Enhanced carbon dioxide causing the dust storm‐related increase in high‐altitude photoelectron fluxes at Mars

Xu, Shaosui; Liemohn, Michael W.; Bougher, S. W.; Mitchell, David

doi:10.1002/2015gl066043

Cited by 28 publications

(25 citation statements)

References 46 publications

(60 reference statements)

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“…Our simulation, shown in Figure , perfectly reproduced this phenomenon. In fact, according to recent observations, the increase of neutral density in Martian upper atmosphere can significantly increase the photoelectron flux across all energy ranges (Xu et al, ); therefore, the lift of the upper ionosphere may also be related to the variations of neutral density, especially the variations of CO 2 density, which is the main source of the electrons in this region (Wang & Nielsen, ). The latest observations of MAVEN have strongly demonstrated the obvious increase of CO 2 density between 170 and 220 km during dust storms (Liu et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, Liu et al () even found that the thermosphere (170–220 km) moved upward by about 10 km during a regional storm, which also suggests that the lift of upper ionosphere may be influenced by the lift of neutral atmosphere. According to Xu et al (), the levels where CO 2 density increases during dust storms can extend up to 400 km. The confirmation of extreme height of dust impact on the neutral atmosphere and ionosphere needs further observational data from Mars missions such as MAVEN and Mars Express.…”

Section: Discussionmentioning

confidence: 99%

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Effects of Local Dust Storms on the Upper Atmosphere of Mars: Observations and Simulations

Qin

Zou

et al. 2019

JGR Planets

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The effects of a local dust storm on the upper atmosphere of Mars are researched through the observations of the lower and upper Martian atmosphere in the MGS (Mars Global Surveyor) radio occultation experiments. The ionosphere profiles in the high‐latitude region of northern hemisphere are thought to be under the influence of a local dust storm occurring in the low‐latitude areas during Ls 135–150°, Mars Year (MY) 27. A method to estimate the Martian upper neutral densities via the heights of ionospheric main peak is presented. Through the method, the 130‐km atmospheric neutral densities (or CO2 densities) of the area during the dust storm were calculated. MCD V4.3 (Mars Climate Database, Version 4.3) is used to derive the normal (or dust‐storm‐free) neutral densities of the same region and period. By analyzing the differences between the calculated densities and MCD (V4.3) simulated ones, the influence of the local dust storm on the upper atmosphere densities can be quantitatively derived. Based on the variation of the upper atmosphere densities, the behavior of regional ionospheric main peak under the dust storm can be simulated by a photochemical equilibrium model. The simulated ionosphere parameters are compared with the MGS‐observed ones, and it is found that two profile data sets are consistent with one another, thus indicating that the method employed to estimate the upper neutral densities is accurate.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Effects of Local Dust Storms on the Upper Atmosphere of Mars: Observations and Simulations

Qin

Zou

et al. 2019

JGR Planets

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“…The influence of the other parameters—EUV, SZAm and LT—is less clear and depends on the frame considered (for the LT influence in MSO versus MSE) or on cross‐correlations biases with the major drivers (for SZA near noon, as detailed above), even if the risks of artificial correlations as determined from Fisher's tests are always below 1%, except for the SZA influence (risk of ≈2%). Regarding the EUV influence, we point out that if EUV is a major driver for the photoelectron fluxes (Trantham et al, ; Xu et al, ) through the production mechanisms, its influence on the PEB should be less strong (e.g., the MGS data could not see any EUV influence on the ionopause, Mitchell et al, ). The EUV influence corresponds to an enhanced thermal pressure that will act against the solar wind confinement and thus push the draping of the IMF.…”

