The Martian Bow Shock Over Solar Cycle 23–24 as Observed by the Mars Express Mission

Hall, B. E. S.; Sánchez–Cano, Beatriz; Wild, J. A.; Lester, M.; Holmström, Mats

doi:10.1029/2018ja026404

Cited by 36 publications

(95 citation statements)

References 39 publications

(89 reference statements)

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“…The solar ionizing flux seems to affect the bow shock location more than the magnetic pileup boundary location (

γ = 0.205

vs.

γ = 0.094

). This bow shock location variability is consistent with a significant bow shock distance increase during the solar maximum as compared to the solar minimum reported by Hall et al (2019). The ionospheric densities and conductivity are higher at the times of higher total solar ionizing flux, which should, in turn, result in more effective formation of induced magnetic fields and induced magnetosphere shielding from the impinging solar wind.…”

Section: Discussionsupporting

confidence: 91%

“…Figure 8b shows a histogram of differences between the model and observed radial distances by the blue color. For comparison, the red histogram shows the differences obtained using the fitting formula and parameters suggested by Hall et al (2019) for the same data set. It can be seen that the two histograms are quite comparable, but the model suggested in the recent study results in a bit narrower distribution.…”

Section: Resultsmentioning

confidence: 99%

“…Assuming the cylindrical symmetry, we opt for a parabola dependence with the focus located on the x ‐axis, but not necessarily in the planet center:

ρ^{2} = α false(x_{0} - x false),

where x and ρ (in R M ) are MSO abberation corrected cylindrical coordinates of a given point at the boundary, α is a fitted parameter representing the boundary flaring, and x 0 is the subsolar standoff distance. The parabolic approximation of the boundary shape is justified by the fact that former studies which assumed the boundary shapes to be general conic sections revealed the boundaries to be very close to parabolas (Hall et al, 2019; Trotignon et al, 2006). Moreover, possible deviations of the parabola shapes from similarly shaped conic sections may eventually become significant only at far flanks, which are not sufficiently sampled in the used data set.…”

Section: Resultsmentioning

confidence: 99%

“…Vignes et al (2000) compared the bow shock locations identified in MGS and Phobos 2 data sets, finding good agreement and concluding that the mean bow shock and magnetic pileup boundary locations are mostly independent of the solar cycle phase. On the other hand, the analysis of Martian bow shock observations by the Mars Express spacecraft over the period 2004 to 2017 showed that the bow shock radial distance increases on average by as much as 7% between the solar minimum and solar maximum (Hall et al, 2019). Hall et al (2016) used a large set of bow shock crossings identified in the Mars Express data to investigate annual variations of the Martian bow shock location.…”

Section: Introductionmentioning

confidence: 99%

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Martian Bow Shock and Magnetic Pileup Boundary Models Based on an Automated Region Identification

et al. 2020

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Empirical models of bow shock and magnetic pileup boundary locations are typically based on the identification of individual boundary crossings and their subsequent fitting by properly chosen dependences. Such an approach, however, requires a large set of identified crossings, whose compilation can be easily a source of a significant bias. Moreover, the method is inherently biased by the spacecraft orbit: the more time the spacecraft spends in a given region, the more likely it is for a crossing to be identified in there. We use a different approach based on an automated region identification and Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft data to derive empirical models of both the bow shock and magnetic pileup boundary locations around Mars. We use statistically known parameters in the solar wind, magnetosheath, and induced magnetosphere, along with the observed ratios of measured solar wind parameters, to automatically identify the region where the spacecraft is located at any given time. A simple empirical relation is then assumed for a boundary shape and location, and its free parameters are adapted to optimize the resulting model classification of individual data points. This procedure allows us to model both the bow shock and magnetic pileup boundary locations, reproducing successfully observed variations with the solar wind dynamic pressure, solar ionizing flux, and crustal magnetic fields. However, due to the sparse data coverage, the models are deemed unreliable beyond the terminator. Plain Language Summary Solar wind interaction with Mars results in the formation of two distinct boundaries, bow shock and magnetic pileup boundary. Their exact locations depend on various parameters, and they are typically described by empirical models based on individual boundary crossings identified in spacecraft data. However, this requires many boundary crossings to be identified, and moreover, the locations of these crossings are inherently biased toward the regions where the spacecraft spends more time. We use a different approach based on an automated identification of whether the spacecraft is located inside or outside a given boundary. An empirical dependence of the boundary shape and location is then designed in such a way that the model region classification fits the observations as closely as possible. This removes the necessity to rely on the crossing identification and the related sampling bias. Empirical models of the boundaries derived by our simple and robust method reproduce well observed dependences on solar wind dynamic pressure, solar ionizing flux, and remnant crustal magnetic fields.

