Exospheric Na distributions along the Mercury orbit with the THEMIS telescope

2020 ◽  
Author(s):  
Anna Milillo ◽  
Valeria Mangano ◽  
Stefano Massetti ◽  
alessandro Mura ◽  
christina Plainaki ◽  
...  
Keyword(s):  
Local Time ◽  
Seasonal Variations ◽  
Column Density ◽  
True Anomaly ◽  
Solar Telescope ◽  
General Increase ◽  
The Past ◽  
Dust Disk ◽  
Peak Emission ◽  
Release Processes

<p>The variability of Na exosphere of Mercury shows time scales from less than one hour to seasonal variations. While the faster variations, accounting of about 10-20% of fluctuations are probably linked to the planet response to solar wind and IMF variability, the seasonal variations (up to about 80%) should be explained by a complex mechanisms involving different surface release processes, loss, source and migrations of the exospheric Na atoms. Eventually, a Na annual cycle can be identified. In the past, integrated disk emission from ground-based observations and equatorial density from MESSENGER have been analysed. In this study, for a better investigation of the exospheric Na features, we have studied the local time and latitudinal distributions of the exospheric Na column density as a function of the True Anomaly Angle (TAA) of Mercury by means of the extended dataset of images, collected from 2009 to 2013, by the THEMIS solar telescope. In particular, THEMIS images, in agreement with previous results, registered a strong general increase at aphelion and a dawn ward emission predominance with respect to dusk ward and subsolar region between 90° and 150° TAA. We find a predominance of subsolar column density along the rest of the Mercury orbit. Also an unexpected relation between Northward or Southward peak emission and both TAA and local time is evidenced by our analysis requiring further investigations. Possible relationship with distance from the dust disk or IMF polarity is being considering.</p>

Exospheric Na distributions along the Mercury orbit with the THEMIS telescope

2020 ◽  
Author(s):  
Anna Milillo ◽  
Valeria Mangano ◽  
Stefano Massetti ◽  
Alessandro Mura ◽  
Christina Plainaki ◽  
...  
Keyword(s):  
Local Time ◽  
Seasonal Variations ◽  
Column Density ◽  
True Anomaly ◽  
Data Sets ◽  
General Increase ◽  
The Past ◽  
Field Variability ◽  
Peak Emission ◽  
Release Processes

<p>The variability of Na exosphere of Mercury shows time scales from less than one hour to seasonal variations. While the faster variations, accounting of about 10-20% of fluctuations are probably linked to the planetary response to solar wind and Interplanetary Magnetic Field variability, the seasonal variations (up to about 80%) should be explained by complex mechanisms involving different surface release processes, loss, source and migrations of the exospheric Na atoms. Eventually, a Na annual cycle can be identified. In the past, ground-based observations and equatorial density from MESSENGER data have been analysed. In this study, for a better investigation of the exospheric Na features, we have studied the local time and latitudinal distributions of the exospheric Na column density as a function of the True Anomaly Angle (TAA) of Mercury by means of the extended dataset of images, collected from 2009 to 2013, by the THEMIS solar telescope. Our results show that the THEMIS images, in agreement with previous results, registered a strong general increase at aphelion and a dawn ward emission predominance with respect to dusk ward and subsolar region between 90° and 150° TAA. Unlikely other analyses, ours evidences a predominance of subsolar column density along the rest of Mercury’s orbit. An unexpected relationship between Northward or Southward peak emission and both TAA and local time is also evidenced by our analysis. This result seems to contradict previous results obtained from different data sets and it is not easily explained, thus it requires further investigations.</p>

Uneven Wear of Vehicle Tires

1993 ◽  
Vol 21 (4) ◽  
pp. 202-219 ◽  
Author(s):  
M. H. Walters
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Experimental Techniques ◽  
Lateral Stiffness ◽  
General Increase ◽  
Element Analysis ◽  
The Past ◽  
Uneven Wear

Abstract Advances in tire construction have led to major increases in tire life over the past twenty years, mainly by increasing the lateral stiffness and thus reducing slip during cornering. However, this general increase in tire life has tended to highlight the problem of uneven wear. In the present paper, three new experimental techniques are described which have been developed to study treadwear distributions. These techniques are evaluated and their results compared with a finite element analysis. Taken together, they indicate some of the causes of uneven wear and may be used to identify tire design and service features which contribute to uneven wear.

