Analyzed the use of the term «irregularity changes of technical condition of element’s vehicle» to certain stages of the operational cycle. Specific examples and quantitative assessment of ...irregularity changes the structural parameters for the elements, working independently, and interacting in the units or systems of the vehicle.
Based on observations of the Jicamarca Unattended Long‐term investigations of the Ionosphere and Atmosphere (JULIA) radar, we perform statistical analysis on the occurrence of 3‐m‐scale E‐region ...irregularities and F‐region irregularities (FRI) in Jicamarca region of South America. The results show that there is a negative correlation between the occurrence rates of equatorial irregularities in E‐ and F‐region. When the equatorial spread F appears, the occurrence rate of irregularities in E‐layer decreases. By analyzing the ion zonal drift velocity detected by JULIA radar, it is proposed that the vertically polarized electric field in the bottom F‐layer could extend downward to E‐layer when FRI appears, leading to the weakening or even reversal of E‐layer electric field. As a result, the electron vertical drift velocity in the E‐layer decreases so as to suppress the growth rate of two‐stream instability, which cause a weakening or even disappearance of equatorial irregularities in E‐region.
Plain Language Summary
For the equatorial region, the previous researches on E‐ and F‐region coupling are mainly focused on the relationship between valley region irregularities and F‐region irregularities (FRI). Up to now, the connection between the E‐region irregularities (ERI) existing in Equatorial Electrojet and FRI at night in the equatorial region has not been revealed and needs to be further studied and supplemented. Based on observations of the Jicamarca Unattended Long‐term investigations of the Ionosphere and Atmosphere radar from 2018 to 2022, we conduct a statistical study on the occurrence rate of 3 m‐scale irregularities in the E‐ and F‐layer at Jicamarca at night. The results show that there is a negative correlation between the occurrence rates of ERI and FRI. Based on the observation of ion drift, the vertical polarized electric field in the FRI is suggested to suppress the ERI.
Key Points
Occurrence distributions of E‐region irregularities (ERI) and F‐region irregularities (FRI) in the equatorial ionosphere are obtained
The occurrence rates of equatorial irregularities in E‐region and F‐region is negatively correlated
The vertical polarized electric field in the FRI is suggested to suppress the ERI in the equatorial ionosphere
•We reviewed the state of art of the aerodynamics of nominally circular cylinders.•We consider only experimental results.•Deviations are classified into cylinder and flow irregularities.•Cylinder ...irregularities are classified in surface, section and spanwise irregularities.
Fluid-dynamic loads have a great influence on the design of many Civil Engineering structures. In particular, circular sections are widely used in constructions, yet when it comes to aero- or hydro-dynamics simple geometry brings a complex behavior, as the features of flow separation strongly depend on Reynolds number. This has triggered a remarkable research effort towards the understanding of the aerodynamic behavior of circular cylinders. Indeed, circular cylinders used in Engineering applications are seldom perfect ones. In many cases, it has been observed that imperfections affect aerodynamics to a large extent. For this reason, a considerable effort has also been devoted to the understanding of how aerodynamics is modified by imperfections. This paper contains a review of existing literature on experimental results of interest for Civil Engineering applications on the aerodynamics of cylinders, whose geometry deviates from that of a perfect circular cylinder. Such deviations are classified into cylinder and flow irregularities, and the former are further subdivided into surface, section and spanwise irregularities. The need for further research is pointed out at the end of the paper.
This research is a development work on the total edge irregularity strength of series-parallel graphs. The total edge irregularity strength of series composition of isomorphic uniform theta graphs ...has been determined. But the total edge irregularity strength of uniform theta graphs itself is an open problem. In this paper, we determine the total edge irregularity strength of uniform theta graphs with one variable is fixed. In the end we determine the total edge irregularity strength of uniform theta graphs in general.
Amplitudes of two‐stream irregularities and equatorial electrojet (EEJ) current are known to peak around the same altitude. Sounding rocket‐borne magnetometer experiments have consistently shown that ...the EEJ current density maximizes around 105‐km altitude whereas the theoretical models predict the EEJ peak around 100 km. One of the propositions to bridge this difference in the altitude has been based on the inclusion of small‐scale turbulence (wavelength of <100 m) with the large‐scale dynamics (kilometer size). This proposition is examined based on in situ measurements of E region electron density and plasma irregularities (two‐stream and gradient‐drift irregularities) obtained at different times of the day and night. These measurements were obtained based on sounding rocket flight experiments conducted from Thumba Equatorial Rocket Launching Station (8.54° N, 76.86° E), a facility in the vicinity of the dip equator. Whenever two‐stream irregularities are present, the minimum electrojet current density is estimated based on the threshold velocity required for generation of these plasma irregularities. This method provides estimates of nighttime E region current also, which is difficult to measure. It is found that amplitudes of both two‐stream irregularities and the estimated EEJ current peak around 105‐km altitude irrespective of the presence or absence of the gradient‐drift irregularities at the base of electrojet (95‐ to 100‐km altitude).
