Modelling the electron density distribution in the Io Plasma Torus using Juno radio occultations

The innermost galileian moon Io hosts an intense volcanic activity, which ejects about 103 kg/s of gas into Jupiter's magnetosphere. Here these neutrals are ionized by interaction with the background plasma and they are accelerated from keplerian velocity to corotation velocity thanks to Alfv&#233;n's theorem. This plasma cloud around the planet (the so-called Io Plasma Torus or IPT) slowly diffuses across Jupiter's magnetic field, but high electron densities (>1000-2000 cm-3) are found between 5-8 RJ.Juno is travelling along highly eccentric, polar orbits around the planet and flies very close to Jupiter's surface during each perijove. Thus, the radio links used for ground communication and radio science cross the IPT both in the uplink and the downlink leg. Being a dispersive medium, the torus introduces a different path delay on the X/X and Ka/Ka links established between the Ground Station and the spacecraft. Thus, the path delay can be extracted through a linear combination of the two links, and then quantitatively analyzed and fitted to different parametric models of the IPT.In this work we have used almost all the available Juno radio occultations of the IPT in order to improve an already existing model by introducing both longitudinal and temporal variations of the electron density. To this end, we looked for the 2D Fourier expansion in longitude and time of the parameters of this model with the goal of minimizing the residuals of the fit and pointing out periodicities in the morphology of the torus.

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Some new features of electron density irregularities over SHAR during strong spread F

Annales Geophysicae ◽

10.1007/s00585-000-0141-8 ◽

2000 ◽

Vol 18 (2) ◽

pp. 141-151 ◽

Cited By ~ 16

Author(s):

S. Raizada ◽

H. S. S. Sinha

Keyword(s):

Growth Rate ◽

Electron Density ◽

Large Scale ◽

Density Fluctuations ◽

High Electron ◽

Intermediate Scale ◽

Radio Science ◽

Ionospheric Physics ◽

Scale Size ◽

Spread F

Abstract. An RH-560 rocket flight was conducted from Sriharikota rocket range (SHAR) (14°N, 80°E, dip latitude 5.5°N) to study electron density and electric field irregularities during spread F. The rocket was launched at 2130 local time (LT) and it attained an apogee of 348 km. Results of electron density fluctuations are presented here. Two extremely sharp layers of very high electron density were observed at 105 and 130 km. The electron density increase in these layers was by a factor of 50 in a vertical extent of 10 km. Large depletions in electron density were observed around 175 and 238 km. Both sharp layers as well as depletions were observed also during the descent. The presence of sharp layers and depletions during the ascent and the descent of the rocket as well as an order of magnitude less electron density, in 150-300 km region during the descent, indicate the presence of strong large-scale horizontal gradients in the electron density. Some of the valley region irregularities (165-178 km), in the intermediate scale size range, observed during this flight, show spectral peaks at 2 km and can be interpreted in terms of the image striation theory suggested by Vickrey et al. The irregularities at 176 km do not exhibit any peak at kilometer scales and appear to be of new type. The growth rate of intermediate scale size irregularities, produced through generalized Rayleigh Taylor instability, was calculated for the 200-330 km altitude, using observed values of electron density gradients and an assumed vertically downward wind of 20 ms-1. These growth rate calculations suggest that the observed irregularities could be produced by the gradient drift instability.Key words: Ionosphere (equatorial ionosphere; ionospheric irregularities) - Radio science (ionospheric physics)

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Electron density and temperature in the Io plasma torus from Ulysses thermal noise measurements

Planetary and Space Science ◽

10.1016/0032-0633(93)90105-b ◽

1993 ◽

Vol 41 (11-12) ◽

pp. 1011-1020 ◽

Cited By ~ 13

Author(s):

Sang Hoang ◽

Nicole Meyer-Vernet ◽

Michel Moncuquet ◽

Alain Lecacheux ◽

Bent M. Pedersen

Keyword(s):

Electron Density ◽

Thermal Noise ◽

Noise Measurements ◽

Electron Density And Temperature ◽

Plasma Torus ◽

Io Plasma Torus

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Remote sensing of the Io torus plasma ribbon using natural radio occultation of the Jovian radio emissions

Annales Geophysicae ◽

10.5194/angeo-32-1119-2014 ◽

2014 ◽

Vol 32 (9) ◽

pp. 1119-1128 ◽

Cited By ~ 1

Author(s):

M. Y. Boudjada ◽

P. H. M. Galopeau ◽

S. Sawas ◽

H. Lammer

Keyword(s):

