have any axial symmetry and then presents a flattening in a privileged direction. This flattening appears to be more important for the northern emission (34.8%) than for the southern emission (12.5%) probably due to the fact that the angle between the directions of <strong>B</strong> and <strong>∇</strong><em>B</em> is greater in the North (~10°) than in the South (~4°).</p>

Beaming cone of the Jovian decameter emission derived from different magnetic field models

2021 ◽  
Author(s):  
Patrick Galopeau ◽  
Mohammed Boudjada
Keyword(s):  
Magnetic Field ◽  
Angular Distribution ◽  
Source Region ◽  
Recent Model ◽  
Local Magnetic Field ◽  
Occurrence Probability ◽  
Hollow Cone ◽  
The North ◽  
Cyclotron Maser ◽  
Specific Direction

<p>Five different Jupiter’s magnetic field models (O6, VIP4, VIT4, VIPAL and JRM09) are used to investigate the angular distribution of the Jovian decameter radiation occurrence probability, relatively to the local magnetic field<strong> B</strong> and its gradient <strong>∇</strong><em>B</em> in the source region. The most recent model JRM09, proposed by Connerney et al. [<em>Geophys. Res. Lett.</em>, <em>45</em>, 2590-2596, 2018], and derived from Juno’s first nine orbits observations, confirms the results obtained several years ago using older models (O6, VIP4, VIT4 and VIPAL): the radio emission is beamed in a hollow cone presenting a flattening in a specific direction. In this study, the same assumptions were made as in the previous ones: the Jovian decameter radiation is supposed to be produced by the cyclotron maser instability (CMI) in a plasma where <strong>B</strong> and <strong>∇</strong><em>B</em> are not parallel. The main result of our study is that the emission cone does not have any axial symmetry and then presents a flattening in a privileged direction. This flattening appears to be more important for the northern emission (34.8%) than for the southern emission (12.5%) probably due to the fact that the angle between the directions of <strong>B</strong> and <strong>∇</strong><em>B</em> is greater in the North (~10°) than in the South (~4°).</p>

A satellite study of dayside auroral conjugacy

1995 ◽  
Vol 13 (11) ◽  
pp. 1134-1143 ◽  
Author(s):  
H. B. Vo ◽  
J. S. Murphree ◽  
D. Hearn ◽  
P. T. Newell ◽  
C.-I. Meng
Keyword(s):  
Magnetic Field ◽  
Field Model ◽  
Conjugate Point ◽  
Source Region ◽  
Conjugate Points ◽  
Opposite Hemisphere ◽  
The North ◽  
Magnetic Field Model ◽  
Field Lines ◽  
Dipole Tilt

Abstract. A study of dayside auroral conjugacy has been done using the cleft/boundary layer auroral particle boundaries observed by the DMSP-F7 satellite in the southern hemisphere and the global UV auroral images taken by the Viking spacecraft in the northern hemisphere. The 22 events have been studied on the basis of an internal IGRF 1985 magnetic field; it is shown that there is a displacement of up to 4° in latitude from the conjugate points with the northern aurora appearing to be located poleward of the conjugate point. No local time dependence of the north-south auroral location difference was seen. The use of a more realistic magnetic field model for tracing field lines which incorporates the dipole tilt angle and Kp index, the Tsyganenko 1987 long model plus the IGRF 1985 internal magnetic field model, appears to organize the data better. Although with this external plus internal model some tracings did not close in the opposite hemisphere, 70% of those that did indicated satisfactory conjugacy. The study shows that the degree of auroral conjugacy is dependent upon the accuracy of the magnetic field model used to trace to the conjugate point, especially in the dayside region where the field lines can either go to the dayside magnetopause near the subsolar point or sweep all the way back to the flanks of the magnetotail. Also the discrepancy in the latitude of northern and southern aurora can be partially explained by the displacement of the neutral sheet (source region of the aurora) by the dipole tilt effect.

scholarly journals A case study of the plasma in the magneto-sheath using the numerical magnetosheath-magnetosphere model and THEMIS measure-ments

2018 ◽  
Vol 145 ◽  
pp. 03004
Author(s):  
Polya Dobreva ◽  
Olga Nitcheva ◽  
Monio Kartalev
Keyword(s):  
Magnetic Field ◽  
Field Model ◽  
Specific Aspect ◽  
Plasma Parameters ◽  
Ion Density ◽  
Magnetic Field Model ◽  
Wind Spacecraft ◽  
The Mean ◽  
The Magnetic Field

