Effects of solar irradiance on the upper ionosphere and oxygen ion escape at Mars: MAVEN observations

Dubinin, E.; Fräenz, M.; Pätzold, M.; McFadden, J. P.; Mahaffy, P. R.; Eparvier, F.; Halekas, J. S.; Connerney, J. E. P.; Brain, David; Jakosky, B. M.; Вайсберг, О. Л.; Zelenyǐ, L. M.

doi:10.1002/2017ja024126

Cited by 34 publications

(57 citation statements)

References 47 publications

(61 reference statements)

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“…When compared to previous results, these first estimates based on MAVEN data seem to be significantly lower, something that could be related to the weakness of solar cycle 24 which translates into lower EUV fluxes and, as different authors have pointed out, this leads to lower ionospheric escape (e.g., Dong et al, , ; Dubinin et al, ; Ramstad et al, ). In addition to these cyclical variations, the location where the ions are measured, the energy ranges included in the analyses, and in general the way data are treated differ among the studies and are also a cause of the observed variations that span over 2 orders of magnitude.…”

Section: Introductionmentioning

confidence: 48%

“…The vertical axis corresponds to the Z axis while the horizontal one corresponds to the magnetic field as measured by the MAG instrument at distances along the X axis between −2 and −1 R M . This coordinate system allows for a better separation of the regions occupied by the planetary ions of different origin (Dubinin et al, ).…”

Section: Ion Escape As Detected By Mavenmentioning

confidence: 99%

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Multispecies and Multifluid MHD Approaches for the Study of Ionospheric Escape at Mars

Regoli

Dong

et al. 2018

JGR Space Physics

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A detailed model‐model comparison between the results provided by a multispecies and a multifluid magnetohydrodynamic (MHD) code for the escape of heavy ions in the Martian‐induced magnetosphere is presented. The results from the simulations are analyzed and compared against a statistical analysis of the outflow of heavy ions obtained by the Mars Atmosphere and Volatile EvolutioN/Suprathermal and Thermal Ion Composition instrument over an extended period of time in order to estimate the influence of magnetic forces in the ion escape. Both MHD models are run with the same chemical reactions and ion species in a steady state mode under idealized solar conditions. Apart from being able to reproduce the asymmetries observed in the ion escape, it is found that the multifluid approach provides results that are closer to those inferred from the ion data. It is also found that the j × B force term is less effective in accelerating the ions in the models when compared with the Mars Atmosphere and Volatile EvolutioN results. Finally, by looking at the contribution of the plume and the ion escape rates at different distances along the tail with the multifluid model, it is also found that the escape of heavy ions has important variabilities along the tail, meaning that the apoapsis of a spacecraft studying atmospheric escape can affect the estimates obtained.

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Section: Introductionmentioning

confidence: 48%

Section: Ion Escape As Detected By Mavenmentioning

confidence: 99%

Multispecies and Multifluid MHD Approaches for the Study of Ionospheric Escape at Mars

Regoli

Dong

et al. 2018

JGR Space Physics

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“…Strong induced magnetic fields are required to balance the solar wind, providing a hypothetical explanation: The corresponding powerful J × B forces could collect nearly all outflowing ions in a plasma sheet compressed by the same forces to the point that it might have been completely missed on MEX orbit #9606, despite traversing deep into the tail. Indeed, accelerated populations are largely confined to the plasma sheet as recently shown by Dubinin et al () and increased n sw redistributes the cold ion outflow to accelerated populations (Ramstad, Barabash, Futaana, Nilsson, et al, ). Similar changes in ion distributions during CMEs are also seen in models (Luhmann et al, ).…”

Section: Discussionmentioning

confidence: 83%

Mars Under Primordial Solar Wind Conditions: Mars Express Observations of the Strongest CME Detected at Mars Under Solar Cycle #24 and its Impact on Atmospheric Ion Escape

