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Topic: Ionospheric reflection

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	Groundwave - Wikipedia, the free encyclopedia
		Ionospheric reflection is taken into consideration as well.
		The ionosphere reflects frequencies in a certain band, which often changes due to solar conditions.
		Because the solar wind "blows" the ionosphere toward the Earth on the day side, and away from it on the night side, this natural radio "mirror" is much closer to the surface during the day.
	en.wikipedia.org /wiki/Groundwave (162 words)

	Radio propagation - Wikipedia, the free encyclopedia
		On discovery of the other propagation modes possible at medium wave and short wave frequencies, these became much more useful for commercial and military purposes, and amateur experimentation was then confined only to authorized frequencies in the range.
		Ground plane reflection effects are an important factor in VHF line of sight propagation.
		Sky-wave propagation is any of the modes that rely on reflection of radio waves from the ionosphere, which is made up of one or more ionized layers in the upper atmosphere.
	en.wikipedia.org /wiki/Radio_propagation (861 words)

	Sudden ionospheric disturbance (Site not responding. Last check: 2007-09-20)
		A sudden ionospheric disturbance (SID) is an abnormally high plasma density in the ionosphere caused by an occasional sudden solar flare, which often interrupts or interferes with telecommunication s systems.
		Earth's ionosphere reacts to the intense x-ray and ultraviolet radiation released during a solar flare.
		RF Energy via Ionospheric Reflection Presents a concept and experiment data for extracting RF energy from the Solar excitation of the ionospheric layers and a simple reflecting antenna system.
	www.serebella.com /encyclopedia/article-Sudden_ionospheric_disturbance.html (506 words)

	Solar Elec. Energy via Ionospheric RF Antenna Resonance
		The physical process by which the ionic energy and the ionosphere's wave energy stimulate the resonant RF radiation may be compared to the operation of lasers, masers, parametric down converters and optical phase conjunction.
		The two conducting spheres, the earth-sphere and the ionosphere, must be involved, acting as a resonant waveguide with the atmosphere as an insulating medium.
		The priming would furnish the energy for the first reflections, and the tuning was adjusting the antenna and tank circuit to a frequency compatible with the ionosphere and the reflective antenna/ground system.
	home.netcom.com /~sbyers11/RFenergy_Iono.html (2003 words)

	Radio Waves and Aurora, Alaska Science Forum (Site not responding. Last check: 2007-09-20)
		One is to cause absorption of radio waves that normally would be reflected by the mirror-like ionospheric layers.
		Then long distance communication that depends upon ionospheric reflection may cease simply because of the absorption.
		In such instances it may be possible for a ham operator in Anchorage to talk with one in Fairbanks even though both their antennas are pointed northward--in such a case they are actually bouncing their signals off the auroral region.
	www.gi.alaska.edu /ScienceForum/ASF1/117.html (235 words)

	Air Force 2025 - Appendix
		The interaction of the ionosphere on impinging electromagnetic radiation depends on the properties of the ionospheric layer, the geometry of transmission, and the frequency of the radiation.
		The reflective and refractive properties of the ionosphere provide a means to transmit radio signals beyond direct "line-of-sight" transmission between a transmitter and receiver.
		However, these bands are also subject to degradation caused by ionospheric scintillation, a phenomenon induced by abrupt variations in electron density along the signal path, resulting in signal fade caused by rapid signal path variations and defocusing of the signal's amplitude and/or phase.
	members.fortunecity.com /groom51/af2025ap.html (930 words)

	Compact Intracloud Discharges (Site not responding. Last check: 2007-09-20)
		The ionospheric reflections of the signal can be seen in the waveforms of all four stations.
		Depending on the source/receiver distance, ionospheric reflection may provide multiple pulses in the NBE waveforms due to the different travel times of the multiple paths for the VLF signal from lightning to a single LASA station.
		Ionospheric reflections are visible in all three waveforms immediately following the groundwave signal.
	nis-www.lanl.gov /~heavner/ildc2000/node7.html (372 words)

