Ionospheric plasma transport and loss in auroral downward current regions

Zettergren, M.; Semeter, J. L.

doi:10.1029/2012ja017637

Cited by 58 publications

(125 citation statements)

References 82 publications

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“…Zettergren and Snively [2013] demonstrates a similar use of these models under a much narrower range of locations and conditions. Although these models have been documented elsewhere, i.e., by Snively and Pasko [2008] and Zettergren and Semeter [2012], several components have changed in significant ways since they were originally reported. Therefore, descriptions of these models in their present forms, in a consistent notation, are provided in appendices, and a brief overview is included in this section.…”

Section: Modeling Approachmentioning

confidence: 99%

“…Note that this steady state perpendicular drift assumption is consistent with the use of an electrostatic description for the fields, (cf. Zettergren and Semeter [2012], for a complete discussion).…”

Section: A2 Ionospheric Modelmentioning

confidence: 99%

“…The 2-D ionospheric model (described in detail in section A2) used in this study is based on the model developed in Zettergren and Semeter [2012] and later extended in Zettergren and Snively [2013] and Zettergren et al [2014]. This model comprises a fluid system of equations [Schunk, 1977;Blelly and Schunk, 1993;Huba et al, 2000a], describing dynamics of the ionospheric plasma, self-consistently coupled to an electrostatic treatment of auroral and neutral dynamo currents.…”

Section: Ionospheric Modelmentioning

confidence: 99%

“…In this expression, s⟂ is the ion mobility tensor and s is the total ion-neutral collision frequency [Zettergren and Semeter, 2012]. A static geomagnetic field is used to compute the ion mobilities in equation (A11).…”

Section: A2 Ionospheric Modelmentioning

confidence: 99%

“…A set of two models is used to simulate the ionospheric response to ground level perturbations: (1) A neutral dynamics model based on Snively and Pasko [2008] is used to simulate atmospheric dynamics, viz., acoustic and gravity wave generation, propagation, and dissipation in the lower thermosphere; and (2) a comprehensive ionospheric model based on Zettergren and Semeter [2012], which encapsulates the ionospheric response to neutral forcing through neutral drag, dynamo currents, and modifications to thermospheric densities.…”

Section: Modeling Approachmentioning

confidence: 99%

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Ionospheric response to infrasonic‐acoustic waves generated by natural hazard events

2015

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Recent measurements of GPS‐derived total electron content (TEC) reveal acoustic wave periods of ∼1–4 min in the F region ionosphere following natural hazard events, such as earthquakes, severe weather, and volcanoes. Here we simulate the ionospheric responses to infrasonic‐acoustic waves, generated by vertical accelerations at the Earth's surface or within the lower atmosphere, using a compressible atmospheric dynamics model to perturb a multifluid ionospheric model. Response dependencies on wave source geometry and spectrum are investigated at middle, low, and equatorial latitudes. Results suggest constraints on wave amplitudes that are consistent with observations and that provide insight on the geographical variability of TEC signatures and their dependence on the geometry of wave velocity field perturbations relative to the ambient geomagnetic field. Asymmetries of responses poleward and equatorward from the wave sources indicate that electron perturbations are enhanced on the equatorward side while field aligned currents are driven principally on the poleward side, due to alignments of acoustic wave velocities parallel and perpendicular to field lines, respectively. Acoustic‐wave‐driven TEC perturbations are shown to have periods of ∼3–4 min, which are consistent with the fraction of the spectrum that remains following strong dissipation throughout the thermosphere. Furthermore, thermospheric acoustic waves couple with ion sound waves throughout the F region and topside ionosphere, driving plasma disturbances with similar periods and faster phase speeds. The associated magnetic perturbations of the simulated waves are calculated to be observable and may provide new observational insight in addition to that provided by GPS TEC measurements.

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Section: Modeling Approachmentioning

confidence: 99%

Section: A2 Ionospheric Modelmentioning

confidence: 99%

Section: Ionospheric Modelmentioning

confidence: 99%

Section: A2 Ionospheric Modelmentioning

confidence: 99%

Section: Modeling Approachmentioning

confidence: 99%

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Ionospheric response to infrasonic‐acoustic waves generated by natural hazard events

2015

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Ionospheric signatures of acoustic waves generated by transient tropospheric forcing

Zettergren

Snively

2013

Geophysical Research Letters

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[1] Acoustic waves generated by tropospheric sources may attain significant amplitudes in the thermosphere and overlying ionosphere. Although they are weak precursors to gravity waves in the mesosphere below, acoustic waves may achieve temperature and vertical wind perturbations on the order of approximately tens of Kelvin and m/s throughout the E and F regions. Their perturbations to total electron content are predicted to be detectable by groundbased radar and GPS receivers; they also drive field-aligned currents that may be detectable in situ via magnetometers. Although transient and short lived, ionospheric signatures of acoustic waves may provide new and quantitative insight into the forcing of the upper atmosphere from below.Citation: Zettergren, M. D., and J. B. Snively (2013), Ionospheric signatures of acoustic waves generated by transient tropospheric forcing, Geophys. Res. Lett., 40,[5345][5346][5347][5348][5349]

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Auroral ionospheric F region density cavity formation and evolution: MICA campaign results

et al. 2014

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Scatter Radar) during the MICA (Magnetosphere-Ionosphere Coupling in the Alfvén Resonator) sounding rocket campaign are critically examined alongside complementary numerical simulations. Particular processes of interest include cavity formation due to intense frictional heating and Pedersen drifts, evolution in the presence of structured precipitation, and refilling due to impact ionization and downflows. Our analysis uses an ionospheric fluid model which solves conservation of mass, momentum, and energy equations for all major ionospheric species. These fluid equations are coupled to an electrostatic current continuity equation to self-consistently describe auroral electric fields. Energetic electron precipitation inputs for the model are specified by inverting optical data, and electric field boundary conditions are obtained from direct PFISR measurements. Thus, the model is driven in as realistic a manner as possible. Both incoherent scatter radar (ISR) data and simulations indicate that the conversion of the F region plasma to molecular ions and subsequent recombination is the dominant process contributing to the formation of the observed cavities, all of which occur in conjunction with electric fields exceeding ∼90 mV/m. Furthermore, the cavities often persist several minutes past the point when the frictional heating stops. Impact ionization and field-aligned plasma flows modulate the cavity depth in a significant way but are of secondary importance to the molecular generation process. Informal comparisons of the ISR density and temperature fits to the model verify that the simulations reproduce most of the observed cavity features to a reasonable level of detail.

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Ionospheric plasma transport and loss in auroral downward current regions

Cited by 58 publications

References 82 publications

Ionospheric response to infrasonic‐acoustic waves generated by natural hazard events

Ionospheric response to infrasonic‐acoustic waves generated by natural hazard events

Ionospheric signatures of acoustic waves generated by transient tropospheric forcing

Auroral ionospheric F region density cavity formation and evolution: MICA campaign results

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