Inductive‐Dynamic Coupling of the Ionosphere With the Thermosphere and the Magnetosphere

Song, P.; Vasyliūnas, V. M.

doi:10.1002/9781118704417.ch17

Cited by 6 publications

(9 citation statements)

References 40 publications

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“…When the nonlinear effects are neglected, in an idealized situation, perturbations at the source can be decomposed in Fourier frequency space and each of them propagates independently. The oscillations at a given location and time are a result of the superposition of all incident and reflected waves (Song & Vasyliūnas, ; Tu et al, , ), from the source region in the entire polar cap via various paths with propagation time delays. The net perturbation is greater when the incidence and reflection are in constructive interference and smaller when the interference is destructive.…”

Section: Resultsmentioning

confidence: 99%

On the Momentum Transfer From Polar to Equatorial Ionosphere

Song

2019

JGR Space Physics

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During space weather events, a large amount of energy and momentum from the solar wind inputs into the ionosphere‐thermosphere. A critical question is that if the solar wind‐magnetosphere interaction drives only the open field region in the polar caps, how the solar wind energy and momentum are transmitted to the low latitude and equatorial ionosphere. This important issue has been studied over decades and is still poorly understood, impeding space weather forecasting ability. Here we use our newly developed 2.5‐D ionosphere‐thermosphere simulation model that self‐consistently solves the density, velocity, and temperature for electrons, multiple ion and neutral species, and electromagnetic fields to study this challenging problem. The focus of the present study is on the prompt response of the ionosphere to a convection disturbance from the polar magnetosphere. The longer time scale responses caused by the neutral winds from the polar caps will be the topic of future studies. We show that the momentum is transferred from polar to equatorial ionosphere predominately by fast magnetosonic waves, and propagation of perturbations from the source region experiences delay, damping, and substantial reflection, and the ionosphere/thermosphere behaves like a low‐band‐pass filter. The finding from this study sheds new insight onto coupling processes within the magnetosphere‐ionosphere system.

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Section: Resultsmentioning

confidence: 99%

On the Momentum Transfer From Polar to Equatorial Ionosphere

Song

2019

JGR Space Physics

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“…The global ionosphere should be viewed as driven by, e.g., enhanced magnetospheric convection. The enhancement acts, at least initially, only on relatively small areas at high latitudes, which suggests the basic idea discussed by, e.g., Song and Vasyliūnas , []: antisunward flow imposed in the open field line region (the polar cap) creates a higher pressure at the nightside interface to the closed field line region and a lower pressure at the dayside interface, launching fast mode compression and rarefaction waves, respectively, which by continuity produce convection cells in the polar ionosphere, from where they propagate, at the fast mode speed, into the low‐latitude and equatorial ionosphere (producing equatorial upward motions, among other effects).…”

Section: Coupling Through Mhd Wavesmentioning

confidence: 87%

Inductive‐dynamic magnetosphere‐ionosphere coupling via MHD waves

Song

Vasyliūnas

2014

JGR Space Physics

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In the present study, we investigate magnetosphere-ionosphere/thermosphere (M-IT) coupling via MHD waves by numerically solving time-dependent continuity, momentum, and energy equations for ions and neutrals, together with Maxwell's equations (Ampère's and Faraday's laws) and with photochemistry included. This inductive-dynamic approach we use is fundamentally different from those in previous magnetosphere-ionosphere (M-I) coupling models: all MHD wave modes are retained, and energy and momentum exchange between waves and plasma are incorporated into the governing equations, allowing a self-consistent examination of dynamic M-I coupling. Simulations, using an implicit numerical scheme, of the 1-D ionosphere/thermosphere system responding to an imposed convection velocity at the top boundary are presented to show how magnetosphere and ionosphere are coupled through Alfvén waves during the transient stage when the IT system changes from one quasi steady state to another. Wave reflection from the low-altitude ionosphere plays an essential role, causing overshoots and oscillations of ionospheric perturbations, and the dynamical Hall effect is an inherent aspect of the M-I coupling. The simulations demonstrate that the ionosphere/thermosphere responds to magnetospheric driving forces as a damped oscillator.

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“…Magnetic tension in the ionosphere will accelerate the plasma, and this disturbance propagates to surrounding field lines as a compressive wave. The disturbance spreads out in the entire ionosphere in a few seconds [ Song and Vasyliūnas , ] and creates the two‐cell convection patterns.…”

Section: Discussionmentioning

confidence: 99%

“…It is well known that momentum and magnetic tension are transmitted by shear Alfvén waves from the magnetosphere to the ionosphere [e.g., Song and Vasyliūnas , ]. The Alfvén wave is reflected above the ionosphere, and the magnetic perturbation will be the sum of the incident and reflected wave.…”

Section: Discussionmentioning

confidence: 99%

Dayside and nightside magnetic field responses at 780 km altitude to dayside reconnection

et al. 2017

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During southward interplanetary magnetic field, dayside reconnection will drive the Dungey cycle in the magnetosphere, which is manifested as a two‐cell convection pattern in the ionosphere. We address the response of the ionospheric convection to changes in the dayside reconnection rate by examining magnetic field perturbations at 780 km altitude. The Active Magnetosphere and Planetary Electrodynamics Response Experiment data products derived from the Iridium constellation provide global maps of the magnetic field perturbations. Cluster data just upstream of the Earth's bow shock have been used to estimate the dayside reconnection rate. By using a statistical model where the magnetic field can respond on several time scales, we confirm previous reports of an almost immediate response both near noon and near midnight combined with a 10–20 min reconfiguration time of the two‐cell convection pattern. The response of the ionospheric convection has been associated with the expansion of the polar cap boundary in the Cowley‐Lockwood paradigm. In the original formulation of this paradigm the expansion spreads from noon to midnight in 15–20 min. However, also an immediate global response has been shown to be consistent with the paradigm when the previous dayside reconnection history is considered. In this paper we present a new explanation for how the immediate response can be accommodated in the Cowley‐Lockwood paradigm. The new explanation is based on how MHD waves propagate in the magnetospheric lobes when newly reconnected open flux tubes are added to the lobes, and the magnetopause flaring angle increases.

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Inductive‐Dynamic Coupling of the Ionosphere With the Thermosphere and the Magnetosphere

Cited by 6 publications

References 40 publications

On the Momentum Transfer From Polar to Equatorial Ionosphere

On the Momentum Transfer From Polar to Equatorial Ionosphere

Inductive‐dynamic magnetosphere‐ionosphere coupling via MHD waves

Dayside and nightside magnetic field responses at 780 km altitude to dayside reconnection

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