	Radio Systems
		An underlying theme of the projects is the development of a better understanding of the effects of the atmospheric (principally the ionospheric) environment on the propagation characteristics of radio waves, and the development of techniques to account for these effects in radio system planning, development and operation.
		Experimental investigations of the accuracy and performance of HF direction finders as a function of signal frequency, propagation mode content, path geometry and ionospheric propagation conditions with particular reference to signals traversing the high latitude region is a long standing interest.
		All of the group's ionospheric work during this period was of direct relevance to the aim of this COST action.
	www.le.ac.uk /engineering/emw/projects.html (916 words)

	Ionopheric Propagation explained
		The virtual height of an ionospheric layer is the equivalent altitude of a reflection that would produce the same effect as the actual refraction.
		In 1924, Appleton discovered two additional layers in the ionosphere, as he and Robert Watson-Watt named this atmospheric region, and noted them with the letters D and F. Appleton was reluctant to alter this arbitrary nomenclature for fear of discovering yet other layers, so it has stuck to the present day.
		The basic physics of ionospheric propagation was largely worked out by the 1920s, yet both amateur and professional experimenters made further discoveries through the 1930s and 1940s.
	homepages.picknowl.com.au /wavetel/propagation.htm (808 words)

	IDS 1st Paper (Site not responding. Last check: 2007-09-20)
		The centroid height of the ionosphere is approximated to be at 300 km altitude.
		As far as the azimuthal dependence of TEC on the location of the surface reflection point is concerned we found that the gradient approach provides similar improvement over the non-gradient approach regardless of the surface reflection point which may be located north, south, east or west of the satellite nadir point.
		The RMS agreement between the constructed surface reflection TEC and the TOPEX TEC is typically at the 3.3 TECU versus 4 TECU for the non-gradient approach at 40 degrees elevation angle.
	ccar.colorado.edu /~komjathy/ids/ids1.html (1561 words)

	HF Channel Simulation
		Ionospheric turbulence causes distortion in both signal amplitude and phase, in addition, different ionospheric layers move up or down, which leads to independent Doppler shift on each propagation mode.
		Ionospheric skywave HF, multipath arises from paths with different number of multiple reflections between earth and the ionosphere (multiple-hop paths) and from paths at multiple elevation angles connecting the same end points ("high" or "low" rays).
		The effect of these natural inhomogeneities in the ionosphere causes multipath spreads of 20 to 40 µs on each path or mode, and the high/low and ordinary/extraordinary rays results in a path spread of about 200 µs.
	www.johanforrer.net /SIMULR (1554 words)

	HFRadio.org - Propagation - Maximum Usable Frequency, MUF Basics - high frequency radio
		The ionosphere is that part of the atmosphere, extending from about 70 to 500 kilometers, in which ions and free electrons exist in sufficient quantities to reflect and/or refract electromagnetic waves.
		The amount of radio wave bending depends on the extent of penetration (which is a function of frequency), the angle of incidence, polarization of the wave, and ionospheric conditions, such as the ionization density.
		Frequency of Optimum Transmission (FOT): In the transmission of radio waves via ionospheric reflection, the FOT is the highest effective frequency (or best working frequency) for a given path that is predicted to be usable for a specified time for a percentage of the days of the month.
	www.hfradio.org /muf_basics.html (891 words)

	[No title]
		Pedersen, A. "Measurements of ion concentrations in the D-region of the ionosphere with a Gerdien condenser rocket probe." Tellus 17(1).
		Stoffregen, W. "On radio reflections from the E- and D-levels during auroral activity." Annals of the IGY 11(I).
		Stoffregen, W. "Response of an Adcock direction-finder to the ground wave and to ionospheric reflections." Kleinheubacher Berichte 15: 115-120.
	www.irfu.se /IRF-U/publications/Publ_abc.html (12375 words)

