The electron density distribution in the D- and E-regions during days of anomalous radio wave absorption in winter

1968 ◽  
Vol 30 (6) ◽  
pp. 1211-1217
Author(s):  
L. Thomas
Keyword(s):  
Density Distribution ◽  
Radio Wave ◽  
Electron Density ◽  
Electron Density Distribution ◽  
Wave Absorption ◽  
Radio Wave Absorption

scholarly journals On the factors controlling occurrence of F-region coherent echoes

2002 ◽  
Vol 20 (9) ◽  
pp. 1385-1397 ◽  
Author(s):  
D. W. Danskin ◽  
A. V. Koustov ◽  
T. Ogawa ◽  
N. Nishitani ◽  
S. Nozawa ◽  
...  
Keyword(s):  
Density Distribution ◽  
Radio Wave ◽  
Electron Density ◽  
Electron Density Distribution ◽  
Propagation Path ◽  
Occurrence Rate ◽  
Wave Refraction ◽  
F Region ◽  
D Region ◽  
Field Lines

Abstract. Several factors are known to control the HF echo occurrence rate, including electron density distribution in the ionosphere (affecting the propagation path of the radar wave), D-region radio wave absorption, and ionospheric irregularity intensity. In this study, we consider 4 days of CUTLASS Finland radar observations over an area where the EISCAT incoherent scatter radar has continuously monitored ionospheric parameters. We illustrate that for the event under consideration, the D-region absorption was not the major factor affecting the echo appearance. We show that the electron density distribution and the radar frequency selection were much more significant factors. The electron density magnitude affects the echo occurrence in two different ways. For small F-region densities, a minimum value of 1 × 1011 m-3 is required to have sufficient radio wave refraction so that the orthogonality (with the magnetic field lines) condition is met. For too large densities, radio wave strong "over-refraction" leads to the ionospheric echo disappearance. We estimate that the over-refraction is important for densities greater than 4 × 1011 m-3. We also investigated the backscatter power and the electric field magnitude relationship and found no obvious relationship contrary to the expectation that the gradient-drift plasma instability would lead to stronger irregularity intensity/echo power for larger electric fields.Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; auroral ionosphere)

scholarly journals On the determination of ionospheric electron density profiles using multi-frequency riometry

2021 ◽  
Author(s):  
Derek McKay ◽  
Juha Vierinen ◽  
Antti Kero ◽  
Noora Partamies
Keyword(s):  
Radio Wave ◽  
Electron Density ◽  
Density Profile ◽  
Electron Density Profile ◽  
Cosmic Radio ◽  
Density Profiles ◽  
Wave Absorption ◽  
Altitude Profile ◽  
Radio Wave Absorption ◽  
Electron Density Profiles

Abstract. Radio wave absorption in the ionosphere is a function of electron density, collision frequency, radio wave polarisation, magnetic field and radio wave frequency. Several studies have used multi-frequency measurements of cosmic radio noise absorption to determine electron density profiles. Using the framework of statistical inverse problems, we investigated if an electron density altitude profile can be determined by using multi-frequency, dual-polarisation measurements. It was found that the altitude profile cannot be uniquely determined from a complete measurement of radio wave absorption for all frequencies and two polarisation modes. This implies that accurate electron density profile measurements cannot be ascertained using multi-frequency riometer data alone, but that the reconstruction requires a strong additional a priori assumption of the electron density profile, such as a parameterised model for the ionisation source. Nevertheless, the spectral index of the absorption could be used to determine if there is a significant component of hard precipitation that ionises the lower part of the D region, but it is not possible to infer the altitude distribution uniquely with this technique alone.

scholarly journals A new method of studying the relation between ionization rates and radio-wave absorption in polar-cap absorption events

2005 ◽  
Vol 23 (2) ◽  
pp. 359-369 ◽  
Author(s):  
J. K. Hargreaves
Keyword(s):  
Radio Wave ◽  
Production Rate ◽  
Electron Density ◽  
Recombination Coefficient ◽  
Square Root ◽  
Polar Cap ◽  
Height Profile ◽  
Wave Absorption ◽  
Radio Wave Absorption ◽  
D Region

Abstract. During polar-cap absorption events, which are caused by the incidence of energetic solar protons, the high-latitude ionospheric D region is extended down to relatively low altitudes. While the incoming proton fluxes may be monitored by satellite-borne detectors, and the resulting radio-wave absorption with a ground-based riometer, the enhancement of electron density at a given altitude is less easily determined. Direct measurements by incoherent-scatter radar are infrequent and they tend to lack the necessary sensitivity at the lower levels. Computations of the electron density from the observed particle fluxes are handicapped by uncertainties in the height profile of the effective recombination coefficient. This paper describes a new approach based on finding the best-fit solution to an over-determined set of equations. The D region is treated as a set of slabs, each contributing to the total radio absorption, and the method relies on the fact that the proton spectrum varies during the event. The analysis produces a set of coefficients relating the absorption increment in the slab to the square root of the production rate, as a function of height. Values of effective recombination coefficient are also deduced over a range of heights, and these agree with previous estimates (Gledhill, 1986) to within a factor of 2. However, whereas the latter do not generally go below 60km altitude the new determination extends the values down to 40km. The new method provides a measurement of the height profile of the absorption in PCA events. It is shown that the slabs centred from 45 to 65km typically account for 80% of the total daytime absorption, and that less than 1% of the total arises above 80km or below 30km. At night most of the absorption comes from the slabs at 75 and 80km, with no significant contribution from slabs below 75 or above 85km. These results would not differ significantly from estimates based on the Gledhill profiles if extrapolated downward. Predictions based on the coefficients generated by the procedure are compared with the polar-cap absorption observed during some recent events. Typical electron-density values are derived, and the study provides an independent confirmation that the electron density and the production rate are related by a square-root law.

scholarly journals Remote sensing and modeling of lightning caused long recovery events within the lower ionosphere using VLF/LF radio wave propagation

2014 ◽  
Vol 12 ◽  
pp. 241-250 ◽  
Author(s):  
E. D. Schmitter
Keyword(s):  
Wave Propagation ◽  
Density Distribution ◽  
Radio Wave ◽  
Electron Density ◽  
Electron Density Distribution ◽  
Current Model ◽  
Lower Ionosphere ◽  
Radio Wave Propagation ◽  
Return Stroke ◽  
The North

Abstract. On the 4 November 2012 at 3:04:27 UT a strong lightning in the midst of the North Sea affected the propagation conditions of VLF/LF transmitter radio signals from NRK (Iceland, 37.5 kHz) and GBZ (UK, 19.58 kHz) received at 5246° N 8° E (NW Germany). The amplitude and phase dips show a recovery time of 6–12 min pointing to a LOng Recovery Early VLF (LORE) event. Clear assignment of the causative return stroke in space and time was possible with data from the WWLLN (Worldwide Lightning Location Network). Based on a return stroke current model the electric field is calculated and an excess electron density distribution which decays over time in the lower ionosphere is derived. Ionization, attachment and recombination processes are modeled in detail. Entering the electron density distribution in VLF/LF radio wave propagation calculations using the LWPC (Long Wavelength Propagation Capability) code allows to model the VLF/LF amplitude and phase behavior by adjusting the return stroke current moment. The results endorse and quantify the conception of lower ionosphere EMP heating by strong – but not necessarily extremely strong – return strokes of both polarities.

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