Article
Geosciences, Multidisciplinary
Y. -T. Cao, J. Cui, X. -S. Wu, D. -D. Niu, H. -R. Lai, B. -B. Ni, Q. Luo, J. Yu, Y. Wei
Summary: This study presents a statistical survey of nightside photoelectrons on Mars using measurements from the MAVEN spacecraft. Nearly 30% of the available nightside measurements show clear photoelectron signatures, with occurrence rate decreasing with solar zenith angle. The observations suggest that nightside photoelectrons exhibit preferentially field-aligned pitch angle distribution and are less likely to be observed under high solar wind conditions.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Astronomy & Astrophysics
Shiqi Wu, Xiaoshu Wu, Jun Cui, Yutian Cao, Shuxin Liao, Haoyu Lu, Lei Li
Summary: Ionospheric chemistry is important for planetary habitability. This study models the nightside Martian ionospheric structure and composition, using measurements from the Mars Atmosphere and Volatile Evolution. Results show a well-defined ionospheric peak at 146 km with a peak density of 8500 cm(-3), driven by atmospheric absorption of precipitating electrons. The nightside ionospheric composition has a higher proportion of NO+ and lower proportion of CO2 (+) compared to the dayside.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
P. Withers, M. Felici, M. Mendillo, M. F. Vogt, E. Barbinis, D. Kahan, K. Oudrhiri, C. Gray, C. O. Lee, S. Xu, M. Lester, B. Sanchez-Cano, B. M. Jakosky, S. Curry
Summary: Unusually large peak electron density values have been sporadically observed in the nightside ionosphere of Mars in regions of strong and open crustal magnetic field. However, the vertical structure of the ionosphere has not been observed before. This study presents three vertical electron density profiles from the nightside ionosphere of Mars, showing comparably large values of peak electron density. These findings contradict previous research by associating the large nightside electron density values with protons, rather than electrons.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Paul Withers, M. Felici, K. Hensley, M. Mendillo, E. Barbinis, D. Kahan, K. Oudrhiri, Z. Girazian
Summary: Changes in the ionosphere of Mars due to solar irradiance have been well-characterized, but the upper regions of the photochemical ionosphere have not been extensively studied. In this research, ionospheric electron density profiles were analyzed during solar minimum and solar maximum using data from two Mars satellites. The results showed that electron density and peak electron density increase similarly from solar minimum to solar maximum, while the scale height of the photochemical ionosphere remains constant and the neutral temperature increases by 50%. These findings provide insights into the dynamics of the ionosphere on Mars.
Article
Astronomy & Astrophysics
E. Golden-Marx, P. Withers, A. J. Kopf
Summary: Unusually large peak electron density values are occasionally observed in the ionosphere of Mars, particularly in cusp-like regions of crustal magnetic field, displaying atypical examples of oblique echoes in ionograms. However, the vertical extent and physical processes behind these features are still not well understood.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Z. Girazian, J. Halekas, R. J. Lillis
Summary: Using MAVEN observations, we studied the variations in the structure and composition of the nightside ionosphere on Mars on solar cycle and seasonal timescales. Plasma densities vary significantly at fixed altitudes due to variations in thermospheric pressure levels. The electron impact ionization (EII) rate, influenced by solar cycle and seasonal trends, also affects the nightside densities. High-altitude nightside ionosphere densities vary significantly over the solar cycle, with topside O+ and O+2 densities changing by factors of -50 and -40, respectively. Topside ion densities remained relatively stable during the solar minimum of 2018-2019.
Article
Geochemistry & Geophysics
Robert J. Lillis, Shaosui Xu, David Mitchell, Ed Thiemann, Frank Eparvier, Mehdi Benna, Meredith Elrod
Summary: Efficiency of ionization on Mars is investigated using MAVEN data, showing a positive correlation with solar activity but negligible dependence on crustal magnetic fields. The increase in ionization efficiency is mainly attributed to solar EUV levels and variability in neutral composition, rather than spectral changes.
