The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform

S W Bougher - One of the best experts on this subject based on the ideXlab platform.

  • hot oxygen corona at mars and the photochemical escape of oxygen improved description of the thermosphere ionosphere and exosphere
    Journal of Geophysical Research, 2015
    Co-Authors: Yuni Lee, S W Bougher, Michael R Combi, Valeriy Tenishev, Robert J Lillis
    Abstract:

    The Mars Adaptive Mesh Particle Simulator model is coupled with the Mars Global Ionosphere Thermosphere Model for the first time to provide an improved description of the Martian hot O corona based on our modeling studies of O2+ dissociative recombination. A total of 12 cases comprising three solar activity levels and four orbital positions is considered to study the solar cycle and seasonal variability. The newly coupled framework includes two additional thermospheric species and adopts a realistic forward scattering scheme using the angular differential cross sections. We present the effects of these changes on the resulting hot O corona and escape rate. A comparison between the simulated hot O corona and the recent observations from the ALICE/Rosetta instrument showed a reasonable agreement, considering the large uncertainties in the data. We assume that some discrepancies near the transition altitude may be originated from the averaging over the altitude range, where the cold and hot O densities become comparable. The revised O escape rates by our new coupled framework range from ~1.21 × 1025 s−1 to ~5.43 × 1025 s−1.

  • solar wind interaction with the martian upper atmosphere crustal field orientation solar cycle and seasonal variations
    Journal of Geophysical Research, 2015
    Co-Authors: Chuanfei Dong, S W Bougher, Yuni Lee, Michael R Combi, Valeriy Tenishev, Gabor Toth, A F Nagy, Dave Pawlowski, Dalal Najib
    Abstract:

    A comprehensive study of the solar wind interaction with the Martian upper atmosphere is presented. Three global models: the 3-D Mars multifluid Block Adaptive Tree Solar-wind Roe Upwind Scheme MHD code (MF-MHD), the 3-D Mars Global Ionosphere Thermosphere Model (M-GITM), and the Mars exosphere Monte Carlo model Adaptive Mesh Particle Simulator (M-AMPS) were used in this study. These models are one-way coupled; i.e., the MF-MHD model uses the 3-D neutral inputs from M-GITM and the 3-D hot oxygen corona distribution from M-AMPS. By adopting this one-way coupling approach, the Martian upper atmosphere ion escape rates are investigated in detail with the combined variations of crustal field orientation, solar cycle, and Martian seasonal conditions. The calculated ion escape rates are compared with Mars Express observational data and show reasonable agreement. The variations in solar cycles and seasons can affect the ion loss by a factor of ∼3.3 and ∼1.3, respectively. The crustal magnetic field has a shielding effect to protect Mars from solar wind interaction, and this effect is the strongest for perihelion conditions, with the crustal field facing the Sun. Furthermore, the fraction of cold escaping heavy ionospheric molecular ions [( 2+ and/or 2+)/Total] are inversely proportional to the fraction of the escaping (ionospheric and corona) atomic ion [O+/Total], whereas 2+ and 2+ ion escape fractions show a positive linear correlation since both ion species are ionospheric ions that follow the same escaping path.

  • hot carbon corona in mars upper thermosphere and exosphere 2 solar cycle and seasonal variability
    Journal of Geophysical Research, 2014
    Co-Authors: Yuni Lee, Michael R Combi, Valeriy Tenishev, S W Bougher
    Abstract:

    This work presents the variability over seasons (i.e., orbital position) and solar cycle of the Martian upper atmosphere and hot carbon corona. We investigate the production and distribution of energetic carbon atoms and the impacts on the total global hot carbon loss from dominant photochemical processes at five different cases: AL (aphelion and low solar activity), EL (equinox and low solar activity), EH (equinox and high solar activity), PL (perihelion and low solar activity), and PH (perihelion and high solar activity). We compare our results with previously published results but only on the limited cases due to the dearth of studies on solar EUV flux and seasonal variabilities. Photodissociation of CO and dissociative recombination of CO+ are generally regarded as the two most important source reactions for the production of hot atomic carbon. Of these two, photodissociation of CO is found to be the dominant source in all cases considered. To describe self-consistently the exosphere and the upper thermosphere, a 3-D kinetic Particle simulator, the Adaptive Mesh Particle Simulator, and the 3-D Mars Thermosphere General Circulation Model are one-way coupled. The basic description of this hot carbon calculation can be found in the companion paper to this one. The spatial distributions and profiles of density and temperature and atmospheric loss rates are discussed for the cases considered. Finally, our computed global escape rate of hot carbon ranges from 5.28 × 1023 s−1 (AL) to 55.1 × 1023 s−1 (PL).

