Parametric study of density cavities caused by ion outflow in the topside ionosphere

Mei, Liyuan; Lotko, W.; Varney, R. H.; Huba, J. D.

doi:10.1016/j.jastp.2017.02.013

Cited by 3 publications

(3 citation statements)

References 68 publications

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“…The SITE model, which calculates average ion temperature, does not provide information about the ion temperature anisotropy that may be present at high latitudes for relative ion drift speeds comparable to the neutral thermal speed. The partitioning coefficients of the ion frictional heating, needed to separately model parallel and perpendicular ion temperatures (Balmforth et al, 1999;Mei et al, 2017), depend on the ion composition (e.g., Lockwood et al, 1993), which can deviate dramatically from pure O + even in the upper F region (Schunk et al, 1975(Schunk et al, , 1976. Unavailability of information about ion composition and assumptions behind the Swarm LP data processing (e.g.…”

Section: Discussion and Summarymentioning

confidence: 99%

Estimation of Ion Temperature in the Upper Ionosphere Along the Swarm Satellite Orbits

Lomidze

Burchill

Knudsen

et al. 2021

Earth and Space Science

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Ion temperature is one of the key parameters that provides insight into the thermal balance of the coupled ionosphere‐thermosphere system. Together with the temperatures of neutral and electron gases, it affects physical and chemical processes and parameters in the upper atmosphere. These include the ion‐neutral collision frequencies, chemical reaction rates and plasma scale height, all of which influence the variation and distribution of ionospheric plasma. The European Space Agency's three, nearly polar‐orbiting Swarm satellites at about 500 km altitude measure ionospheric electron temperature, density, and ion drifts using electric field instrument (EFI) Langmuir probes and Thermal Ion Imagers. Measurements of the ion temperature, though initially planned, are not available due to technical problems with the ion imagers. This paper describes a model that estimates the ion temperature along the orbits of Swarm satellites and evaluates the validity of the corresponding data. This data‐driven, physics‐based model combines an ion heat balance equation of the upper ionosphere, the Swarm EFI measurements, and empirical models for neutral composition, winds, and electric field. The validity of this approach was investigated using a physics‐based ionosphere model (SAMI3) for different geophysical conditions. We have studied the effects of various assumptions and input data limitations to the model accuracy, and have validated the estimated ion temperature against independent measurements from low, middle, and high‐latitude incoherent scatter radars (ISRs). When compared with the ISR data, the obtained Swarm‐based ion temperature shows small systematic errors (1%–2%), high correlations (Swarm A/C 0.8, Swarm B 0.6), and random errors of 10%–20%.

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Section: Discussion and Summarymentioning

confidence: 99%

Estimation of Ion Temperature in the Upper Ionosphere Along the Swarm Satellite Orbits

Lomidze

Burchill

Knudsen

et al. 2021

Earth and Space Science

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“…Ions traveling in the opposite direction, out of the converging field, will gain velocity parallel to the magnetic field, and at Earth such ions can be accelerated out of the ionosphere along the diverging magnetic field. This acceleration produces ion outflows that can lead to ion loss from the terrestrial ionosphere (e.g., Chaston et al, ; Knudsen et al, ; Mei et al, ; Miyake et al, , ; Pollock et al, ; Strangeway et al, ). A review of ion energization processes in the terrestrial magnetosphere can be found in André and Yau (), for example.…”

Section: Introductionmentioning

confidence: 99%

“…Ions traveling in the opposite direction, out of the converging field, will gain velocity parallel to the magnetic field, and at Earth such ions can be accelerated out of the ionosphere along the diverging magnetic field. This acceleration produces ion outflows that can lead to ion loss from the terrestrial ionosphere (e.g., Chaston et al, 2006;Knudsen et al, 1994;Mei et al, 2017; The much smaller mass of Mars means that the escape velocity for ionospheric (and neutral) species is much lower than at Earth; the escape energy of O + is ∼2 eV at Mars, compared to ∼10 eV at Earth, for example. Energization mechanisms thus need only to weakly energize ionospheric particles at Mars, relative to their terrestrial counterparts, in order to achieve escape energy.…”

Section: Introductionmentioning

confidence: 99%

Ion Heating in the Martian Ionosphere

et al. 2017

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Energetic O+ and O 2+ ions with energies of up to a few hundred eV are observed in the Martian ionosphere. Corresponding ion velocity distributions show ion conics, suggesting that the observed ion populations have been heated perpendicular to the local magnetic field before experiencing a magnetic mirror force. Magnetic field observations support these interpretations: wave power at the local O+ and O 2+ gyrofrequencies in the spacecraft frame is observed coincident with the energetic ions, within an apparent magnetic field bottle‐like topology. Analysis of the observed ion conics leads to estimates of ion temperatures of 10–30 eV. We suggest that the ion populations are initially heated perpendicular to the local magnetic field by wave power propagating inward from the Mars‐solar wind interaction. The local magnetic field “balloons out” in response to these enhanced ion temperatures and pressures. The resultant magnetic field topology is bottle like; the transversely heated ions would subsequently experience a magnetic mirror force in the converging field regions, agreeing with the reported observations. Such strong heating events that significantly increase the ion temperature and pressure, thereby decreasing the net magnetic field, are rare and seem to occur under specific interplanetary magnetic field orientations. Events were observed to span the upper exobase region and just above, a region characterized by significant ion densities in an increasingly collisionless domain. Ion heating in this region has the potential to drive significant ion outflows, thus contributing to atmospheric loss from the planet.

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Creation of solitons and density cavities by lower hybrid waves

Saleem

Shan

2022

Physics of Plasmas

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Formation of Korteweg-de Vries (KdV) solitons by nonlinear lower hybrid waves (LHWs) is not possible in usual electron ion plasma because a dispersive term does not have a suitable form. It is pointed out that the dispersion characteristics of electrostatic LHWs are modified in the presence of field-aligned shear flow to produce KdV solitons with negative electrostatic potential as it has been observed by satellites in the upper ionosphere. Plasma density decreases within the solitary structures. The parallel electron velocity shear [Formula: see text] also gives rise to unstable waves in the intermediate frequency range in linear limit whereas the ambient magnetic field [Formula: see text] is assumed to be constant. The instability and structure size depend upon the electron parallel velocity shear parameter [Formula: see text] (where [Formula: see text] is the electron gyrofrequency) and the propagation direction with respect to the ambient magnetic field B0. The theoretical model is applied to the upper ionosphere, and the estimated width of the structures turns out to be of the order of 70 m, which is closer to the observations.

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Parametric study of density cavities caused by ion outflow in the topside ionosphere

Cited by 3 publications

References 68 publications

Estimation of Ion Temperature in the Upper Ionosphere Along the Swarm Satellite Orbits

Estimation of Ion Temperature in the Upper Ionosphere Along the Swarm Satellite Orbits

Ion Heating in the Martian Ionosphere

Creation of solitons and density cavities by lower hybrid waves

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