Key Points
Equatorial E region plasma density and irregularities in different scale sizes have been obtained based on sounding rocket experiments
Two‐stream irregularities and EEJ peak around 105 km irrespective of the presence or absence of gradient‐drift irregularities at base of EEJ
Dip‐equatorial E region current densities are estimated during a daytime counter electrojet event and at nighttime
In the high-speed railway industry, the pantograph-catenary system is responsible to provide continuous electric energy for the high-speed train. The pantograph-catenary system suffers multiple ...impacts from the complex work environment. The vehicle-track excitation is one of the normal disturbances to the pantograph-catenary interaction. Previous studies only consider the vertical effect of the vehicle-track vibration on the pantograph-catenary interaction. To address this deficiency, both of the pantograph-catenary and vehicle-track models are constructed in this paper. The validations of both models are verified by the experimental test and the world benchmark, respectively. The pantograph base follows the translations and rotations of the car-body caused by random rail irregularities. In combination with a spatial contact model between the contact wire and the pantograph strip, the spatial vibration of the carbody can be fully considered in the pantograph-catenary interaction. The statistical analysis, stochastic analysis and frequency analysis are performed to make sense of the effect of the random track irregularities on the pantograph-catenary interaction. The deviation of the contact point away from the strip centre caused by the carbody vibration is also analysed. The results show that the reliability of the pantograph-catenary system shows a continuous decrease in the degradation of rail quality. The carbody vibration may cause the de-wirement of the pantograph in extreme conditions. Finally, an application example is given to evaluate the dynamic performance of the pantograph-catenary system running on the China high-speed network with realistic rail irregularities.
Long‐lived nonspecular meteor echoes backscattered from meteor trail nonfield‐aligned irregularities (NFAIs) were observed sporadically at high latitudes. In this study, we employ the observations by ...the all‐sky radar of Meteor and ionospheric Irregularity Observation System (MIOS) at Ledong (18.4°N, 109°E) in October 2018, January, April, and July 2019, to investigate the occurrences of meteor trail NFAIs at low latitudes. A deep learning method was developed to identify long‐lived meteor echo events with durations of more than 5 s. The long‐lived echo events with triangular shape (a typical feature of nonspecular echo) in radar range‐time intensity maps were manually distinguished from those with nontriangular shape. Based on the cutoff magnetic aspect angle 12° of nonspecular meteor echoes from field‐aligned irregularities (FAIs), the local time and altitude dependences of meteor NFAIs producing long‐lived nonspecular echoes are investigated. A total of 846 meteor events due to the backscatters of NFAIs were observed. These events peak around the morning hours, with the beginning (end) altitudes up to (down to) 120 km (∼80 km). Their mean heights are about 2–6 km higher than specular meteor echoes. The occurrence of NFAI echoes peaks on certain days that is likely associated with meteor showers. The ratio of the observed NFAI echo to specular echo events is, on average, less than 1‰. Possible factors responsible for the NFAIs at low latitudes are discussed based on the current understanding of meteor dust trail.
Key Points
The statistical features of triangular‐shaped nonfield‐aligned meteor plasma irregularity (NFAI) echoes at low latitudes were first investigated
The NFAI echoes occur in all parts of the sky, with the beginning and end heights ranging 90–120 km and 80–100 km, respectively
The ratio of the observed NFAI echo to specular echo events at low latitudes is very low, less than 1‰ on average
The effect of eastward zonal wind speed (EZWS) on vertical drift velocity (E × Bdrift) that mainly controls the equatorial ionospheric irregularities has been explained theoretically and through ...numerical models. However, its effect on the seasonal and longitudinal variations of E × B and the accompanying irregularities has not yet been investigated experimentally due to lack of F‐layer wind speed measurements. Observations of EZWS from GOCE and ion density and E × B from C/NOFS satellites for years 2011 and 2012 during quite times are used in this study. Monthly and longitudinal variations of the irregularity occurrence, E × B, and EZWS show similar patterns. We find that at most 50.85% of longitudinal variations of E × B can be explained by the longitudinal variability of EZWS only. When the EZWS exceeds 150 m/s, the longitudinal variation of EZWS, geomagnetic field strength, and Pedersen conductivity explain 56.40–69.20% of the longitudinal variation of E × B. In Atlantic, Africa, and Indian sectors, from 42.63% to 79.80% of the monthly variations of the E × B can be explained by the monthly variations of EZWS only. It is found also that EZWS and E × B may be linearly correlated during fall equinox and December solstice. The peak occurrence of irregularity in the Atlantic sector during November and December is due to the combined effect of large wind speed, solar terminator‐geomagnetic field alignment, and small geomagnetic field strength and Pedersen conductivity. Moreover, during June solstices, small EZWS corresponds to vertically downward E × B, which suggests that other factors dominate the E × B drift rather than the EZWS during these periods.
