scholarly journals Type-1 echoes from the mid-latitude E-Region ionosphere

1997 ◽  
Vol 15 (7) ◽  
pp. 908-917 ◽  
Author(s):  
C. Haldoupis ◽  
D. T. Farley ◽  
K. Schlegel
Keyword(s):  
Doppler Radar ◽  
Spectral Component ◽  
Equatorial Electrojet ◽  
Metallic Ions ◽  
Sporadic E Layers ◽  
E Region ◽  
Sporadic E ◽  
The Right

Abstract. This paper presents more data on the properties of type-1 irregularities in the nighttime mid-latitude E-region ionosphere. The measurements were made with a 50-MHz Doppler radar system operating in Crete, Greece. The type-1 echoes last from several seconds to a few minutes and are characterized by narrow Doppler spectra with peaks corresponding to wave phase velocities of 250–350 m/s. The average velocity of 285 m/s is about 20% lower than nominal E-region ion-acoustic speeds, probably because of the presence of heavy metallic ions in the sporadic-E-layers that appear to be associated with the mid-latitude plasma instabilities. Sometimes the type-1 echoes are combined with a broad spectrum of type-2 echoes; at other times they dominate the spectrum or may appear in the absence of any type-2 spectral component. We believe these echoes are due to the modified two-stream plasma instability driven by a polarization electric field that must be larger than 10 mV/m. This field is similar in nature to the equatorial electrojet polarization field and can arise when patchy nighttime sporadic-E-layers have the right geometry.

scholarly journals Plasma structures of 3-meter type 1 and type 2 irregularities in nighttime midlatitude sporadic E region

2002 ◽  
Vol 107 (A12) ◽  
pp. SIA 8-1-SIA 8-11 ◽  
Author(s):  
Yen-Hsyang Chu ◽  
Chien-Ya Wang
Keyword(s):  
E Region ◽  
Sporadic E

Intradural Extramedullary Lesions in Cervical Spine in Neurofibromatosis

2021 ◽  
pp. 22
Author(s):  
Rana Moshref
Keyword(s):  
Multidisciplinary Approach ◽  
Cervical Lesions ◽  
Cervical Mass ◽  
Gradual Onset ◽  
Autosomal Dominant Fashion ◽  
Intradural Extramedullary ◽  
The Right ◽  
Spastic Quadriparesis

Introduction: Neurofibromatosis (NF) is isolated into three diseases: NF type 1, type 2, and schwannoma. NF type 2 could be a disorder that's found roughly in 1/25,000–33,000 births with a mutation in gene 22q11.2, and it is passed through eras in an autosomal dominant fashion. Diagnosis is made with both clinical and radiological features. A few clinical features have been characterized in conclusion counting Manchester criteria. There is a scarce number of NF type 2 patients diagnosed with cervical lesions which are 25 in number. We report a case of an intradural extramedullary cervical lesion in a patient later diagnosed with NF type 2. Case Report: A 30-year-old male presenting with gradual onset and progressive course of spastic quadriparesis of six months’ duration was admitted through the emergency unit. MRI spine showed intradural extramedullary masses in the right side of C4 and left side of C6. The patient underwent cervical intradural excision of two masses under general anesthesia with neuromonitoring. The tumor was sent for histopathology and reported as NF type 2. Conclusion: NF is a common entity, but the diagnosis of cervical mass is judicious to avoid any complication in neurological function. It further needs a multidisciplinary approach and screening modalities.

Investigation on the role of E-F region coupling processes on the generation of nighttime MSTIDs: Case studies over northern Germany

2021 ◽  
Author(s):  
Mani Sivakandan ◽  
Jorge L Chau ◽  
Carlos Martinis ◽  
Yuichi Otsuka ◽  
Jens Mielich ◽  
...  
Keyword(s):  
Gps Tec ◽  
F Region ◽  
Perkins Instability ◽  
Sporadic E Layers ◽  
Spread F ◽  
E Region ◽  
Sporadic E ◽  
Low Latitude Ionosphere ◽  
Atmospheric Gravity

