Ionospheric effects of the August 11, 2018, solar eclipse over the People’s Republic of China

Heading: 
Dynamics and Physics of Solar System Bodies
1Chernogor, LF, Milovanov, YB
1V.N. Karazin Kharkiv National University, Kharkiv, Ukraine
Kinemat. fiz. nebesnyh tel (Online) 2020, 36(6):37-64
https://doi.org/10.15407/kfnt2020.06.037
Start Page: Dynamics and Physics of Bodies of the Solar System
Language: Ukrainian
Abstract: 

The purpose of the work is to describe the ionospheric effects of the August 11, 2018 partial solar eclipse (SE) that occurred over the People’s Republic of China, as observed via GPS technology. SEs present rare phenomena of nature. In the course of 2 to 3 hours, the rearrangement of processes acting at the Earth’s surface, in the atmosphere, geospace, i.e., in the Earth — atmosphere — ionosphere — magnetosphere system (EAIMS), occurs. The response of this system depends on the solar activity, season, time of day, and on the state of atmospheric and space weather. Therefore, the study of the EAIMS response to SEs remains an urgent need. The response is accompanied by controllable dynamic processes, the study of which improves our understanding of the near-Earth environment. The study of the EAIMS response to SEs is of fundamental importance to science. Its practical applications include the following. The SE give rise to significant perturbations in the EAIMS, which affect the propagation of radio waves virtually in all frequency bands, and consequently deteriorate the operation of radar, radio astronomy, and radio navigation systems, as well as the instruments for remotely sensing the medium. The SE effects have been studied for over more than about 100 years. Thus far, the following regular effects have been quite well studied: decreases in the electron density, electron and ion temperatures, variations in ion composition, and plasma vertical movements. The irregular effects have been studied to a significantly smaller degree, and they can vary from one solar eclipse to another. The main feature of the SE over the PRC was the fact that it was observed during before local time sunset period. The maximum phase of the eclipse within the PRC area varied from 0.07 to 0.52, while the Sun’s surface area occulted by the moon was observed to be 0.02—0.42. The beginning of the eclipse over the PRC was observed to occur in the 09:54—10:05 UT period, and the end varied from 10:07 UT to 11:10 UT. The SE duration varied from a few minutes to approximately 67 min. The insignificant duration of the eclipse and the dusk terminator affected the SE effects. The state of space weather during the solar eclipse was conducive to observing the SE effects occurring in the ionosphere. To reveal the ionospheric response to the August 11, 2018, SE, the global navigation satellite system data were processed. The ionospheric time delay and, respectively, the vertical total electron content (TEC), were calculated combining the pseudo range and integrated phase data at two frequencies. Regardless of the dusk terminator influence, we have managed to confidently detect the ionospheric SE effects, which proved to be sufficiently small because of small values of the SE phase. Over the People’s Republic of China area, a funnel-shaped decrease in TEC was observed to occur approximately 1,300 km in latitude and 2,000 km in longitude. The TEC decrease was observed to be 7 %. The solar eclipse was accompanied by the generation of aperiodic TEC disturbances at a rate of 0.4—0.8 TEC unit/h and 105-min in duration. Wave disturbances caused by the SE were not observed confidently, which is due to the small value of the SE phase and insignificant disturbances in the electron density.
Keywords: aperiodic disturbances, GPS-technology, ionosphere, solar eclipse, total electron content

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References: 

1. Akimov A. L., Akimov L. A., Chernogor L. F. (2007). Turbulence Parameters in the Atmosphere Associated with Solar Eclipses. Radio Phys. and Radio Astron. 12(2). 117—134 (In Russian).

2. Akimov A. L., Chernogor L. F. (2010). Effects of the Solar Eclipse of August 1, 2008 on the Earth’s Lower Atmosphere. Kimematics and Phys. Celestial Bodies. 26(3). 135—145. 
https://doi.org/10.3103/S0884591310030050

3. Akimov L. A., Bogovskii V. K., Grigorenko E. I., Taran V. I., Chernogor L. F. (2005). Atmospheric-Ionospheric Effects of the Solar Eclipse of May 31, 2003, in Kharkov. Geomagnetism and Aeronomy. 45(4). 494—518. 

