- Email: [email protected]
COST 251 recommended instantaneous mapping model of ionospheric characteristics — PLES
Phys.Chem.Eurth(C),Vol. 25,No.4, pp.29l -294,200O 0 2000Elsevier ScienceLtd
Pergamon
All rights reserved 1464-1917/00/$ - see front matter
PII: S1464-1917(00)00019-2
COST 251 Recommended Characteristics - PLES
Instantaneous
Mapping Model of Ionospheric
1. Stanislawska’, G. Juchnikowski’, R. Hanbaba’, H. Rothkael’, G. Sole3, Z. Zbyszynski’ ‘Space Research Centre PAS, ul. Bartycka 18a, 00-716 Warsaw, Poland 2France Telecom CNET, 2 av. Pierre Marzin, 22307 Lannion Cedex, France 30bservatori de I’Ebre, CSIC-URL, Roquetes, Spain Received 31 May 1999; accepted 18 October 1999
Abstract. Monthly median maps of ionospheric foF2 parameter show considerable discrepancies between the actual measurements and the values detected from the maps. Different instantaneous mapping techniques applied to randomly sparsed measurements give better agreement than monthly median maps. The objective of this paper is to present the PLES instantaneous mapping model for foF2 and M(3OOO)F2 that has been recommended as the best achievement of the COST 251 European Action. The method combines monthly median maps of ionospheric characteristic and a set of screen points consisting of measurements for a single moment of time as wel1 as single station long-term models. 0 2000 Elsevier Science Ltd. Al1 rights reserved
1 Introduction The monthly median maps of the ionospheric characteristics provide USwith values of various parameters at the selected locations (ITU-R, 1997, Bradley, 1995, and references therein). Parameters derived from the maps for a selected moment differ significantly from actual measurements. The median value obtained Erom such a map obviously differs more or less from the actual value which causes the models to be insufficient source of information. More information can be obtained by using different instantaneous maps of ionospheric parameters (Bradley, 1995, and references therein, Mikhailov et al., 1995, Stanislawska et al., 1996a). Instantaneous mapping is defined as the technique that is applied when simultaneously measured or forecast values of ionospheric characteristics at limited numbers of locations are used for map generation at a single moment of time. These randomly sparsed data can be of different origin: vertical incidence, radar, or in situ measurements from satellites and rockets, as wel1 as predicted of forecast values. Generally, the number of measurement locations is insufficient for the Correspondence to: IStanislawska
production of fully accurate maps, even over a restricted geographical region, and utilization must be made of artifïcial screen-point values to constrain the mapping contours in remote areas without no-physical gradients of electron concentration. The methods are composed of choosing the form of the smoothing function between the measurements and of adopting screen-point values in region where there are no measurements. COST (Co-operation in Scientific and Technological Research) is an initiative of the European Union bringing together scientists and engineers from Member States to work on common research problems. COST Action 251 IITS (Improved Quality of Service in Ionospheric Telecommunication Systems Planning and Operation) is a four-year project 1995 - 1999 producing improved maps and ionosphere for radiomodels of the European communication applications: ionospheric characteristics maps, electron concentration height profile and TEC (Hanbaba, 1999). In the framework of COST 251 European Project, several limited-area instantaneous mapping models have been developed to provide foF2 and M(3OOO)F2maps within European region (Hanbaba, 1999). Currently, only one method for producing global instantaneous maps of foF2 ionospheric characteristic is available (Rush and Edwards, 1976). The instantaneous mapping methods developed within COST 251 can be easy to spread into the whole globe, however it has to be mentioned that respective tests has not been done yet. The availability of maps has got particular importante in HF propagation assessments and Earth-space communication. Needed tool to generate a map for a single moment of time requires an easy access to data. Up to now, availability of data for maps construction has been realised by on-line exchange of forecaster analysis and prediction information between space weather services, mainly provided by the International space Environment Service (ISES gives current access to the most recent ionospheric information), an internet access to the ionosondes data from different observatories distributed al1 over the world, to which a separate access is not convenient for the
292
1.Stanislawska et al.: COST 251 Recommended lnstantaneous MappingModelof Ionospheric Characteristics - PLES
telecommunication service’s purposes and to ionospheric data gathered in COST 251 Ionospheric Despatch Centre in Europe - IDCE (Stanislawska et al., 1999a) (http:/www. cbk.waw.pl/rwc/idce.html). IDCE allows individuals in different part of the world to have an access to the actual ionospheric parameters.