<p>Northwest to southeast phase fronts with southwestward moving features are commonly observed in the nighttime midlatitude ionosphere during the solstice months at low solar activity. These features are identified as nighttime MSTIDs (medium scale traveling ionospheric disturbances). Initially, they were considered to be a manifestation of neutral atmospheric gravity waves. Later on, investigations showed that the nighttime MSTIDs are electrified in nature and mostly confined to the mid and low latitude ionosphere. Although the overall characteristics of the nighttime MSTIDs are mostly well understood, the causative mechanisms are not well known. Perkins instability mechanism was believed to be the cause of nighttime MSTIDs, however, the growth rate of the instability is too small to explain the perturbations observed. Recently, model simulations and observational studies suggest that coupling between sporadic-E layers and other type of E-region instabilities, and the F region may be relevant to explain the generation of the MSTIDs.</p><p>In the present study simultaneous observation from OI 630 nm all-sky airglow imager, GPS-TEC, ionosonde and Meteor radars, are used to investigate the role of E and F region coupling on the generation of MSTIDs .Nighttime MSTIDs observed on three nights (14 March 2020, 23 March 2020 and 28 May 2020) in the OI 630 nm airglow images over Kuehlungsborn (54°07'N; 11°46'E, 53.79N  mag latitude), Germany, are presented. Simultaneous detrended GPS-TEC measurements also shows presence of MSTIDs on these nights. In addition, simultaneous ionosonde observations over Juliusruh (54°37.7'N 13°22.5'E) show spread-F in the ionograms as well as sporadic-E layer occurrence.  Furthermore, we also investigate the MLT region wind variations during these nights. The role of Es-layers and the interplay between the winds and Es-layers role on the generation of the MSTIDs will be discussed in detail in this presentation.</p><p> </p>

scholarly journals 50 MHz continuous wave interferometer observations of the unstable mid-latitude E-region ionosphere

2003 ◽  
Vol 21 (7) ◽  
pp. 1589-1600 ◽  
Author(s):  
C. Haldoupis ◽  
A. Bourdillon ◽  
A. Kamburelis ◽  
G. C. Hussey ◽  
J. A. Koehler
Keyword(s):  
Electric Fields ◽  
Continuous Wave ◽  
Isotropic Turbulence ◽  
Doppler Radar ◽  
Active Regions ◽  
Field Of View ◽  
Ionosphere Plasma ◽  
First Results ◽  
Sporadic E

Abstract. In this paper we describe the conversion of SESCAT (Sporadic-E SCATter experiment), a bistatic 50 MHz continuous wave (CW) Doppler radar located on the island of Crete, Greece, to a single (east-west) baseline interferometer. The first results show that SESCAT, which provides high quality Doppler spectra and excellent temporal resolution, has its measurement capabilities enhanced significantly when operated as an interferometer, as it can also study short-term dynamics of localized scattering regions within mid-latitude sporadic E-layers. The interferometric observations reveal that the aspect sensitive area viewed by the radar often contains a few zonally located backscatter regions, presumably blobs or patches of unstable metallic ion plasma, which drift across the radar field-of-view with the neutral wind. On average, these active regions of backscatter have mean zonal scales ranging from a few kilometers to several tens of kilometers and drift with westward speeds from ~ 20 m/s to 100 m/s, and occasionally up to 150 m/s. The cross-spectral analysis shows that mid-latitude type 1 echoes occur much more frequently than has been previously assumed and they originate in single and rather localized areas of elevated electric fields. On the other hand, typical bursts of type 2 echoes are often found to result from two adjacent regions in azimuth undergoing the same bulk motion westwards but producing scatter of opposite Doppler polarity, a fact that contradicts the notion of isotropic turbulence to which type 2 echoes are attributed. Finally, quasi-periodic (QP) echoes are observed simply to be due to sequential unstable plasma patches or blobs which traverse across the radar field-of-view, sometimes in a wave-like fashion.Key words. Ionosphere (ionospheric irregularities; mid-latitude ionosphere; plasma waves and instabilities)

scholarly journals Interhemispheric transport of metallic ions within ionospheric sporadic E layers by the lower thermospheric meridional circulation

2020 ◽  
Author(s):  
Bingkun Yu ◽  
Xianghui Xue ◽  
Christopher J. Scott ◽  
Jianfei Wu ◽  
Xinan Yue ◽  
...  
Keyword(s):  
Large Scale ◽  
Climate Model ◽  
Meridional Circulation ◽  
Strong Support ◽  
Metallic Ions ◽  
Meridional Transport ◽  
Summer Circulation ◽  
Sporadic E Layers ◽  
Sporadic E ◽  
Interhemispheric Transport

