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56. Martian magnetic storms

Author

Luhmann, J. G., primary, Dong, C. F., additional, Ma, Y. J., additional, Curry, S. M., additional, Xu, S., additional, Lee, C. O., additional, Hara, T., additional, Halekas, J., additional, Li, Y., additional, Gruesbeck, J. R., additional, Espley, J., additional, Brain, D. A., additional, Russell, C. T., additional, and Jakosky, B. M., additional

Published
2017
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57. Survey of magnetic reconnection signatures in the Martian magnetotail with MAVEN

Author

Harada, Y., primary, Halekas, J. S., additional, McFadden, J. P., additional, Espley, J., additional, DiBraccio, G. A., additional, Mitchell, D. L., additional, Mazelle, C., additional, Brain, D. A., additional, Andersson, L., additional, Ma, Y. J., additional, Larson, D. E., additional, Xu, S., additional, Hara, T., additional, Ruhunusiri, S., additional, Livi, R., additional, and Jakosky, B. M., additional

Published
2017
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58. Variations of the Martian plasma environment during the ICME passage on 8 March 2015: A time‐dependent MHD study

Author

Ma, Y. J., primary, Russell, C. T., additional, Fang, X., additional, Dong, C. F., additional, Nagy, A. F., additional, Toth, G., additional, Halekas, J. S., additional, Connerney, J. E. P., additional, Espley, J. R., additional, Mahaffy, P. R., additional, Benna, M., additional, McFadden, J., additional, Mitchell, D. L., additional, Andersson, L., additional, and Jakosky, B. M., additional

Published
2017
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61. Solar Wind Interaction Effects On The Magnetic Fields Around Mars: Consequences For Interplanetary And Crustal Field Measurements

Author

Luhmann, J. G., Ma, Y. -J., Brain, D. A., Ulusen, D., Lillis, R. J., Halekas, J. S., and Espley, J. R.

Subjects
Physics::Space Physics, Astrophysics::Earth and Planetary Astrophysics
Abstract

The first unambiguous detections of the crustal remanent magnetic fields of Mars were obtained by Mars Global Surveyor (MGS) during its initial orbits around Mars, which probed altitudes to within similar to 110 km of the surface. However, the majority of its measurements were carried out around 400 km altitude, fixed 2 a.m. to 2 p.m. local time, mapping orbit. While the general character and planetary origins of the localized crustal fields were clearly revealed by the mapping survey data, their effects on the solar wind interaction could not be investigated in much detail because of the limited mapping orbit sampling. Previous analyses (Brain et al., 2006) of the field measurements on the dayside nevertheless provided an idea of the extent to which the interaction of the solar wind and planetary fields leads to non-ideal field draping at the mapping altitude. In this study we use numerical simulations of the global solar wind interaction with Mars as an aid to interpreting that observed non-ideal behavior. In addition, motivated by models for different interplanetary field orientations, we investigate the effects of induced and reconnected (planetary and external) fields on the Martian field's properties derived at the MGS mapping orbit altitude. The results suggest that inference of the planetary low order moments is compromised by their influence. In particular, the intrinsic dipole contribution may differ from that in the current models because the induced component is so dominant. (C) 2015 Elsevier Ltd. All rights reserved.

Published
2015

62. Ultrastrong and Stiff Carbon Nanotube/Aluminum–Copper Nanocomposite via Enhancing Friction between Carbon Nanotubes

Author

Wang, G. J., Cai, Y. P., Ma, Y. J., Tang, S. C., Syed, J. A., Cao, Z. H., and Meng, X. K.

Abstract

Researchers have been aiming to replace copper with carbon nanotube/copper nanocomposites, which are lighter and exhibit better electrical, mechanical, and thermal properties. However, the strength is far below pure carbon nanotube assembly and even much lower than some copper-based alloys. This disadvantage hinders the extensive application of carbon nanotube/copper nanocomposites. In this study, the carbon nanotube/aluminum–copper nanocomposites with ultra-strength and stiffness were prepared. The strength and elasticity modulus of composite reached as high as 6.6 and 500 GPa, respectively, while a high conductivity of 1.8 × 107S/m was maintained. This can be attributed to the diffusion of Cu and Al atoms into the carbon nanotube fiber, which enhances friction between the carbon nanotubes by “pinning” and “bridging”. This structure provides us with novel insights into the design of carbon nanotubes/metal nanocomposites with ultrahigh strength and conductivity.