The instantaneous semivariograms are useless while averaged data give a reasonable semivariogram that can be approximated by a linear function. Semivariogram = c, + ct.d
(2) For mid-latitudes where the staling factor is equal about 2, the parameter c, occurs to be smal1 so that it can be neglected and the approximation takes the form:
2 PLES - COST 251 Model For Instantaneous Mapping
Semivariogram = ct*d (3) where d - ionospheric distance, cl- constant.
Two different interpolation techniques are applied in the mapping model PLES (Poland - PL, Spain - ES): the modified Kriging (Stanislawska et al.,1996a, Stanislawska and Juchnikowski, 1997) and the ‘fitting’ methods (Rush and Edwards, 1976, Juchnikowski and Zbyszynski, 1991). The model combines monthly median maps of ionospheric characteristics and a set of measurements for a single moment of time. Interpolation technique is applied to the deviations of the measurements from the monthly median model which is considered as a background for mapping. The weak point of every mapping procedure is generally the number and/or the distribution of measurement locations (usually insufficient for construction of the maps). Specific ionospheric structures are more accurately reproduced together with the monthly median model (part of information about physical gradients of electron concentration is retained even when the measurements are made far away Erom them). This technique smoothes out many discontinuities. Thus the values of the considered parameter obtained from the map constructed on the base of deviations demonstrate considerable improvement. The monthly median COST 251 model (Hanbaba, 1999) is used as the base for PLES.
The values from semivariogram enter into the system of linear equations from which the weights can be obtained. The resultant weights do not depend on the value of “cl”, so finally “d” itself can be used instead of the semivariogram (Stanislawska et al., 1996a). The input data set for interpolation consists of N points. For each i-th point the coordinates Xi,Yi are given and Z the value of ionospheric parameter in point (Xi,Yi). On output the method gives Z,, - the interpolated value in a given point (X,,,Y,). The result is a weighted average of al1 input Z+
2.1 Modified Kriging Method is based on the characteristic variability demonstrated using variogram, i.e. function that illustrates differentiation of value of parameter depending on the measurements. different distance between the Semivariogram summarises the general farm of the variation, its magnitude and the spatial scale. The precision of the estimated semi-variances depends on the sample size and on the distribution of the data. If the semivariogram is anisotropic, i.e. it is systematically different in different geographical azimuths, the coordinate-dependent staling factor to the latitude is introduced. This factor is estimated on the base of calculated axial ratio of correlation ellipse (latitudinablongitudinal distance) (Stanislawska et al., 1998a). A factor of 2 was found for the mid-latitudes (Stanislawska et al., 1996a) in comparison to the low and equatorial latitudes where it is about 0.8 (Stanislawska et al., 1996b). The data set for semivariogram construction can be obtained where each point represents X=ionospheric distance between two stations (a) and (b) and Y= (foF2(a)-foF2(b))2. The term “ionospheric distance” is defined as follows: d= ~(Long(a)-Long(b))z+(SF(Lat(a)-Lat(b)))2
(1)
(4)
Z=~(WiZi)
The weights Wi are obtained from the system of N+l linear equations: z(VijWi) = Vjo-h aWi=l
j-th equation N+l -th equation
(5) (6)
where: VtJ value of the semivariogram for the “ionospheric distance” between points i-th and j-th, kLagrange factor (not necessary in Kriging). The following notation is assumed for these equations: A*W=B (7) where: A - (N+l)*(N+l) array and W,B - (N+l) vectors. Vector W consists of N weights and A. These equations allow to produce a stand alone modified Ktiging code for ionospheric purposes. 2.2. Fitting The symbols used in this section have the following meaning: - coordinates of the point on a sphere where CP,1 the model is improved, - the model before improvement, f = f(G) f: = f:(cp&) - the improved model, cp’,$ _ coordinates of the i-th point where fol?! is measured, i = g(cp’,h’) - the experimental values, - number of data points, N P i = f(cp’,h’) -,value of the model at an experimental point, w = w(cp,li,cp’,h’-) the factor of influence of a data point on the model. Input to the method consists of the following quantities: 1) twodimensional function f(cp& that represents monthly median model of foF2 on a sphere, 2) a set of N measured
