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Published on February 12, 2008

Author: Savin

Source: authorstream.com

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Ionospheric Service and HF Radio Propagation Prediction   Bruno Zolesi Istituto Nazionale di Geofisica e Vulcanologia   EL QAHIRA 29-31 March 2004 :  Ionospheric Service and HF Radio Propagation Prediction   Bruno Zolesi Istituto Nazionale di Geofisica e Vulcanologia   EL QAHIRA 29-31 March 2004 Slide3:  Summary   1 Historical Inntroduction   2 Ionospheric Vertical Soundings and Service Ionograms, Interpretation , Presentation and Processing of Ionospheric Data   3 Ionospheric Radio Propagation Prediction Ionospheric Mapping and Modelling Instantaneous Mapping HF Ionospheric long term Prediction HF point to point monthly median prediction HF Monthly median prediction of the MUF and skip distance areas Slide4:  Ionospheric Vertical Soundings The existence of ionized layers on the upper atmosphere was predicted by Kennelly and Heavised in 1901 and explained the first trans oceanic radio link realized by Guglielmo Marconi on 12th December of the same year . Guglielmo Marconi I:  I Ionospheric Vertical Soundings After the first experiments in 1926 of E.V. Appleton in U.K. and Breit and Tuve in USA the experimental method was improved and widely used to determine the characteristic of ionospheric regions. Slide6:  Starting from about 1930 the network of ionospheric vertical stations was expanded considerably and their data contributed to a better knowledge of the ionospheric phenomena . While the first routine ionospheric sounding stations were set primarly for scientiphic purposes, the great expansion it was during the second world war due to the need to make predictions on long distance radio links. Finally the maximum expansion was reached during the International Geophysical Year in 1958. Slide9:  Italian Ionospheric Observatories Italian Ionospheric Observatories Slide11:  Of course in addition to vertical sounding other strumental tecniques were added such rockets and satellites. However these methods cannot replace the space time coverage obtained by ground based mesaruments Slide12:  Considering that the mainteanance of an adequate network of stations for scientiphic and pratctical purposes depends on the cooperation of organizations involved in geophysical studies of the ionosphere or involved in studies concerning radio propagation problems. Some international organizations as URSI and ITU , the former CCIR, encouraged investigations and observations on ionosphere and the exchange of the data through the World data Centers. Slide13:  Ionospheric measurements by Vertical Radio Soundings. The method and the instrumentation used for electronic density measurements is based on the principle that when an electromagnetic wave penetrates vertically in the ionospheric plasma the reflection occurs at the level where the refractive index becomes zero. This parameter is dependent by the electron density N and by incident frequency. Slide14:  An ionospheric vertical sounder uses basic radar tecniques to detect electron density of ionospheric plasma as a function of the height by scanning the trasmitting frequency from 1 MHz to 20MHz and measuring the time delay of any echoes. Slide16:  Ionograms : interpretation and presentation of the data The principal routine work of every standard station is: To monitor the ionosphere above the station. To obtain significant median data to evaluate long term changes. To study phenomena peculiar to the region To study the global morphology of the ionosphere Slide17:  Of course These objectives need a set of standard tecniques and conventions applicable to the general interpretation of the ionospheric measurements in order to give a simplified description of the ionosphere above the station. Slide18:  The Ionogram The ionogram is the record produced by the ionosonde which shows the time delay between the trasmission time and the received echo from the ionospheric layer( proportional to the altitude) as function of the radio frequency. Since the signal travels more slowly in the ionosphere than in the free space the heights observed exceed the true height reflections and are so called virtual heights Slide19:  The Ionogram If the frequency of the signa1 is increased the virtua1 height increases more rapid1y than the true height. When the level of the maximum electron density in the layer is reached the virtual height becomes infinite. This frequency is called the critical frequency of the layer     Slide25:  Another important effect of the propagation of a radio signal is the double refraction due to the interaction between the electrons in the plasma and the magnetic fìeld. The two waves reflected independently in the ionosphere, known as magnetoionic components, are called, by analogy with optical double reflection, the ordinary and the extraordinary wave     Slide26:  The Maximum Usable Frequency Factor M   The M factor is a conversion factor to obtain the Maximum usable frequency over a given oblique propagation distance. The M factor for a standard distance of 3000 Km is called M(3000), this parameter, related to the MUF(3000) and to the critical frequency fo by   M(3000) = MUF(3000)/foF2   The M factor is very useful for practica1 ionospheric radio propagation predictions. Slide27:  The Maximum usable frequency factor can easily be obtained