Advances in the aeronomy of Venus and Mars

Fox, Jane L.

doi:10.1016/j.asr.2003.08.014

Cited by 28 publications

(14 citation statements)

References 41 publications

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“…The metallic ions cannot be observed directly by this method; rather the observed electron density is used as a proxy. These data have indeed confirmed the presence of such an ionospheric layer -the so-called "third layer" -at the predicted altitude range (Fox 2004;Pätzold et al 2005) and found that this layer is time-variable and localized. Work by Withers et al (2006) on the MGS dataset showed that occurrences of the layer are not uniformly distributed over time but tend to cluster at particular solar longitudes (L S ), some repeating from year to year.…”

Section: Meteoroid Effects On the Earth's Ionosphere And Expectationssupporting

confidence: 66%

The dust trail complex of comet 79P/du Toit-Hartley and meteor outbursts at Mars

Christou¹,

Vaubaillon²,

Withers³

2007

A&A

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Aims. Meteoroid trails ejected during past perihelion passages of the Mars-orbit-intersecting comet 79P/du Toit-Hartley have the potential of generating meteor outbursts in the Martian atmosphere. Depending on timing and intensity, the effects of these outbursts may be detectable by instrumentation operating in the vicinity of Mars. We aim to generate predictions for meteor activity in the martian atmosphere related to that comet; to search for evidence, in planetary mission data, that such activity took place; and to make predictions for potentially detectable future activity. Methods. We have modelled the stream by integrating numerically the states of particle ensembles, each ensemble representing a trail of meteoroids ejected from the comet during 39 perihelion passages from 1803, and propagated them forward in time, concentrating on those particles that physically approach Mars in the recent past and near future. Results. We find several instances where meteor outbursts of low to moderate intensity may have taken place at Mars since 1997. A search through Mars Global Surveyor (MGS) radio science data during two periods in 2003 and 2005 when data coverage was available showed that a plasma layer did indeed form in the martian ionosphere for a period of a few hours in April 2003 as a direct consequence of the predicted outburst. The apparent failure to identify such an event in 2005 could be due to those meteoroids ablating lower in the atmosphere or that the cometary dust follows a different particle size distribution than what was assumed. Our study highlights the need for further theoretical modelling of the response of the martian ionosphere to a time-variable meteoroid flux, observations of the comet itself and, most importantly, regular monitoring of the martian ionosphere during future outbursts predicted by our model.

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Section: Meteoroid Effects On the Earth's Ionosphere And Expectationssupporting

confidence: 66%

The dust trail complex of comet 79P/du Toit-Hartley and meteor outbursts at Mars

Christou¹,

Vaubaillon²,

Withers³

2007

A&A

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“…Although P. Withers and A. A. Christou (Early observations of meteoric plasma layers in the dayside ionospheres of Venus and Mars, submitted to Geophysical Research Letters , 2008) have suggested that meteoric layers are detectable in some electron density profiles obtained by Mariner 9 in 1971, the theoretical simulations of Pesnell and Grebowsky [2000] and Molina‐Cuberos et al [2003] preceded the first detections of Martian meteoric layers [ Fox , 2004a; Pätzold et al , 2005; Withers et al , 2006]. Also, infrared remote sensing observations have detected spectral features associated with Mg + · CO 2 [ Aikin and Maguire , 2005; Maguire and Aikin , 2006].…”

Section: Effects Of Meteoroids On Planetary Ionospheresmentioning

confidence: 99%

Physical characteristics and occurrence rates of meteoric plasma layers detected in the Martian ionosphere by the Mars Global Surveyor Radio Science Experiment

et al. 2008

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[1] Low-altitude plasma layers are present in 71 of 5600 electron density profiles from the Martian ionosphere obtained by the Mars Global Surveyor Radio Science experiment. These layers are produced by the ablation of meteoroids and subsequent ionization of meteoric atoms. The mean altitude of the meteoric layer is 91.7 ± 4.8 km. The mean peak electron density in the meteoric layer is (1.33 ± 0.25) Â 10 10 m À3. The mean width of the meteoric layer is 10.3 ± 5.2 km. The occurrence rate of meteoric layers varies with season, solar zenith angle, and latitude. Seasonal variations in occurrence rate are particularly strong, often exceeding an order of magnitude. Meteoric layer altitude, peak electron density, and width are all positively correlated, with correlation coefficients of 0.3-0.4. Other correlation coefficients between the physical characteristics of meteoric layers and atmospheric or observational properties, such as scale height, solar zenith angle, and solar flux, have absolute values that are significantly smaller, indicating lack of correlation. The photochemical lifetime of plasma in meteoric layers is $12 days and depends on altitude.

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“…On basic physical grounds, increased radio wave absorption is likely to occur on Mars as well during a solar flare, but this has not been detected to date [ Withers , 2011]. Generally similar behaviors are anticipated in other planetary ionospheres, especially that of Venus, which is highly analogous to Mars [ Chamberlain and Hunten , 1987; Luhmann et al , 1992; Fox , 2004b].…”

Section: Introductionmentioning

confidence: 99%

Numerical simulations of the ionosphere of Mars during a solar flare

et al. 2012

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[1] Electron densities in planetary ionospheres increase substantially during solar flares in response to the increased solar irradiance at soft X-ray and extreme ultraviolet wavelengths. Here we modify an existing model of the ionosphere of Mars to incorporate time-dependent solar irradiances and use it to simulate ionospheric conditions during the X14.4 and M7.8 solar flares of 15 and 26 April 2001, respectively. Simulations were validated by comparison to Mars Global Surveyor radio occultation measurements of vertical profiles of ionospheric electron density. Adjustments to the model's representation of the neutral atmosphere were required to adequately reproduce the observations before and during these solar flares. An accurate representation of electron-impact ionization, an important process in the lower ionosphere of Mars, is required in order to adequately simulate the doubling of electron densities that can occur in the lower ionosphere of Mars during a solar flare. We used the W-value representation of electron-impact ionization, in which the number of ion-electron pairs created per photon absorbed equals the ratio of the difference between photon energy and the ionization potential of carbon dioxide to the W-value. A range of possible W-values for Mars have been suggested in the literature, and a value of 28 eV led to the best reproduction of flare-affected observations. Simulated enhancements in the electron density are largest and persist the longest in the M1 region. We predict that the peak electron density in the M1 region can exceed that of the M2 region for short periods during intense solar flares.

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Advances in the aeronomy of Venus and Mars

Cited by 28 publications

References 41 publications

The dust trail complex of comet 79P/du Toit-Hartley and meteor outbursts at Mars

The dust trail complex of comet 79P/du Toit-Hartley and meteor outbursts at Mars

Physical characteristics and occurrence rates of meteoric plasma layers detected in the Martian ionosphere by the Mars Global Surveyor Radio Science Experiment

Numerical simulations of the ionosphere of Mars during a solar flare

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