1. Stanislawska et al.: COST 251 Recommended Instantaneous Mapping Model of Ionospheric Characteristics - PLES
values of foF2 - g’ = g(cp’,h’),3) weighting functions w’ = w(cp,h,cp’,k’which ) are a measure of statistical dependence of foF2 between points (cp,h) and (cpi&‘).The weight wi =l when (cp’,X’)= (cp,1) and OIw
s’=
Cs’
293
3 Mapping Results Statistical analysis shows that the accuracy achieved by both methods for different ionospheric parameters is almost the same. Figure 1 presents the percentage deviation for M(3OOO)F2characteristic for years 1956 - 1995 for both methods. Modified Kriging algorithm works better for foF2, while fitting is better for M(3OOO)F2, so that both methods have been combined to produce one COST 251 instantaneous mapping model for ionospheric characteristics - PLES. Figure 2 presents the percentage deviation of foF2 and M(3000)F2 created by PLES model.
(8)
w’+e
1-W’+&
; E - smal1 number e.g. 1V6.
j=l
The variable si a is measure similar to wi, but in the range (O,+oo). The use of E reduces the problem of infinite s’ when wi = 1 or al1 wi = 0 . The weight w,*, like ti, is a measure of influence of the data at the point (cpi&‘)on the model at (cp,h) with the screening effect of al1 other data points considered. The corrected model f reproduces the data points. If there is only one data point (N = 1) then the corrected weighting function w* is equal to the original w. When there are more data points, but one is close to one of them and far from al1 the others, then the weighting factor w,‘, representing the influence of this closest point, is almost equal to the original wi. A screening effect can be observed: close to one of the data points the weighting factors wi* from remote data points are reduced in comparison with w. For two points which ‘are close in space one to the other and characterised by the same values, they carry a redundant information. Thus the resultant f* returns the same value when either one or both data points are inserted into the equations.
Fig.1. Yearly average of the percentage deviation of M(3OOO)F2.Full line - fitting, dotted line Kriging.
0 55
MI
65
70
75 Ye*R*
80
85
90
95
Fig. 2. Yearly average of percentage deviation of model from al1 available measurements since 1957 year. Full line - foF2, dotted line - M(3OOO)FQ.
Samples of M(3OOO)F2and foF2 maps are shown for 4 and 16 June 1993 at 19 UT for disturbed and quiet conditions respectively in Figure 3.
Fig.3. Sample of M(3OOQF2 (upper panels) and foF2 (lower panels) maps for quiet (16.06.1993 19UT - left panels) and disturbed (4.06.1993 19UT - right panels) conditions.
294
1.Stanislawska er al. : COST 251 Recommended Instantaneous Mapping Model of Ionospheric Characteristics - PLES
4 Additional Applications Acknowledgements. Research partly supported by Polish Committee of
The accuracy of the ionospheric map depends on its ability to describe the different phenomena. Only by improving the variety phenomena description the usefulness of the map for different users can be proven further. In more advanced versions of PLES model additional modifïcations have been consist of introduced. These modifications the morphological modelling of the physical phenomena such as the mid-latitude ionospheric trough model (Stanislawska et al., 1999b). For map construction it supplies additional screen-points for gridding (Bradley et al., 1998). Sample of a map with the mid-latitude trough model for April 3 1979 00 UT is shown in Figure 4. The single station long-term models show better accuracy for these locations than global models and provide remarkable advantage in mapping technique (Alberca et al., 1998). The best COST 251 Single Station Models developed by Sole (1998) for foF2 and for M(3000)F2 parameter supplements the montbly median
-UP
ll*
100
MO
w
400
w
Q
Longitude(deg)
model (Stanislawska et al., 1998~). Fig. 4. Sample of fol?? map for April 3 1979 OOUTwith the mid-latitude trough model.
Scientitlc Research Gram No.2 PO3C 006 17.
