DIURNAL VARIATIONS IN THE NUMBER OF SHOWER METEORS DETECTED BY THE FORWARD-SCATTERING OF RADIO WAVES: PART II. EXPERIMENT

1955 ◽  
Vol 33 (10) ◽  
pp. 600-606 ◽  
Author(s):  
P. A. Forsyth ◽  
C. O. Hines ◽  
E. L. Vogan
Keyword(s):  
Specular Reflection ◽  
Forward Scattering ◽  
Diurnal Variations ◽  
Radio Waves ◽  
Forward Scatter ◽  
Transmission Path ◽  
Signal Rate ◽  
Cedar Rapids ◽  
Good Agreement

The theory developed in Part I is applied to derive the expected diurnal variations of the meteor signal rate for four showers as observed by means of a particular forward-scatter transmission path (Cedar Rapids – Ottawa). These results are then compared with the experimental signal rates. The good agreement obtained indicates that the approximations inherent in the theory are sufficiently accurate for practical purposes. The results also indicate that very few meteors, if any, are observed under conditions which do not satisfy the requirements for specular reflection.

DIURNAL VARIATIONS IN THE NUMBER OF SHOWER METEORS DETECTED BY THE FORWARD-SCATTERING OF RADIO WAVES: PART III. ELLIPSOIDAL THEORY

1958 ◽  
Vol 36 (1) ◽  
pp. 117-126 ◽  
Author(s):  
C. O. Hines
Keyword(s):  
Forward Scattering ◽  
Diurnal Variations ◽  
New Method ◽  
Radio Waves ◽  
Meteor Showers ◽  
Rigorous Results ◽  
Forward Scatter ◽  
Scatter Process ◽  
Full Development

A theory of meteor 'observability' relating to forward-scatter radio experiments was developed in Part I of this series, with the use of a simplifying 'cylindrical approximation'. The application of the theory to data obtained during meteor showers provides a promising new method for studying the intrinsic strengths of the showers. The principal limitation of the method is due to the inaccuracies of the cylindrical approximation. In the present paper, these inaccuracies are removed by a full development of the ellipsoidal geometry inherent in the forward-scatter process. The more rigorous results are compared with the approximate results at various stages throughout the analysis.

Ionization profile of meteors from simultaneous video and radio forward scatter observations

2020 ◽  
Author(s):  
Hervé Lamy ◽  
Michel Anciaux ◽  
Sylvain Ranvier ◽  
Antoine Calegaro ◽  
Carl Johannink
Keyword(s):  
Peak Power ◽  
Specular Reflection ◽  
Radio Waves ◽  
Line Density ◽  
Science And Engineering ◽  
Forward Scatter ◽  
Electron Line ◽  
Power Profile ◽  
Video Observations ◽  
Polarization Factor

<p>In this study, optical video observations of meteors with the CAMS (Camera for All-sky Meteor Surveillance)-BeNeLux network and radio forward scatter observations with the BRAMS (Belgian RAdio Meteor Stations) network obtained on 4-5 October 2018  are combined in order to obtain an ionization profile along a meteor path.</p><p>The trajectory, initial speed and deceleration parameters of a given meteor are provided by the CAMS-BeNeLux data. For a given trajectory, the positions of the specular reflection points for radio waves are computed for each combination of a given BRAMS receiving station and the BRAMS transmitter. For each receiving station which recorded a meteor echo (depending on the geometry and the SNR ratio), the power profile is computed and the peak power values of the underdense meteor profiles are used to determine the ionization (electron line density) at the various specular reflection points along the meteor path. This is done using the McKinley (1961) formula which is strictly valid for underdense meteor echoes.  We discuss how we compute the gains of the antennas, the polarization factor, and how the peak power values are transformed from arbitrary units into watts using the signal recorded from a device called the BRAMS calibrator. We also discuss how to extend this study to overdense meteor echoes or those with intermediate electron line densities.</p><p>Finally, these results are combined with a simple ablation meteor model in order to obtain an estimate of the initial mass of the meteoroid.</p><p>Mc Kinley D.W.R., Meteor science and engineering, Mc Graw-Hill eds, 1961</p>

DIURNAL VARIATIONS IN THE NUMBER OF SHOWER METEORS DETECTED BY THE FORWARD-SCATTERING OF RADIO WAVES: PART I. THEORY

1955 ◽  
Vol 33 (9) ◽  
pp. 493-503 ◽  
Author(s):  
C. O. Hines
Keyword(s):  
Diurnal Variation ◽  
Incidence Rate ◽  
Forward Scattering ◽  
Diurnal Variations ◽  
Time Interval ◽  
Weight Factor ◽  
Radio Waves ◽  
Meteor Trails

Various observational factors affect the number of shower meteors which can be detected, in a given time interval, by the scattering of radio waves from the ionized meteor trails. The pertinent factors in the case of forward-scattering, where the transmitter and receiver are widely separated, are expressed approximately as functions of the position of the shower radiant. In combination, they provide an observational weight factor which may change appreciably as the radiant moves in the course of a day. The consequent diurnal variation in the occurrence of scattered signals may then be determined, and distinguished from variations due to random changes in the incidence rate of the meteors.