This paper presents a case study of the plasma parameters in the magnetosheath, based on THEMIS measurements. As a theoretical tool we apply the self-consistent magnetosheath-magnetosphere model. A specific aspect of the model is that the positions of the bow shock and the magnetopause are self-consistently determined. In the magnetosheath the distribution of the velocity, density and temperature is calculated, based on the gas-dynamic theory. The magnetosphere module allows for the calculation of the magnetopause currents, confining the magnetic field into an arbitrary non-axisymmetric magnetopause. The variant of the Tsyganenko magnetic field model is applied as an internal magnetic field model. As solar wind monitor we use measurements from the WIND spacecraft. The results show that the model quite well reproduces the values of the ion density and velocity in the magnetosheath. The simlicity of the model allows calulations to be perforemed on a personal computer, which is one of the mean advantages of our model.

scholarly journals Retrieving lithospheric magnetisation distribution from magnetic field models

2019 ◽  
Author(s):  
V Lesur ◽  
F Vervelidou
Keyword(s):  
Magnetic Field ◽  
Cost Function ◽  
Spherical Harmonic ◽  
Field Model ◽  
Harmonic Model ◽  
Whole Process ◽  
Magnetic Field Model ◽  
The Cost ◽  
Spherical Harmonic Model ◽  
The Magnetic Field

Summary We investigate to which extent the radially averaged magnetisation of the lithosphere can be recovered from the information content of a spherical harmonic model of the generated magnetic field when combined with few simple hypotheses. The results obtained show firstly that a hypothesis of magnetisation induced by a field of internal origin, even over a localised area, is not sufficient to recover uniquely the radially averaged magnetisation and, secondly, that this magnetisation can be recovered when a constant magnetisation direction is assumed. An algorithm to recover the magnetisation direction and distribution is then described and tested over a synthetic example. It requires to introduce a cost function that vanishes when estimated in a system of coordinates with its Z axis aligned with the magnetisation direction. Failing to find a vanishingly small value for the cost function is an indication that a constant magnetisation direction is not a valid hypothesis for the studied magnetic field model. The range of magnetisation directions that are compatible with the magnetic field model and a given noise level, can also be estimated. The whole process is illustrated by analysing a local, isolated maximum of the Martian magnetic field.

scholarly journals Velocity-Magnetic Field Correlation of Pulsars

1996 ◽  
Vol 160 ◽  
pp. 49-50
Author(s):  
Naoki Itoh ◽  
Takemi Kotouda
Keyword(s):  
Magnetic Field ◽  
Constant Magnetic Field ◽  
Field Model ◽  
Transverse Velocity ◽  
Distribution Model ◽  
Recent Measurement ◽  
Apparent Correlation ◽  
Magnetic Field Model ◽  
Field Correlation ◽  
The Magnetic Field

Monte Carlo simulations of the evolution of pulsars are carried out in order to compare with the recent measurement of the pulsar transverse velocity by Lyne & Lorimer (1994). The new electron density distribution model of Taylor & Cordes (1993) is adopted in the simulation. Accurate pulsar orbits in the Galactic gravitational field are calculated. It is found that the constant magnetic field model of pulsars can account for the new measurement of the pulsar transverse velocity and the apparent correlation between the strength of the magnetic field and the transverse velocity of the pulsars. The present finding confirms the validity of the constant magnetic field model of pulsars and consolidates the idea that the apparent correlation between the strength of the magnetic field and the transverse velocity of the pulsars is caused by observational selection effects.

scholarly journals Analysis of Juno perijove 1 magnetic field data using the Jovian paraboloid magnetospheric model

2018 ◽  
Author(s):  
Ivan A. Pensionerov ◽  
Elena S. Belenkaya ◽  
Stanley W. H. Cowley ◽  
Igor I. Alexeev ◽  
Vladimir V. Kalegaev ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Field Model ◽  
Outer Edge ◽  
Optimal Parameters ◽  
Magnetic Field Data ◽  
Analytic Expressions ◽  
Magnetic Field Model ◽  
Current Systems ◽  
The Magnetic Field

Abstract. One of the main features of Jupiter's magnetosphere is its equatorial magnetodisc, which significantly increases the field strength and size of the magnetosphere. Juno measurements of the magnetic field during the perijove 1 pass have allowed us to determine optimal parameters of the magnetodisc using the paraboloid magnetospheric magnetic field model, which employs analytic expressions for the magnetospheric current systems. Specifically within the model we determine the size of the Jovian magnetodisc and the magnetic field strength at its outer edge.