References Alberca, L. F., G. Juchnikowski, G. J. Sole, and LStanislawska, 1998, Single-station models of ionospheric characteristic fol?2 parameter usable for prediction and instantaneous mapping, Acta Geophys. Pol., 46,2, 217-227. Bradley, P.A., 1995, PRIME (Prediction and Retrospective lonospheric Modeling over Europe), Finul Report, Commission of the European Communities, ECSC-EEC-EAEC, Brussels. Bradley, P.A., G. Juchnikowski, H. Rothkaehl, H., and 1. Stanislawska, 1998, Instantaneous maps of the European middle and high-latitude ionosphere for HF propagation assessments, Adv. Space Research, 22, 6, 861-864.
Hanbaba, R., 1999,, COST 2.51 Finul Report, SRC Printing Office, Warsaw. ITU-R Reference Ionospheric Charactetistics, 1997, Recommendution ITU-R P. 1239, International Telecommunication Union, Geneva. ITU-R Document 3U38, 1999, Chairman’s Report (2 - 9 March 1999). Ionospheric Propagation. Juchnikowski, G. and ZZbyszynski, 1991, Proceedings of the PRIME III Workshop, Rome, January 1991,222-224. Mikhailov, A. V., V. V. Mikhailov, and M. G. Scoblin, 1995, A method for fol?? anf M(3OOO)F2instantaneous mapping over Europe (MQMF2 IM), Proc. COS7238 Workshop, El Arenosillo, September 1994, 115121. Rush, C. M. and W. R. Edwards Jr., 1976, An automated mapping technique for representing the hourly behavior of the ionosphem, Radio Sci., 11,931-937. Sole, G. J., 1998, Relation between hourly monthly median values of fol?? and some geophysical indices. Their application to an ionospheric single station model, Acta Geophys. Pol., 46, 1,77-88. Stanislawska, I., G. Juchnikowski, and Lj. R. Cander, 1996a, The Rriging method of ionospheric parameter foF2 instantaneous mapping, Annali di Geofsica, 39, 4, 845-852.
78
Stanislawska, L, G. Juchnikowski, and Lj. R. Cander, 1996b. Kriging method for instantaneous mapping at low and equatorial latitudes, Adv. in Space Res., 18, 6, 172-176. Stanislawska, 1. and G. Juchnikowski, 1997, A note on use of screen points in regional ionospheric mapping Acts Geophysica Polonica, 45, 4, 355362.
-14
0
19
ti
XP
48
56
6lP
Longitude(deg) Fig. 5. Sample of foE map for 4 June 1993 12 UT.
It has to be mentioned that PLES model can effectively characteristics create maps of other ionospheric (Stanislawska et al., 1998b) (see Fig.5). The potential applications of PLES, including ionospheric and transionospheric propagation, radio direction finding, GPS and over-the-horizon radar investigations, have been recognised by the ITU-R (1999).
Stanislawska, 1.. T. L. Gulyaeva, and G. Juchnikowski, 1998a, Correlation Distances Based on Ionospheric and Geomagnetic Catalogue, Solar Terresttial Predictions - V Proc. of a Workshop, RWC Tokyo, Hiiso Solar Terrestrial Research Center, Communications Research Laboratory, Hitachinaka, lbaraki, Japan, 387-390. Stanislawska, 1.. G. Juchnikowski,, and Z. Zbyszynski, 1998b, Updateing of the monthly median fol?2 maps with the use of screen points, Proc. of the 2-nd COST 251 Workshop, Side, Turkey, 182-189. Stanislawska, I., G. J. Sole, G. Juchnikowski, and Z. Zbyszynski, 1998c, SSMs used for the monthly median foF2 maps construction, Technicul Document of Munagement Committee COST 251 (98)014, El Arenosillo, Spain, October 1998. Stanislawska, L, T. L. Gulyaeva, and R. Hanbaba, 1999a, Ionospheric Despatch Centre in Europe, Physics and Chernistty of the Earth, Part C: Solar-Terrestriol and Planetary Science, 24, (4), 355-357.