4. Akimov L. A., Grigorenko E. I., Taran V. I., Tyrnov O. F., Chernogor L. F. (2002). Complex Radar and Optical Studies of Dynamic Processes in the Atmosphere and Geospace, Related to the Solar Eclipse of August 11, 1999. Usp. Sovrem. Radioelektron. 2. 25—63 (In Russian).

5. Akimov L. A., Grigorenko E. I., Taran V. I., Chernogor L. F. (2005). The features fatmosphere and ionosphere effects of May 31, 2003 solar eclipse: optical and radiophysical observations results in Kharkiv. The Modern Radio Electronics Successes. 3. 55—70 (In Russian).

6. Al’pert Ya. L., Gorojankin B. N. (1944). Solar eclipses and ionosphere radio investigations. Izv. AN USSR. Geophysica Series. 8. 85 p. (In Russian).

7. Afraimovich E. L., Voeykov S. V., Perevalova N. P., Vodyannikov V. V., Gordienko G. I., Litvinov Yu. G., Yakovets A. F. (2007). Ionospheric effects of the March 29, 2006, solar eclipse over Kazakhstan. Geomagnetism and Aeronomy. 47(4). 461— 469. 
https://doi.org/10.1134/S0016793207040068

8. Afraimovich E. L., Perevalova N. P. GPS-monitoring of the Earth upper atmosphere. Irkutsk: Solar-Terrestrial Physics Institute SD RAS: SI SC RRS ESSC SD RAMS, 479 p.(In Russian).

9. Bezrodny V. G., Bliokh P. B., Shubova R. S., Yampolskiy Yu. M. (1984). Fluctuations of superlong radio waves in the Earth-Ionosphere waveguide. Moscow: Nauka, 144. (in Russian).

10. Boitman O. N., Kalihman A. D., Tashilin A. V. (1999). Mid-latitude ionosphere during 09 March, 1997 solar eclipse. 1. Modeling effects of eclipse. Geomagnetism and Aeronomy. 39(6). 45—51 (In Russian).

11. Boitman O. N., Kalikhman A. D., Tashchilin A. V. (1999). The midlatitude ionosphere during the total solar eclipse of March 9, 1997. Geomagnetism and Aeronomy. 39(6). 52—60 (In Russian).
https://doi.org/10.1029/1999JA900228

12. Bolshakova O. V., Kurashkovskaya N. A., Troickaya V. A. (1987). Solar eclipse effect in Pc 3 geomagnetic pulses. Geomagnetism and Aeronomy. 27(1). 122—125 (In Russian).

13. Borisov B. B., Egorov D. A., Egorov N. E., Kolesnik A. G., Kolesnik S. A., Melchinov V. P., Nagorskij P. M., Parfenov S. S., Reshetnikov D. D., Smirnov V. F., Stepanov A. E., Tarashuk Yu. E., Telpuhovskij E. D., Cybikov B. B., Shinkevich B. M. (2000). The complex experimental investigation of ionosphere effect on March 09, 1997 solar eclipse. Geomagnetism and Aeronomy. 40(3). 94—103 (In Russian).

14. Burmaka V. P., Grigorenko E. I., Emel’yanov L. Ya., Lysenko V. N., Lyashenko M. V., Chernogor L. F. (2007). Radar observations of effects in the geospace, caused by the partial solar eclipse of March 29, 2006. Usp. Sovrem. Radioelektron. 3. 38—53 (In Russian).

15. Burmaka V. P., Domnin I. F., Chernogor L. F. (2012). Radiophysical Observations of Acoustic-Gravity Waves in the Ionosphere during Solar Eclipse of January 4, 2011. Radio Phys. and Radio Astron. 17(4). 344—352. (In Russian).

