Experimental estimates of electron density variations at the reflection height of VLF signals

1987 ◽  
Vol 49 (2) ◽  
pp. 129-133 ◽  
Author(s):  
Olga I. Pintado ◽  
Sandro M. Radicella ◽  
Patricia M. Fernández
Keyword(s):  
Electron Density ◽  
Reflection Height

scholarly journals Classification of X-ray solar flares regarding their effects on the lower ionosphere electron density profile

2008 ◽  
Vol 26 (7) ◽  
pp. 1731-1740 ◽  
Author(s):  
D. P. Grubor ◽  
D. M. Šulić ◽  
V. Žigman
Keyword(s):  
Electron Density ◽  
Solar Flares ◽  
Low Frequency ◽  
Lower Ionosphere ◽  
Electron Density Profile ◽  
Height Range ◽  
X Ray ◽  
Reflection Height ◽  
Single Trace

Abstract. The classification of X-ray solar flares is performed regarding their effects on the Very Low Frequency (VLF) wave propagation along the Earth-ionosphere waveguide. The changes in propagation are detected from an observed VLF signal phase and amplitude perturbations, taking place during X-ray solar flares. All flare effects chosen for the analysis are recorded by the Absolute Phase and Amplitude Logger (AbsPal), during the summer months of 2004–2007, on the single trace, Skelton (54.72 N, 2.88 W) to Belgrade (44.85 N, 20.38 E) with a distance along the Great Circle Path (GCP) D≈2000 km in length. The observed VLF amplitude and phase perturbations are simulated by the computer program Long-Wavelength Propagation Capability (LWPC), using Wait's model of the lower ionosphere, as determined by two parameters: the sharpness (β in 1/km) and reflection height (H' in km). By varying the values of β and H' so as to match the observed amplitude and phase perturbations, the variation of the D-region electron density height profile Ne(z) was reconstructed, throughout flare duration. The procedure is illustrated as applied to a series of flares, from class C to M5 (5×10−5 W/m2 at 0.1–0.8 nm), each giving rise to a different time development of signal perturbation. The corresponding change in electron density from the unperturbed value at the unperturbed reflection height, i.e. Ne(74 km)=2.16×108 m−3 to the value induced by an M5 class flare, up to Ne(74 km)=4×1010 m−3 is obtained. The β parameter is found to range from 0.30–0.49 1/km and the reflection height H' to vary from 74–63 km. The changes in Ne(z) during the flares, within height range z=60 to 90 km are determined, as well.

scholarly journals Simulation of Gravity Wave D-region disturbance and its effect on the LWPC simulated VLF signal

2021 ◽  
Author(s):  
Abdellatif Benchafaa ◽  
Samir Nait Amor ◽  
Ghazali Mebarki
Keyword(s):  
Gravity Wave ◽  
Electron Density ◽  
Gravity Waves ◽  
Low Frequency ◽  
Ionization Rate ◽  
Neutral Atmosphere ◽  
Long Wave ◽  
Reflection Height ◽  
D Region ◽  
Atmosphere Density

Abstract. In this work we show the result of the numerical simulation of the gravity waves (GWs) D region disturbance. Effectively, using the Glukhov-Pasko-Inan (GPI) model of the electron density in the D region we were figured out the response of the electron density due to gravity wave neutral atmosphere oscillation. As a consequence to the D region disturbance, the electron density sometimes increases when the neutral atmosphere density decreases and vice versa. This behavior was interpreted by the decreases or increases of ionization rate by chemical loss process. In a second simulation work, we used the Long Wave Propagation Capability (LWPC) code to simulate the Very Low Frequency (VLF) signal when the gravity wave disturbance crossed the VLF path. The effect of the disturbance is to decrease the VLF signal reflection height below the ambient altitude (87 km) when the electron density increases. On the other hand and when the electron density drops, the VLF reflection altitude increased higher than 87 km.