Stanislawska, L, G. Juchnikowski, H. Rothkaehl, Z. Zbyszynski, and Y. Tulunay, 1999b. Considering the trough phenomena in COST 251 models, Porc. COST251 Workshop, El Arenosillo, Spain, October 1998, 65-74.
Pergamon
All rights reserved 1464-1917/00/$ - see front matter
PII: S1464-1917(00)00019-2
COST 251 Recommended Characteristics - PLES
Instantaneous
Mapping Model of Ionospheric
1. Stanislawska’, G. Juchnikowski’, R. Hanbaba’, H. Rothkael’, G. Sole3, Z. Zbyszynski’ ‘Space Research Centre PAS, ul. Bartycka 18a, 00-716 Warsaw, Poland 2France Telecom CNET, 2 av. Pierre Marzin, 22307 Lannion Cedex, France 30bservatori de I’Ebre, CSIC-URL, Roquetes, Spain Received 31 May 1999; accepted 18 October 1999
Abstract. Monthly median maps of ionospheric foF2 parameter show considerable discrepancies between the actual measurements and the values detected from the maps. Different instantaneous mapping techniques applied to randomly sparsed measurements give better agreement than monthly median maps. The objective of this paper is to present the PLES instantaneous mapping model for foF2 and M(3OOO)F2 that has been recommended as the best achievement of the COST 251 European Action. The method combines monthly median maps of ionospheric characteristic and a set of screen points consisting of measurements for a single moment of time as wel1 as single station long-term models. 0 2000 Elsevier Science Ltd. Al1 rights reserved
1 Introduction The monthly median maps of the ionospheric characteristics provide USwith values of various parameters at the selected locations (ITU-R, 1997, Bradley, 1995, and references therein). Parameters derived from the maps for a selected moment differ significantly from actual measurements. The median value obtained Erom such a map obviously differs more or less from the actual value which causes the models to be insufficient source of information. More information can be obtained by using different instantaneous maps of ionospheric parameters (Bradley, 1995, and references therein, Mikhailov et al., 1995, Stanislawska et al., 1996a). Instantaneous mapping is defined as the technique that is applied when simultaneously measured or forecast values of ionospheric characteristics at limited numbers of locations are used for map generation at a single moment of time. These randomly sparsed data can be of different origin: vertical incidence, radar, or in situ measurements from satellites and rockets, as wel1 as predicted of forecast values. Generally, the number of measurement locations is insufficient for the Correspondence to: IStanislawska
production of fully accurate maps, even over a restricted geographical region, and utilization must be made of artifïcial screen-point values to constrain the mapping contours in remote areas without no-physical gradients of electron concentration. The methods are composed of choosing the form of the smoothing function between the measurements and of adopting screen-point values in region where there are no measurements. COST (Co-operation in Scientific and Technological Research) is an initiative of the European Union bringing together scientists and engineers from Member States to work on common research problems. COST Action 251 IITS (Improved Quality of Service in Ionospheric Telecommunication Systems Planning and Operation) is a four-year project 1995 - 1999 producing improved maps and ionosphere for radiomodels of the European communication applications: ionospheric characteristics maps, electron concentration height profile and TEC (Hanbaba, 1999). In the framework of COST 251 European Project, several limited-area instantaneous mapping models have been developed to provide foF2 and M(3OOO)F2maps within European region (Hanbaba, 1999). Currently, only one method for producing global instantaneous maps of foF2 ionospheric characteristic is available (Rush and Edwards, 1976). The instantaneous mapping methods developed within COST 251 can be easy to spread into the whole globe, however it has to be mentioned that respective tests has not been done yet. The availability of maps has got particular importante in HF propagation assessments and Earth-space communication. Needed tool to generate a map for a single moment of time requires an easy access to data. Up to now, availability of data for maps construction has been realised by on-line exchange of forecaster analysis and prediction information between space weather services, mainly provided by the International space Environment Service (ISES gives current access to the most recent ionospheric information), an internet access to the ionosondes data from different observatories distributed al1 over the world, to which a separate access is not convenient for the
292
1.Stanislawska et al.: COST 251 Recommended lnstantaneous MappingModelof Ionospheric Characteristics - PLES
telecommunication service’s purposes and to ionospheric data gathered in COST 251 Ionospheric Despatch Centre in Europe - IDCE (Stanislawska et al., 1999a) (http:/www. cbk.waw.pl/rwc/idce.html). IDCE allows individuals in different part of the world to have an access to the actual ionospheric parameters.