16. Burmaka V. P., Lysenko V. N., Lyashenko M. V., Chernogor L. F. (2007). Tropospheric-ionospheric effects of the 3 October 2005 partial solar eclipse in Kharkiv. 1. Observations. Kosm. nauka tehnol. 13(6). 74—86 (In Russian). 
https://doi.org/10.15407/knit2008.01.057

17. Burmaka V. P., Taran V. I., Chernogor L. F. (2006). Wave-like processes in the ionosphere under quiet and disturbed conditions. 1. Kharkov incoherent scatter radar observations. Geomagnetism and Aeronomy. 46(2). 183—198. 
https://doi.org/10.1134/S0016793206020071

18. Burmaka V. P., Taran V. I., Chernogor L. F. (2006). Wave-like processes in the ionosphere under quiet and disturbed conditions. 2. Analysis of observations and simulation. Geomagnetism and Aeronomy. 46(2). 199—208. 
https://doi.org/10.1134/S0016793206020083

19. Burmaka V. P., Chernogor L. F. (2013). Solar eclipse of August 1, 2008, above Kharkov: 2. Observation results of wave disturbances in the ionosphere. Geomagnetism and Aeronomy. 53(4). 479—491. 
https://doi.org/10.1134/S001679321304004X

20. Garmash K. P., Leus S. G., Chernogor L. F. (2011). January 4, 2011 Solar eclipse effects over radio circuits at oblique incidence. Radio Phys. and Radio Astron. 16(2). 164—176 (In Russian).
https://doi.org/10.1615/RadioPhysicsRadioAstronomy.v2.i4.50

21. Gokov A. M., Chernogor L. F. (2000). Processes in lower ionosphere during August 11, 1999 solar eclipse. Radio Phys. and Radio Astron. 5(4). 348—360 (In Russian).

22. Grigorenko E. I., Lyashenko M. V., Chernogor L. F. (2008). Effects of Solar Eclipse of March 29, 2006, in the Ionosphere and Atmosphere. Geomagnetism and Aeronomy. 48(3). 337—351. 
https://doi.org/10.1134/S0016793208030092

23. Grigorenko Ye. I., Pazura S. A., Puliaiev V. A., Taran V. I., Chernogor L. F. (2004). Dynamic processes in the ionosphere during the geospace storm on 30 May and Solar eclipse on 31 May 2003. Kosm. nauka tehnol. 10(1). 12—25. (In Russian).
https://doi.org/10.15407/knit2004.01.012

24. Dzyubanov D. A., Emelyanov L. Ya., Chernogor L. F. (2009). Plasma dynamics of the ionosphere above Kharkiv during the solar eclipse of 1 August 2008. Kosm. nauka tehnol. 15(3). 62—69. (In Russian).
https://doi.org/10.15407/knit2009.03.062

25. Domnin I. F., Yemel’yanov L. Ya., Kotov D. V., Lyashenko M. V., Chernogor L. F. (2013). Solar eclipse of August 1, 2008, above Kharkov: 1. Results of Incoherent Scatter Observations. Geomagnetism and Aeronomy. 53(1). 113—123. 

26. Domnin I. F., Emelyanov L. Y., Lyashenko M. V., Chernogor L. F. (2014). Partial solar eclipse of January 4, 2011 above Kharkiv: Observation and simulations results. Geomagnetism and Aeronomy. 54(5). 583—592
https://doi.org/10.1134/S0016793214040112

27. Domnin I. F., Emelyanov L. Ya., Chernogor L. F. (2012). The dynamics of ionosphere plasma over Kharkiv during the solar eclipse of January 4, 2011. Radio Phys. and Radio Astron. 17(2). 132—146 (In Russian).
https://doi.org/10.1615/RadioPhysicsRadioAstronomy.v3.i4.50

