Empirical model of the Martian dayside ionosphere: Effects of crustal magnetic fields and solar ionizing flux at higher altitudes

Němec, F.; Morgan, D. D.; Gurnett, D. A.; Andrews, David

doi:10.1002/2015ja022060

Cited by 36 publications

(37 citation statements)

References 49 publications

(85 reference statements)

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“…Němec et al () used 30,283 MARSIS radar sounding profiles and almost 200,000 local electron density measurements to develop an empirical model of electron densities above the peak altitude, which assumes a Chapman dependence at altitudes below about 200 km (photochemically controlled region) and smoothly transits to an exponential dependence at altitudes above about 325 km (diffusion‐controlled region). The model performance at altitudes higher than about 200 km was later improved by incorporating dependences on crustal magnetic field magnitude and solar ionizing flux (Němec, Morgan, Gurnett, & Andrews, ).…”

Section: Introductionmentioning

confidence: 99%

Characterizing Average Electron Densities in the Martian Dayside Upper Ionosphere

et al. 2019

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We use more than 10 years of the Martian topside ionospheric data measured by the Mars Advanced Radar for Subsurface and Ionosphere Sounding radar sounder on board the Mars Express spacecraft to derive an empirical model of electron densities from the peak altitude up to 325 km. Altogether, 16,044 electron density profiles obtained at spacecraft altitudes lower than 425 km and at solar zenith angles lower than 80° are included in the analysis. Each of the measured electron density profiles is accurately characterized by the peak electron density, peak altitude, and three additional parameters describing the profile shape above the peak: (i) steepness at high altitudes, (ii) main layer thickness, and (iii) transition altitude. The dependence of these parameters on relevant controlling factors (solar zenith angle, solar irradiance, crustal magnetic field magnitude, and Sun‐Mars distance) is evaluated, allowing for a formulation of a simple empirical model. Mars Atmosphere and Volatile EvolutioN Extreme Ultraviolet monitor data are used to show that the solar ionizing flux can be accurately approximated by the F10.7 index when taking into account the solar rotation. Electron densities predicted by the resulting empirical model are compared with electron densities locally evaluated based on the Mars Advanced Radar for Subsurface and Ionosphere Sounding measurements, with the Langmuir Probe and Waves electron density measurements on board the Mars Atmosphere and Volatile EvolutioN spacecraft, and with electron densities obtained by radio occultation measurements. Although the electron densities measured by the Langmuir Probe and Waves instrument are systematically somewhat lower than the model electron densities, consistent with former findings, the model performs reasonably well.

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Section: Introductionmentioning

confidence: 99%

Characterizing Average Electron Densities in the Martian Dayside Upper Ionosphere

et al. 2019

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“…However, crustal magnetic fields have an important role at high altitudes. As Nĕmec et al 2016 have recently demonstrated, electron densities at high altitudes (in the diffusive region) are significantly increased over crustal magnetic field areas, while peak electron densities are nearly unaffected. Moreover, there is clear evidence that solar flux at these high altitudes is still significant (Nĕmec et al, 2016), the evolution of which with the solar cycle constitutes a clear future line of work.…”

Section: Discussion: Earth Ionosphere Comparisonmentioning

confidence: 65%

Variaciones de la ionosfera de Marte debidas al ciclo solar

et al. 2016

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Solar cycle variations in solar radiation create notable changes in the Martian ionosphere, which have been analysed with Mars Express plasma datasets in this paper. In general, lower densities and temperatures of the ionosphere are found during the low solar activity phase, while higher densities and temperatures are found during the high solar activity phase. In this paper, we assess the degree of influence of the long term solar flux variations in the ionosphere of Mars. Key words: solar cycle; ionosphere of Mars; TEC. Variaciones de la ionosfera de Marte debidas al ciclo solarResumen La radiación solar en cada fase del ciclo solar crea importantes variaciones en la ionosfera de Marte, las cuales son analizadas en este artículo con datos de la sonda Mars Express. En general, las densidades y temperaturas más bajas de la ionosfera se encuentran durante la fase de baja actividad solar, mientras que las densidades y temperaturas más elevadas se encuentran durante la fase de alta actividad solar. Este artículo evalúa el efecto que las variaciones del flujo solar tienen a largo plazo en la ionosfera. Palabras clave: ciclo solar; ionosfera de Marte; TEC.