The instantaneous semivariograms are useless while averaged data give a reasonable semivariogram that can be approximated by a linear function. Semivariogram = c, + ct.d
(2) For mid-latitudes where the staling factor is equal about 2, the parameter c, occurs to be smal1 so that it can be neglected and the approximation takes the form:
2 PLES - COST 251 Model For Instantaneous Mapping
Semivariogram = ct*d (3) where d - ionospheric distance, cl- constant.
Two different interpolation techniques are applied in the mapping model PLES (Poland - PL, Spain - ES): the modified Kriging (Stanislawska et al.,1996a, Stanislawska and Juchnikowski, 1997) and the ‘fitting’ methods (Rush and Edwards, 1976, Juchnikowski and Zbyszynski, 1991). The model combines monthly median maps of ionospheric characteristics and a set of measurements for a single moment of time. Interpolation technique is applied to the deviations of the measurements from the monthly median model which is considered as a background for mapping. The weak point of every mapping procedure is generally the number and/or the distribution of measurement locations (usually insufficient for construction of the maps). Specific ionospheric structures are more accurately reproduced together with the monthly median model (part of information about physical gradients of electron concentration is retained even when the measurements are made far away Erom them). This technique smoothes out many discontinuities. Thus the values of the considered parameter obtained from the map constructed on the base of deviations demonstrate considerable improvement. The monthly median COST 251 model (Hanbaba, 1999) is used as the base for PLES.
The values from semivariogram enter into the system of linear equations from which the weights can be obtained. The resultant weights do not depend on the value of “cl”, so finally “d” itself can be used instead of the semivariogram (Stanislawska et al., 1996a). The input data set for interpolation consists of N points. For each i-th point the coordinates Xi,Yi are given and Z the value of ionospheric parameter in point (Xi,Yi). On output the method gives Z,, - the interpolated value in a given point (X,,,Y,). The result is a weighted average of al1 input Z+
2.1 Modified Kriging Method is based on the characteristic variability demonstrated using variogram, i.e. function that illustrates differentiation of value of parameter depending on the measurements. different distance between the Semivariogram summarises the general farm of the variation, its magnitude and the spatial scale. The precision of the estimated semi-variances depends on the sample size and on the distribution of the data. If the semivariogram is anisotropic, i.e. it is systematically different in different geographical azimuths, the coordinate-dependent staling factor to the latitude is introduced. This factor is estimated on the base of calculated axial ratio of correlation ellipse (latitudinablongitudinal distance) (Stanislawska et al., 1998a). A factor of 2 was found for the mid-latitudes (Stanislawska et al., 1996a) in comparison to the low and equatorial latitudes where it is about 0.8 (Stanislawska et al., 1996b). The data set for semivariogram construction can be obtained where each point represents X=ionospheric distance between two stations (a) and (b) and Y= (foF2(a)-foF2(b))2. The term “ionospheric distance” is defined as follows: d= ~(Long(a)-Long(b))z+(SF(Lat(a)-Lat(b)))2
(1)
(4)
Z=~(WiZi)
The weights Wi are obtained from the system of N+l linear equations: z(VijWi) = Vjo-h aWi=l
j-th equation N+l -th equation
(5) (6)
where: VtJ value of the semivariogram for the “ionospheric distance” between points i-th and j-th, kLagrange factor (not necessary in Kriging). The following notation is assumed for these equations: A*W=B (7) where: A - (N+l)*(N+l) array and W,B - (N+l) vectors. Vector W consists of N weights and A. These equations allow to produce a stand alone modified Ktiging code for ionospheric purposes. 2.2. Fitting The symbols used in this section have the following meaning: - coordinates of the point on a sphere where CP,1 the model is improved, - the model before improvement, f = f(G) f: = f:(cp&) - the improved model, cp’,$ _ coordinates of the i-th point where fol?! is measured, i = g(cp’,h’) - the experimental values, - number of data points, N P i = f(cp’,h’) -,value of the model at an experimental point, w = w(cp,li,cp’,h’-) the factor of influence of a data point on the model. Input to the method consists of the following quantities: 1) twodimensional function f(cp& that represents monthly median model of foF2 on a sphere, 2) a set of N measured
1. Stanislawska et al.: COST 251 Recommended Instantaneous Mapping Model of Ionospheric Characteristics - PLES
values of foF2 - g’ = g(cp’,h’),3) weighting functions w’ = w(cp,h,cp’,k’which ) are a measure of statistical dependence of foF2 between points (cp,h) and (cpi&‘).The weight wi =l when (cp’,X’)= (cp,1) and OIw
s’=
Cs’
293
3 Mapping Results Statistical analysis shows that the accuracy achieved by both methods for different ionospheric parameters is almost the same. Figure 1 presents the percentage deviation for M(3OOO)F2characteristic for years 1956 - 1995 for both methods. Modified Kriging algorithm works better for foF2, while fitting is better for M(3OOO)F2, so that both methods have been combined to produce one COST 251 instantaneous mapping model for ionospheric characteristics - PLES. Figure 2 presents the percentage deviation of foF2 and M(3000)F2 created by PLES model.
