The ionosphere of Mars from solar minimum to solar maximum: Dayside electron densities from MAVEN and Mars Global Surveyor radio occultations

Withers, Paul; Felici, M.; Hensley, Kerry; Mendillo, M.; Barbinis, E.; Kahan, Daniel; Oudrhiri, Kamal; Girazian, Z.

doi:10.1016/j.icarus.2021.114508

Cited by 13 publications

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References 52 publications

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“…These three solar irradiance categories are not intended to correspond to any standard definitions of levels of solar activity. Indeed, solar irradiance was generally modest throughout the entire period studied here (e.g., Withers et al., 2021). Instead, they provide useful organizational structures for the work reported here.…”

Section: Datamentioning

confidence: 88%

“…In many instances, limitations in spatial and temporal overlap between different measurements have precluded such comparisons. Here, we exploit the excellent observational coverage provided at Mars by the MAVEN spacecraft to compare numerous electron density measurements from two instruments, the Radio Occultation Science Experiment (ROSE, a remote sensing investigation; Felici et al, 2020;Withers et al, 2021Withers et al, , 2018Withers et al, , 2020aWithers et al, , 2020b and Langmuir Probe and Waves (LPW, an in situ instrument; Andersson et al, 2015;Ergun et al, 2021Ergun et al, , 2015Fowler et al, 2015). The aim of this article is to quantify the difference between electron densities measured by these two instruments, then interpret whether that difference is consistent with inherent geophysical variations in the ionosphere of Mars or whether that difference indicates systematic contrasts between the electron density measurements made by these two instruments.…”

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confidence: 99%

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Electron Densities in the Ionosphere of Mars: Comparison of MAVEN/ROSE and MAVEN/LPW Measurements

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An ionosphere is a region of thermal plasma of planetary origin (i.e., as opposed to solar wind origin) that is found within and above the upper atmosphere of a solar system body (Bauer & Lammer, 2004;Schunk & Nagy, 2009;Witasse et al., 2008). An ionosphere is part of the interface between the gravitationally controlled neutral environment of the solar system body (e.g., atmosphere and interior) and the electromagnetically controlled plasma environment that surrounds it (i.e., magnetosphere and solar wind; i.e., Cravens, 2004;Schrijver & Siscoe, 2010;Schunk & Nagy, 2009). As such, an ionosphere plays an important role in mediating coupling between these two domains, including the transfer of mass, momentum, and energy.Ionospheric plasma is generally produced by the photoionization of neutral atmospheric species. The primary ions produced by photoionization may undergo further chemical reactions with those neutral atmospheric species, such as charge exchange reactions that modify the abundances of ion species (Bauer & Lammer, 2004;Hargreaves, 1992;Schunk & Nagy, 2009). Hence, ionospheric properties reflect conditions in the neutral upper atmosphere. Ionospheric processes can also influence neutral atmospheric conditions (a) chemically, by participating in chemical reactions that produce and destroy neutral atmospheric species; (b) dynamically, by collisions between plasma and neutrals; and (c) energetically, by either transfer of thermal energy from the relatively warm plasma to the relatively cool neutral atmosphere or by Joule heating. Over longer timescales, ionospheric processes can also affect the total mass of the atmosphere. Many atmospheric escape processes that can lead to loss of atmospheric species and reduction in surface pressure involve the ionosphere. One such process is photochemical escape (e.g.,

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Section: Datamentioning

confidence: 88%

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confidence: 99%

Electron Densities in the Ionosphere of Mars: Comparison of MAVEN/ROSE and MAVEN/LPW Measurements

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“…The large nightside electron densities of 2-4 × 10 10 m −3 are much greater than usually seen in the nightside ionosphere. Peak electron density generally decreases with increasing solar zenith angle, but the MAVEN ROSE observations of large electron densities of 2-4 × 10 10 m −3 at solar zenith angles of 105°-110° are comparable to the characteristic value of peak electron density at the day/night terminator (solar zenith angle of 90°) of ∼3 × 10 10 m −3 (e.g., Figure 4 of Withers et al [2021]). Zhang et al (1990) examined 50 nightside radio occultation profiles from the Viking spacecraft.…”