	What is...
		measuring the height of the ionosphere in 1925, by
		The ionospheric reflection process is strongly 'dispersive', or frequency-dependent, each frequency being reflected by one, two, or even three specific ionization densities, because the ionized plasma is 'magnetoactive'.
		Among the ionospheric properties are varying solar, auroral, meteoric and other ionization production sources, chemical reactions by which ionization returns to the neutral state, motions induced by winds, turbulence and electric fields, all resulting in very wide spectra of spatial irregularities and motions.
	www.ngdc.noaa.gov /stp/IONO/Dynasonde/whatis.htm (1028 words)

	UMass Lowell Center for Atmospheric Research/ Digisonde DPS (Site not responding. Last check: 2007-09-20)
		Because the physical parameters of the ionospheric plasma affect the way radio waves reflect from or pass through the ionosphere, it is possible by measuring all of these observable parameters at a number of discrete heights and discrete frequencies to map out and characterize the structure of the plasma in the ionosphere.
		The total internal reflection from the ionosphere is similar to reflection of radio frequency (RF) energy from a metal surface in that the re-radiation of the incident energy is caused by the free electrons in the medium.
		The major difference between ionospheric reflection and reflection from a metallic surface is that the latter has a uniform electron density while the ionospheric density increases roughly parabolically with altitude, with densities starting at essentially zero at stratospheric altitudes and rising to a peak at about 200 to 400 km.
	umlcar.uml.edu /DPS.htm (9712 words)

	Ionosonde (Site not responding. Last check: 2007-09-20)
		In the frequency range from 1 to 40 MHz short pulses are vertically transmitted and received after ionospheric reflection.
		amplitude, runtime, doppler shift, polarization and angle of incidence are derived from the ionospheric echo and represented versus frequency as ionogramm.
		Ionospheric standard parameters (critical frequencies and special heights of the ionospheric E-, Es-, F1- and F2-layers)
	www.iap-kborn.de /radar/Radars/Ionosonde (113 words)

	page146
		An ionospheric storm is caused by corpuscular radiation emitted from solar flares at the same time flare emits ultraviolet and X-ray radiation which produce the SID.
		The reflection properties of the aurora vary quite rapidly, with the result that the reflected vhf sig- nal is badly distorted by multipath effects.
		Waves entering this area at a favorable angle are reflected considerable distances be- tween the sides of the bulge, resulting in a long, single- hop opening, without intermediate ground reflection, of up to 5000 miles (8000 km).
	www.ktbx.demon.co.uk /page146.htm (2165 words)

	Use of the HAARP Science Observatory Instruments (Site not responding. Last check: 2007-09-20)
		Use of the HAARP Ionospheric Observatory Instruments To Analyze Effects of the Geomagnetic Storm of August 3, 1997
		A coronal mass ejection from the sun produced disturbed ionospheric conditions on August 3, 1997 and degraded communication conditions on the High Frequency bands that rely on ionospheric reflection for signal propagation.
		One of the main goals of ionospheric research is to be able to predict such sun-induced effects reliably and with enough advanced warning that any ensuing disruption of services can be minimized or avoided.
	www.haarp.alaska.edu /haarp/inst.html (439 words)

	NGDC/STP - Ionospheric Data
		The Ionospheric Physics Group of NGDC operates the Ionosphere portion of the World Data Center for Solar-Terrestrial Physics, Boulder, which seeks out and archives data, data products, and information related to the Ionosphere.
		Most of the current effort at NGDC is in the Ionospheric Vertical Incidence Sounding discipline.
		Ionospheric characteristics can be selected by geographic location, station name or by event and downloaded to our ftp anonymous site or directly to your computer.
	www.ngdc.noaa.gov /stp/IONO/ionohome.html (371 words)

	Ionospheric sounding (Site not responding. Last check: 2007-09-20)
		In telecommunication an ionospheric sounding is a technique that provides real-time data on high-frequency ionospheric-dependent radio propagation using a basic system consisting of a synchronized transmitter and
		Vertical incident sounding uses a collocated transmitter and receiver involves directing a range of frequencies vertically the ionosphere and measuring the values of the returned signals to determine the effective ionosphere altitude.
		The measurement converts time delay to effective altitude of the ionospheric layer.
	www.freeglossary.com /Ionospheric_sounding (309 words)