A THEORETICAL RATE–AMPLITUDE RELATION IN METEORIC FORWARD-SCATTERING

1958 ◽  
Vol 36 (5) ◽  
pp. 539-554 ◽  
Author(s):  
C. O. Hines
Keyword(s):  
Observational Data ◽  
Forward Scattering ◽  
Occurrence Rate ◽  
Radio Waves ◽  
Scaling Factors ◽  
Meteor Trails ◽  
Amplitude Level ◽  
Good Agreement

The theory of the forward-scattering of radio waves by ionized meteor trails is applied to the development of a rate-amplitude relation. This relation expresses the anticipated occurrence rate of scattered signals which exceed a chosen amplitude level, as a function of that level. It is compared with preliminary observational data, and found to be in good agreement both qualitatively and quantitatively. Closest agreement is obtained only with an appropriate choice of two scaling factors. These provide an abstract of the observations in a form which is convenient for further study and interpretation.

scholarly journals Optical Monitoring of Microplastics Filtrated from Wastewater Sludge and Suspended in Ethanol

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 871
Author(s):  
Benjamin O. Asamoah ◽  
Pauliina Salmi ◽  
Jukka Räty ◽  
Kalle Ryymin ◽  
Julia Talvitie ◽  
...  
Keyword(s):  
Polyethylene Terephthalate ◽  
Optical Method ◽  
Specular Reflection ◽  
Speckle Pattern ◽  
Wastewater Sludge ◽  
Natural Environments ◽  
Optical Monitoring ◽  
Detection And Identification ◽  
Essential Parameter ◽  
Good Agreement

The abundance of microplastics (MPs) in the atmosphere, on land, and especially in water bodies is well acknowledged. In this study, we establish an optical method based on three different techniques, namely, specular reflection to probe the medium, transmission spectroscopy measurements for the detection and identification, and a speckle pattern for monitoring the sedimentation of MPs filtrated from wastewater sludge and suspended in ethanol. We used first Raman measurements to estimate the presence and types of different MPs in wastewater sludge samples. We also used microscopy to identify the shapes of the main MPs. This allowed us to create a teaching set of samples to be characterized with our optical method. With the developed method, we clearly show that MPs from common plastics, such as polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), and polyethylene (PE), are present in wastewater sludge and can be identified. Additionally, the results also indicate that the density of the plastics, which influences the sedimentation, is an essential parameter to consider in optical detection of microplastics in complex natural environments. All of the methods are in good agreement, thus validating the optics-based solution.

scholarly journals A climatology of the diurnal variations in stratospheric and mesospheric ozone over Bern, Switzerland

2014 ◽  
Vol 14 (12) ◽  
pp. 5905-5919 ◽  
Author(s):  
S. Studer ◽  
K. Hocke ◽  
A. Schanz ◽  
H. Schmidt ◽  
N. Kämpfer
Keyword(s):  
Interannual Variability ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Diurnal Variations ◽  
Interannual Variations ◽  
Data Set ◽  
Unique Data ◽  
Ozone Variation ◽  
Mesospheric Ozone ◽  
Good Agreement

Abstract. The ground-based radiometer GROMOS, stationed in Bern (47.95° N, 7.44° E), Switzerland, has a unique data set: it obtains ozone profiles from November 1994 to present with a time resolution of 30 min and equivalent quality during night- and daytime. Here, we derive a monthly climatology of the daily ozone cycle from 17 years of GROMOS observation. We present the diurnal ozone variation of the stratosphere and mesosphere. Characterizing the diurnal cycle of stratospheric ozone is important for correct trend estimates of the ozone layer derived from satellite observations. The diurnal ozone cycle from GROMOS is compared to two models: the Whole Atmosphere Community Climate Model (WACCM) and the Hamburg Model of Neutral and Ionized Atmosphere (HAMMONIA). Generally, observation and models show a good agreement: in the lower mesosphere, daytime ozone is for both GROMOS and models around 25% less than midnight ozone. In the stratosphere, ozone reaches its maximum in the afternoon showing values several percent larger than the midnight value. Further, GROMOS and models indicate a seasonal behaviour of the diurnal ozone variations in the stratosphere with a larger afternoon maximum during daytime in summer than in winter. Using the 17 years of ozone profiles from GROMOS, we find strong interannual variations in the diurnal ozone cycle for both the stratosphere and the mesosphere. Interannual variability in temperature, atmospheric circulation and composition may explain the observed interannual variability of the diurnal ozone cycle above Bern.

IONOSPHERIC REFLECTION OF VERY LONG RADIO WAVES

1950 ◽  
Vol 28a (6) ◽  
pp. 549-557 ◽  
Author(s):  
J. P. Stanley
Keyword(s):  
Magnetic Field ◽  
Reflection Coefficient ◽  
Wave Reflection ◽  
Simplified Model ◽  
Angle Of Incidence ◽  
Vertical Magnetic Field ◽  
Radio Waves ◽  
Long Wave ◽  
Theoretical Results ◽  
Good Agreement

A simplified model of the long-wave-reflecting region of the ionosphere, first considered in a previous paper, is used to calculate the theoretical variation of sky wave reflection coefficient with angle of incidence and with the angle of dip of the earth's magnetic field. The resulting curves are found to be in good agreement with experiment. They lead to the conclusion that theoretical results based on the assumption of a vertical magnetic field will not lead to errors in vertical incidence sky wave reflection coefficient greater than about 10%, even though the field is inclined at an angle of as much as 23° to the vertical.

