Ionospheres

Schunk, R. W.; Nagy, Andrew F.

doi:10.1017/cbo9780511551772

Cited by 722 publications

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“…Rishbeth and Setty [1962] developed a theoretical understanding for the winter anomaly based on neutral composition. This can best be understood in terms of the ion continuity equation [e.g., Schunk and Nagy, 2000] for O + , as that species is the dominant ion near the F 2 peak.…”

Section: Introductionmentioning

confidence: 99%

On the solar cycle variation of the winter anomaly

et al. 2014

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Constellation Observing System for Meteorology, Ionosphere and Climate, Ionosonde, and Global Ultraviolet Imager data have been used to investigate the solar cycle changes in the winter anomaly (the winter anomaly is defined as the enhancement of the F 2 peak electron density in the winter hemisphere over that in the summer hemisphere) in the last solar cycle. There is no winter anomaly in solar minimum, and an enhancement of about 50% in winter over summer ones on the same day of the year at solar maximum. This solar cycle variation in the winter anomaly is primarily due to greater winter to summer differences of [O]/[N 2 ] in solar maximum than in solar minimum, with a secondary contribution from the effects of temperature on the recombination coefficient between O + and the molecular neutral gas. The greater winter increases in electron density in the Northern Hemisphere than in the Southern Hemisphere appear to be related to the greater annual variation of [O]/[N 2 ] in the north than in the south.

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Section: Introductionmentioning

confidence: 99%

On the solar cycle variation of the winter anomaly

et al. 2014

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“…The five species solved for include two ion species, H + and O + , two neutral stream species, H and O, and electrons. The time-dependent continuity equation for both ions and neutrals is [Schunk and Nagy, 2000] …”

Section: Transport Equationsmentioning

confidence: 99%

“…where t represents the interacting species, s 0 is the particle species before a charge exchange reaction, n st is the collision frequency and F st is a complicated velocitydependent factor that depends on the type of collision [Schunk and Nagy, 2000]. It has a value of 1 for lowvelocity interactions, and it acts to reduce the collision frequency as relative velocities between interacting species increase.…”

Section: Transport Equationsmentioning

confidence: 99%

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Global neutral polar wind model

Gardner

Schunk

2005

J. Geophys. Res.

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[1] The neutral polar wind shows a highly dynamic structure that depends on the characteristics of convection and precipitation. The ions in the polar wind are highly dependent on convection electric fields at high latitudes, and their outflow dynamics are modified by the heat input of precipitating electrons in the auroral zone. A new three-dimensional model of the neutral polar wind has been developed which takes into account the convecting ion polar wind and heating due to precipitating electrons in the auroral zone, along with charge exchange between the ion polar wind and the background thermal and geocoronal neutral atoms. The results show that over the polar caps the neutral polar wind particles exhibit extremely large fluxes in both the horizontal and vertical directions, and to a fixed observer it would appear that the neutral polar wind particles are moving in all directions. The results also show that the heating that occurs during geomagnetic storms leads to a significant coupling between the ionosphere and magnetosphere via both ion and neutral particles.

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“…where L is the inverse gradient scale length and ν in is the ion neutral collision frequency (see Schunk & Nagy, 2000). A local perturbation in the plasma can grow linearly and take the form of a plasma bubble that may eventually grow further and rise upwards due to buoyant forces to height regions where the linear theory of RTI predicts no irregularities.…”

Section: Introductionmentioning

confidence: 99%

Equatorial F-region irregularities generated by the Rayleigh-Taylor instability mechanism: rocket observations from Brazil

Muralikrishna¹,

Vieira²

2007

Rev. Bras. Geof.

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ABSTRACT. Several sounding rockets carrying plasma diagnostic experiments were launched from the Brazilian rocket launching stations in Natal (5.9 • S, 35.2 • W Geog. Lat.) and Alcântara (2.31 • S, 44.4 • W Geog. Lat.). Langmuir Probes (LP) were used to measure the height profiles of electron density and electron temperature and High Frequency Capacitance (HFC) probes were used to measure electron density. The LP's were also used to measure the amplitude of electron density fluctuations.A detailed study of the characteristic features of electron density irregularities in the scale size range of less than a meter to a few kilometres, observed by rocket-borne electron density probes under different ionospheric conditions is presented here. The main objective of these studies is the identification of these irregularities from the point of view of the dynamic and electrodynamic processes responsible for their generation. The existing theories of the Rayleigh Taylor Instability (RTI) mechanism applicable for conditions of the geomagnetic equatorial ionosphere over Brazil are critically examined in the light of the observations. The observed characteristics of the irregularities during four rocket launches are compared with the theoretically expected characteristics. These results confirm the operation of a cascade process that is responsible for the generation of a wide spectrum of irregularities. The large-scale irregularities are first generated probably by the RTI mechanism that creates conditions favourable for the operation of the Cross-Field (CFI) or the Gradient Drift Instability (GDI) mechanism. From the k-spectra of irregularities it is possible to obtain the spectral index n corresponding to the height chosen. In most of the cases the estimated spectral indices agree well with those published in the literature for the cases of irregularities generated by the GDI mechanism.Keywords: space plasma, ionosphere, F-region, Rayleigh-Taylor instability, Cross-Field instability. RESUMO. Vários foguetes de sondagem carregando experimentos de diagnóstico de plasma foram lançados dos centros Brasileiros de lançamento de foguetesem Natal (5.9 • S, 35.2 • O Lat. Geog.) e Alcântara (2.31 • S, 44.4 • O Lat. Geog.). Sondas de Langmuir (LP) foram usadas para medir os perfis de densidade e temperatura do plasma e Sondas Capacitivas em Alta Freqüência (HFC) foram usadas para medir a densidade eletrônica. As LP's foram usadas também para medir a amplitude das flutuações de densidade eletrônica. Um estudo detalhado dos aspectos característicos das irregularidades de densidade eletrônica da escala de menos de um metro a alguns quilômetros, observadas pelas sondas de densidade eletrônica a bordo dos foguetes sob condições diferentes da ionosferaé apresentado aqui.O objetivo principal destes estudosé a identificação destas irregularidades do ponto de vista dos processos dinâmicos e eletrodinâmicos responsáveis pela geração delas. As teorias existentes do mecanismo de instabilidade de Rayleigh-Taylor aplicáveis para as condições da ...

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Ionospheres

Cited by 722 publications

References 0 publications

On the solar cycle variation of the winter anomaly

On the solar cycle variation of the winter anomaly

Global neutral polar wind model

Equatorial F-region irregularities generated by the Rayleigh-Taylor instability mechanism: rocket observations from Brazil

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