Ramstad

Barabash

Futaana

et al. 2017

Geophysical Research Letters

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An extremely strong Coronal Mass Ejection (CME) impacted Mars on 12 July 2011, while the Mars Express spacecraft was present inside the nightside ionosphere. Estimated solar wind density and speed during the event are 39 particles cm −3 and 730 km/s, corresponding to nominal solar wind flux at Mars when the solar system was ∼1.1 Ga old. Comparing with expected average atmospheric heavy ion fluxes under similar XUV conditions, the CME impact is found to have no significant effect on the escape rate 3.3 × 10 24 s −1 , with an upper limit at 10 25 s −1 if the observed tail contraction is not taken into account. On the subsequent orbit, 7 h later after magnetosphere response, fluxes were only 2.4% of average. As such, even under primordial solar wind conditions we are unable to find support for a strong solar wind-driven ion escape, rather the main effect appears to be acceleration of the escaping ions by ×10-×20 typical characteristic energy.

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“…Effects of a weak intrinsic magnetic field on atmospheric escape from Mars. Geophysical Research Letters, 45, 9336-9343. https://doi.org/10.1029/ 2018GL079972 recent MAVEN mission revealed that the low-energy (<30 eV) O + escape rate increases to a few times 10 25 s À1 under solar EUV irradiances higher than 0.1 W/m 2 (Dubinin et al, 2017). Some numerical simulations also investigated the effect of the solar conditions on the ion escape rate.…”

Section: Citationmentioning

confidence: 99%

Effects of a Weak Intrinsic Magnetic Field on Atmospheric Escape From Mars

Sakai

Seki

Terada

et al. 2018

Geophysical Research Letters

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The magnetization of a planet significantly changes the nature of atmospheric escape, and the question of whether a planetary field shields atmosphere from erosion by the solar wind or not remains open. Ion escape processes from Mars are investigated under two hypothetical conditions, namely, no intrinsic magnetic field and weak intrinsic dipole field cases under present solar wind conditions based on multispecies magnetohydrodynamics simulations. The existence of a weak dipole field results in an enhancement of the tailward flux of planetary ions through the four escape channels. Two channels are associated with the open fields at the poles, and the others are caused by magnetic reconnection between the planetary and solar wind magnetic fields at the flank magnetopause. The ion escape rate with the weak dipole is greater than in the no-dipole case. The enhancement is significant for O 2 + and CO 2 + , suggesting ion escape from the low-altitude ionosphere.Plain Language Summary Present Mars has a thin atmosphere and little water on the surface.Space missions have provided some evidences for the existence of liquid water and a thick atmosphere on ancient Mars. These evidences suggest Mars has experienced significant atmospheric loss up to the present. Ion outflow is one of the important atmospheric loss mechanisms. In the present day, Mars does not have a global magnetic field such as that of Earth, and thus, ions escape by the direct interaction with the solar wind (influenced to some extent by Mars' crustal fields). In contrast, it is expected that ancient Mars had a global magnetic field. The global magnetic field forms the magnetosphere around the planet, perhaps changing the ion escape mechanisms. In this study, a numerical simulation of the Mars-solar wind interaction is used to compare ion escape for the case of no planetary field with a case where a weak global magnetic field is assumed. The weak global magnetic field yields four escape routes associated with open magnetic fields and magnetic reconnection. The escape rate of heavy ions increases by~25% compared to the nondipole case, particularly facilitating the escape of O 2 + and CO 2 + present in the low-altitude ionosphere.

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Effects of solar irradiance on the upper ionosphere and oxygen ion escape at Mars: MAVEN observations

Cited by 34 publications

References 47 publications

Multispecies and Multifluid MHD Approaches for the Study of Ionospheric Escape at Mars

Multispecies and Multifluid MHD Approaches for the Study of Ionospheric Escape at Mars

Mars Under Primordial Solar Wind Conditions: Mars Express Observations of the Strongest CME Detected at Mars Under Solar Cycle #24 and its Impact on Atmospheric Ion Escape

Effects of a Weak Intrinsic Magnetic Field on Atmospheric Escape From Mars

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