28. Emelyanov L. Ya., Lyashenko M. V., Chernogor L. F. (2009). Some effects in the geospace plasma during partial Solar eclipse of 1 august 2008 above Kharkiv. 1. The observation results. Kosm. nauka tehnol. 15(3). 70—81 (In Russian).
https://doi.org/10.15407/knit2009.03.070

29. Emelyanov L. Ya., Sklyarov I. B., Chernogor L. F. (2009). Ionosphere response to the solar eclipse on 1 august 2008: Some results of vertical sounding. Kosm. nauka tehnol. 15(4). 12—21 (In Russian).
https://doi.org/10.15407/knit2009.04.012

30. Kolokolov L. E., Legenka A. D., Pulinets S. A. (1993). Ionospheric effects accompanied March 18, 1988 solar eclipse. Geomagnetism and Aeronomy. 33(1). 49—57 (In Russian).

31. Kostrov L. S., Chernogor L. F. (2000). Processes in Bottomside Ionosphere during August 11, 1999 Solar Eclipse. Radio Phys. and Radio Astron. 5(4). 361—370 (In Russian).

32. Lyashenko M. V., Chernogor L. F. (2008). Tropospheric-ionospheric effects of the 3 October 2005 partial solar eclipse in Kharkiv. 2. Modeling and discussion. Kosm. nauka tehnol. 14(1). 57—64 (In Russian). 
https://doi.org/10.15407/knit2008.01.057

33. Lyashenko M. V., Chernogor L. F. (2009). Some effects in the geospace plasma during the partial Solar eclipse of 1 august 2008 above Kharkov. 2. Calculation results and discussion. Kosm. nauka tehnol. 15(4). 3—11 (In Russian). 
https://doi.org/10.15407/knit2009.04.003

34. Lyashenko M. V., Chernogor L. F. (2013). Solar eclipse of August 1, 2008, over Kharkov: 3. Calculation Results and discussion. Geomagnetism and Aeronomy. 53(3). 367—376. 
https://doi.org/10.1134/S0016793213020096

35. Sokolov V. D., Bezrodnyh I. P., Kuzmin V. A., Skryabin N. G. (1999). Solar eclipse effect in riomethric data in Yakutsk on March 09, 1997. Geomagnetism and Aeronomy. 39(2). 139—140 (In Russian).

36. Uryadov V. P., Leonov A. M., Ponyatov A. A., Boiko G. N., Terent’ev S. P. (2000). Variations in the Characteristics of a HF Signal over an Oblique Sounding Path during the Solar Eclipse on August 11, 1999. Radiophys. and Quantum Electronics. 43. 614—618. 
https://doi.org/10.1023/A:1004801201847

37. Chernogor L. F. (2000). Magnetosphere electron precipitation induced by a solar eclipse. Radio Phys. and Radio Astron. 5(4). 371—375 (In Russian).

38. Chernogor L. F. (2010).Variations in the amplitude and phase of VLF radiowaves in the ionosphere during the August 1, 2008, solar eclipse. Geomagnetism and Aeronomy. 50(1). 96—106. 
https://doi.org/10.1134/S0016793210010111

39. Chernogor L. F. (2010). Wave Response of the Ionosphere to the Partial Solar Eclipse of August 1, 2008. Geomagnetism and Aeronomy. 50(3). 346—361. 
https://doi.org/10.1134/S0016793210030096

40. Chernogor L. F. (2011). Dynamic processes in the near-ground atmosphere during the solar eclipse of August 1, 2008. Izvestiya. Atmospheric and Oceanic Phys. 47(1). 77—86.
https://doi.org/10.1134/S000143381101004X

41. Chernogor L. F. (2012). Effects of solar eclipses in the ionosphere: Results of Doppler sounding: 1. Experimental data. Geomagnetism and Aeronomy. 52(6). 768—778. 
https://doi.org/10.1134/S0016793212050039

42. Chernogor L. F. (2012). Effects of Solar Eclipses in the Ionosphere: Doppler Sounding Results: 2. Spectral Analysis. Geomagnetism and Aeronomy. 52(6). 779—792. 
https://doi.org/10.1134/S0016793212050040

43. Chernogor L. F. (2013). Physical effects of solar eclipses in atmosphere and geospace: monograph. Kharkiv: V. N. Karazin Kharkiv National University Publ., 480. (in Russian).