  • hot carbon corona in mars upper thermosphere and exosphere 1 mechanisms and structure of the hot corona for low solar activity at equinox
    Journal of Geophysical Research, 2014
    Co-Authors: Yuni Lee, Michael R Combi, Valeriy Tenishev, S W Bougher
    Abstract:

    Two important source reactions for hot atomic carbon on Mars are photodissociation of CO and dissociative recombination of CO+; both reactions are highly sensitive to solar activity and occur mostly deep in the dayside thermosphere. The production of energetic Particles results in the formation of hot coronae that are made up of neutral atoms including hot carbon. Some of these atoms are on ballistic trajectories and return to the thermosphere, and others escape. Understanding the physics in this region requires modeling that captures the complicated dynamics of hot atoms in 3-D. This study evaluates the carbon atom inventory by investigating the production and distribution of energetic carbon atoms using the full 3-D atmospheric input. The methodology and details of the hot atomic carbon model calculation are given, and the calculated total global escape of hot carbon from the assumed dominant photochemical processes at a fixed condition, equinox (Ls = 180°), and low solar activity (F10.7 = 70 at Earth) are presented. To investigate the dynamics of these energetic neutral atoms, we have coupled a self-consistent 3-D global kinetic model, the Adaptive Mesh Particle Simulator, with a 3-D thermosphere/ionosphere model, the Mars Thermosphere General Circulation Model to provide a self-consistent global description of the hot carbon corona in the upper thermosphere and exosphere. The spatial distributions of density and temperature and atmospheric loss are simulated for the case considered.

Michael R Combi - One of the best experts on this subject based on the ideXlab platform.

  • three dimensional direct simulation monte carlo modeling of the coma of comet 67p churyumov gerasimenko observed by the virtis and rosina instruments on board rosetta
    Astronomy and Astrophysics, 2016
    Co-Authors: N Fougere, Michael R Combi, Kathrin Altwegg, Jeanjacques Berthelier, Andre Bieler, D Bockeleemorvan, Ursina Calmonte, F Capaccioni, J De Keyser, V Debout
    Abstract:

    Since its rendezvous with comet 67P/Churyumov-Gerasimenko (67P), the Rosetta spacecraft has provided invaluable information contributing to our understanding of the cometary environment. On board, the VIRTIS and ROSINA instruments can both measure gas parameters in the rarefied cometary atmosphere, the so-called coma, and provide complementary results with remote sensing and in situ measurement techniques, respectively. The data from both ROSINA and VIRTIS instruments suggest that the source regions of H2O and CO2 are not uniformly distributed over the surface of the nucleus even after accounting for the changing solar illumination of the irregularly shaped rotating nucleus. The source regions of H2O and CO2 are also relatively different from one another. Aims. The use of a combination of a formal numerical data inversion method with a fully kinetic coma model is a way to correlate and interpret the information provided by these two instruments to fully understand the volatile environment and activity of comet 67P. Methods. In this work, the nonuniformity of the outgassing activity at the surface of the nucleus is described by spherical harmonics and constrained by ROSINA-DFMS data. This activity distribution is coupled with the local illumination to describe the inner boundary conditions of a 3D direct simulation Monte-Carlo (DSMC) approach using the Adaptive Mesh Particle Simulator (AMPS) code applied to the H2O and CO2 coma of comet 67P. Results. We obtain activity distribution of H2O and CO2 showing a dominant source of H2O in the Hapi region, while more CO2 is produced in the southern hemisphere. The resulting model outputs are analyzed and compared with VIRTIS-M/-H and ROSINA-DFMS measurements, showing much better agreement between model and data than a simpler model assuming a uniform surface activity. The evolution of the H2O and CO2 production rates with heliocentric distance are derived accurately from the coma model showing agreement between the observations from the different instruments and ground-based observations. Conclusions. We derive the activity distributions for H2O and CO2 at the surface of the nucleus described in spherical harmonics, which we couple to the local solar illumination to constitute the boundary conditions of our coma model. The model presented reproduces the coma observations made by the ROSINA and VIRTIS instruments on board the Rosetta spacecraft showing our understanding of the physics of 67P’s coma. This model can be used for further data analyses, such as dust modeling, in a future work.