(8)
w’+e
1-W’+&
; E - smal1 number e.g. 1V6.
j=l
The variable si a is measure similar to wi, but in the range (O,+oo). The use of E reduces the problem of infinite s’ when wi = 1 or al1 wi = 0 . The weight w,*, like ti, is a measure of influence of the data at the point (cpi&‘)on the model at (cp,h) with the screening effect of al1 other data points considered. The corrected model f reproduces the data points. If there is only one data point (N = 1) then the corrected weighting function w* is equal to the original w. When there are more data points, but one is close to one of them and far from al1 the others, then the weighting factor w,‘, representing the influence of this closest point, is almost equal to the original wi. A screening effect can be observed: close to one of the data points the weighting factors wi* from remote data points are reduced in comparison with w. For two points which ‘are close in space one to the other and characterised by the same values, they carry a redundant information. Thus the resultant f* returns the same value when either one or both data points are inserted into the equations.
Fig.1. Yearly average of the percentage deviation of M(3OOO)F2.Full line - fitting, dotted line Kriging.
0 55
MI
65
70
75 Ye*R*
80
85
90
95
Fig. 2. Yearly average of percentage deviation of model from al1 available measurements since 1957 year. Full line - foF2, dotted line - M(3OOO)FQ.
Samples of M(3OOO)F2and foF2 maps are shown for 4 and 16 June 1993 at 19 UT for disturbed and quiet conditions respectively in Figure 3.
Fig.3. Sample of M(3OOQF2 (upper panels) and foF2 (lower panels) maps for quiet (16.06.1993 19UT - left panels) and disturbed (4.06.1993 19UT - right panels) conditions.
294
1.Stanislawska er al. : COST 251 Recommended Instantaneous Mapping Model of Ionospheric Characteristics - PLES
4 Additional Applications Acknowledgements. Research partly supported by Polish Committee of
The accuracy of the ionospheric map depends on its ability to describe the different phenomena. Only by improving the variety phenomena description the usefulness of the map for different users can be proven further. In more advanced versions of PLES model additional modifïcations have been consist of introduced. These modifications the morphological modelling of the physical phenomena such as the mid-latitude ionospheric trough model (Stanislawska et al., 1999b). For map construction it supplies additional screen-points for gridding (Bradley et al., 1998). Sample of a map with the mid-latitude trough model for April 3 1979 00 UT is shown in Figure 4. The single station long-term models show better accuracy for these locations than global models and provide remarkable advantage in mapping technique (Alberca et al., 1998). The best COST 251 Single Station Models developed by Sole (1998) for foF2 and for M(3000)F2 parameter supplements the montbly median
-UP
ll*
100
MO
w
400
w
Q
Longitude(deg)
model (Stanislawska et al., 1998~). Fig. 4. Sample of fol?? map for April 3 1979 OOUTwith the mid-latitude trough model.
Scientitlc Research Gram No.2 PO3C 006 17.