Section: Electron Density Valuesmentioning

confidence: 91%

“…Peak electron density generally decreases with increasing solar zenith angle, but the MAVEN ROSE observations of large electron densities of 2–4 × 10 10 m −3 at solar zenith angles of 105°–110° are comparable to the characteristic value of peak electron density at the day/night terminator (solar zenith angle of 90°) of ∼3 × 10 10 m −3 (e.g., Figure 4 of Withers et al. [2021]). Zhang et al.…”

Section: Electron Density Valuesmentioning

confidence: 95%

Observations of High Densities at Low Altitudes in the Nightside Ionosphere of Mars by the MAVEN Radio Occultation Science Experiment (ROSE)

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The nightside ionosphere of Mars is patchy and variable. It is patchy because its properties are strongly influenced by the strength, direction, and topology of patchy crustal magnetic fields (Girazian et al., 2017). It is variable due to the influence of magnetosphere-ionosphere coupling, whereby the energy and momentum of particles originating in the time-variable upstream solar wind and surrounding space environment are transferred into the neutral atmosphere. It plays an important role in the Mars atmosphere/space environment system because of this coupling and because it is a reservoir from which atmospheric species can escape to space.Electron densities in the nightside ionosphere of Mars are generally small (e.g., Němec et al., 2010; Withers, Fillingim, et al., 2012;Zhang et al., 1990). The peak electron density is rarely greater than 5 × 10 9 m −3 , in contrast to the dayside ionosphere in which the peak electron density at the subsolar point can be on the order of 2 × 10 11 m −3 . Nevertheless, much larger electron densities are occasionally found on the nightside. Using observations from the MARSIS radar sounder on the Mars Express spacecraft, Němec et al. (2011) reported peak electron density values up to 5 × 10 10 m −3 in regions of strong and open magnetic field. They did not report an association with extreme solar events. Harada et al. (2018) reported similar peak density values in several similar observations acquired during the intense solar events of September 2017.It is generally accepted that these large nightside electron density values are caused by electron precipitation. As summarized by Girazian et al. (2017), "the largest peak densities are found near vertical crustal fields, which form cusps that allow superthermal electrons to precipitate into the atmosphere. In contrast, smaller peak densities are found near horizontal crustal fields, which prevent superthermal electrons from precipitating into the atmosphere (

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“…Similar measurements of the ionospheric peaks by RO experiments onboard other Mars missions reveal that the October 2016 ROSE profiles had unusually high peak altitudes. The bottom panel in Figure 4 of Withers et al (2021) heights at ∼125 km at SZA close to 56°. The LPW onboard MAVEN measured the ionospheric peak heights during the deep dip campaign in September 2015 at SZA in the range of 77°-87°.…”

Section: Rose/maven Observationsmentioning

confidence: 99%

Atypically Intense and Delayed Response of the Martian Ionosphere to the Regional Dust Storm of 2016: A Study Using MAVEN Observations and Models

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Based on their spatial and temporal extent, Martian dust storms are classified into three types viz. local, regional, and global dust storms. Being of relatively low dust opacity and limited spatial extent, local dust storms are the ones that occur most commonly. Regional dust storms, formed by the coalescence of the local storms, have a larger spatial and temporal coverage and have a higher dust opacity. Sometimes these storms grow globally, engulfing the planet for several months. Such events are known as global dust storms or planet-encircling dust events. Even though dust storms are lower atmospheric events, their impact on the atmosphere extends well up into the thermosphere. The dust particles loaded into the atmosphere absorbs solar radiation and result in excessive heating. The lower atmosphere thus heats and expands, pushing the thermosphere above it upward. The expansion of the neutral atmosphere subsequently gets reflected in the ionospheric features. The M2 peak, where the Martian electron density profile shows maximum density, is known to form at fixed neutral pressure

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The ionosphere of Mars from solar minimum to solar maximum: Dayside electron densities from MAVEN and Mars Global Surveyor radio occultations

Cited by 13 publications

References 52 publications

Electron Densities in the Ionosphere of Mars: Comparison of MAVEN/ROSE and MAVEN/LPW Measurements

Electron Densities in the Ionosphere of Mars: Comparison of MAVEN/ROSE and MAVEN/LPW Measurements

Observations of High Densities at Low Altitudes in the Nightside Ionosphere of Mars by the MAVEN Radio Occultation Science Experiment (ROSE)

Atypically Intense and Delayed Response of the Martian Ionosphere to the Regional Dust Storm of 2016: A Study Using MAVEN Observations and Models

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