Kinetic modeling of the polar wind

Tam, Sunny Wing-Yee; Chang, Tom; Pierrard, Viviane

doi:10.1016/j.jastp.2007.08.006

Cited by 34 publications

(25 citation statements)

References 124 publications

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“…Nevertheless, O + ions have been observed above the polar caps and in the lobes (Nagai et al, 1984;Waite Jr. et al, 1985;Abe et al, 1993;Su et al, 1998a). Many additional mechanisms have been proposed to explain this (see, e.g., Tam et al, 2007, for an overview).…”

Section: Introductionmentioning

confidence: 99%

Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

2016

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Abstract. The cold ions (energy less than several tens of electronvolts) flowing out from the polar ionosphere, called the polar wind, are an important source of plasma for the magnetosphere. The main source of energy driving the polar wind is solar illumination, which therefore has a large influence on the outflow. Observations have shown that solar illumination creates roughly two distinct regimes where the outflow from a sunlit ionosphere is higher than that from a dark one. The transition between both regimes is at a solar zenith angle larger than 90 • . The rotation of the Earth and its orbit around the Sun causes the magnetic polar cap to move into and out of the sunlight. In this paper we use a simple set-up to study qualitatively the effects of these variations in solar illumination of the polar cap on the ion flux from the whole polar cap. We find that this flux exhibits diurnal and seasonal variations even when combining the flux from both hemispheres. In addition there are asymmetries between the outflows from the Northern Hemisphere and the Southern Hemisphere.

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Section: Introductionmentioning

confidence: 99%

Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

2016

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“…This is suggestive of Abe (2004) possible enhancement in the ambipolar electric field amplitude or presence of additional ion acceleration on the dayside due to escaping atmospheric photoelectrons (Tam et al 2007). The averaged O + velocity begins to increase near 5000 km.…”

Section: High Latitude Ionospheric Plasmamentioning

confidence: 96%

The Earth: Plasma Sources, Losses, and Transport Processes

et al. 2015

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This paper reviews the state of knowledge concerning the source of magnetospheric plasma at Earth. Source of plasma, its acceleration and transport throughout the system, its consequences on system dynamics, and its loss are all discussed. Both observational and modeling advances since the last time this subject was covered in detail (Hultqvist et al., Magnetospheric Plasma Sources and Losses, 1999) are addressed.

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“…Also, Barakat and Barghouthi (1994); Barghouthi et al (1998); Lemaire et al (2007); and Tam et al (2007) found that wave-particle interactions (WPI) play an important role in determining the behavior of ion outflows in the polar wind region. To include the effect of WPI in a collisionless region, we replace the right-hand side of Boltzmann equation by the term that represents the interaction between ions and the electromagnetic turbulence, which is resonant interactions at ion gyrofrequency.…”

Section: Theoretical Formulationsmentioning

confidence: 99%

“…To our knowledge, most of the comparisons between observations (ion velocity distribution, density, drift velocity, parallel and perpendicular temperatures, anisotropy, etc.) and simulations obtained from different models produce few agreements and fail to explain many observations (see Yau et al, 2007;Lemaire et al, 2007;Tam et al, 2007;Su et al, 1998;Engwall et al, 2009). This paper presents many close agreements between observations and simulations obtained by Barghouthi model, for O + and H + ions at different altitudes i.e.…”

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confidence: 99%

A comparison study between observations and simulation results of Barghouthi model for O<sup>+</sup> and H<sup>+</sup> outflows in the polar wind

2011

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Abstract. To advance our understanding of the effect of wave-particle interactions on ion outflows in the polar wind region and the resulting ion heating and escape from low altitudes to higher altitudes, we carried out a comparison between polar wind simulations obtained using Barghouthi model with corresponding observations obtained from different satellites. The Barghouthi model describes O + and H + outflows in the polar wind region in the range 1.7 R E to 13.7 R E , including the effects of gravity, polarization electrostatic field, diverging geomagnetic field lines, and waveparticle interactions. Wave-particle interactions were included into the model by using a particle diffusion equation, which depends on diffusion coefficients determined from estimates of the typical electric field spectral density at relevant altitudes and frequencies. We provide a formula for the velocity diffusion coefficient that depends on altitude and velocity, in which the velocity part depends on the perpendicular wavelength of the electromagnetic turbulence λ ⊥ . Because of the shortage of information about λ ⊥ , it was included into the model as a parameter. We produce different simulations (i.e. ion velocity distributions, ions density, ion drift velocity, ion parallel and perpendicular temperatures) for O + and H + ions, and for different λ ⊥ . We discuss the simulations in terms of wave-particle interactions, perpendicular adiabatic cooling, parallel adiabatic cooling, mirror force, and ion potential energy. The main findings of the simulations are as follows: (1) O + ions are highly energized at all altitudes in the simulation tube due to wave-particle interactions that heat the ions in the perpendicular direction, and part of this gained energy transfer to the parallel direction by mirror force, resulting in accelerating O + ions along geomagnetic field lines from lower altitudes to higher altitudes.(2) The effect of wave-particle interactions is negligible for Correspondence to: I. A. Barghouthi (barghouthi@science.alquds.edu) H + ions at altitudes below ∼7 R E , while it is important for altitudes above 7 R E . For O + wave particle interaction is very significant at all altitudes. (3) For certain λ ⊥ and at points, altitudes, where the ion gyroradius is equal to or less than λ ⊥ , the effect of wave-particle interactions is independent of the velocity and it depends only on the altitude part of the velocity diffusion coefficient; however, the effect of waveparticle interactions reduce above that point, called saturation point, and the heating process turns to be self-limiting heating. (4) The most interesting result is the appearance of O + conics and toroids at low altitudes and continue to appear at high altitudes; however, they appear at very high altitudes for H + ions. We compare quantitatively and qualitatively between the simulation results and the corresponding observations. As a result of many comparisons, we find that the best agreement occurs when λ ⊥ equals to 8 km. The quantitative comparisons show that ma...

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Kinetic modeling of the polar wind

Cited by 34 publications

References 124 publications

Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

The Earth: Plasma Sources, Losses, and Transport Processes

A comparison study between observations and simulation results of Barghouthi model for O<sup>+</sup> and H<sup>+</sup> outflows in the polar wind

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Kinetic modeling of the polar wind

Cited by 34 publications

References 124 publications

Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

Seasonal variations and north–south asymmetries in polar wind outflow due to solar illumination

The Earth: Plasma Sources, Losses, and Transport Processes

A comparison study between observations and simulation results of Barghouthi model for O&lt;sup&gt;+&lt;/sup&gt; and H&lt;sup&gt;+&lt;/sup&gt; outflows in the polar wind

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A comparison study between observations and simulation results of Barghouthi model for O<sup>+</sup> and H<sup>+</sup> outflows in the polar wind