Published
2024
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63. Space Weather Storm Responses at Mars: Lessons from A Weakly Magnetized Terrestrial Planet

Author

Luhmann, J. G., primary, Dong, C. F., additional, Ma, Y. J., additional, Curry, S. M., additional, Li, Yan, additional, Lee, C. O., additional, Hara, T., additional, Lillis, R., additional, Halekas, J., additional, Connerney, J. E., additional, Espley, J., additional, Brain, D. A., additional, Dong, Y., additional, Jakosky, B. M., additional, Thiemann, E., additional, Eparvier, F., additional, Leblanc, F., additional, Withers, P., additional, and Russell, C. T., additional

Published
2016
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69. OBSERVATION OF DOUBLET BANDS IN 130Pr

Author

Ma, K. Y., primary, Lu, J. B., additional, Yang, D., additional, Liu, Y. Z., additional, Ma, Y. J., additional, Wu, X. G., additional, Li, G. S., additional, and He, C. Y., additional

Published
2016
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72. Pentraxin-3 level at admission is a strong predictor of short-term mortality in a community-based hospital setting

Author

Bastrup-Birk, S, Munthe-Fog, L, Skjødt, Mikkel-Ole, Ma, Y J, Nielsen, H, Køber, L, Nielsen, O W, Iversen, K, Garred, P, Bastrup-Birk, S, Munthe-Fog, L, Skjødt, Mikkel-Ole, Ma, Y J, Nielsen, H, Køber, L, Nielsen, O W, Iversen, K, and Garred, P

Abstract

BACKGROUND: The pattern recognition molecule pentraxin-3 (PTX3) is a novel potential marker of prognosis, as elevated levels are associated with both disease severity and mortality in patients with a wide range of conditions. However, the usefulness of PTX3 as a prognostic biomarker in a general hospital setting is unknown.PATIENTS AND METHODS: The study cohort consisted of 1326 unselected, consecutive patients (age >40 years) admitted to a community hospital in Copenhagen, Denmark. Patients were followed until death or for a median of 11.5 years after admission. The main outcome measure was all-cause mortality. Serum samples collected from patients at admission and from 192 healthy control subjects were quantified for PTX3 level by enzyme-linked immunosorbent assay.RESULTS: PTX3 was elevated in patients (median 3.7 ng mL(-1) , range 0.5-209.8) compared with healthy nonhospitalized subjects (median 3.5 ng mL(-1) , range 0.0-8.3; P = 0.0003). Elevated PTX3 levels, defined as above the 95th percentile of the concentration in healthy subjects, were associated with increased overall mortality during the study (P < 0.0001). This increase in mortality was greatest in the short term, with an unadjusted hazard ratio (HR) of 6.4 [95% confidence interval (CI) 3.8-11.0] at 28 days after admission, compared to 1.7 (95% CI 1.4-2.0) at the end of follow-up. These results were still significant after adjustment for age, gender and glomerular filtration rate: adjusted HR of 5.0 (95% CI 2.9-8.8) and 1.4 (95% CI 1.2-1.8), respectively.CONCLUSION: These results suggest that PTX3 could be a widely applicable marker of short-term mortality in hospitalized patients and may be useful in the initial risk stratification.

Published
2015

74. Response of Mars O + pickup ions to the 8 March 2015 ICME: Inferences from MAVEN data‐based models

Author

Curry, S. M., primary, Luhmann, J. G., additional, Ma, Y. J., additional, Dong, C. F., additional, Brain, D., additional, Leblanc, F., additional, Modolo, R., additional, Dong, Y., additional, McFadden, J., additional, Halekas, J., additional, Connerney, J., additional, Espley, J., additional, Hara, T., additional, Harada, Y., additional, Lee, C., additional, Fang, X., additional, and Jakosky, B., additional

Published
2015
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75. MHD model results of solar wind interaction with Mars and comparison with MAVEN plasma observations

Author

Ma, Y. J., primary, Russell, C. T., additional, Fang, X., additional, Dong, Y., additional, Nagy, A. F., additional, Toth, G., additional, Halekas, J. S., additional, Connerney, J. E. P., additional, Espley, J. R., additional, Mahaffy, P. R., additional, Benna, M., additional, McFadden, J. P., additional, Mitchell, D. L., additional, and Jakosky, B. M., additional

Published
2015
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78. Perovskite LaBaCo2O5+δ (LBCO) single-crystal thin films for pressure sensing applications.

Author

Ma, Y. J., Xiao, J. Y., Zhang, Q. Y., Ma, C. Y., Jiang, X. N., Wu, B. Y., and Zeng, X. Y.

