Nearly real time IRI correction by TEC-GPS data
Abstract
Monitoring the ionosphere by means of TEC is rather a new tool in comparison with ground monitoring by ionosondes. Such monitoring became truly global after starting GPS-systems of satellites. It is appropriate to study a possibility to use TEC-GPS data for the correction of empirical models, for example, IRI in nearly real time. Two main ways of the IRI-correction can be distinguished: (1) method of Komjathy, (2) using an ionospheric equivalent slab thickness tau=TEC/ NmF2. The first method is global. It modifies all coefficients of the IRI-model taking a lot of resources. The second method is rather simple and can be used as a regional or local variant. Moreover, it can be realized by several algorithms. In our case the corrected foF2 (corr) - values are determined by the factor K=1-alfa(c-1)/c which connects observational tau (obs) with tau (IRI). It is known that IRI-model fails to predict TEC for all seasons and levels of solar activity. The differences between observational and IRI-values can reach 1.5-2 times. The shape of the topside IRI profile is considered to be responsible for such a discrepancy. The factor K is determinated by parameters alfa and c. The parameter alfa is a contribution of topside TEC to the whole TEC (IRI) value. The parameter c is determined analytically by a transition from one shape of the topside profile to another one or as an empirical factor not connected with the shape of the topside profile. Correction algorithms were tested using published experimental data. Differences between corrected and experimental foF2- values were estimated by root mean squares. This paper presents first results of our IRI-correction effort. The examples are given of successful correction. It is shown that the most effective way is to use an empirical factor c.
- Publication:
-
35th COSPAR Scientific Assembly
- Pub Date:
- 2004
- Bibcode:
- 2004cosp...35..403B