Forward Reflection Characteristics of Typical Smooth Building Walls and the Simulation Analysis

2014 ◽  
Vol 513-517 ◽  
pp. 3601-3606
Author(s):  
Shen You Zhao ◽  
Kai Da Xu ◽  
Su Qiu ◽  
Wei Qi Jin ◽  
Hui Guo ◽  
...  
Keyword(s):  
Simulation Analysis ◽  
Specular Reflection ◽  
Forward Scattering ◽  
Line Of Sight ◽  
Angle Of Incidence ◽  
Imaging Technology ◽  
Reflective Surface ◽  
Building Walls ◽  
Reflection Characteristics ◽  
Non Line Of Sight

Non-line-of-sight optical imaging technology is a novel application of imaging technology developed recently, achieving the effective imaging of the corner, basements and other scenes which are difficult to be directly observed by traditional vision with intermediate reflective surface. Smooth building walls, such as tiles and marbles, are typical intermediate reflective surfaces. Because reflecting surface is neither ideal specular reflective nor Lambertian reflective, the reflection characteristics of the intermediate reflective surface have a significant impact on the non-line-of-sight imaging. Based on the test data of the spectral bidirectional reflectance distribution function (BRDF) of common smooth tiles, the surface transfer function and angle spread function of smooth tiles are established according to the Harvey-Shack surface scatter theory in the paper. And the descriptions of the characteristics of specular reflection and forward scattering are implemented. Furthermore, according to the measured BRDF data at a certain wavelength for a certain angle of incidence, we can predict the reflection and scattering distribution at any other wavelengths or for other incident angles. The simulation results indicate that the curves fitted by the model basically are in agreement with the measured data, so that the simulation of the specular reflection and the forward scattering in the model is valid.

scholarly journals Tropospheric OH and Cl levels deduced from non-methane hydrocarbon measurements in a marine site

2007 ◽  
Vol 7 (3) ◽  
pp. 6329-6356 ◽  
Author(s):  
C. Arsene ◽  
A. Bougiatioti ◽  
M. Kanakidou ◽  
B. Bonsang ◽  
N. Mihalopoulos
Keyword(s):  
Eastern Mediterranean ◽  
Regional Scale ◽  
Diurnal Variations ◽  
Oh Radicals ◽  
Atom Concentration ◽  
Marine Site ◽  
Cl Atoms ◽  
Cl Atom ◽  
Good Agreement

Abstract. In situ continuous hourly measurements of C2-C8 non-methane hydrocarbons (NMHCS) have been performed from March to October 2006 at two coastal locations on the island of Crete, in the Eastern Mediterranean. Well defined diurnal variations were observed for several short lived NMHCS (including ethene, propene, n-butane, n-pentane, n-hexane, 2-methyl-pentane). The daytime concentration of hydroxyl (OH) radicals estimated from these experimental data varied from 1.3×106 to ~4.0×106 radical cm−3, in good agreement with box-model simulations. In addition the relative variability of various hydrocarbon pairs (at least 7) was used to derive the tropospheric levels of Cl atoms. The Cl atom concentration has been estimated to range between 0.6×104 and 4.7×104 atom cm−3, in good agreement with gaseous hydrochloric acid (HCl) observations in the area. Such levels of Cl atoms can be of considerable importance for the oxidation capacity of the troposphere on a regional scale.

scholarly journals Determining characteristics of HF communications links using SuperDARN

2002 ◽  
Vol 20 (7) ◽  
pp. 1023-1030 ◽  
Author(s):  
J. M. Hughes ◽  
W. A. Bristow ◽  
R. A. Greenwald ◽  
R. J. Barnes
Keyword(s):  
Real Time ◽  
Space Weather ◽  
Radio Waves ◽  
New Techniques ◽  
Radio Science ◽  
F Region ◽  
Instruments And Techniques ◽  
Using Data ◽  
Hf Communications ◽  
Good Agreement

Abstract. Space weather effects can strongly influence high-frequency (HF) communications by changing the ionospheric environment through which the radio waves propagate. Since many systems utilize HF communications, the ability to make real-time assessments of propagation conditions is an important part of space weather monitoring systems. In this paper, we present new techniques for measuring high-latitude HF communications link parameters using data from SuperDARN radars. These techniques use ground-scatter returns to define the variation in skip distance with frequency. From these data, the maximum usable frequency (MUF) as a function of range is determined and ionospheric critical frequencies are estimated. These calculations are made in near-real-time and the results are made available on the World Wide Web. F-region critical frequencies calculated using this method show good agreement with ionosonde data.Key words. Ionosphere (active experiments; instruments and techniques) – Radio science (ionospheric propagation)

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