On the Dynamics of the Jovian Ionosphere and Thermosphere III. The Modelling of Auroral Conductivity

Millward, G. H.

doi:10.1006/icar.2002.6951

Cited by 70 publications

(115 citation statements)

References 30 publications

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“…10a and b, respectively. A positive correlation of P with ε 0 is obvious since the ionization at low altitude contributes effectively. At the energy range <60 keV our values estimated in a simple manner agree well with the results by Millward et al (2002) using the data of JIM. It is expected that the increasing rate in this range is quite similar to that of R(ε 0 ), however, in fact, it is slightly steeper (∝ ε 1.65 0 ).…”

Section: Discussion On Conductancesupporting

confidence: 89%

Parameterization of ionization rate by auroral electron precipitation in Jupiter

Hiraki

Tao

2008

Ann. Geophys.

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Abstract. We simulate auroral electron precipitation into the Jovian atmosphere in which electron multi-directional scattering and energy degradation processes are treated exactly with a Monte Carlo technique. We make a parameterization of the calculated ionization rate of the neutral gas by electron impact in a similar way as used for the Earth's aurora. Our method allows the altitude distribution of the ionization rate to be obtained as a function of an arbitrary initial energy spectrum in the range of 1-200 keV. It also includes incident angle dependence and an arbitrary density distribution of molecular hydrogen. We show that there is little dependence of the estimated ionospheric conductance on atomic species such as H and He. We compare our results with those of recent studies with different electron transport schemes by adapting our parameterization to their atmospheric conditions. We discuss the intrinsic problem of their simplified assumption. The ionospheric conductance, which is important for Jupiter's magnetosphere-ionosphere coupling system, is estimated to vary by a factor depending on the electron energy spectrum based on recent observation and modeling. We discuss this difference through the relation with fieldaligned current and electron spectrum.

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Section: Discussion On Conductancesupporting

confidence: 89%

Parameterization of ionization rate by auroral electron precipitation in Jupiter

Hiraki

Tao

2008

Ann. Geophys.

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“…Atreya (1986) has derived height-integrated conductivities of 0.2 mho at the equator and 10 mho at the auroral regions. To an order of magnitude, these estimates agree with the Voyager 2 and Galileo observations analyzed by Hinson et al (1998) and other theoretical models of the auroral ionosphere (e.g., Millward et al 2002). Thus, the height-integrated conductivities on EGPs are likely to be several orders of magnitude higher than the corresponding conductivities on Jupiter.…”

Section: Conductivitiessupporting

confidence: 85%

Ionization of Extrasolar Giant Planet Atmospheres

Koskinen

Cho

Achilleos

et al. 2010

ApJ

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Many extrasolar planets orbit close in and are subject to intense ionizing radiation from their host stars. Therefore, we expect them to have strong, and extended, ionospheres. Ionospheres are important because they modulate escape in the upper atmosphere and can modify circulation, as well as leave their signatures, in the lower atmosphere. In this paper, we evaluate the vertical location Z I and extent D I of the EUV ionization peak layer. We find that Z I ≈ 1-10 nbar-for a wide range of orbital distances (a = 0.047-1 AU) from the host star-and D I /H p 15, where H p is the pressure scale height. At Z I , the plasma frequency is ∼80-450 MHz, depending on a. We also study global ion transport, and its dependence on a, using a three-dimensional thermosphere-ionosphere model. On tidally synchronized planets with weak intrinsic magnetic fields, our model shows only a small, but discernible, difference in electron density from the dayside to the nightside (∼9 × 10 13 m −3 to ∼2 × 10 12 m −3 , respectively) at Z I . On asynchronous planets, the distribution is essentially uniform. These results have consequences for hydrodynamic modeling of the atmospheres of close-in extrasolar giant planets.

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“…The auroral enhancement is described using the same function as Nichols and Cowley (2004). This function was developed through detailed manipulation of the modelling results of Millward et al (2002). In order to maximise our consistency with their model, we adopt the same form:…”

Section: Horizontal Distributionmentioning

confidence: 99%

Coupled rotational dynamics of Jupiter's thermosphere and magnetosphere

2009

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Abstract.We describe an axisymmetric model of the coupled rotational dynamics of the thermosphere and magnetosphere of Jupiter that incorporates self-consistent physical descriptions of angular momentum transfer in both systems. The thermospheric component of the model is a numerical general circulation model. The middle magnetosphere is described by a simple physical model of angular momentum transfer that incorporates self-consistently the effects of variations in the ionospheric conductivity. The outer magnetosphere is described by a model that assumes the existence of a Dungey cycle type interaction with the solar wind, producing at the planet a largely stagnant plasma flow poleward of the main auroral oval. We neglect any decoupling between the plasma flows in the magnetosphere and ionosphere due to the formation of parallel electric fields in the magnetosphere. The model shows that the principle mechanism by which angular momentum is supplied to the polar thermosphere is meridional advection and that mean-field Joule heating and ion drag at high latitudes are not responsible for the high thermospheric temperatures at low latitudes on Jupiter. The rotational dynamics of the magnetosphere at radial distances beyond ∼30 R J in the equatorial plane are qualitatively unaffected by including the detailed dynamics of the thermosphere, but within this radial distance the rotation of the magnetosphere is very sensitive to the rotation velocity of the thermosphere and the value of the Pedersen conductivity. In particular, the thermosphere connected to the inner magnetosphere is found to super-corotate, such that true Pedersen conductivities smaller than previously predicted are required to enforce the observed rotation of the magnetosphere within ∼30 R J . We find that increasing the Joule heating at high latitudes by adding a component due to rapidly fluctuating electric fields is unable to explain the Correspondence to: C. G. A. Smith (cgasmith@gmail.com) high equatorial temperatures. Adding a component of Joule heating due to fluctuations at low latitudes is able to explain the high equatorial temperatures, but the thermospheric wind systems generated by this heating cause super-corotation of the inner magnetosphere in contradiction to the observations. We conclude that the coupled model is a particularly useful tool for study of the thermosphere as it allows us to constrain the plausibility of predicted thermospheric structures using existing observations of the magnetosphere.

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On the Dynamics of the Jovian Ionosphere and Thermosphere III. The Modelling of Auroral Conductivity

Cited by 70 publications

References 30 publications

Parameterization of ionization rate by auroral electron precipitation in Jupiter

Parameterization of ionization rate by auroral electron precipitation in Jupiter

Ionization of Extrasolar Giant Planet Atmospheres

Coupled rotational dynamics of Jupiter's thermosphere and magnetosphere

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