A theoretical study of diurnal shift in reflection height of VLF waves using IRI electron density model

2012 ◽  
Vol 86 (11) ◽  
pp. 947-950 ◽  
Author(s):  
T. Madhavi Latha ◽  
P. Peddi Naidu ◽  
D. N. Madhusudhana Rao ◽  
M. Indira Devi
Keyword(s):  
Electron Density ◽  
Theoretical Study ◽  
Density Model ◽  
Reflection Height ◽  
Vlf Waves

scholarly journals Influences of the state of ionospheric background on ionospheric heating effects

2014 ◽  
Vol 56 (5) ◽  
Author(s):  
Shuji Hao ◽  
Li Qingliang ◽  
Che haiqin ◽  
Yang Jutao ◽  
Yan Yubo ◽  
...  
Keyword(s):  
Density Gradient ◽  
Electron Density ◽  
Large Scale ◽  
Ionospheric Heating ◽  
Adverse Conditions ◽  
F Region ◽  
Heating Effects ◽  
Reflection Height ◽  
Electron Density Gradient ◽  
Radiative Power

According to the well-performed ionospheric heating experiments at Arecibo in the low latitudes as well as at Tromsø in the high latitudes, the large-scale modification effects are simulated under an assumption of equivalent conditions, i.e., with the same effective radiative power and the same ratio of the heating frequency fHF to the critical frequency of ionospheric F region foF2. The findings are extensively exploited to verify the validation of our model by comparison to the experimental results. Further, a detailed study is carried out on the influences of the background electron density gradient as well as the ratio of fHF to foF2 on heating effects. Conclusions are drawn as follows: under certain conditions, a smaller electron density gradient of background ionospheric F region leads to a better ionospheric heating effect; during over-dense heating, the heating effects are enhanced if the ratio of fHF to foF2 increases, which is slightly limited by the resultant elevation of the reflection height. However, there might be a better ratio range with small values of the ratio of fHF to foF2, e.g., [0.5, 0.7] in the current study. Finally, we analyzed how to select heating parameters efficiently under adverse conditions so to obtain relatively effective results.

scholarly journals Upper atmospheric remote sensing using ELF – VLF lightning generated tweek and whistler sferics

2016 ◽  
Vol 34 (1) ◽  
pp. 12
Author(s):  
Amol Kishore ◽  
Anil Deo ◽  
Sushil Kumar
Keyword(s):  
Magnetic Field ◽  
Remote Sensing ◽  
Standard Deviation ◽  
Harmonic Analysis ◽  
Electron Density ◽  
Pacific Region ◽  
Low Latitude ◽  
Atmospheric Remote Sensing ◽  
Reflection Height ◽  
D Region

Tweek and whistler atmospherics (sferics) recorded at a low latitude station, Suva (18.2oS, 178.3oE, geomag. lat. 22.2oS, L = 1.17) Fiji, in the South Pacific region, during September 2003–July 2004 and March–December 2006 were analyzed to probe the nighttime D-region ionosphere and plasmasphere. From the first harmonic analysis of the selected 1063 tweeks, the path integrated ionospheric reflection height was estimated mostly between 75–97 km with median and standard deviation of 83.6 and 4.1 km, respectively. The path integrated mean electron density was estimated to vary from 24.4–31.5 cm–3 over the reflection heights. The whistler recorded on 20 September 2006, a magnetically quite day with maximum three hourly Kp value of 2o, most likely propagated in the ducted mode to this station. The whistler spectrum was used to calculate the equatorial magnetic field and the equatorial electron density at L = 1.3 which are in agreement with low latitude whistler observations.

White-Light Coronal Structures: Streamers and CMEs

1994 ◽  
Vol 144 ◽  
pp. 82
Author(s):  
E. Hildner
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
White Light ◽  
Coronal Mass Ejections ◽  
X Rays ◽  
Solar Cycles ◽  
Temperature Function ◽  
X Ray ◽  
Eclipse Observations ◽  
Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

Glycogen in guinea pig neutrophils: Ultrastructural study of neutrophils at the intradermal site of BCG injection