Key Points
Zonal neutral wind controls more the seasonal variations of E × B drift than the longitudinal variations of E × B drift
At most 50.85% of the longitudinal variations of E × B drift are accounted for by the eastward zonal neutral wind speed only
Zonal neutral wind speed and E × B drift may be linearly correlated during fall equinox and December solstice
We use multiple instruments data to investigate the behavior of the equatorial and low‐latitude ionosphere during the geomagnetically active and quiet period of November 1–6, 2021. In this context, ...total electron content (TEC) data obtained from the Global Positioning System (GPS) receivers in the equatorial and low‐latitude regions of Asia, Africa, and America are used to assess variations in plasma density during the storm. The storm‐time ionization levels were found to vary significantly in the crests of the Equatorial Ionization Anomaly (EIA) region over the 3 longitudes. The Rate of Change TEC Index (ROTI) derived from GPS receiver measurements, is used to study the equatorial/low‐latitude ionospheric plasma irregularities at various longitudes under geomagnetically quiet and disturbed conditions. Observations showed longitudinal variations in the ionospheric irregularities under both quiet and disturbed conditions. Some days exhibit a decrease in the strength of the midnight plasma irregularities toward the East, that is, the irregularities are more pronounced in West America, less common in East America, and almost non‐existent in Africa and Asia. Our investigations show this storm prevented the occurrence of plasma irregularities at the equatorial/low‐latitude region in the American sector during the night following the main phase. In general, no significant storm effects were observed at the target locations in Africa and Asia. The existence of westward Prompt Penetration Electric Field (PPEF) and the Equatorial Electrojet (EEJ) during the main phase, from midnight to noon, is clearly related with the constriction of plasma diffusion and the consequent suppression of plasma irregularities. Thus, the longitudinal dependence for the generation of midnight plasma irregularities during this storm is mainly influenced by local time occurrence of maximum ring current, and the ionospheric electric fields.
Key Points
On certain days, the midnight plasma irregularities are most pronounced in America, and almost absent in Africa and Asia
Under geomagnetically active conditions, midnight plasma irregularities inhibited in the American sector during the main phase of storm
Physical factors such as time of maximum ring current and ionospheric electric fields are responsible for this longitudinal variability
The abundant observations and research established a detailed category of the terrestrial ionospheric irregularities, which significantly advanced our understanding of how the Earth system's ...complicated physical and chemical process generates the intermediate‐scale structures of the charged particles. Motivated by a future attempt at categorizing the Martian ionospheric irregularity, this study designs a method for naive classification of the plasma density depletion, enhancement, and oscillation based on the in situ measurements of the Martian ionosphere. The technique consists of several procedures: trend estimation, detrending and candidate extraction, and parameterization. The classification is achieved through a machine‐learning‐like process using some testing artificial density profiles. A preliminary credence test shows a good performance in separating the terrestrial low‐latitude Equatorial Plasma bubble (depletion) and mid‐latitude Median‐scale Traveling Ionospheric Disturbance (oscillation). Another detection experiment of the Martian plasma depletion events (collected by Basuvaraj et al. (2022a, https://doi.org/10.1029/2022je007302)) showed a recall rate (i.e., true positive) of 38% but with a high precision of 67.8%. Therefore, we believe the proposed method could convincingly extract different Martian ionospheric irregularities and help uncover the climatological characteristics in the future.
Plain Language Summary
Ionospheric irregularities refer to the inhomogeneous distribution of the charged particles in the ionosphere, which would affect radio wave transmission and thus pose threats to tremendous human‐made assets deployed in terrestrial outer space and on other planets such as Mars. Unlike the terrestrial ionospheric irregularities, whose categories and physical mechanisms are well‐understood, the Martian counterparts are still in poor understanding. Previous studies have indicated the diversity, but the category has yet to be built. The large data set provided by the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission allows a more detailed investigation of the Martian ionospheric irregularities. Therefore, an automatic method to extract the ionospheric density enhancement, depletion, and oscillation would be a first step to figuring out the exact types of the Martian ionospheric irregularities, thus helping to extend our knowledge of how the finer ionospheric structures are formed backgrounded by the region crustal magnetic field other than the global dipole field.
Key Points
A modified rolling‐barrel algorithm extracts the candidate irregularities
Classification of the candidates into depletion, enhancement, and oscillation is achieved through a few parameterization processes
Initial testing shows good performance on the Martian and terrestrial ionospheric irregularities
PDF