Subjects
*ELECTRIC properties, *PEROVSKITE, *MAGNETRON sputtering, *POLYCRYSTALS, *PRESSURE sensors, *THIN films
Abstract

Perovskite LaBaCo2O5+δ (LBCO) single-crystal films were deposited on (001) MgO substrates by a magnetron sputtering method and processed into Pirani sensors for investigation of pressure measurements. In comparison to the poly-crystal film deposited under the same condition, the single-crystal LBCO films exhibited rather a large temperature coefficient of resistance and a high sensitivity in response to pressure. The LBCO sensors with dimensions of 30 to 200 μm, which are different from resistor-on-dielectric membrane or micro-beam structures, demonstrated to be capable of making response to the pressures ranging from 5 × 10–2 to 105 Pa with a real dynamic range of 3 to 2 × 103 Pa. [ABSTRACT FROM AUTHOR]

Published
2018
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79. Dynamical and magnetic field time constants for Titan's ionosphere: Empirical estimates and comparisons with Venus

Author

Cravens, T. E., Richard, M., Ma, Y. J., Bertucci, Cesar, Luhmann, J. G., Ledvina, S., Robertson, I. P., Wahlund, J. E., Ågren, K., Cui, J., Muller Wodarg, I., Waite, J. H., Dougherty, M., Bell, J., and Ulusen, D.

Subjects
purl.org/becyt/ford/1 [https], Ionosphere/magnetosphere interactions [Ionosphere], Astronomía, Ciencias Físicas, Ionosphere/atmosphere interactions [Ionosphere], purl.org/becyt/ford/1.3 [https], Ionospheric dynamics [Ionosphere], CIENCIAS NATURALES Y EXACTAS, Comets and Small Bodies: Ionospheres (2459), Planetary Sciences: Solar System Objects: Titan [Planetary Sciences]
Abstract

Plasma in Titan´s ionosphere flows in response to forcing from thermal pressure gradients, magnetic forces, gravity, and ion-neutral collisions. This paper takes an empirical approach to the ionospheric dynamics by using data from Cassini instruments to estimate pressures, flow speeds, and time constants on the dayside and nightside. The plasma flow speed relative to the neutral gas speed is approximately 1 m s‑1 near an altitude of 1000 km and 200 m s‑1 at 1500 km. For comparison, the thermospheric neutral wind speed is about 100 m s‑1. The ionospheric plasma is strongly coupled to the neutrals below an altitude of about 1300 km. Transport, vertical or horizontal, becomes more important than chemistry in controlling ionospheric densities above about 1200-1500 km, depending on the ion species. Empirical estimates are used to demonstrate that the structure of the ionospheric magnetic field is determined by plasma transport (including neutral wind effects) for altitudes above about 1000 km and by magnetic diffusion at lower altitudes. The paper suggests that a velocity shear layer near 1300 km could exist at some locations and could affect the structure of the magnetic field. Both Hall and polarization electric field terms in the magnetic induction equation are shown to be locally important in controlling the structure of Titan´s ionospheric magnetic field. Comparisons are made between the ionospheric dynamics at Titan and at Venus. Fil: Cravens, T. E.. University of Kansas; Estados Unidos Fil: Richard, M.. University of Kansas; Estados Unidos Fil: Ma, Y. J.. University of California; Estados Unidos Fil: Bertucci, Cesar. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina Fil: Luhmann, J. G.. University of California; Estados Unidos Fil: Ledvina, S.. University of California; Estados Unidos Fil: Robertson, I. P.. University of Kansas; Estados Unidos Fil: Wahlund, J. E.. Swedish Institute of Space Physics; Suecia Fil: Ågren, K.. Swedish Institute of Space Physics; Suecia Fil: Cui, J.. Imperial College London; Reino Unido Fil: Muller Wodarg, I.. Imperial College London; Reino Unido Fil: Waite, J. H.. Southwest Research Institute; Estados Unidos Fil: Dougherty, M.. Imperial College London; Reino Unido Fil: Bell, J.. Southwest Research Institute; Estados Unidos Fil: Ulusen, D.. University of California; Estados Unidos

Published
2010

86. Time-dependent global MHD simulations of Cassini T32 flyby: From magnetosphere to magnetosheath

Author

Ma, Y. J., Russell, C. T., Nagy, A. F., Toth, G., Bertucci, Cesar, Dougherty, M. K., Neubauer, F. M., Wellbrock, A., Coates, A. J., Garnier, P., Wahlund, J. E., Cravens, T. E., and Crary, F. J.