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“…Turning to the empirical representation of the topside ionosphere in the model by Němec et al () resulted in better agreement with MAVEN results (Mendillo, Narvaez, Vogt, Mayyasi, Mahaffy, et al, ). To achieve full altitude coverage in MIRI, we took the normalized shapes of the Němec et al () profiles above h max for all SZAs and merged them with the normalized shapes of the theoretical profile below h max for all SZAs. These are shown as Figure .…”

Section: The Miri Approachmentioning

confidence: 85%

“…Electron density profiles formed by merging the topside of normalized climatological profiles (Němec et al, ) and the bottomside of normalized theoretical profiles (Mayyasi & Mendillo, ) for each solar zenith angle bin. These are calibrated by the peak density MIRI‐2013 predicts.…”

Section: The Miri Approachmentioning

confidence: 99%

“…There are many examples for 1‐D models (Fox, ; Martinis et al, ; Mayyasi & Mendillo, , and references therein). For (b), data‐driven 1‐D models are typified by the approaches of Sanchez‐Cano et al () and Němec et al (). For (c), the Mars Initial Reference Ionosphere (MIRI) approach to be described here uses photochemical‐equilibrium (PCE) theory as the framework for transforming observations into predictive schemes (Mendillo et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Mars Initial Reference Ionosphere (MIRI) Model: Updates and Validations Using MAVEN, MEX, and MRO Data Sets

et al. 2018

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The Mars Initial Reference Ionosphere (MIRI) model is a semiempirical formulation designed to provide climatological estimates of key parameters of the Martian ionosphere. For the new MIRI‐2018 version, an expanded database is used from the Mars Express/Mars Advanced Radar for Subsurface and Ionosphere Sounding/Active Ionospheric Sounding (MEX/MARSIS/AIS) instrument, consisting of 215,818 values of maximum electron density of the M2‐layer (NmM2) from the years 2005–2015. These data are organized by photochemical‐equilibrium equations to obtain a functional dependence of NmM2 upon solar drivers (flux and solar zenith angle). The resulting peak density is used to calibrate normalized electron density profiles [Ne (h)] derived from theory and an empirical model. The MIRI‐2018 thus provides estimates of NmM2, Ne (h), and total electron content (TEC) for any date past or future. Validation using Mars Atmosphere and Volatile EvolutioN (MAVEN)'s new radio occultation science experiment (ROSE) was successful for NmM2 values, but MIRI was found to overestimate TEC values. The validation failure for TEC was traced to overestimates of plasma at low altitudes (M1 layer). A separate module for TEC was derived using 126,055 values from the Mars Reconnaissance Orbiter/SHAllow RADar (MRO/SHARAD) TEC database from 2006 to 2014. Validation of this new TEC module with ROSE data was successful. Future improvements to MIRI‐2018 require new ways to characterize the bottomside ionosphere's contribution to the TEC integral for midday (low solar zenith angle) conditions. This requires new simulation studies of secondary ionization rates by photoelectrons produced via the primary X‐ray ionization process for the M1 layer.

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Empirical model of the Martian dayside ionosphere: Effects of crustal magnetic fields and solar ionizing flux at higher altitudes

Cited by 36 publications

References 49 publications

Characterizing Average Electron Densities in the Martian Dayside Upper Ionosphere

Characterizing Average Electron Densities in the Martian Dayside Upper Ionosphere

Variaciones de la ionosfera de Marte debidas al ciclo solar

Mars Initial Reference Ionosphere (MIRI) Model: Updates and Validations Using MAVEN, MEX, and MRO Data Sets

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