Impact of dust and sand storms on the aviation operation and assessment of conditions for their occurrence at aerodromes in European Russia

2020 ◽  
Vol 4 ◽  
pp. 78-95
Author(s):  
A.R. Ivanova ◽  
◽  
E.N. Skriptunova ◽  
N.I. Komasko ◽  
A.A. Zavialova ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Dust Storms ◽  
European Russia ◽  
Air Transport ◽  
Review Of Literature ◽  
Dust Transport ◽  
Air Masses ◽  
The Past ◽  
Sand Storm ◽  
The Impact

A review of literature on the impact of dust and sand storms on the air transport operation is presented. Observational data on dust storms at the aerodromes of European Russia for the period of 2001-2019 are analyzed. The seasonal variations in dust transport episodes at aerodromes and its relationship with visibility changes are discussed. The characteristics of dusty air masses and advection are given. It is concluded that the frequency of dust transfer episodes for the aerodromes under study has decreased over the past five years, except for Gumrak aerodrome (Volgograd). Keywords: dust storm, sand storm, aviation, visibility, seasonal variations, aerodrome оf European Russia

scholarly journals Mid-Pleistocene transition in glacial cycles explained by declining CO2and regolith removal

2019 ◽  
Vol 5 (4) ◽  
pp. eaav7337 ◽  
Author(s):  
M. Willeit ◽  
A. Ganopolski ◽  
R. Calov ◽  
V. Brovkin
Keyword(s):  
Climate Variability ◽  
Carbon Cycle ◽  
Northern Hemisphere ◽  
Seasonal Variations ◽  
Ice Sheets ◽  
Glacial Cycles ◽  
Solar Insolation ◽  
The Past ◽  
Transient Simulations

Variations in Earth’s orbit pace the glacial-interglacial cycles of the Quaternary, but the mechanisms that transform regional and seasonal variations in solar insolation into glacial-interglacial cycles are still elusive. Here, we present transient simulations of coevolution of climate, ice sheets, and carbon cycle over the past 3 million years. We show that a gradual lowering of atmospheric CO2and regolith removal are essential to reproduce the evolution of climate variability over the Quaternary. The long-term CO2decrease leads to the initiation of Northern Hemisphere glaciation and an increase in the amplitude of glacial-interglacial variations, while the combined effect of CO2decline and regolith removal controls the timing of the transition from a 41,000- to 100,000-year world. Our results suggest that the current CO2concentration is unprecedented over the past 3 million years and that global temperature never exceeded the preindustrial value by more than 2°C during the Quaternary.

Use of a National Library: A Survey of Readers in the Humanities and Social Sciences Reading Rooms of the British Library

1992 ◽  
Vol 4 (3) ◽  
pp. 197-211 ◽  
Author(s):  
Graham Cranfield ◽  
Joe Hellowell
Keyword(s):  
Social Sciences ◽  
Seasonal Variations ◽  
Questionnaire Survey ◽  
Survey Methods ◽  
Academic Staff ◽  
British Library ◽  
National Library ◽  
The Past ◽  
The Uk ◽  
National Libraries

A questionnaire survey was carried out in the humanities reading rooms of the British Library one day each month from September 1990 to August 1991 with the aim of providing information of help in planning services, particularly at the new building in St Pancras. Readers were asked about their occupations, nationalities, the location of the academic institutions to which they were affiliated, the reasons for and frequency of their visits etc. 65% of readers were academic staff or students, and 33% lived outside the UK; 31% said they had visited the library over 50 times in the past year. The results were compared, where appropriate, with earlier surveys in 1968 and 1977. These comparisons highlighted significant seasonal variations in patterns of usage. It was not possible to compare the results with those from surveys by other national libraries, because of widely differing survey methods and content of reports.

Characteristics of Non-Methane Hydrocarbons in the Atmosphere of Guangzhou

2011 ◽  
Vol 66-68 ◽  
pp. 59-64
Author(s):  
Long Feng Li ◽  
Xin Ming Wang
Keyword(s):  
Local Time ◽  
Aromatic Hydrocarbons ◽  
Seasonal Variations ◽  
Urban Site ◽  
Diurnal Pattern ◽  
Air Samples ◽  
Mixing Ratios