  • hot oxygen corona at mars and the photochemical escape of oxygen improved description of the thermosphere ionosphere and exosphere
    Journal of Geophysical Research, 2015
    Co-Authors: Yuni Lee, S W Bougher, Michael R Combi, Valeriy Tenishev, Robert J Lillis
    Abstract:

    The Mars Adaptive Mesh Particle Simulator model is coupled with the Mars Global Ionosphere Thermosphere Model for the first time to provide an improved description of the Martian hot O corona based on our modeling studies of O2+ dissociative recombination. A total of 12 cases comprising three solar activity levels and four orbital positions is considered to study the solar cycle and seasonal variability. The newly coupled framework includes two additional thermospheric species and adopts a realistic forward scattering scheme using the angular differential cross sections. We present the effects of these changes on the resulting hot O corona and escape rate. A comparison between the simulated hot O corona and the recent observations from the ALICE/Rosetta instrument showed a reasonable agreement, considering the large uncertainties in the data. We assume that some discrepancies near the transition altitude may be originated from the averaging over the altitude range, where the cold and hot O densities become comparable. The revised O escape rates by our new coupled framework range from ~1.21 × 1025 s−1 to ~5.43 × 1025 s−1.

  • solar wind interaction with the martian upper atmosphere crustal field orientation solar cycle and seasonal variations
    Journal of Geophysical Research, 2015
    Co-Authors: Chuanfei Dong, S W Bougher, Yuni Lee, Michael R Combi, Valeriy Tenishev, Gabor Toth, A F Nagy, Dave Pawlowski, Dalal Najib
    Abstract:

    A comprehensive study of the solar wind interaction with the Martian upper atmosphere is presented. Three global models: the 3-D Mars multifluid Block Adaptive Tree Solar-wind Roe Upwind Scheme MHD code (MF-MHD), the 3-D Mars Global Ionosphere Thermosphere Model (M-GITM), and the Mars exosphere Monte Carlo model Adaptive Mesh Particle Simulator (M-AMPS) were used in this study. These models are one-way coupled; i.e., the MF-MHD model uses the 3-D neutral inputs from M-GITM and the 3-D hot oxygen corona distribution from M-AMPS. By adopting this one-way coupling approach, the Martian upper atmosphere ion escape rates are investigated in detail with the combined variations of crustal field orientation, solar cycle, and Martian seasonal conditions. The calculated ion escape rates are compared with Mars Express observational data and show reasonable agreement. The variations in solar cycles and seasons can affect the ion loss by a factor of ∼3.3 and ∼1.3, respectively. The crustal magnetic field has a shielding effect to protect Mars from solar wind interaction, and this effect is the strongest for perihelion conditions, with the crustal field facing the Sun. Furthermore, the fraction of cold escaping heavy ionospheric molecular ions [( 2+ and/or 2+)/Total] are inversely proportional to the fraction of the escaping (ionospheric and corona) atomic ion [O+/Total], whereas 2+ and 2+ ion escape fractions show a positive linear correlation since both ion species are ionospheric ions that follow the same escaping path.

  • hot carbon corona in mars upper thermosphere and exosphere 2 solar cycle and seasonal variability
    Journal of Geophysical Research, 2014
    Co-Authors: Yuni Lee, Michael R Combi, Valeriy Tenishev, S W Bougher
    Abstract:

