Pergamon Adv. SpaceRes. Vol. 14, No. 12, pp. (12)83--(12)86, 1994

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COMPARING THE IMPROVED DI GIOVANNI/RADICELLA MODEL WITH SOUNDING-BASED ELECTRON DENSITY PROFILES AND WITH THE IRI MODEL

W. Singer, J. Weiss and J. Bremer

Institute of Atmospheric Physics, D(0)-2565 Ktihlungsborn, Germany

ABSTRACT

rhe Di Giovanni/Radicella model (DGR) /1/ determines a bottom side electron densty profile alone from

the set of routinely scaled ionogram parameters foE, foF1, foF2 and M(3000)F2 and the total electron content; the smoothed sunspot number R12 appears in the calculation. Present designations are DGR2/2/ and DRR3/31 [see Appendix]; they are valid in the northern hemisphere. DGR is compared with electron

density profiles derived from ionograms obtained at Juliusrnh (54.60N, 13.4°E), and with the (URSI- based) IRIg0 at different conditiones. Experimental total electron content (TEC) data are compared to both models. At the considered station, the profiles obtained by both models are reasonably in agreement amongst themselves and with the experimental data.

rhe TEC derived from the DGR3 model is in good agreement with experimental TEC, whereas, at high ~olar activity, IRI90 gives too high TEC values, especially during daytime.

COMPARING DGR2 MODEL PROFILES WITH THOSE FROM

IONOGRAM INVERSION

For four seasons a set of true height profiles has been computed by Jackson's method/4,5/from vertical sounding data for all even hours in years of low (1976/R12=15) and very high solar activity

(1980/R12=155).

FABLE 1 Data set: Number of Profiles

Period Number R12 Period Number R12

19.-21.01.1976 34 15 15.-17.01.1980 36 164

15.-17.04.1976 36 13 15.-17.04.1980 36 159 13.-15.07.1976 34 13 8.-10.07.1980 36 153 19.-21.10.1976 32 14 7.-09.10.1980 35 150

[nstantaneonsly measured values of the routine parameters were taken as input to DGR2. DGR2 approximates the true height profiles sufficiently well by day; differences were found in July/Rmin with too great and in October/Rmax with too low values from the model. During nighttime DGR2 model gives generally lower values; a good agreement is only fround in July (Rmin and October/Rmax.

~ome examples are shown in Figure 1.

(12)s3

(12)84 W. Singer et al.

km

400"

300'

100

October 1980

DGRZ~ EXP - -

Zl~19.

OOUT

/ /

/

I

06UT

i d

/

"*'" I ! / i # • //

• /,s ¢,,

/ / /

I lO s

16UT

N, Icm'~

Ib4 lbs 166 lb~ Fig. 1. Electron density profiles from i o n o ~ inversion (---) and from DGI~ model ( - - ) for October 1980, R12=150

km

~00-

DGR 2 ~'~ ~".,-nua, z 1 9 8 0 1 9 7 6

IRl 90

j 300. 02UT /

• "

2OO

IV, [ c m a

Ib~ ~' lbs i6s Fig. 2. Electron density profiles from IRI90 (Bo-Oulyeva, measured F2 peak data) and from the DGR2 model using monthly medians of ionospheric characteristics (Juliusruh) for January (1976/R12ffi15, 1980/R12ffi164)

Sounding-Based Electron Density Profiles (12)85

TEG (I0..151m*.2) 120

100

80

60

40

20

0 . I , 1 , 1 , 1 , I . 1 , 1 , 1 , 1 , I , I , I 2 4 6 8 10 12 14 16 18 20 22 24

LT

120

100

8 0

-60

-40

20

0

TEC (10..15/m*.2)

7001| t 700600 eoo, ~

°001 ,oo I

F oo 200~

, I , I , I , I , I , I , I , 1 , I , I , I , I

0 2 4 6 8 10 12 14 16 18 20 22 24 LT

TEC (10..15/m*.2) 500 500

400

300

200

100 July 1980 R12=153

. 1 , 1 , 1 , 1 , I , I , I , I , I , I , I , I

2 4 6 8 10 12 14 16 18 20 22 24 LT

400

300

200

100

0

exp -& ' - IRIgO (F2 exp) ~ IRI90 (URSI) - 0 - DGR3

Fig. 3. Diurnal variat ion o f T E C f rom IRI90 (F2 peak: URSI-based and exper imenta l ) and f rom D G R 3 model using month ly medians o f i onosphedc characterist ics (Juliusruh) in compar ison with exper imental T E C d a ~

(12)86 W. Singer etal.

COMPARISON WITH IRI90

As shown in Figure 2 both models agree sufficiently well for all considered conditiones. At very high solar activity, IRI90 gave too low electron densities compared to the mid-April observations. Note that mouthly average foF2 was used as input to IRI90, not the individually observed values. [hmF2 was put equal to the DGR2 value].

COMPARISON OF TEC DERIVED FROM BOTH MODELS

As for IRI90 the total electron content (90...1200 km) was computed by numerical integration with the

bottomside thickness parameter parameter Bo after Gulyaeva and experimental F2 peak data on the one hand and with URSI F2 peak data on the other. The DGR3 model has an analytical expression for the TEC using foE, foF1, foF2, M(3000)F2 and R12. The total electron content for both models is calcilated using monthly medians of ionospheric characteristics measured at Juliusruh in January, April, July and October for low and high solar activity and compared with monthly median TEC data derived from Differential Doppler on the signal of polar orbiting satellites (NNSS) 161. The data for high solar activity correspond to the period 1972-1982 at 60°N and the data for low solar activity to 1975-1978 at 50°N. At low solar activity both models are in good agreement with the experimental data (Fig. 3). Around noon IRI90 gives slightly lower values in April, July and October and DGR3 in July and October. At very high solar activity, around noon, IRI90 generally gives too high values in particular in January, April and October whereas DGR3 agrees with the experimental in all considered conditiones (Fig. 3).

CONCLUSIONS

Both models agree sufficiently well with the observed data sets.

REFERENECES

1. G. Di Giovanni and S. M. Radicella, An analytical model of the electron density in the ionosphere, Adv. Space Res. 10#11, 27-30 (1980).

2. S.M. Radicella and G. Di Giovanni, Improvement of the Di Giovanni-Radicella model of electron density profiles, manuscript awaiting publication.

3. G. Di Giovanni, S. M. Radicella and M.-L. Zhang, Further development of the DGR ionospheric model and comparison with the current IRI model, COST 238 (PRIME)/URSI Joint Workshop, Roquetes, Spain, 4-6 May (1992).

4. J.E. Jackson, The P'(f) to N(h) inversion problem in ionospheric soundings, Goddard Space Flight Center, preprint X-625-71-188 (1971).

5. G. Johanning, C.-U. Wagner and J. Weiss, Calculation of electron density profiles from ionosonde records, Phys. Solariterr. (Potsdam) 22, 52-93 (1983).

6. R. Leitinger and E. Feichter, A regional model for ionospheric electron content, "Working Book", PRIME Meeting, Roma, Italy, January 1991.