Subjects
Astronomía, purl.org/becyt/ford/1 [https], Interaction, MHD, Ciencias Físicas, purl.org/becyt/ford/1.3 [https], Titan, CIENCIAS NATURALES Y EXACTAS, Simulation
Abstract

When the Cassini spacecraft flew by Titan on 13 June 2007, at 13.6 Saturn local time, Titan was directly observed to be outside Saturn′s magnetopause. Cassini observations showed dramatic changes of magnetic field orientation as well as other plasma flow parameters during the inbound and outbound segments. In this paper, we study Titan's ionospheric responses to such a sudden change in the upstream plasma conditions using a sophisticated multispecies global MHD model. Simulation results of three different cases (steady state, simple current sheet crossing, and magnetopause crossing) are presented and compared against Cassini Magnetometer, Langmuir Probe, and Cassini Plasma Spectrometer observations. The simulation results provide clear evidence for the existence of a fossil field that was induced in the ionosphere. The main interaction features, as observed by the Cassini spacecraft, are well reproduced by the time-dependent simulation cases. Simulation also reveals how the fossil field was trapped during the interaction and shows the coexistence of two pileup regions with opposite magnetic orientation, as well as the formation of a pair of new Alfven wings and tail disconnection during the magnetopause crossing process. Fil: Ma, Y. J.. University of California; Estados Unidos Fil: Russell, C. T.. University of California; Estados Unidos Fil: Nagy, A. F.. University of Michigan; Estados Unidos Fil: Toth, G.. University of Michigan; Estados Unidos Fil: Bertucci, Cesar. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina Fil: Dougherty, M. K.. Imperial College London; Reino Unido Fil: Neubauer, F. M.. University of Cologne; Alemania Fil: Wellbrock, A.. University College London; Estados Unidos Fil: Coates, A. J.. University College London; Estados Unidos Fil: Garnier, P.. Swedish Institute of Space Physics; Suecia Fil: Wahlund, J. E.. Swedish Institute of Space Physics; Suecia Fil: Cravens, T. E.. University of Kansas; Estados Unidos Fil: Crary, F. J.. Southwest Research Institute; Estados Unidos

Published
2009

87. An overview on smart distribution grid.

Author

Zhou, X. S., Xiang, P. D., and Ma, Y. J.

Subjects
SMART power grids, ELECTRIC power distribution grids, ELECTRICAL energy, POWER distribution networks, ELECTRIC networks
Published
2016

88. OBSERVATION OF DOUBLET BANDS IN 130Pr.

Author

Ma, K. Y., Lu, J. B., Yang, D., Liu, Y. Z., Ma, Y. J., Wu, X. G., Li, G. S., and He, C. Y.

Subjects
PARITY (Physics), CHIRALITY, CHIRAL stationary phases, PROPERTIES of nuclear particles, DISCRETE symmetries
Published
2016

90. Plasma Flow and Related Phenomena in Planetary Aeronomy

Author

Ma, Y.-J., primary, Altwegg, K., additional, Breus, T., additional, Combi, M. R., additional, Cravens, T. E., additional, Kallio, E., additional, Ledvina, S. A., additional, Luhmann, J. G., additional, Miller, S., additional, Nagy, A. F., additional, Ridley, A. J., additional, and Strobel, D. F., additional

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97. Comparisons of Cassini flybys of the Titan magnetospheric interaction with an MHD model : Evidence for organized behavior at high altitudes

Author

Ulusen, D., Luhmann, J. G., Ma, Y. J., Mandt, K. E., Waite, J. H., Dougherty, M. K., Wahlund, Jan-Erik, Russell, C. T., Cravens, T. E., Edberg, Niklas J. T., Ågren, Karin, Ulusen, D., Luhmann, J. G., Ma, Y. J., Mandt, K. E., Waite, J. H., Dougherty, M. K., Wahlund, Jan-Erik, Russell, C. T., Cravens, T. E., Edberg, Niklas J. T., and Ågren, Karin

Abstract

Recent papers suggest the significant variability of conditions in Saturn's magnetosphere at the orbit of Titan. Because of this variability, it was expected that models would generally have a difficult time regularly comparing to data from the Titan flybys. However, we find that in contrast to this expectation, it appears that there is underlying organization of the interaction features roughly above similar to 1800 km (1.7 Rt) altitude by the average external field due to Saturn's dipole moment. In this study, we analyze Cassini's plasma and magnetic field data collected at 9 Titan encounters during which the external field is close to the ideal southward direction and compare these observations to the results from a 2-fluid (1 ion, 1 electron) 7-species MHD model simulations obtained under noon SLT conditions. Our comparative analysis shows that under noon SLT conditions the Titan plasma interaction can be viewed in two layers: an outer layer between 6400 and 1800 km where interaction features observed in the magnetic field are in basic agreement with a purely southward external field interaction and an inner layer below 1800 km where the magnetic field measurements show strong variations and deviate from the model predictions. Thus the basic features inferred from the Voyager 1 flyby seem to be generally present above similar to 1800 km in spite of the ongoing external variations from SLT excursions, time variability and magnetospheric current systems as long as a significant southward external field component is present. At around similar to 1800 km kinetic effects (such as mass loading and heavy ion pickup) and below 1800 km ionospheric effects (such as drag of ionospheric plasma due to coupling with neutral winds and/or magnetic memory of Titan's ionosphere) complicate what is observed.