44. Chernogor L. F. (2013). Physical Processes in the Middle Ionosphere Accompanying the Solar Eclipse of January 4, 2011, in Kharkov. Geomagnetism and Aeronomy. 53(1). 19—31. 
https://doi.org/10.1134/S0016793213010052

45. Chernogor L. F. (2016). Atmosphere—Ionosphere response to Solar Eclipse over Kharkiv on March 20, 2015. Geomagnetism and Aeronomy. 56(5). 592—603. 
https://doi.org/10.1134/S0016793216050030

46. Chernogor L. F., Barabash V. V. (2011). The response of the middle ionosphere to the solar eclipse of 4 January 2011 in Kharkiv: some results of vertical sounding. Kosm. nauka tehnol. 17(4). 41—52 (In Russian).
https://doi.org/10.15407/knit2011.04.041

47. Chernogor L. F., Barabash V. V. The effects of solar eclipse of March 20, 2015 over ionosphere of Europe: Ionosonde observations. Radio Phys. and Radio Astron. 20(4). 311—331 (In Russian). 
https://doi.org/10.15407/rpra20.04.311

48. Beynon W. J. G., Brown G. M. (1956). Solar eclipses and the ionosphere. London: Elsevier. 330.

49. Chandra H., Sethia G., Vyas G. D., Deshpande M. R., Vats H. O. (1980). Ionospheric effects of the total solar eclipse of 16 Feb. 1980. Proc. Indian Nat. Acad. Sci. A47(1). 57—60.

50. Chernogor L. F. (2011).The Earth-atmosphere-geospace system: main properties and processes. Int. J. Remote Sensing. 32(11). 3199—3218. 
https://doi.org/10.1080/01431161.2010.541510

51. Chernogor L. F. (2016) Wave processes in the ionosphere over Europe that accompanied the solar eclipse of March 20, 2015. Kinematics Phys. Celestial Bodies. 32(4). 196—206.
https://doi.org/10.3103/S0884591316040024

52. Chernogor L. F., Garmash K. P. (2017). Magneto-ionospheric effects of the solar eclipse of March 20, 2015, over Kharkov. Geomagn. Aeron. 57(1). 72—83. 
https://doi.org/10.1134/S0016793216060062

53. Chimonas G., Hines C. (1970). Atmospheric gravity waves induced by a solar eclipse. J. Geophys. Res. 75(4). 875. 
https://doi.org/10.1029/JA075i004p00875

54. Coster A. J., Goncharenko L., Zhang S. R., Erickson P. J., Rideout W., Vierinen J. (2017).GNSS observations of ionospheric variations during the 21 August 2017 solar eclipse. Geophys. Res. Lett. 44(24). 12,041—12,048.
https://doi.org/10.1002/2017GL075774

55. Deshpande M. R., Chandra H., Sethia G., Vats Hari Om, Vyas G. D., Iyer K. N., Janve A. V. (1982) Effects of the total solar eclipse of 16 February 1980 on TEC at low latitudes. Proc. Indian. Nat. Acad. Sci. A48(3). 427—433.