    This work presents the variability over seasons (i.e., orbital position) and solar cycle of the Martian upper atmosphere and hot carbon corona. We investigate the production and distribution of energetic carbon atoms and the impacts on the total global hot carbon loss from dominant photochemical processes at five different cases: AL (aphelion and low solar activity), EL (equinox and low solar activity), EH (equinox and high solar activity), PL (perihelion and low solar activity), and PH (perihelion and high solar activity). We compare our results with previously published results but only on the limited cases due to the dearth of studies on solar EUV flux and seasonal variabilities. Photodissociation of CO and dissociative recombination of CO+ are generally regarded as the two most important source reactions for the production of hot atomic carbon. Of these two, photodissociation of CO is found to be the dominant source in all cases considered. To describe self-consistently the exosphere and the upper thermosphere, a 3-D kinetic Particle simulator, the Adaptive Mesh Particle Simulator, and the 3-D Mars Thermosphere General Circulation Model are one-way coupled. The basic description of this hot carbon calculation can be found in the companion paper to this one. The spatial distributions and profiles of density and temperature and atmospheric loss rates are discussed for the cases considered. Finally, our computed global escape rate of hot carbon ranges from 5.28 × 1023 s−1 (AL) to 55.1 × 1023 s−1 (PL).

  • hot carbon corona in mars upper thermosphere and exosphere 1 mechanisms and structure of the hot corona for low solar activity at equinox
    Journal of Geophysical Research, 2014
    Co-Authors: Yuni Lee, Michael R Combi, Valeriy Tenishev, S W Bougher
    Abstract:

    Two important source reactions for hot atomic carbon on Mars are photodissociation of CO and dissociative recombination of CO+; both reactions are highly sensitive to solar activity and occur mostly deep in the dayside thermosphere. The production of energetic Particles results in the formation of hot coronae that are made up of neutral atoms including hot carbon. Some of these atoms are on ballistic trajectories and return to the thermosphere, and others escape. Understanding the physics in this region requires modeling that captures the complicated dynamics of hot atoms in 3-D. This study evaluates the carbon atom inventory by investigating the production and distribution of energetic carbon atoms using the full 3-D atmospheric input. The methodology and details of the hot atomic carbon model calculation are given, and the calculated total global escape of hot carbon from the assumed dominant photochemical processes at a fixed condition, equinox (Ls = 180°), and low solar activity (F10.7 = 70 at Earth) are presented. To investigate the dynamics of these energetic neutral atoms, we have coupled a self-consistent 3-D global kinetic model, the Adaptive Mesh Particle Simulator, with a 3-D thermosphere/ionosphere model, the Mars Thermosphere General Circulation Model to provide a self-consistent global description of the hot carbon corona in the upper thermosphere and exosphere. The spatial distributions of density and temperature and atmospheric loss are simulated for the case considered.

Yuni Lee - One of the best experts on this subject based on the ideXlab platform.

  • hot oxygen corona at mars and the photochemical escape of oxygen improved description of the thermosphere ionosphere and exosphere
    Journal of Geophysical Research, 2015
    Co-Authors: Yuni Lee, S W Bougher, Michael R Combi, Valeriy Tenishev, Robert J Lillis
    Abstract:

    The Mars Adaptive Mesh Particle Simulator model is coupled with the Mars Global Ionosphere Thermosphere Model for the first time to provide an improved description of the Martian hot O corona based on our modeling studies of O2+ dissociative recombination. A total of 12 cases comprising three solar activity levels and four orbital positions is considered to study the solar cycle and seasonal variability. The newly coupled framework includes two additional thermospheric species and adopts a realistic forward scattering scheme using the angular differential cross sections. We present the effects of these changes on the resulting hot O corona and escape rate. A comparison between the simulated hot O corona and the recent observations from the ALICE/Rosetta instrument showed a reasonable agreement, considering the large uncertainties in the data. We assume that some discrepancies near the transition altitude may be originated from the averaging over the altitude range, where the cold and hot O densities become comparable. The revised O escape rates by our new coupled framework range from ~1.21 × 1025 s−1 to ~5.43 × 1025 s−1.