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“…The solar ionizing flux seems to affect the bow shock location more than the magnetic pileup boundary location (

γ = 0.205

vs.

γ = 0.094

Section: Discussionsupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

“…Assuming the cylindrical symmetry, we opt for a parabola dependence with the focus located on the x ‐axis, but not necessarily in the planet center:

ρ^{2} = α false(x_{0} - x false),

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Martian Bow Shock and Magnetic Pileup Boundary Models Based on an Automated Region Identification

et al. 2020

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“…In contrast, at planetary objects without a global intrinsic field but a significant ionosphere, ion pickup becomes important for this interaction and the standing‐off distance for this type of bow shock is much closer to the planet, within two planetary radii for Mars (e.g., Gruesbeck et al., 2018; Trotignon et al., 2006; Vignes et al., 2000) and Venus (e.g., Luhmann, 1986). Many shock properties have been well investigated at Earth (e.g., Formisano, 1974; Wilkinson, 2003) and Mars (e.g., Burne et al., 2020; Gruesbeck et al., 2018; Halekas et al., 2017; Hall et al., 2019; Mazelle et al., 2004; Nagy et al., 2004).…”

Section: Introductionmentioning

confidence: 99%

Cross‐Shock Electrostatic Potentials at Mars Inferred From MAVEN Measurements

Schwartz

Mitchell

et al. 2021

JGR Space Physics

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The interaction between the supersonic solar wind flow and planetary intrinsic dipole fields (e.g., Earth, Jupiter, and Saturn) or ionospheres (e.g., Venus, Mars, and comets) results in the formation of a shock wave, or termed as the bow shock. Planets with a strong intrinsic dipole field, thus a strong magnetic pressure, have large stand-off distances at the nose that depend on the strength of the dipole. In contrast, at planetary objects without a global intrinsic field but a significant ionosphere, ion pickup becomes important for this interaction and the standing-off distance for this type of bow shock is much closer to the planet, within two planetary radii for Mars (e.g.,

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Mars' ionospheric interaction with comet C/2013 A1 Siding-Spring's coma at their closest approach as seen by Mars Express

Sánchez‐Cano

Lester

Witasse

et al. 2019

Preprint

Self Cite

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On 19 October 2014, Mars experienced a close encounter with Comet C/2013 A1 Siding Spring. Using data from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board Mars Express (MEX), we assess the interaction of the Martian ionosphere with the comet's coma and possibly magnetic tail during the orbit of their closest approach. The topside ionospheric electron density profile is evaluated from the altitude of the peak density of the ionosphere up to the MEX altitude. We find complex and rapid variability in the ionospheric profile along the MEX orbit, not seen even after the impact of a large coronal mass ejection. Before closest approach, large electron density reductions predominate, which could be caused either by comet water damping or comet magnetic field interactions. After closest approach, a substantial electron density rise predominates. Moreover, several extra topside layers are visible along the whole orbit at different altitudes, which could be related to different processes as we discuss.

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The Martian Bow Shock Over Solar Cycle 23–24 as Observed by the Mars Express Mission

Cited by 36 publications

References 39 publications

Martian Bow Shock and Magnetic Pileup Boundary Models Based on an Automated Region Identification

Martian Bow Shock and Magnetic Pileup Boundary Models Based on an Automated Region Identification

Cross‐Shock Electrostatic Potentials at Mars Inferred From MAVEN Measurements

Mars' ionospheric interaction with comet C/2013 A1 Siding-Spring's coma at their closest approach as seen by Mars Express

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