56. Eclipse supplement. Nature. 1970. 226, 1097—1155.
https://doi.org/10.1038/2261097a0

57. Founda D., Melas D., Lykoudis S., Lisaridis I., Gerasopoulos E., Kouvarakis G., Petrakis M., Zerefos C. (2007). The effect of the total solar eclipse of 29 March 2006 on meteorological variables in Greece. Atmos. Chem. Phys. 7. 5543—5553. 
https://doi.org/10.5194/acp-7-5543-2007

58. Guo Q., Chernogor L. F., Garmash K. P., Rozumenko V. T., Zheng Y. (2020). Radio monitoring of dynamic processes in the ionosphere over china during the partial solar eclipse of 11 August 2018. Radio Sci. 55 (2). e2019RS006866.
https://doi.org/10.1029/2019RS006866

59. Higgs A. J. (1942). Ionospheric measurements made during the total Solar eclipse of 1940, October 1-st, South Africa. Mon. Notic. Roy. Astron. Soc. 102. 24—34.
https://doi.org/10.1093/mnras/102.1.24

60. Hofmann-Wellenhof B., Lichtenegger H., Collins J. (1994). Global Positioning System. Theory and Practice. New York: Springer-Verlag Wien. 382.
https://doi.org/10.1007/978-3-7091-3311-8

61. Jakowski N., Stankov S. M., Wilken V., Borries C., Altadill D., Chum J., Buresova D., Boska J., Sauli P., Hruska F., Cander Lj. R. (2008). Ionospheric behavior over Europe during the solar eclipse of 3 October 2005. J. Atmos. and Solar-Terr. Phys. 70 (6). 836—853.
https://doi.org/10.1016/j.jastp.2007.02.016

62. Liu J. Y., Hsiao C. C., Tsai L. C., Liu C. H., Kuo F. S., Lue H. Y., Huang C. M. (1998). Vertical phase and group velocities of internal gravity waves derived from ionograms during the solar eclipse of 24 October 1995. J. Atmos. and Solar-Terr. Phys. 60(17). 1679—1686.
https://doi.org/10.1016/S1364-6826(98)00103-5

63. Marlton G. J., Williams P. D., Nicoll K. A. (2016). On the detection and attribution of gravity waves generated by the 20 March 2015 solar eclipse. Phil. Trans. Roy. Soc. A. 374(2077).
https://doi.org/10.1098/rsta.2015.0222

64. Mona Z., Boka J., Knov P. K., indelov T., Kouba D., Chum J., Rejfek L., Potunkov K., Arikan F., Toker C. (2018). Observation of the solar eclipse of 20 March 2015 at the Pruhonice station. J. Atmos. and Solar-Terr. Phys.171, 277—284.
https://doi.org/10.1016/j.jastp.2017.07.011

65. Mller-Wodarg I. C. F., Aylward A. D., Lockwood M. (1998). Effects of a mid-latitude solar eclipse on the thermosphere and ionosphere — a modeling study. Geophys. Res. Lett. 25(20). 3787—3790. 
https://doi.org/10.1029/1998GL900045

66. Nykiel G., Zanimonskiy Y. M., Yampolski Y. M., Figurski M. (2017). Efficient usage of dense GNSS networks in central Europe for the visualization and investigation of ionospheric TEC variations. Sensors. 17(10). 2298. 
https://doi.org/10.3390/s17102298

67. Otsuka Y., Suzuki K., Nakagawa S., Nishioka M., Shiokawa K., Tsugawa T. (2013). GPS observations of medium-scale traveling ionospheric disturbances over Europe. Ann. Geophys. 31(2). 163—172. 
https://doi.org/10.5194/angeo-31-163-2013

68. Panasenko S. V., Otsuka Y., van de Kamp M., Chernogor L. F., Shinbori A., Tsugawa T., Nishioka M. (2019). Observation and characterization of traveling ionospheric disturbances induced by solar eclipse of 20 March 2015 using incoherent scatter radars and GPS networks. J. Atmos. Solar-Terr. Phys. 191. 105051. 
https://doi.org/10.1016/j.jastp.2019.05.015

69. Partial Solar Eclipse of 2018 Aug 11: URL: http://www.eclipsewise.com/solar/ SEgmap/2001-2100/SE2018Aug11Pgmap.html

70. Rama Rao P. V. S., Rao B. V. P. S., Nru D., Niranjan K. (1982). TEC observations at Waltair during the total solar eclipse of 16 Februrary 1980. Proc. Indian Nat. Acad. Sci. 48(3). 434—438.