Electron Density ◽

Radio Occultation ◽

Central Meridian ◽

Radio Emissions ◽

Late Afternoon ◽

Common Features ◽

Refraction Effect ◽

Plasma Torus ◽

Io Plasma Torus ◽

Local Time Dependence

Abstract. We study the Jovian hectometric (HOM) emissions recorded by the RPWS (Radio and Plasma Wave Science) experiment onboard the Cassini spacecraft during its Jupiter flyby. We analyze the attenuation band associated with the intensity extinction of HOM radiation. This phenomenon is interpreted as a refraction effect of the Jovian hectometric emission inside the Io plasma torus. This attenuation band was regularly observed during periods of more than 5 months, from the beginning of October 2000 to the end of March 2001. We estimate for this period the variation of the electron density versus the central meridian longitude (CML). We find a clear local time dependence. Hence the electron density was not higher than 5.0 × 104 cm−3 during 2 months, when the spacecraft approached the planet on the dayside. In the late afternoon and evening sectors, the electron density increases to 1.5 × 105 cm−3 and reach a higher value at some specific occasions. Additionally, we show that ultraviolet and hectometric wavelength observations have common features related to the morphology of the Io plasma torus. The maxima of enhancements/attenuations of UV/HOM observations occur close to the longitudes of the tip of the magnetic dipole in the southern hemisphere (20° CML) and in the northern hemisphere (200° CML), respectively. This is a significant indication about the importance of the Jovian magnetic field as a physical parameter in the coupling process between Jupiter and the Io satellite.

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Electron microscope study of the secretory activity of epithelial cells in embryonic thymus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010015945x ◽

1990 ◽

Vol 48 (3) ◽

pp. 382-383

Author(s):

H. Alasam

Keyword(s):

Cell Differentiation ◽

T Cell ◽

Epithelial Cells ◽

Electron Density ◽

Secretory Activity ◽

T Cell Differentiation ◽

High Electron ◽

Transmission Electron ◽

Medullary Epithelial Cells ◽

Thymic Factor

The possibility that intrathymic T-cell differentiation involves stem cell-lymphoid interactions in embryos led us to study the ultrastructure of epithelial cell in normal embryonic thymus. Studies in adult thymus showed that it produces several peptides that induce T-cell differentiation. Several of them have been chemically characterized, such as thymosin α 1, thymopoietin, thymic humoral factor or the serum thymic factor. It was suggested that most of these factors are secreted by populations of A and B-epithelial cells.Embryonic materials were obtained from inbred matings of Swiss Albino mice. Thymuses were disected from embryos 17 days old and prepared for transmission electron microscopy. Our studies showed that embryonic thymus at this stage contains undifferentiated and differentiated epithelial cells, large lymphoblasts, medium and few small lymphocytes (Fig. 5). No differences were found between cortical and medullary epithelial cells, in contrast to the findings of Van Vliet et al,. Epithelial cells were mostly of the A-type with low electron density in both cytoplasm and nucleus. However few B-type with high electron density were also found (Fig. 7).

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Effective Dielectric Function of Porous Silicon: the Transverse Component

MRS Proceedings ◽

10.1557/proc-358-49 ◽

1994 ◽

Vol 358 ◽

Author(s):

G. Gumbs

Keyword(s):

Absorption Spectrum ◽

Absorption Coefficient ◽

Electron Density ◽

Quantum Wires ◽

Interband Transition ◽

Incident Light ◽

Transverse Component ◽

Effect Of Temperature ◽

High Electron ◽

Confining Potential

ABSTRACTA self-consistent many-body theory is developed to study the effect of temperature and electron density on the interband absorption coefficient and the frequency-dependent refractive index for an array of isolated quantum wires. The peaks in the absorption coefficient correspond to interband transitions resulting in the resonant absorption of light. The oscillations in the derivative spectrum are due to the quantization of the energy levels related to the in-plane confining potential for such reduced dimensional systems. There are appreciable changes in the absorption spectrum when the electron density or temperature is increased. One interband transition peak is suppressed in the high electron density limit and the thermal depopulation effect on the electron subbands can be easily seen when the temperature is high. We also find that the exciton coupling weakens the shoulder features in the absorption spectrum. This study is relevant to optical characterization of the confining potential and the areal density of electrons using photoreflectance. By using incident light with tunable frequencies in the interband excitation regime, contactless photoreflectance measurements may be carried out and the data compared with our calculations. By fitting the numerical results to the peak positions of the photoreflectance spectrum, the number of electrons in each wire may be extracted.

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