	Radio and Space Plasma Physics Group
		The influence of the ionospheric propagation medium on HF radio signals is a field of particular interest which is supported by many years research, both experimental and theoretical, into the physics of the ionosphere.
		Particular attention is currently being given to situations where the ionospheric reflection is non-specular and the signal energy arrives at the receiver over a range of angles in both azimuth and elevation.
		For a trans-auroral path, for which the ionospheric reflection points were sub-auroral, standard deviations of up to around 2.5° were observed in the azimuthal power distribution of the received energy.
	ion.le.ac.uk /postgrad/PG_opportunities.html (3399 words)

	Insight Into Marsis Radar Data Analysis \| SpaceRef - Your Space Reference
		The ionosphere is more energised during the daytime and disturbs the radio signals used for subsurface observations.
		Estimate large-scale topography, roughness and reflectivity of the surface.
		The first surface reflection echoes of MARSIS operating as a sounder are processed to give estimates of the average height, roughness and reflection coefficient of the surface layer.
	www.spaceref.com /news/viewpr.html?pid=17845 (1780 words)

	The Ionosphere (Site not responding. Last check: 2007-09-20)
		The performance of high frequency skywave radio circuits is degraded by the presence of irregularities near the ionospheric reflection point.
		Doppler sounders are used to probe these ionospheric disturbances whilst simultaneously monitoring the variations in the magnetic field at the reflection point with ground based induction magnetometers.
		Imaging riometers are ideal for studying ionospheric plasma dynamics associated with high latitude phenomena on both the day and night side of the magnetosphere.
	plasma.newcastle.edu.au /spwg/Research/iono.htm (308 words)

	PIXIE Experiment Overview (Site not responding. Last check: 2007-09-20)
		The footprints of geomagnetic activity are made visible in the auroral zone where energetic electrons precipitate into the atmosphere and produce brilliant displays of light.
		One of the results of this precipitation is an increase in the local ionospheric density and hence conductivity.
		It is useful to be able to remotely sense the ionospheric effects of the electron precipitation.
	pixie.spasci.com /pixie/homepage/pixoverview.html (351 words)

	[No title]
		The Ionosphere does not in practice exist as discrete 'layers' these are rather definitions of regions of altitude, and relate to levels between which the ionising processes change.
		This means that the 'reflection' level moves downwards, reducing the amount amount of absorption the signal experiences during its passage to the 'reflection' level.
		This model of a 'mirror' reflection is not accurate and the wavefront may stay within the ionosphere for anything upwards of 1000kms being slowly refracted groundwards.
	www.alan.melia.btinternet.co.uk /hcf2001.htm (4912 words)

	ANTENNA BASICS AND THEORY FROM THE U.S. NAVY TRAINING CENTER
		ionospheric layers, it also has the longest propagation capability.
		ionospheric reflection mostly occurs at long wavelengths,(low frequencies).
		of ionospheric storms are a turbulent ionosphere and
	www.hamuniverse.com /anttheory1.html (3051 words)

	Title
		While the ionospheric propagation used by OTH skywave radars has the advantage of increased range coverage, the ionosphere itself fluctuates, which in turn causes Doppler shifts on the backscattered radiation.
		A much more difficult problem, however, is ionospheric disturbances that cause the radar radiation to be reflected off multiple ionospheric sublayers before returning to the receiving antenna.
		The reason for the dual-frequency altimeter is to minimize the error from ionospheric electron content by combining data from the two frequencies (Fu et al., 1994).
	ccar.colorado.edu /~harlanj/yucchan.html (3856 words)

	Ionospheric reflection - Wikipedia, the free encyclopedia
		Ionospheric reflection: Of electromagnetic waves propagating in the ionosphere, a redirection, i.e., bending--by a complex process involving reflection and refraction--of the waves back toward the Earth.
		Note: The amount of bending depends on the extent of penetration (which is a function of frequency), the angle of incidence, polarization of the wave, and ionospheric conditions, such as the ionization density.
		This page was last modified 12:15, 4 June 2004.
	en.wikipedia.org /wiki/Ionospheric_reflection (85 words)

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