71. Roble R. G., Emery B. A., Ridley E. C. (1986). Ionospheric and thermospheric response over Millstone Hill to the May 30, 1984, annual solar eclipse. J. Geophys. Res. 91(А2). 1661—1670. 
https://doi.org/10.1029/JA091iA02p01661

72. Salah J. E., Oliver W. L., Foster J. C., Holt J. M., Emery B. A., Roble R. G. (1986). Observations of the May 30, 1984, annual solar eclipse at Millstone Hill. J. Geophys. Res. 91(A2). 1651—1660. 
https://doi.org/10.1029/JA091iA02p01651

73. auli P., Roux S. G., Abry P., Boka J. (2007). Acoustic-gravity waves during solar eclipses: Detection and characterization using wavelet transforms. J. Atmos. and Solar-Terr. Phys. 69(17-18). 2465—2484. 
https://doi.org/10.1016/j.jastp.2007.06.012

74. SenGurta A., Goel G. K., Mathur B. S. (1980).Effect of the 16 February 1980 solar eclipse on VLF propagation. J. Atmos. and Terr. Phys. 42(11/12). 907—909. 
https://doi.org/10.1016/0021-9169(80)90107-5

75. Special Eclipse Issue (The eclipse of 7 March 1970).  J. Atmos. and Solar-Terr. Phys. 1972. 34. 559—739.

76. Special Issue of Atmospheric Chemistry and Physics. 2007. 7.

77. Stankov S. M., Bergeot N., Berghmans D., Bolse D., Bruyninx C., Chevalier J. M., Clette F., De Backer H., De Keyser J., D’Huys E., Dominique M., Lemaire J. F., Magdaleni J., Marqu C., Pereira N., Pierrard V., Sapundjiev D., Seaton D. B., Stegen K., Linden R. V., Verhulst T. G. W., West M. J. (2017). Multi-instrument observations of the solar eclipse on 20 March 2015 and its effects on the ionosphere over Belgium and Europe. J. Space Weather Space Clim. 7(A19). 
https://doi.org/10.1051/swsc/2017017

78. The Crustal Dynamics Data Information System: A resource to support scientific analysis using space geodesy. URL:  ftp://cddis.nasa.gov/gnss/products/bias/, ftp:// igs.ign.fr/pub/igs/products/mgex/dcb

79. Tsugawa T., Nishioka M., Ishii M., Hozumi K., Saito S., Shinbori A., Otsuka Y., Saito A., Buhari S. M., Abdullah M., Supnithi P. (2018). Total electron content observations by dense regional and worldwide international networks of GNSS. J. Disaster Res. 13(3). 535—545. 
https://doi.org/10.20965/jdr.2018.p0535

80. Universitt Bern Astronomisches Institut. URL: ftp.aiub.unibe.ch/CODE/ and www. aiub.unibe.ch/download/CODE/

81. Uryadov V. P., Kolchev A. A., Vybornov F. I., Shumaev V. V., Egoshin A. I., Chernov A. G. (2016).Ionospheric effects of a solar eclipse of March 20, 2015 on oblique sounding paths in the Eurasian longitudinal sector. Radiophys. and Quantum Electronics.59(6). 431—441.
https://doi.org/10.1007/s11141-016-9711-9

82. Verhulst T. G. W., Sapundjiev D., Stankov S. M. (2016). High-resolution ionospheric observations and modeling over Belgium during the solar eclipse of 20 March 2015 including first results of ionospheric tilt and plasma drift measurements. Adv. Space Res. 57(11). 2407—2419. 
https://doi.org/10.1016/j.asr.2016.03.009

83. Wang N., Yuan Y., Li Z., Montenbruck O., Tan B. (2016). Determination of differential code biases with multi-GNSS observations. J. Geodesy. 90(3). 209—228. 
https://doi.org/10.1007/s00190-015-0867-4