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2021)
Article
Geosciences, Multidisciplinary
R. E. Ergun, L. A. Andersson, C. M. Fowler, S. A. Thaller, R. Yelle
Summary: The study recalibrated dayside electron temperature and density altitude profiles at Mars from MAVEN satellite deep-dip orbits, with measured Te values higher than predicted by models at lower altitudes. Heat transfer analysis supported CO2 excitation/de-excitation as dominating energy transfer, possibly leading to the discrepancy between measured and modeled Te values.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Geochemistry & Geophysics
Praveen Basuvaraj, Frantisek Nemec, Zdenek Nemecek, Jana Safrankova
Summary: The Martian ionosphere has unique structures different from Earth and Venus, and integrated observations show evidence of ionospheric plasma depletions independent of seasonal variations. These depletions are more prominent on the nightside, possibly occurring in regions with strong crustal magnetic fields, and are bubble-like structures elongated horizontally.
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2022)
Article
Astronomy & Astrophysics
Fanfan Su, Wenbin Wang
Summary: This paper investigates the longitudinal variations of topside Ne at middle latitudes during 2007-2009 using in situ Ne measurements from the DEMETER satellite and electron density profiles retrieved from the COSMIC data. The study finds that the reversal phase of the longitudinal peaks/valleys of topside Ne is not very common and the phase shift of the longitudinal variations is less in winter. The transition longitudes of topside Ne have a westward trend from winter to summer in the daytime and an eastward trend from summer to winter, but in some cases, they are located within a certain range of longitude at 52 degrees N.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Chemistry, Multidisciplinary
Weiqi Liu, Peiyao Bai, Shilin Wei, Chuangchuang Yang, Lang Xu
Summary: This study combines the advantages of single-atom catalysts and conventional nanoparticle catalysts to improve the selectivity and current density of CO2 reduction. The developed Ni-Gd-N-doped carbon black electrocatalyst exhibits a high CO faradaic efficiency and a large current density, with outstanding stability.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Environmental Sciences
Xiong Hu, Xiaocheng Wu, Shuli Song, Maoli Ma, Weili Zhou, Qingchen Xu, Lei Li, Cunying Xiao, Xie Li, Chi Wang, Qinghui Liu, Lue Chen, Guangming Chen, Jianfeng Cao, Mei Wang, Peijia Li, Zhanghu Chu, Bo Xia, Junfeng Yang, Cui Tu, Dan Liu, Simin Zhang, Quan Zhang, Zheng Li
Summary: The radio-occultation technique is crucial for studying planetary climate and space weather. The Tianwen-1 mission successfully retrieved Mars ionospheric and atmospheric parameters, providing reliable and valuable data for further research on Mars climate and space weather.
Article
Astronomy & Astrophysics
Maodong Yan, Tong Dang, Yu-Tian Cao, Jun Cui, Binzheng Zhang, Zerui Liu, Jiuhou Lei
Summary: This study investigates the ionospheric response of Earth, Venus, and Mars to solar flares using self-consistent planetary ionospheric models. The results show significant increases in electron density in the lower ionosphere region, with notable differences in the maximum relative change between the planets. The ion temperature response to flares is similar for Earth and Venus, but different for Mars. The electron temperature response also varies among the planets. The vertical plasma velocity increases during solar flares at all three planets.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
M. Felici, P. Withers, M. F. Vogt, K. G. Hensley, L. Andersson
Summary: By comparing electron density measurements from different instruments, this study finds that electron densities in the dawn ionosphere are more variable than those in the dusk ionosphere.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Environmental Sciences
Haris Haralambous, Theodoros Leontiou, Vasilis Petrou, Arun Kumar Singh, Marios Charalambides, Nikos Lithoxopoulos, Agis Agisilaou
Summary: This article introduces a concept for local ionospheric mitigation in single-frequency GNSS positioning, which utilizes input parameters and measurements to improve accuracy and reduce positioning errors.