directly from the ionograms. There is a well known relationship between an oblique frequency fob and the equiva1ent vertica1 frequency fv at an equivalent virtua1 height h' for a given distance D:  fob= fv sec ( φ) where φ , the angle of incidence, is, for a curved earth and a flat ionosphere, φ= arctan ( sin /2)/ (1+h’/R- cos /2) with  the angle at the center or the earth subtended at the distance D and R the Earth radius. Slide29:  Presentation and Processing of ionospheric Data The measurements of the principal ionospheric characteristics coming from scaling the ionograms , maually or automatic and validated, are reported in daily and monthly tables Slide30:  9 STATION ROME LAT 41.8 N LONG 12.5 E AUT. SWEEP 1 TO 20 MHz   **************************************************************************************************************************** * * * UNIVERSAL TIME CHARACTERISTIC 00 F0F2 UNIT 0.1 MHZ JAN 03 * * * * 000 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 * * * **************************************************************************************************************************** 1 * 47 43 45 44 46 46 52 89 90 105 107 113 94 106 89 89 77 53 39 36 32 37 34 36 * 2 * 39 39 39 40 42 44 40 70 101 127 118 102 93 100 94 80 72 57 52 45 37 35 37 31 * 3 * 35 35 36 37 39 44 40 60 98 117 108 102 90 102 92 81 65 56 42 45 48 51 51 45 * 4 * 46 42 42 41 40 38 43 99 121 118 111 109 111 106 93 86 75 60 40 28 30 33 34 36 * 5 * 37 36 33 34 35 30 34 69 84 108 127 98 104 100 93 86 70 59 42 31 29 31 35 34 * 6 * 36 38 39 40 34 31 39F 68 78 109 104H 95H 100 84 86 74 66 59 39 35 32 38 38V 38 * 7 * 40 39 40 47 53 38 35 62 96 103 111 100 96 101 96 89 75 59 41 I 33A 25 31 32 35 * 8 * 34 36 37 39 39 31 28 65 84 110 96 92 93 94 82 71 66 57 49 31 30 30 31 33 * 9 * 37 38 37 39 40 34 36 74 77H 105 110 90 91 102 100 93 73 64 59 42 28 32 32 34 * 10 * 37 39 39 34 33 28 36 64 81 99 102 92H 98 99 95 87 82 78 64 48 38 38 40 42 * 11 * 43 40 42 39 39 35 37 63 95 105 106H 103 101 111 101 86 77 72 55 38 33 37 37V 37 * 12 * 39 39 39 40 38 36 37 62 86 111 123 103 106 100 99 90 86 79 71 47 27 33 35 38 * 13 * 39 36 35 37 40 36 35 64R 80 109 103 100 97 101 106 101 75 64 44 I 38A 31 32 I 34A 35 * 14 * 38 36 38 36 38 40 36 67 91 91 102 110 114 107 102 93 82 77 62 46R 37 38 39 39 * 15 * 44 45 46 42 46 37 38 81 89 101 99 104 99 112 102 89 88 82 63 41 40 39 38 36 * 16 * 44 46 49 49 51 35 38 68 85 98 102 96 100 96 91 85 79 64 46 38 29 32 34 35 * 17 * 39 39 38 39 37 I 42A 47 76 97 99 105 99 94 98 105 95 73 65 58 52 38 40 44 46 * 18 * 45 45 47 46 43 40 43 71 87 121 117 103 103 115 110 83 79 82 67 51 40 36 40 42 * 19 * 45 45 44 44 43 37 39 71 96 125 126 124 109 102 94 81H 66 69 71 40 47 34 36 37 * 20 * 38 39 41 39 34 27 37 76 84 100 96 108 106 109 112 95 71 50 50 45 33 34 33 34 * 21 * 35 36 35 36 36 30 38 77 96 94 110 104 97 109 103 88 89 58 49 37 26 30 31 32 * 22 * 32 34 34 35 40 33 36 73 95 105 110 109 108 105 104 96 79 62 51 38 40 43 41 45 * 23 * 45 42 49 44 45 41 51 83 110 109 96 107 104 107 103 96 79 56 46 40 38 42 45 45 * 24 * 46 46 43 42 41 36 39 76 86 107 116 104 96 98 100 80 65 53 51 47 51 48 43 44 * 25 * 45 44 44 45 43 37 39 63 87 102 104 99 95 96 89 85 76 78 79 55 42 35 37 36 * 26 * 37F 40 41 43F 44F 43 48 75 82 92 107 97 104 97 90 78 68 58 52 47 42 I 41A 39 38 * 27 * 38 40 39 42 43 43 46 74 94 104 103 88 87 87 86 82 72 52 47 34 40 40 43 43 * 28 * 45 47 48 45 40 36 54 81 70 94 112 E113Y 104H 89 93 88 75 66 66 48 41 39 36 41F * 29 * 43 44 45 46 46 47 52 80 84 98 103 108 90 93 102 89 80 68 45 38 37 40 39 41 * 30 * 40 40 38 36 37 38 43 69 89 106 118 113 99 98 100 95 97 79 51 48 43 41 43 42 * 31 * 41 38 38 39 37F 32 35 69 89 108 109 105 96 103 111 101 77 52 53 42 40 40 40 38 * **************************************************************************************************************************** C * 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 * * * M * 39 39 39 40 40 37 39 71 89 105 107 103 99 101 99 88 75 62 51 41 37 37 37 38 * * * UQ * 45 44 44 44 43 41 43 76 96 109 112 108 104 106 103 93 79 72 62 47 40 40 40 42 * LQ * 37 38 38 37 37 33 36 65 84 99 103 98 94 97 92 82 71 57 45 37 30 33 34 35 * QR * 8 6 6 7 6 8 7 11 12 10 9 10 10 9 11 11 8 15 17 10 10 7 6 7 * Qualifying Letters The following letters are entered in the first column before a numerical value on the monthly tabulation sheets, if necessary . A Less than. Used only when fbEs is deduced from foEs because total blanketing of higher layer is present. D Greater than E Less than. I Missing value has been replaced by an interpolated value. J Ordinary component characteristic deduced from the extraordinary component.     U Value determined by a sequence of observationsJ the actua1 observation being inconsistent or doubtfuI. Uncertain or doubtfuI numerical value. :    Qualifying Letters The following letters are entered in the first column before a numerical value on the monthly tabulation sheets, if necessary . A Less than. Used only when fbEs is deduced from foEs because total blanketing of higher layer is present. D Greater than E Less than. I Missing value has been replaced by an interpolated value. J Ordinary component characteristic deduced from the extraordinary component.     U Value determined by a sequence of observationsJ the actua1 observation being inconsistent or doubtfuI. Uncertain or doubtfuI numerical value. Slide32:  CD stazione di Roma

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