References Alberca, L. F., G. Juchnikowski, G. J. Sole, and LStanislawska, 1998, Single-station models of ionospheric characteristic fol?2 parameter usable for prediction and instantaneous mapping, Acta Geophys. Pol., 46,2, 217-227. Bradley, P.A., 1995, PRIME (Prediction and Retrospective lonospheric Modeling over Europe), Finul Report, Commission of the European Communities, ECSC-EEC-EAEC, Brussels. Bradley, P.A., G. Juchnikowski, H. Rothkaehl, H., and 1. Stanislawska, 1998, Instantaneous maps of the European middle and high-latitude ionosphere for HF propagation assessments, Adv. Space Research, 22, 6, 861-864.
Hanbaba, R., 1999,, COST 2.51 Finul Report, SRC Printing Office, Warsaw. ITU-R Reference Ionospheric Charactetistics, 1997, Recommendution ITU-R P. 1239, International Telecommunication Union, Geneva. ITU-R Document 3U38, 1999, Chairman’s Report (2 - 9 March 1999). Ionospheric Propagation. Juchnikowski, G. and ZZbyszynski, 1991, Proceedings of the PRIME III Workshop, Rome, January 1991,222-224. Mikhailov, A. V., V. V. Mikhailov, and M. G. Scoblin, 1995, A method for fol?? anf M(3OOO)F2instantaneous mapping over Europe (MQMF2 IM), Proc. COS7238 Workshop, El Arenosillo, September 1994, 115121. Rush, C. M. and W. R. Edwards Jr., 1976, An automated mapping technique for representing the hourly behavior of the ionosphem, Radio Sci., 11,931-937. Sole, G. J., 1998, Relation between hourly monthly median values of fol?? and some geophysical indices. Their application to an ionospheric single station model, Acta Geophys. Pol., 46, 1,77-88. Stanislawska, I., G. Juchnikowski, and Lj. R. Cander, 1996a, The Rriging method of ionospheric parameter foF2 instantaneous mapping, Annali di Geofsica, 39, 4, 845-852.
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Stanislawska, L, G. Juchnikowski, and Lj. R. Cander, 1996b. Kriging method for instantaneous mapping at low and equatorial latitudes, Adv. in Space Res., 18, 6, 172-176. Stanislawska, 1. and G. Juchnikowski, 1997, A note on use of screen points in regional ionospheric mapping Acts Geophysica Polonica, 45, 4, 355362.
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XP
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Longitude(deg) Fig. 5. Sample of foE map for 4 June 1993 12 UT.
It has to be mentioned that PLES model can effectively characteristics create maps of other ionospheric (Stanislawska et al., 1998b) (see Fig.5). The potential applications of PLES, including ionospheric and transionospheric propagation, radio direction finding, GPS and over-the-horizon radar investigations, have been recognised by the ITU-R (1999).
Stanislawska, 1.. T. L. Gulyaeva, and G. Juchnikowski, 1998a, Correlation Distances Based on Ionospheric and Geomagnetic Catalogue, Solar Terresttial Predictions - V Proc. of a Workshop, RWC Tokyo, Hiiso Solar Terrestrial Research Center, Communications Research Laboratory, Hitachinaka, lbaraki, Japan, 387-390. Stanislawska, 1.. G. Juchnikowski,, and Z. Zbyszynski, 1998b, Updateing of the monthly median fol?2 maps with the use of screen points, Proc. of the 2-nd COST 251 Workshop, Side, Turkey, 182-189. Stanislawska, I., G. J. Sole, G. Juchnikowski, and Z. Zbyszynski, 1998c, SSMs used for the monthly median foF2 maps construction, Technicul Document of Munagement Committee COST 251 (98)014, El Arenosillo, Spain, October 1998. Stanislawska, L, T. L. Gulyaeva, and R. Hanbaba, 1999a, Ionospheric Despatch Centre in Europe, Physics and Chernistty of the Earth, Part C: Solar-Terrestriol and Planetary Science, 24, (4), 355-357.
Stanislawska, L, G. Juchnikowski, H. Rothkaehl, Z. Zbyszynski, and Y. Tulunay, 1999b. Considering the trough phenomena in COST 251 models, Porc. COST251 Workshop, El Arenosillo, Spain, October 1998, 65-74.