Abstract. Long-lived metallic ions in the Earth's atmosphere/ionosphere have been investigated for many decades. Although the seasonal variation in ionospheric sporadic E layers was first observed in the 1960s, the mechanism driving the variation remains a long-standing mystery. Here we report a study of ionospheric irregularities using scintillation data from COSMIC satellites and identify a large-scale horizontal transport of long-lived metallic ions, combined with the simulations of the Whole Atmosphere Community Climate Model with the chemistry of metals and ground-based observations from two meridional chains of stations from 1975–2016. We find that the lower thermospheric meridional circulation influences the meridional transport and seasonal variations of metallic ions within sporadic E layers. The winter-to-summer, meridional velocity of ions is estimated to vary between −1.08 and 7.45 m/s at altitudes of 107–118 km between 10°–60° N latitude. Our results not only provide strong support for the lower thermospheric meridional circulation predicted by a whole atmosphere chemistry-climate model, but also emphasise the influences of this winter-to-summer circulation on the large-scale interhemispheric transport of composition in the thermosphere/ionosphere.

scholarly journals Crista Terminalis, Musculi Pectinati, and Taenia Sagittalis: Anatomical Observations and Applied Significance

ISRN Anatomy ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-6
Author(s):  
Abu Ubaida Siddiqui ◽  
Syed Rehan Hafiz Daimi ◽  
Kusum Rajendra Gandhi ◽  
Abu Talha Siddiqui ◽  
Soumitra Trivedi ◽  
...  
Keyword(s):  
Right Atrium ◽  
Cardiac Conduction ◽  
Type B ◽  
Crista Terminalis ◽  
Type C ◽  
The Right ◽  
Complex Architecture ◽  
Complex Arrangement

Background. The complex architecture of the right atrium, crista terminalis (CT), and the musculi pectinati (MP) poses enormous challenges in electrophysiology and cardiac conduction. Few studies have been undertaken to substantiate the gross features of MP, in relation to the CT, but there is still scarcity of data regarding this. We tried to reinvestigate the gross arrangement of muscle bundles in the right atrium. Methods. Utilizing 151 human hearts and orientation of MP and its variations and relationship to the CT were investigated along with taenia sagittalis (TS). Patterns of MP were grouped in 6 categories and TS under three groups. Result. A plethora of variations were observed. Analysis of all the specimen revealed that 68 samples (45%) were of type 1 category and 27 (18%) fell into type 2 category. Prominent muscular columns were reported in 12 samples (8%). 83 samples (55%) presented with a single trunk of TS. Multiple trunks of TS were reported in 38 samples (25%). Conclusion. Samples with type 6 MP and type B/type C TS, which have a more complex arrangement of fibers, have a tendency to be damaged during cardiac catheterization. Nonetheless, the area as a whole is extremely significant considering the pragmatic application during various cardiac interventions.

scholarly journals Multistation digisonde observations of equatorial spread F in South America

2004 ◽  
Vol 22 (9) ◽  
pp. 3145-3153 ◽  
Author(s):  
B. W. Reinisch ◽  
M. Abdu ◽  
I. Batista ◽  
G. S. Sales ◽  
G. Khmyrov ◽  
...  
Keyword(s):  
South America ◽  
Field Line ◽  
Magnetic Equator ◽  
Simple Correlation ◽  
Equatorial Spread F ◽  
F Region ◽  
Sporadic E Layers ◽  
Spread F ◽  
E Region ◽  
Sporadic E

Abstract. Directional ionogram and F-region drift observations were conducted at seven digisonde stations in South America during the COPEX campaign from October to December 2002. Five stations in Brazil, one in Argentina, and one in Peru, monitored the ionosphere across the continent to study the onset and development of F-region density depletions that cause equatorial spread F (ESF). New ionosonde techniques quantitatively describe the prereversal uplifting of the F layer at the magnetic equator and the eastward motion of the depletions over the stations. Three of the Brazilian stations were located along a field line with a 350-km apex over the equator to investigate the relation of the occurrence of ESF and the presence of sporadic E-layers at the two E-region intersections of the field line. No simple correlation was found.