  • solar wind interaction with the martian upper atmosphere crustal field orientation solar cycle and seasonal variations
    Journal of Geophysical Research, 2015
    Co-Authors: Chuanfei Dong, S W Bougher, Yuni Lee, Michael R Combi, Valeriy Tenishev, Gabor Toth, A F Nagy, Dave Pawlowski, Dalal Najib
    Abstract:

    A comprehensive study of the solar wind interaction with the Martian upper atmosphere is presented. Three global models: the 3-D Mars multifluid Block Adaptive Tree Solar-wind Roe Upwind Scheme MHD code (MF-MHD), the 3-D Mars Global Ionosphere Thermosphere Model (M-GITM), and the Mars exosphere Monte Carlo model Adaptive Mesh Particle Simulator (M-AMPS) were used in this study. These models are one-way coupled; i.e., the MF-MHD model uses the 3-D neutral inputs from M-GITM and the 3-D hot oxygen corona distribution from M-AMPS. By adopting this one-way coupling approach, the Martian upper atmosphere ion escape rates are investigated in detail with the combined variations of crustal field orientation, solar cycle, and Martian seasonal conditions. The calculated ion escape rates are compared with Mars Express observational data and show reasonable agreement. The variations in solar cycles and seasons can affect the ion loss by a factor of ∼3.3 and ∼1.3, respectively. The crustal magnetic field has a shielding effect to protect Mars from solar wind interaction, and this effect is the strongest for perihelion conditions, with the crustal field facing the Sun. Furthermore, the fraction of cold escaping heavy ionospheric molecular ions [( 2+ and/or 2+)/Total] are inversely proportional to the fraction of the escaping (ionospheric and corona) atomic ion [O+/Total], whereas 2+ and 2+ ion escape fractions show a positive linear correlation since both ion species are ionospheric ions that follow the same escaping path.

  • hot carbon corona in mars upper thermosphere and exosphere 2 solar cycle and seasonal variability
    Journal of Geophysical Research, 2014
    Co-Authors: Yuni Lee, Michael R Combi, Valeriy Tenishev, S W Bougher
    Abstract:

    This work presents the variability over seasons (i.e., orbital position) and solar cycle of the Martian upper atmosphere and hot carbon corona. We investigate the production and distribution of energetic carbon atoms and the impacts on the total global hot carbon loss from dominant photochemical processes at five different cases: AL (aphelion and low solar activity), EL (equinox and low solar activity), EH (equinox and high solar activity), PL (perihelion and low solar activity), and PH (perihelion and high solar activity). We compare our results with previously published results but only on the limited cases due to the dearth of studies on solar EUV flux and seasonal variabilities. Photodissociation of CO and dissociative recombination of CO+ are generally regarded as the two most important source reactions for the production of hot atomic carbon. Of these two, photodissociation of CO is found to be the dominant source in all cases considered. To describe self-consistently the exosphere and the upper thermosphere, a 3-D kinetic Particle simulator, the Adaptive Mesh Particle Simulator, and the 3-D Mars Thermosphere General Circulation Model are one-way coupled. The basic description of this hot carbon calculation can be found in the companion paper to this one. The spatial distributions and profiles of density and temperature and atmospheric loss rates are discussed for the cases considered. Finally, our computed global escape rate of hot carbon ranges from 5.28 × 1023 s−1 (AL) to 55.1 × 1023 s−1 (PL).

  • hot carbon corona in mars upper thermosphere and exosphere 1 mechanisms and structure of the hot corona for low solar activity at equinox
    Journal of Geophysical Research, 2014
    Co-Authors: Yuni Lee, Michael R Combi, Valeriy Tenishev, S W Bougher
    Abstract:

    Two important source reactions for hot atomic carbon on Mars are photodissociation of CO and dissociative recombination of CO+; both reactions are highly sensitive to solar activity and occur mostly deep in the dayside thermosphere. The production of energetic Particles results in the formation of hot coronae that are made up of neutral atoms including hot carbon. Some of these atoms are on ballistic trajectories and return to the thermosphere, and others escape. Understanding the physics in this region requires modeling that captures the complicated dynamics of hot atoms in 3-D. This study evaluates the carbon atom inventory by investigating the production and distribution of energetic carbon atoms using the full 3-D atmospheric input. The methodology and details of the hot atomic carbon model calculation are given, and the calculated total global escape of hot carbon from the assumed dominant photochemical processes at a fixed condition, equinox (Ls = 180°), and low solar activity (F10.7 = 70 at Earth) are presented. To investigate the dynamics of these energetic neutral atoms, we have coupled a self-consistent 3-D global kinetic model, the Adaptive Mesh Particle Simulator, with a 3-D thermosphere/ionosphere model, the Mars Thermosphere General Circulation Model to provide a self-consistent global description of the hot carbon corona in the upper thermosphere and exosphere. The spatial distributions of density and temperature and atmospheric loss are simulated for the case considered.