1983 ◽  
Vol 41 ◽  
pp. 726-727
Author(s):  
Corazon D. Bucana
Keyword(s):  
Bone Marrow ◽  
Guinea Pig ◽  
Electron Density ◽  
Peritoneal Cavity ◽  
Ultrastructural Study ◽  
Guinea Pigs ◽  
Random Distribution ◽  
Glycogen Content ◽  
Polymorphonuclear Neutrophils ◽  
Ultrastructural Studies

In the circulating blood of man and guinea pigs, glycogen occurs primarily in polymorphonuclear neutrophils and platelets. The amount of glycogen in neutrophils increases with time after the cells leave the bone marrow, and the distribution of glycogen in neutrophils changes from an apparently random distribution to large clumps when these cells move out of the circulation to the site of inflammation in the peritoneal cavity. The objective of this study was to further investigate changes in glycogen content and distribution in neutrophils. I chose an intradermal site because it allows study of neutrophils at various stages of extravasation.Initially, osmium ferrocyanide and osmium ferricyanide were used to fix glycogen in the neutrophils for ultrastructural studies. My findings confirmed previous reports that showed that glycogen is well preserved by both these fixatives and that osmium ferricyanide protects glycogen from solubilization by uranyl acetate.I found that osmium ferrocyanide similarly protected glycogen. My studies showed, however, that the electron density of mitochondria and other cytoplasmic organelles was lower in samples fixed with osmium ferrocyanide than in samples fixed with osmium ferricyanide.

Application of ruthenium red/osmium tetroxide to bacteria, plant and animal tissue

1986 ◽  
Vol 44 ◽  
pp. 54-55
Author(s):  
R. L. Grayson ◽  
N. A. Rechcigl
Keyword(s):  
Electron Microscopy ◽  
Electron Density ◽  
Osmium Tetroxide ◽  
Biological Materials ◽  
Ruthenium Red ◽  
Animal Tissue

Ruthenium red (RR), an inorganic dye was found to be useful in electron microscopy where it can combine with osmium tetroxide (OsO4) to form a complex with attraction toward anionic substances. Although Martinez-Palomo et al. (1969) were one of the first investigators to use RR together with OsO4, our computor search has shown few applications of this combination in the intervening years. The purpose of this paper is to report the results of our investigations utilizing the RR/OsO4 combination to add electron density to various biological materials. The possible mechanisms by which this may come about has been well reviewed by previous investigators (1,3a,3b,4).

A study on α-RuCl3 crystal structure by scanning tunneling microscopy

1989 ◽  
Vol 47 ◽  
pp. 30-31
Author(s):  
H.-J. Cantow ◽  
H. Hillebrecht ◽  
S. Magonov ◽  
H. W. Rotter ◽  
G. Thiele
Keyword(s):  
Crystal Structure ◽  
Density Distribution ◽  
Scanning Tunneling Microscopy ◽  
Electron Density ◽  
Structure Determination ◽  
Electron Density Distribution ◽  
Scanning Tunneling ◽  
Monoclinic Space Group ◽  
Tunneling Microscopy ◽  
X Ray

From X-ray analysis, the conclusions are drawn from averaged molecular informations. Thus, limitations are caused when analyzing systems whose symmetry is reduced due to interatomic interactions. In contrast, scanning tunneling microscopy (STM) directly images atomic scale surface electron density distribution, with a resolution up to fractions of Angstrom units. The crucial point is the correlation between the electron density distribution and the localization of individual atoms, which is reasonable in many cases. Thus, the use of STM images for crystal structure determination may be permitted. We tried to apply RuCl3 - a layered material with semiconductive properties - for such STM studies. From the X-ray analysis it has been assumed that α-form of this compound crystallizes in the monoclinic space group C2/m (AICI3 type). The chlorine atoms form an almost undistorted cubic closed package while Ru occupies 2/3 of the octahedral holes in every second layer building up a plane hexagon net (graphite net). Idealizing the arrangement of the chlorines a hexagonal symmetry would be expected. X-ray structure determination of isotypic compounds e.g. IrBr3 leads only to averaged positions of the metal atoms as there exist extended stacking faults of the metal layers.

Sign in / Sign up

Export Citation Format

Share Document