Analisis Kapasitas Galangan Kapal Ikan Untuk Memenuhi Rencana Pengadaan Kapal Ikan Hibah

2019 ◽  
Vol 13 (1) ◽  
pp. 25-36
Author(s):  
Agus Lubis Fitriansyah ◽  
Heri Supomo
Keyword(s):  
Fishing Vessel ◽  
Fishing Vessels ◽  
Score Method ◽  
The Government ◽  
The Right ◽  
Type 3 ◽  
Selection Of

The government through the Ministry of Marine and Fisheries offers assistance of fishing vessel to achieve fisheries production targets. This procurement plan must be supported by the ability and selection of the right shipyard. Beacuse the information of the capability and capacity of fiber shipyards in Indonesia is unclear, so the realization of the procurement of fishing vessel in previous years did not met the planned targets. The purpose of this study was to analyze shipyard capacity to meet the planned procurement of KKP fishing vessels grant in 2019. First classification of fishing vessels is based on the size of each GT, which is 5 GT (type 1), 5-10 GT (type 2), and 20-30 GT (type 3). The second is the minimum shipyard criteria for building fishing boats. Third, an assessment of the shipyard is based on the criteria that have been made. Fourth, shipyard selection was carried out on each WPPN-RI using the load score method. The fifth calculates the number of ships that can be built by the shipyard. The results of the shipyard assessment found that 43% of shipyards have the ability to build type 1 vessels, around 38% of shipyards have the ability to build type 2 vessels, and around 19% of shipyards have the ability to build type 3 vessels. is 1625 units / period. Referring to shipyard capacity, it can be said that the entire shipyard is able to fulfill the plan to procure assistance for KKP fishing vessels in the 2019 budget year.

scholarly journals EISCAT Svalbard radar observations of SPEAR-induced E- and F-region spectral enhancements in the polar cap ionosphere

2007 ◽  
Vol 25 (8) ◽  
pp. 1801-1814 ◽  
Author(s):  
R. S. Dhillon ◽  
T. R. Robinson ◽  
T. K. Yeoman
Keyword(s):  
High Power ◽  
Polar Cap ◽  
Incoherent Scatter ◽  
F Region ◽  
Sporadic E Layers ◽  
First Results ◽  
Plasma Line ◽  
E Region ◽  
Sporadic E ◽  
Overdense Plasma

Abstract. The Space Plasma Exploration by Active Radar (SPEAR) facility has successfully operated in the high-power heater and low-power radar modes and has returned its first results. The high-power results include observations of SPEAR-induced ion and plasma line spectral enhancements recorded by the EISCAT Svalbard UHF incoherent scatter radar system (ESR), which is collocated with SPEAR. These SPEAR-enhanced spectra possess features that are consistent with excitation of both the purely growing mode and the parametric decay instability. In this paper, we present observations of upper and lower E-region SPEAR-induced ion and plasma line enhancements, together with F-region spectral enhancements, which indicate excitation of both instabilities and which are consistent with previous theoretical treatments of instability excitation in sporadic E-layers. In agreement with previous observations, spectra from the lower E-region have the single-peaked form characteristic of collisional plasma. Our observations of the SPEAR-enhanced E-region spectra suggest the presence of variable drifting regions of patchy overdense plasma, which is a finding also consistent with previous results.

scholarly journals Sporadic <i>E</i> signatures revealed from multi-satellite radio occultation measurements

2010 ◽  
Vol 8 ◽  
pp. 225-230 ◽  
Author(s):  
C. Arras ◽  
C. Jacobi ◽  
J. Wickert ◽  
S. Heise ◽  
T. Schmidt
Keyword(s):  
Radio Occultation ◽  
Signal Amplitude ◽  
Global Scale ◽  
Data Sets ◽  
Data Set ◽  
Huge Data ◽  
Large Correlation ◽  
Sporadic E Layers ◽  
E Region ◽  
Sporadic E

Abstract. Radio occultation measurements performed by the satellites CHAMP, GRACE and FORMOSAT-3/COSMIC provide a huge data set for atmospheric and ionospheric investigations on a global scale. The data sets are used to extract information on sporadic E layers appearing in the lower ionospheric E region. This is done by analyzing signal amplitude variations of the GPS L1 signal. Sporadic E altitudes in northern midlatitudes found from radio occultation measurements are compared with ground-based ionosonde soundings. A large correlation of sporadic E altitudes from these two techniques is found.

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