Valeriy Tenishev - One of the best experts on this subject based on the ideXlab platform.

  • hot oxygen corona at mars and the photochemical escape of oxygen improved description of the thermosphere ionosphere and exosphere
    Journal of Geophysical Research, 2015
    Co-Authors: Yuni Lee, S W Bougher, Michael R Combi, Valeriy Tenishev, Robert J Lillis
    Abstract:

    The Mars Adaptive Mesh Particle Simulator model is coupled with the Mars Global Ionosphere Thermosphere Model for the first time to provide an improved description of the Martian hot O corona based on our modeling studies of O2+ dissociative recombination. A total of 12 cases comprising three solar activity levels and four orbital positions is considered to study the solar cycle and seasonal variability. The newly coupled framework includes two additional thermospheric species and adopts a realistic forward scattering scheme using the angular differential cross sections. We present the effects of these changes on the resulting hot O corona and escape rate. A comparison between the simulated hot O corona and the recent observations from the ALICE/Rosetta instrument showed a reasonable agreement, considering the large uncertainties in the data. We assume that some discrepancies near the transition altitude may be originated from the averaging over the altitude range, where the cold and hot O densities become comparable. The revised O escape rates by our new coupled framework range from ~1.21 × 1025 s−1 to ~5.43 × 1025 s−1.

  • solar wind interaction with the martian upper atmosphere crustal field orientation solar cycle and seasonal variations
    Journal of Geophysical Research, 2015
    Co-Authors: Chuanfei Dong, S W Bougher, Yuni Lee, Michael R Combi, Valeriy Tenishev, Gabor Toth, A F Nagy, Dave Pawlowski, Dalal Najib
    Abstract:

    A comprehensive study of the solar wind interaction with the Martian upper atmosphere is presented. Three global models: the 3-D Mars multifluid Block Adaptive Tree Solar-wind Roe Upwind Scheme MHD code (MF-MHD), the 3-D Mars Global Ionosphere Thermosphere Model (M-GITM), and the Mars exosphere Monte Carlo model Adaptive Mesh Particle Simulator (M-AMPS) were used in this study. These models are one-way coupled; i.e., the MF-MHD model uses the 3-D neutral inputs from M-GITM and the 3-D hot oxygen corona distribution from M-AMPS. By adopting this one-way coupling approach, the Martian upper atmosphere ion escape rates are investigated in detail with the combined variations of crustal field orientation, solar cycle, and Martian seasonal conditions. The calculated ion escape rates are compared with Mars Express observational data and show reasonable agreement. The variations in solar cycles and seasons can affect the ion loss by a factor of ∼3.3 and ∼1.3, respectively. The crustal magnetic field has a shielding effect to protect Mars from solar wind interaction, and this effect is the strongest for perihelion conditions, with the crustal field facing the Sun. Furthermore, the fraction of cold escaping heavy ionospheric molecular ions [( 2+ and/or 2+)/Total] are inversely proportional to the fraction of the escaping (ionospheric and corona) atomic ion [O+/Total], whereas 2+ and 2+ ion escape fractions show a positive linear correlation since both ion species are ionospheric ions that follow the same escaping path.

  • hot carbon corona in mars upper thermosphere and exosphere 2 solar cycle and seasonal variability
    Journal of Geophysical Research, 2014
    Co-Authors: Yuni Lee, Michael R Combi, Valeriy Tenishev, S W Bougher
    Abstract:

