Hot carbon corona in Mars’ upper thermosphere and exosphere: 1. Mechanisms and structure of the hot corona for low solar activity at equinox

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 ( L s  = 180°), and low solar activity ( F 10.7 = 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. Key Points Hot C corona is simulated at the fixed condition within our frameworks Background atmosphere greatly impacts the structure of hot C corona The estimated global escape rates of hot C is 5.9 x 1023 s‐1Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/107587/1/jgre20239.pd

Hot carbon corona in Mars' upper thermosphere and exosphere: 2. Solar cycle and seasonal variability

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).Key PointsSolar cycle and seasonal variability of hot C corona is simulated in 3‐DOur simulation considered PD of CO and DR of CO+ as main sourcesThe estimated escape rates range from 5.28 to 55.1E23 s−1Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110543/1/jgre20338.pd

Developing Customized Employee Engagement Measure in an Indonesian Large Company: Procedure, Validity, and Reliability

Companies have been concerned on measurement and improvement of their employees’ engagement using various conceptual models. Since every company has their own specific vision, mission, and values, customization is needed to measure employee engagement objectively. One of the biggest state-owned company in Indonesia develops a specific model of employee engagement, consisted of 12-dimensions. Those dimensions have been operationalized in order to build a set of questionnaire to measure employee engagement. This study elaborates the procedure taken to create, validate, and testing the reliability of the measure. We administered the newly designed questionnaire (38 items measuring 12-dimensions) as well as Gallup Employee Engagement and Aon Hewitt questionnaires to 869 employees of the company. Significant correlations between measures, significant item-total item correlations, factorial robustness, and discriminative power confirmed the validity of the measure. Internal consistency, test-retest reliability, and Cronbach Alpha confirmed the reliability of the measure. These multiple sources of evidence are discussed

Effects of Global and Regional Dust Storms on the Martian Hot O Corona and Photochemical Loss

We examine here for the first time the effects of both global and regional dust storms on the formation of the Martian hot O corona and associated photochemical loss of O. Our study is conducted by utilizing our integrated model framework, which couples our Martian hot O corona model with a multifluid magnetohydrodynamic model for Mars for the dusty and clear atmospheric condition cases. We present our results with the most up‐to‐date cross sections for the O(3P)‐CO2 collisions. The main effect of dust storms on the ionosphere is the upward shift of the ionosphere on the dayside, which results in an increase in production of hot O at all altitudes above the ionospheric peak. However, the dust‐induced inflation of the neutral upper atmosphere results in an enhancement in collisional loss of hot O and thus effectively suppresses the hot O density, reducing the global photochemical loss rate by ~28% for the global dust storm scenario. The relative density structure of the hot O corona does not show any significant changes, while its magnitude decreases at all altitudes.Key PointsWe investigated the effect of dust storms on photochemical escape from Mars using up‐to‐date cross sections for O‐CO2 collisionsThe storm‐induced upward shift of the ionosphere causes increased production of hot O and efficient thermalization occurs by the inflated thermosphereThe net result is a global photochemical escape rate that is suppressed by ~28% during the global dust storm scenarioPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154658/1/jgra55566_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154658/2/jgra55566.pd

Hot oxygen escape from Mars: Simple scaling with solar EUV irradiance

The evolution of the atmosphere of Mars and the loss of volatiles over the lifetime of the solar system is a key topic in planetary science. An important loss process for atomic species, such as oxygen, is ionospheric photochemical escape. Dissociative recombination of O2+ ions (the major ion species) produces fast oxygen atoms, some of which can escape from the planet. Many theoretical hot O models have been constructed over the years, although a number of uncertainties are present in these models, particularly concerning the elastic cross sections of O atoms with CO2. Recently, the Mars Atmosphere and Volatile Evolution mission has been rapidly improving our understanding of the upper atmosphere and ionosphere of Mars and its interaction with the external environment (e.g., solar wind), allowing a new assessment of this important loss process. The purpose of the current paper is to take a simple analytical approach to the oxygen escape problem in order to (1) study the role that variations in solar radiation or solar wind fluxes could have on escape in a transparent fashion and (2) isolate the effects of uncertainties in oxygen cross sections on the derived oxygen escape rates. In agreement with several more elaborate numerical models, we find that the escape flux is directly proportional to the incident solar extreme ultraviolet irradiance and is inversely proportional to the backscatter elastic cross section. The amount of O lost due to ion transport in the topside ionosphere is found to be about 5–10% of the total.Key PointsPhotochemistry dominates oxygen escape from MarsMartian oxygen escape rate scales linearly with solar activityDependence of O escape rate from Mars on elastic cross section is describedPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136315/1/jgra53155.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136315/2/jgra53155_am.pd

Mars Dust Storm Effects in the Ionosphere and Magnetosphere and Implications for Atmospheric Carbon Loss

Mars regional and global dust storms are able to impact the lower/upper atmospheres through dust aerosol radiative heating and cooling and atmospheric circulation. Here we present the first attempt to globally investigate how the dust impact transfers from the neutral upper atmosphere to the ionosphere and the induced magnetosphere above 100‐km altitude. This is achieved by running a multifluid magnetohydrodynamic model under nondusty and dusty atmospheric conditions for the 2017 late‐winter regional storm and the 1971–1972 global storm. Our results show that the dayside main ionospheric layer (below ∼250‐km altitude) undergoes an overall upwelling, where photochemical reactions dominate. The peak electron density remains unchanged, and the peak altitude shift is in accordance with the upper atmospheric expansion (∼5 and ∼15 km for the regional and global storms, respectively). Controlled by the day‐to‐night transport, the nightside ionosphere responds to the dust storms in a close connection with what happens on the dayside but not apparently with the ambient atmospheric change. At higher altitudes, dust‐induced perturbations propagate upward from the ionosphere to the magnetosphere and extend from the dayside to the nightside, within a broad region bounded by the induced magnetospheric boundary. It is found that the global dust storm is able to dramatically enhance the CO2+ loss by a factor of ∼3, which amounts to an increase of ∼20% or more for total carbon loss (in the forms of neutrals and ions). Strong dust storms are a potentially important factor in atmospheric evolution at Mars.Key PointsThe dayside main ionosphere is lifted in accordance with dust‐induced atmospheric expansion, with peak electron densities unchangedDust‐induced perturbations propagate upward from the ionosphere to the magnetosphere and extend from the dayside to the nightsideStrong dust storms may enhance CO2+ loss by a factor of ∼3 and increase total carbon loss (neutrals and ions) by ∼20% or morePeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154511/1/jgra55184_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154511/2/jgra-sup-0001-2019JA026838-Text_SI-S01.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154511/3/jgra55184.pd

Solar wind interaction with the Martian upper atmosphere: Crustal field orientation, solar cycle, and seasonal variations

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.Key PointsStudy crustal field, solar cycle, and seasons on Mars' upper atmosphere ion escapeTo understand the long‐term evolution of Mars atmosphere over its historyTo support MAVEN spacecraft mission data analysis (2014–2016)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/115901/1/jgra52040.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/115901/2/jgra52040_am.pd