From March to December 2005 NMHCs were measured in an urban site in Guangzhou. Air samples were collected with canister and analyzed for HMHCs by GC-MSD/FID after cryogenic pre-concentration. Mixing ratios of Alkanes accounted for over 43% in total NMHCs in each month while the shares of aromatic hydrocarbons were 19-28%. In average ethyne was the most abundant compound (5.46 ppbv), followed by propane (4.49 ppbv) and toluene (4.19 ppbv). Seasonal variations of most anthropogenic hydrocarbons revealed higher mixing ratios in autumn-winter than in spring-summer. Isoprene, on the contrary, exhibited the the highest levels in summer and the lowest in spring. Anthropogenic NMHCs typically showed a first peak around 8:00 local time in morning and 20:00 local time in the evening, while isoprene revealed a different bimodal diurnal pattern.

scholarly journals Exploring the benefits of minimobility in the urban context: The case of central Stockholm

2021 ◽  
Vol 14 (1) ◽  
pp. 1019-1037
Author(s):  
William Riggs ◽  
Shivani Shukla
Keyword(s):  
Rapid Growth ◽  
Environmental Benefits ◽  
Urban Context ◽  
General Increase ◽  
Urban Transit ◽  
Emergent Technologies ◽  
Advantages And Disadvantages ◽  
The Past ◽  
Logistics Services ◽  
City Network

Over the past decade, there has been rapid growth in the development and infusion of new and disruptive transportation. Some of the pivotal emergent technologies range from micro-mobility and bikeshare to ridesourcing that is set to utilize automated vehicles. This paper introduces and defines minimobility that falls between a regular ridesourcing/taxi option and micromobility, and also providing critical logistics services during the era of COVID-19. In Central Stockholm the platform has provided a safe and environmentally friendly mode choice that occupies limited space and efficiently serves on the congested city network. We explore potential economic and environmental benefits of minimobility, discussing the advantages and disadvantages of deploying such a service. While we demonstrate a general increase in VMT, consistent with other work showing increased travel from new mobility, due to the electric platform this increase in customer access to mobility results in minimal GHG impacts. is informs how planners and engineers can explore minimobility platforms not only as reduced emissions solutions to urban transit issues but as tools to increase total mobility particularly for the most vulnerable.

scholarly journals Low Temperate Zone Sporadic-E: Seasonal and Diurnal Variations at Rarotonga

1986 ◽  
Vol 39 (3) ◽  
pp. 401
Author(s):  
WJ Baggaley
Keyword(s):  
Large Deviations ◽  
Local Time ◽  
Seasonal Variations ◽  
Diurnal Variations ◽  
Formation Processes ◽  
Seasonal Characteristics ◽  
The Pacific ◽  
Seasonal And Diurnal Variations ◽  
Sporadic E ◽  
Diurnal Period

The seasonal variations of strong E s occurrence as a function of diurnal period have been obtained for the Pacific station of Rarotonga (21 0 .2 S). The seasonal characteristics depend markedly on local time with afternoon Es activity showing large deviations-equinoxial enhancements and summer peaks occurring before solstice-from those expected from the formation processes currently understood.

scholarly journals Measurements of atmospheric ethene by solar absorption FTIR spectrometry

2018 ◽  
Vol 18 (7) ◽  
pp. 5075-5088 ◽  
Author(s):  
Geoffrey C. Toon ◽  
Jean-Francois L. Blavier ◽  
Keeyoon Sung
Keyword(s):  
New Mexico ◽  
High Resolution ◽  
Column Density ◽  
Vehicle Exhaust ◽  
Solar Absorption ◽  
Jet Propulsion ◽  
The Past ◽  
Ftir Spectrometry ◽  
Clean Air ◽  
Urban Sites

Abstract. Atmospheric ethene (C2H4; ethylene) amounts have been retrieved from high-resolution solar absorption spectra measured by the Jet Propulsion Laboratory (JPL) MkIV interferometer. Data recorded from 1985 to 2016 from a dozen ground-based sites have been analyzed, mostly between 30 and 67∘ N. At clean-air sites such as Alaska, Sweden, New Mexico, or the mountains of California, the ethene columns were always less than 1 × 1015 molec cm−2 and therefore undetectable. In urban sites such as JPL, California, ethene was measurable with column amounts of 20 × 1015 molec cm−2 observed in the 1990s. Despite the increasing population and traffic in southern California, a factor 3 decrease in ethene column density is observed over JPL over the past 25 years, accompanied by a decrease in CO. This is likely due to southern California's increasingly stringent vehicle exhaust regulations and tighter enforcement over this period.

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