    This work presents the variability over seasons (i.e., orbital position) and solar cycle of the Martian upper atmosphere and hot carbon corona. We investigate the production and distribution of energetic carbon atoms and the impacts on the total global hot carbon loss from dominant photochemical processes at five different cases: AL (aphelion and low solar activity), EL (equinox and low solar activity), EH (equinox and high solar activity), PL (perihelion and low solar activity), and PH (perihelion and high solar activity). We compare our results with previously published results but only on the limited cases due to the dearth of studies on solar EUV flux and seasonal variabilities. Photodissociation of CO and dissociative recombination of CO+ are generally regarded as the two most important source reactions for the production of hot atomic carbon. Of these two, photodissociation of CO is found to be the dominant source in all cases considered. To describe self-consistently the exosphere and the upper thermosphere, a 3-D kinetic Particle simulator, the Adaptive Mesh Particle Simulator, and the 3-D Mars Thermosphere General Circulation Model are one-way coupled. The basic description of this hot carbon calculation can be found in the companion paper to this one. The spatial distributions and profiles of density and temperature and atmospheric loss rates are discussed for the cases considered. Finally, our computed global escape rate of hot carbon ranges from 5.28 × 1023 s−1 (AL) to 55.1 × 1023 s−1 (PL).

  • hot carbon corona in mars upper thermosphere and exosphere 1 mechanisms and structure of the hot corona for low solar activity at equinox
    Journal of Geophysical Research, 2014
    Co-Authors: Yuni Lee, Michael R Combi, Valeriy Tenishev, S W Bougher
    Abstract:

    Two important source reactions for hot atomic carbon on Mars are photodissociation of CO and dissociative recombination of CO+; both reactions are highly sensitive to solar activity and occur mostly deep in the dayside thermosphere. The production of energetic Particles results in the formation of hot coronae that are made up of neutral atoms including hot carbon. Some of these atoms are on ballistic trajectories and return to the thermosphere, and others escape. Understanding the physics in this region requires modeling that captures the complicated dynamics of hot atoms in 3-D. This study evaluates the carbon atom inventory by investigating the production and distribution of energetic carbon atoms using the full 3-D atmospheric input. The methodology and details of the hot atomic carbon model calculation are given, and the calculated total global escape of hot carbon from the assumed dominant photochemical processes at a fixed condition, equinox (Ls = 180°), and low solar activity (F10.7 = 70 at Earth) are presented. To investigate the dynamics of these energetic neutral atoms, we have coupled a self-consistent 3-D global kinetic model, the Adaptive Mesh Particle Simulator, with a 3-D thermosphere/ionosphere model, the Mars Thermosphere General Circulation Model to provide a self-consistent global description of the hot carbon corona in the upper thermosphere and exosphere. The spatial distributions of density and temperature and atmospheric loss are simulated for the case considered.

Dalal Najib - One of the best experts on this subject based on the ideXlab platform.

  • solar wind interaction with the martian upper atmosphere crustal field orientation solar cycle and seasonal variations
    Journal of Geophysical Research, 2015
    Co-Authors: Chuanfei Dong, S W Bougher, Yuni Lee, Michael R Combi, Valeriy Tenishev, Gabor Toth, A F Nagy, Dave Pawlowski, Dalal Najib
    Abstract:

    A comprehensive study of the solar wind interaction with the Martian upper atmosphere is presented. Three global models: the 3-D Mars multifluid Block Adaptive Tree Solar-wind Roe Upwind Scheme MHD code (MF-MHD), the 3-D Mars Global Ionosphere Thermosphere Model (M-GITM), and the Mars exosphere Monte Carlo model Adaptive Mesh Particle Simulator (M-AMPS) were used in this study. These models are one-way coupled; i.e., the MF-MHD model uses the 3-D neutral inputs from M-GITM and the 3-D hot oxygen corona distribution from M-AMPS. By adopting this one-way coupling approach, the Martian upper atmosphere ion escape rates are investigated in detail with the combined variations of crustal field orientation, solar cycle, and Martian seasonal conditions. The calculated ion escape rates are compared with Mars Express observational data and show reasonable agreement. The variations in solar cycles and seasons can affect the ion loss by a factor of ∼3.3 and ∼1.3, respectively. The crustal magnetic field has a shielding effect to protect Mars from solar wind interaction, and this effect is the strongest for perihelion conditions, with the crustal field facing the Sun. Furthermore, the fraction of cold escaping heavy ionospheric molecular ions [( 2+ and/or 2+)/Total] are inversely proportional to the fraction of the escaping (ionospheric and corona) atomic ion [O+/Total], whereas 2+ and 2+ ion escape fractions show a positive linear correlation since both ion species are ionospheric ions that follow the same escaping path.