MGS electron density profiles: Analysis and modeling of peak altitudes

Fox, Jane L.; Weber, Andrew J.

doi:10.1016/j.icarus.2012.10.002

Cited by 49 publications

(73 citation statements)

References 85 publications

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“…The peak altitude and electron density can be easily determined for the M2 layer by locating the maximum electron density in the ionosphere, but determining the width of the M2 layer requires a fitting technique [ Breus et al , ; Withers and Mendillo , ]. Matters are more complicated for the M1 layer, which often appears as a bump or shoulder below the M2 layer with no clear local maximum in electron density [see Fox and Weber , , Figure 4]. This variability in shape makes it difficult to reliably determine the location of the M1 peak and to characterize its structure.…”

Section: Datamentioning

confidence: 99%

“…In this work and in Němec et al [], the Chapman function C h ( χ ) is used in place of sec( χ ). Fox and Weber [] use an effective secant, based on the ratio of line‐of‐sight to vertical column densities in a model thermosphere.…”

Section: Variation In M1 and M2 Layer Properties With Solar Zenith Anglementioning

confidence: 99%

“…This work will provide a foundation for exploring how the differences in ionizing solar irradiance affect ionospheric behavior. Substantial work has been performed in this area by Fox and colleagues [ Fox and Yeager , ; Fox and Weber , ]. However, their analyses of M1 and M2 peak densities [ Fox and Yeager , ] used only ∼10% of the currently available electron density profiles.…”

Section: Introductionmentioning

confidence: 99%

“…However, their analyses of M1 and M2 peak densities [ Fox and Yeager , ] used only ∼10% of the currently available electron density profiles. Additionally, their analyses of M1 properties [ Fox and Yeager , ; Fox and Weber , ] relied on irreproducible visual inspections to identify peak density and altitude. Liao et al [] investigated only the subset of M1 observations where the peak of the layer is easily distinguished (30%).…”

Section: Introductionmentioning

confidence: 99%

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An observational study of the influence of solar zenith angle on properties of the M1 layer of the Mars ionosphere

2015

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Citation:Fallows, K., P. Withers, and M. Matta Here we introduce an automated and repeatable method for determining properties of the M1 and M2 layers simultaneously in 5600 Mars Global Surveyor radio occultation profiles of dayside electron density. The results support previous findings for M1 and M2 subsolar peak densities and the dependence of peak densities on solar zenith angle. The ratio of M1 peak density to M2 peak density remains constant at 0.4 for 70• , in contrast with previous numerical simulations. The M1 altitude increases with solar zenith angle with a lengthscale, L 1 = 2.5 km, which is about half that of the M2 layer, L 2 = 5.2 km, indicating that the two layers become increasingly separated at high solar zenith angles. The vertical width of the M1 layer, H 1 , decreases from 7 km to 5 km as solar zenith angle increases from 70• to 90• , whereas the vertical width of the M2 layer, H 2 , increases from 10 km to 14 km. The prediction of ideal Chapman theory that both the widths H i and the lengthscales L i equal the neutral scale height is not supported by observations. These findings provide meaningful observational constraints for numerical models, which are known to have trouble reproducing observations and observed trends associated with the M1 layer.

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Section: Datamentioning

confidence: 99%

Section: Variation In M1 and M2 Layer Properties With Solar Zenith Anglementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An observational study of the influence of solar zenith angle on properties of the M1 layer of the Mars ionosphere

2015

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“…Wind shears can cause layering of metal atoms, as shown by Lyons et al [] and Moses and Bass []. Although it is usually suggested that the longer‐lived atomic ions react to gravity waves or wind shears by forming layers, evidence of wave activity can also be seen in the Martian electron density profiles that were returned from the Mars Global Surveyor Radio Science experiment [e.g., Hinson and Simpson , ; cf., Fox and Weber , ]. The dominant ion near the peak of the Martian electron density profiles is a molecular ion,

{normalO}_{2}^{+}

[e.g., Hanson et al , ].…”

Section: Introductionmentioning

confidence: 99%

Hydrocarbon ions in the lower ionosphere of Saturn

et al. 2014

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[1] Radio occultation measurements of the Saturn ionosphere have shown that persistent but variable electron density layers appear well below the major peaks. We model here the region of hydrocarbon ions that is below the main peak and is produced by absorption of solar photons in the wavelength range 842 to 1116 Å, which penetrate to altitudes below the methane homopause in the wings of the H 2 absorption lines, and in the gaps between groups of lines. In this wavelength range, H 2 absorbs photons in discrete transitions to rovibrational levels of electronically excited states, which then decay to a range of rovibrational levels of the electronic ground state, or to the continuum of the ground state. The cross sections for these discrete absorptions vary by several orders of magnitude from the peaks to the wings of the absorption lines. We find that the adoption of high resolution photoabsorption cross sections for the H 2 bands leads to different photoionization profiles for both the hydrocarbons and H atoms, and to peak CH + 4 photoproduction profiles that are more than an order of magnitude larger than those computed with low resolution cross sections. For the present model, we find that ionization by energetic electrons that accompany the absorption of soft X-rays appears in the same altitude range. We predict that a broad region of hydrocarbon ions appears well below the main peak, in the altitude range 600 to 1000 km above the 1 bar level (2-0.04 bar) with a maximum electron density of 3 10 3 cm -3 at low solar activity.

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Secondary electron emission from Martian soil simulant

et al. 2014

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In the recent years, growing interest in dust charging physics is connected with several lander missions running on or planned to the Moon, Mars, and Mercury for a near future. In support of these missions, laboratory simulations are a potential tool to optimize in situ exploration and measurements. In the paper, we have investigated electrical properties of a Martian soil simulant prepared at the Johnson Space Center under name JSC Mars‐1 using the dust charging experiment when a single dust grain is trapped in a vacuum chamber and its secondary electron emission is studied. The exposure of the grain to the electron beam revealed that the grain surface potential is low and generally determined by a mean atomic number of the grain material at a low‐energy range (<1 keV), whereas it can reach a limit of the field ion emission being irradiated by more energetic electrons. A comparison of model and experimental results reveals an influence of the grain shape and size predominantly in the range of higher (>2 keV) electron energies. We discuss possible implications of the secondary electron emission for the presence of lightnings on Mars.

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MGS electron density profiles: Analysis and modeling of peak altitudes

Cited by 49 publications

References 85 publications

An observational study of the influence of solar zenith angle on properties of the M1 layer of the Mars ionosphere

An observational study of the influence of solar zenith angle on properties of the M1 layer of the Mars ionosphere

Hydrocarbon ions in the lower ionosphere of Saturn

Secondary electron emission from Martian soil simulant

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