1. Ground-based GNSS data for the correction of the ionospheric model using modified solar index
D.S. Kotova1,2, V. Ovodenko3, Yu.V. Yasyukevich4, I. Nosikov1,2, M.V. Klimenko1,2, A.A. Mylnikova4, K.G. Ratovsky4
1WD IZMIRAN, Kaliningrad, Russia; 2Immanuel Kant Baltic Federal University, Kaliningrad, Russia ;
3Joint Stock Company Scientific Research Institute of Long-Distance Radio Communication, Moscow, Russia
4Institute of Solar-Terrestrial Physics, SB RAS, Irkutsk, Russia

2. Ionospheric Effects on Radio Applications
The creation of the ionospheric plasma is mainly due to the solar radiation. Different kinds of solar spectrum ionize different kinds of ionospheric heights. The ionosphere is very important for application. The ionosphere can reflect high frequency radio waves. In addition, the ionosphere plays an important role for navigation and radar system. A signal passes through the ionosphere from the satellite to the receiver.

3. Ionospheric Effects on Radio Applications
The ionosphere has a significant effect on the propagation of radio waves. Changes in the solar radiation lead to changes in the electron density in the ionosphere. We have different scintillation, propagation delay, interference and magnification radio absorption.

4. ITU-R Recommendations
Radio Communication Sector of the International Telecommunications Union (ITU-R) makes recommendations on the choice of ionospheric models and solar activity indices for these models.
ITU-R recommends using the International Reference Ionosphere model (IRI) or the NeQuick model for a long-term ionospheric forecast.
As indices of the solar activity (as the input parameters of these models, which are predicted), use:
Rz12 - the moving average for 12 months (central for the given month) value of the relative number of sunspots,
F12 - the moving average for 12 months the magnitude of the flux of radio emission of the Sun at the wavelength of 10.7 cm.
TEC
F10.7 Rz

5. ITU-R Recommendations
In this case, ITU-R recommends using Rz12 as the preferred index for forecasting the monthly median foF2.

6. NeQuick model
NeQuick is a three-dimensional and time dependent ionospheric electron density model developed at the Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, Italy and at the University of Graz, Austria.
It is a quick-run model particularly tailored for trans-ionospheric applications that allows to calculate the electron density at any given location in the ionosphere and thus the total electron content (TEC) along any ground-to satellite ray-path by means of numerical integration.
Input
Year, month, day, time, geographic coordinates of lower and higher endpoint, Rz12 or daily F10.7 solar flux.
Output
electron density along the path
~ slant total electron content
Mahrous et al. in “Mitigation of Ionospheric Threats to GNSS: an Appraisal of the Scientific and Technological Outputs of the TRANSMIT Project” DOI: /58773

7. “Climate” or “Weather”?
• Empirical models like IRI and NeQuick have been developed as climatological models, able to reproduce the typical median condition of the ionosphere. • For research purposes and practical applications, in order to pass from “climate” to “weather”, there is a need to have models able to reproduce the current conditions of the ionosphere. • NeQuick model does not describe climatically high latitudes. • Considering that there is an increasing availability of experimental data even in real time (ground and space-based GPS, ionosondes), several assimilation schemes have been developed. They are of different complexity and rely on different kinds of data.

8. Our Motivation
Most of the recent papers based on GNSS data in the mid-latitude ionosphere showed a good agreement between the corrected and the experimental ionospheric data (Maltseva et al., ASR, 2012; Migoya- Orue et al., ASR, 2015; Ovodenko et al., ASR, 2015);
Operational environment model improvement for applications;
The updating ionospheric models in high latitude has not been studied and developed sufficiently.

9. NAVSTAR (Navigation Satellite Timing and Ranging) GPS (Global Positioning System)
Worldwide ground-based network of satellite signal receivers provide a new possibility of real time ionospheric monitoring. This is due to GNSS satellites such as:
GPS (US)
Galileo (EU)
GLONASS (Russia)
ets.

10. GNSS (GPS and other) receivers network
These systems allow us to calculate TEC along radio path between each satellite and the receiver on the ground

11. TEC and profile Ne
TEC
But TEC does not provide any information about the profile of the electron density. In order to solve the practical problem of radio waves propagation, we need to know the profile of Ne. Thus, we use a model to describe the climate and the structural features of the ionosphere, and the data of GNSS signal receivers is used for weather correction of the environment model.

12. GNSS receivers and vertical sounding station
The receivers in Lovozero and Vars will be used by us to correct the NeQuick model to describe the space weather in the considered high-latitude region. Verification of this updating will occur by comparing the model calculations with the data of the vertical sounding station in Sodankylä.
Code
Name
Lat
Lon
LOZ
Lovozero
68.00
35.02
VARS
Vars
70.00
31.00
SOD
Sodankyla
67.37
26.63

13. An updating procedure for ionospheric model
Rz12
α>45˚
360º
Stage 1
NeQuick
sTECobs
LOZ
(68°N, 35°E)
VARS
(70°N, 31°E)
sTECmod
Stage 2
α<45˚
20º
new Rz12
Without correction
Stage 1
Stage 2
Azim
Elev
TECobs
Rz12
TECmod
dTEC
266.5
166.3
199.3
127.9
56.0
53.8
55.4
62.2
43.08
45.12
43.66
10.34
114
29.72
34.10
32.94
13.61
13.36
11.02
10.71
-3.27
150
39.85
46.05
44.82
3.23
-0.93
-1.16
106
134
128
54.67
79.24
87.94
28.25
29.84
19.50
-0.09
0.01
-0.53 72
10.33
104
127.8
15.37

14. The daily foF2 over Sodankylä
The slide shows the comparison of the results of calculating foF2 in the NeQuick model with the observations data of the vertical sounding station. The observation data (violet stars), as a result of model calculations, represented by blue hollow circles and a dashed line correspond to calculations with the forecast Rz12, green circles and a solid line to the first stage of correction, red circles to the second one. For the second stage of updating procedure, azimuths close to 213º (VARS → SOD) and 263º (LOZ → SOD) were considered. You can see that for March, the daily maximum of foF2 after correction is described better than without it. In December - in the evening and in the morning. In December the correction led to the deterioration in comparison with the model calculations with the predicted Rz12

15. Oblique sounding ionogram modelling
The electron density from updating NeQuick model we use as a medium of the HF radio wave propagation
March 22, 2014
06:00 UT

16. Possible reasons 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5
As the studies in these articles (Lunt et al., 1999; Balan et al., 2002; Zakharenkova et al., 2013;Yizengaw et al., 2008; Cherniak et al., 2012; Lee et al., 2013; Klimenko et al., 2015) show, the contribution of the plasmasphere to the value of the total electron content can be compared with the ionospheric contribution.
Therefore, it is important to correctly describe the electron density profile
above the F2 layer.

17. Summary
Preliminary results show that model correction method, which is good for middle latitudes, does not work for high latitudes.
It can be assumed that the degradation of the results of the updating procedure is due to the errors in the description of the electron density profile in the plasmasphere by the NeQuick model.
We also plan to use more GNSS receivers (observational data) in the future research.

18. Thank for your attention!
When human beings start to live in space, research on the ionosphere would become much closer to our daily life.
“Space Meteorology”