A model for meteoric magnesium in the ionosphere

McNeil, William J.; Lai, Shu T.; Murad, Edmond

doi:10.1029/95ja02888

Cited by 58 publications

(37 citation statements)

References 26 publications

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“…The chemistry and temporal and spatial variations have been extensively treated in the literature (Swider 1969;Aikin and Goldbert 1973;Carter and Forbes 1999;Joiner and Aikin 1996). In particular, special attention has been paid to the most abundant metallic species, magnesium (McNeil et al 1996;Plane and Helmer 1995), iron (Helmer et al 1998;Carter and Forbes 1999), silicon (Kopp et al 1995), potassium (Eska et al 1999), sodium and calcium (McNeil et al 1998;) and the chemistry is well known.…”

Section: Earthmentioning

confidence: 99%

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Meteoric Layers in Planetary Atmospheres

2008

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Metallic ions coming from the ablation of extraterrestrial dust, play a significant role in the distribution of ions in the Earth's ionosphere. Ions of magnesium and iron, and to a lesser extent, sodium, aluminium, calcium and nickel, are a permanent feature of the lower E-region. The presence of interplanetary dust at long distances from the Sun has been confirmed by the measurements obtained by several spacecrafts. As on Earth, the flux of interplanetary meteoroids can affect the ionospheric structure of other planets. The electron density of many planets show multiple narrow layers below the main ionospheric peak which are similar, in magnitude, to the upper ones. These layers could be due to long-lived metallic ions supplied by interplanetary dust and/or their satellites. In the case of Mars, the presence of a non-permanent ionospheric layer at altitudes ranging from 65 to 110 km has been confirmed and the ion Mg + ·CO 2 identified. Here we present a review of the present status of observed low ionospheric layers in Venus, Mars, Jupiter, Saturn and Neptune together with meteoroid based models to explain the observations. Meteoroids could also affect the ionospheric structure of Titan, the largest Saturnian moon, and produce an ionospheric layer at around 700 km that could be investigated by Cassini.

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Section: Earthmentioning

confidence: 99%

“…Figure 6 shows a schematic diagram of reactions involving magnesium species, as an example of the chemistry of metallic compounds in the terrestrial atmosphere. It was developed from the works by Plane and Helmer (1995), McNeil et al (1996) and McNeil et al (1998).…”

Section: Earthmentioning

confidence: 99%

Meteoric Layers in Planetary Atmospheres

2008

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“…Recent observations by the GLO instrument on the Space Shuttle have provided the ®rst simultaneous observations of Mg and Mg + in the thermosphere (Gardner et al, 1995). The salient features of the Mg + distributions near the magnetic equator appear to be driven by vertical E´B drifts (McNeil et al, 1996).…”

Section: Brief History Of Observational Workmentioning

confidence: 99%

“…Seasonal-latitudinal and local time distributions of Mg + ions, including equatorial asymmetries due to neutral winds, were shown to be in reasonable accord with in-situ satellite measurements mentioned previously. McNeil et al (1996) recently solved the continuity equations for Mg and Mg + in the geomagnetic equatorial plane, and made comparisons with GLO1 Space Shuttle measurements (Gardner et al, 1994; of 2795A Ê and 2802A Ê emissions. Although the model only included transport by diusion and vertical drifts (neglecting neutral winds and meridional transport), the absolute magnitudes and dawn-dusk asymmetries in predicted radiances were quite similar to those observed.…”

Section: Laboratory Measurements Of Reaction Rates and Previous Theomentioning

confidence: 99%

Global transport and localized layering of metallic ions in the upper atmospherer

Carter

Forbes

1999

Ann. Geophys.

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Abstract. A numerical model has been developed which is capable of simulating all phases of the life cycle of metallic ions, and results are described and interpreted herein for the typical case of Fe + ions. This cycle begins with the initial deposition of metallics through meteor ablation and sputtering, followed by conversion of neutral Fe atoms to ions through photoionization and charge exchange with ambient ions. Global transport arising from daytime electric ®elds and poleward/ downward diusion along geomagnetic ®eld lines, localized transport and layer formation through descending convergent nulls in the thermospheric wind ®eld, and ®nally annihilation by chemical neutralization and compound formation are treated. The model thus sheds new light on the interdependencies of the physical and chemical processes aecting atmospheric metallics. Model output analysis con®rms the dominant role of both global and local transport to the ion's life cycle, showing that upward forcing from the equatorial electric ®eld is critical to global movement, and that diurnal and semidiurnal tidal winds are responsible for the formation of dense ion layers in the 90±250 km height region. It is demonstrated that the assumed combination of sources, chemical sinks, and transport mechanisms actually produces F-region densities and E-region layer densities similar to those observed. The model also shows that zonal and meridional winds and electric ®elds each play distinct roles in local transport, whereas the ion distribution is relatively insensitive to reasonable variations in meteoric deposition and chemical reaction rates.

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“…Hunten et al (1981) suggest that a maximum deposition of dust and smoke particles due to meteors occurs in the height region of 70-90 km. McNeil et al (1996) model a distribution of magnesium ions in the ionosphere, assuming that the main source of these particles is the meteor ablation. A quantitative analysis of the effect of charged dust particles on the electrojet currents needs precise information on the height distribution, as well as the size distribution of the dust particles.…”

Section: Role Of Charged Dust Particlesmentioning

confidence: 99%

On the height variation of the E-region cowling conductivity – effect of charged dust particles

Muralikrishna

Kulkarni

2006

Ann. Geophys.

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Abstract. Height profiles of the Cowling conductivity in the electrojet region, estimated using the atmospheric parameters given by the existing models like CIRA or MSIS and measured electron density profiles, consistently show the heights of the electrojet current intensity peak to be more than 3 km below those estimated from in-situ measurements using magnetometers on board sounding rockets. Kulkarni and Muralikrishna (2005) attempted to explain this to be due to the effect of neutral dust particles. They reported that neutral dust particles, when they exist in sufficient numbers, can modify the collision parameters, especially in the lower E-region, where dust particles of meteoric origin are known to exist in large numbers, and thereby can modify the Cowling conductivity profile in the electrojet region. This work is extended here to include the effect of charged dust particles. Dust particles can become charged negatively by the attachment of ambient free electrons, and can thus reduce the number density of free electrons especially below the electrojet peak. This can alter the vertical profile of the east-west Hall current driven by the vertical Hall polarization field, thereby causing a net reduction in the electrojet current. Such a decrease in the electrojet current may be observed on the ground magnetograms. This mechanism, as proposed here, can operate only during periods of strong meteor shower activity, when the dust particle density at the assumed deposit height of 103 km can reach extreme values (for example, 5×10 4 cm −3 of 1-µm diameter dust particles). Such a dense dust layer may even cause a reversal in the normally upward vertical Hall polarization field, within the dust layer, causing a reversal of the electrojet currents below the current peak.

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A model for meteoric magnesium in the ionosphere

Cited by 58 publications

References 26 publications

Meteoric Layers in Planetary Atmospheres

Meteoric Layers in Planetary Atmospheres

Global transport and localized layering of metallic ions in the upper atmospherer

On the height variation of the E-region cowling conductivity – effect of charged dust particles

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