Published
2012
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98. Investigating magnetospheric interaction effects on Titan's ionosphere with the Cassini orbiter Ion Neutral Mass Spectrometer, Langmuir Probe and magnetometer observations during targeted flybys

Author

Luhmann, J. G., Ulusen, D., Ledvina, S. A., Mandt, K., Magee, B., Waite, J. H., Westlake, J., Cravens, T. E., Robertson, I., Edberg, Niklas, Ågren, Karin, Wahlund, Jan-Erik, Ma, Y. -J, Wei, H., Russell, C. T., Dougherty, M. K., Luhmann, J. G., Ulusen, D., Ledvina, S. A., Mandt, K., Magee, B., Waite, J. H., Westlake, J., Cravens, T. E., Robertson, I., Edberg, Niklas, Ågren, Karin, Wahlund, Jan-Erik, Ma, Y. -J, Wei, H., Russell, C. T., and Dougherty, M. K.

Abstract

In the similar to 6 years since the Cassini spacecraft went into orbit around Saturn in 2004, roughly a dozen Titan flybys have occurred for which the Ion Neutral Mass Spectrometer (INMS) measured that moon's ionospheric density and composition. For these, and for the majority of the similar to 60 close flybys probing to altitudes down to similar to 950 km, Langmuir Probe electron densities were also obtained. These were all complemented by Cassini magnetometer observations of the magnetic fields affected by the Titan plasma interaction. Titan's ionosphere was expected to differ from those of other unmagnetized planetary bodies because of significant contributions from particle impact due to its magnetospheric environment. However, previous analyses of these data clearly showed the dominance of the solar photon source, with the possible exception of the nightside. This paper describes the collected ionospheric data obtained in the period between Cassini's Saturn Orbit Insertion in 2004 and 2009, and examines some of their basic characteristics with the goal of searching for magnetospheric influences. These influences might include effects on the altitude profiles of impact ionization by magnetospheric particles at the Titan orbit location, or by locally produced pickup ions freshly created in Titan's upper atmosphere. The effects of forces on the ionosphere associated with both the draped and penetrating external magnetic fields might also be discernable. A number of challenges arise in such investigations given both the observed order of magnitude variations in the magnetospheric particle sources and the unsteadiness of the magnetospheric magnetic field and plasma flows at Titan's (similar to 20Rs (Saturn Radius)) orbit. Transterminator flow of ionospheric plasma from the dayside may also supply some of the nightside ionosphere, complicating determination of the magnetospheric contribution. Moreover, we are limited by the sparse sampling of the ionosphere during th

Published
2012
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99. The importance of thermal electron heating in Titan's ionosphere : Comparison with Cassini T34 flyby

Author

Ma, Y. J., Russell, C. T., Nagy, A. F., Toth, G., Dougherty, M. K., Wellbrock, A., Coates, A. J., Garnier, P., Wahlund, Jan-Erik, Cravens, T. E., Richard, M. S., Crary, F. J., Ma, Y. J., Russell, C. T., Nagy, A. F., Toth, G., Dougherty, M. K., Wellbrock, A., Coates, A. J., Garnier, P., Wahlund, Jan-Erik, Cravens, T. E., Richard, M. S., and Crary, F. J.

Abstract

We use a new magnetohydrodynamic (MHD) model to study the effects of thermal-electron heating in Titan's ionosphere. This model improves the previously used multispecies MHD model by solving both the electron and ion pressure equations instead of a single plasma pressure equation. This improvement enables a more accurate evaluation of ion and electron temperatures inside Titan's ionosphere. The model is first applied to an idealized case, and the results are compared in detail with those of the single-pressure MHD model to illustrate the effects of the improvement. Simulation results show that the dayside ionosphere thermal pressure is larger than the upstream pressure during normal conditions, when Titan is located in the dusk region; thus Saturn's magnetic field is shielded by the highly conducting ionosphere, similar to the interaction of Venus during solar maximum conditions. This model is also applied to a special flyby of Titan, the T34 flyby, which occurred near the dusk region. It is shown that better agreement with the magnetometer data can be achieved using the two-fluid MHD model with the inclusion of the effects of thermal electron heating. The model results clearly demonstrate the importance of thermal-electron heating in Titan's ionosphere.

Published
2011
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