Section: The Parameters Of Influence For the Peb: Solar Wind Dynamic mentioning

confidence: 94%

The Martian Photoelectron Boundary as Seen by MAVEN

et al. 2017

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Photoelectron peaks in the 20–30 eV energy range are commonly observed in the planetary atmospheres, produced by the intense photoionization from solar 30.4 nm photons. At Mars, these photoelectrons are known to escape the planet down its tail, making them tracers for the atmospheric escape. Furthermore, their presence or absence allow to define the so‐called photoelectron boundary (PEB), which separates the photoelectron dominated ionosphere from the external environment. We provide here a detailed statistical analysis of the location and properties of the PEB based on the Mars Atmosphere and Volatile EvolutioN (MAVEN) electron and magnetic field data obtained from September 2014 to May 2016 (including 1696 PEB crossings). The PEB appears as mostly sensitive to the solar wind dynamic and crustal fields pressures. Its variable altitude thus leads to a variable wake cross section for escape (up to ∼+50%), which is important for deriving escape rates. The PEB is not always sharp and is characterized on average by the following: a magnetic field topology typical for the end of magnetic pileup region above it, more field‐aligned fluxes above than below, and a clear change of the altitude slopes of both electron fluxes and total density (that appears different from the ionopause). The PEB thus appears as a transition region between two plasma and fields configurations determined by the draping topology of the interplanetary magnetic field around Mars and much influenced by the crustal field sources below, whose dynamics also impacts the estimated escape rate of ionospheric plasma.

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“…At the 400‐km MGS altitude, well above the collisional atmosphere, 10‐eV to 20‐keV electrons are typically magnetized (with a guiding center motion following the magnetic field line), so these electrons serve as excellent magnetic field tracers. As noted in previous studies (e.g., Brain et al, ; Xu, Fang, et al, ), magnetic topology inferred from superthermal electron observations is defined with respect to the suprathermal electron exobase (∼160 km, Xu, Liemohn, Bougher, et al, ; Xu, Liemohn, et al, ), or the foot point(s) of a field line, in lieu of the planet surface, only above which can suprathermal electrons move freely and be used to infer topology. Therefore, in this study, a closed field line is defined as both foot points of a field line embedded in the collisional atmosphere; an open field line is defined as one foot point embedded in the collisional atmosphere and the other connected to the solar wind; a draped field line does not intersect the superthermal electron exobase on either end.…”

Section: Methodsmentioning

confidence: 99%

Magnetic Topology Response to the 2003 Halloween ICME Event at Mars

Curry

Mitchell

et al. 2019

JGR Space Physics

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Understanding how the Mars plasma environment responds to space weather events provides insights into the early Sun‐Mars interaction and helps constrain the extrapolation of atmospheric loss back in time. The 2003 Halloween interplanetary coronal mass ejection (ICME) event is one of the most extreme space weather events encountered by Mars during the last two decades. Mars Global Surveyor's circular orbit at ∼400 km allows us to observationally study the magnetic topology response to this extreme event globally for the first time. We analyze the suprathermal electron data and magnetic field measurements from Mars Global Surveyor to infer magnetic topology before, during, and after this ICME event and quantify the variation of the topology over both weak and strong crustal regions and correlate the variation with the upstream dynamic pressure. Over weak crustal regions, more draped field lines and fewer closed field lines are observed under high dynamic pressures, implying a deeper interplanetary magnetic field penetration during the ICME event. Over dayside strong crustal regions, the dominant magnetic topology switches from closed field lines during quiet periods to open field lines during disturbed periods, suggesting more reconnection occurring between the crustal magnetic fields and interplanetary magnetic field. This mixed magnetic topological response is consistent with predictions from magnetohydrodynamic simulations for ICME events in previous studies.

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Enhanced carbon dioxide causing the dust storm‐related increase in high‐altitude photoelectron fluxes at Mars

Cited by 28 publications

References 46 publications

Effects of Local Dust Storms on the Upper Atmosphere of Mars: Observations and Simulations

Effects of Local Dust Storms on the Upper Atmosphere of Mars: Observations and Simulations

The Martian Photoelectron Boundary as Seen by MAVEN

Magnetic Topology Response to the 2003 Halloween ICME Event at Mars

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