EFFECTS OF THE WIGGLER ON THE HEFEI LIGHT SOURCE STORAGE RING

2009 ◽  
Vol 24 (05) ◽  
pp. 1057-1067
Author(s):  
HE ZHANG ◽  
MARTIN BERZ
Keyword(s):  
Magnetic Field ◽  
Light Source ◽  
Storage Ring ◽  
Field Model ◽  
Beta Function ◽  
Nonlinear Effects ◽  
Magnetic Field Model ◽  
Dynamic Aperture ◽  
Linear Effects ◽  
The Magnetic Field

The Hefei light source (HLS) is a second generation synchrotron radiation light source, in which a superconducting wiggler is installed and operating. The effects of the wiggler on the beam dynamics on the HLS storage ring are studied, in order to make sure the wiggler can operate properly when the ring is working in the high brilliance mode. We generate a model of the magnetic field in the midplane of the wiggler. The 3D magnetic field model is also builded up by COSY infinity 9.0. Both the linear and nonlinear effects of the wiggler are discussed. The vertical tune is changed from 2.535 to 2.567 and the vertical beta function is heavily distorted, while a symplectic tracking study shows the dynamic aperture is only slightly affected by the wiggler. And the wiggler should be able to run on the high brilliance mode after the linear effects get compensated.

scholarly journals Juno reveals new insights into Io-related decameter radio emissions

2020 ◽  
Author(s):  
Yasmina M Martos ◽  
Masafumi Imai ◽  
John E.P. Connerney ◽  
Stavros Kotsiaros ◽  
William S. Kurth
Keyword(s):  
Magnetic Field ◽  
Field Model ◽  
Loss Cone ◽  
Radio Emissions ◽  
Cyclotron Maser ◽  
Magnetic Field Model ◽  
Decameter Radio ◽  
Resonant Electron ◽  
Field Geometry ◽  
Improved Accuracy

<p>The Juno spacecraft has been orbiting Jupiter since July 2016 providing stunning new information about the planet and its environment. The new magnetic field model, JRM09, with much improved accuracy near the planet, provides the basis for a better understanding of Io-related decametric radio emissions and implications for auroral processes. Here, we study Io-related DAM events observed by the Juno Waves instrument to estimate the beaming angle, the resonant electron energy and radio source location by forward modeling. The JRM09 magnetic field model is used to better constrain the location and observability of the radio emissions, and characterize the loss cone-driven electron cyclotron maser instability. We obtained good agreement between synthetic and observed arcs. The estimated beaming cone half-angles range from 33° to 85° and the obtained resonant electron energies are up to 23 times higher than previously proposed. Additionally, we quantitatively analyze the higher likelihood of observing groups of arcs originating in the northern hemisphere relative to those originating in the southern hemisphere. This is primarily a consequence of the asymmetry of the magnetic field geometry, observer location, and pitch angles of the electrons at the equator.  </p>

scholarly journals Coronal Loop Mapping to Infer the Best Magnetic Field Models for Active Region Prominences

2013 ◽  
Vol 8 (S300) ◽  
pp. 416-417
Author(s):  
G. Allen Gary ◽  
Qiang Hu ◽  
Jong Kwan Lee
Keyword(s):  
Magnetic Field ◽  
Coronal Loop ◽  
Field Model ◽  
Three Dimensional ◽  
Coronal Loops ◽  
Magnetic Field Model ◽  
Free Parameters ◽  
Field Lines ◽  
Fitness Parameter ◽  
The Magnetic Field

AbstractThis article comments on the results of a new, rapid, and flexible manual method to map on-disk individual coronal loops of a two-dimensional EUV image into the three-dimensional coronal loops. The method by Gary, Hu, and Lee (2013) employs cubic Bézier splines to map coronal loops using only four free parameters per loop. A set of 2D splines for coronal loops is transformed to the best 3D pseudo-magnetic field lines for a particular coronal model. The results restrict the magnetic field models derived from extrapolations of magnetograms to those admissible and inadmissible via a fitness parameter. This method uses the minimization of the misalignment angles between the magnetic field model and the best set of 3D field lines that match a set of closed coronal loops. We comment on the implication of the fitness parameter in connection with the magnetic free energy and comment on extensions of our earlier work by considering the issues of employing open coronal loops or employing partial coronal loop.

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