GPS as a solar observational instrument: Real-time estimation of EUV photons flux rate during strong, medium, and weak solar flares

• Published in: Journal of geophysical research. Space physics 2015-12, Vol.120 (12), p.10,840-10,850
• Main Authors: Singh, Talwinder, Hernandez-Pajares, Manuel, Monte, Enric, Garcia-Rigo, Alberto, Olivares-Pulido, Germán
• Format: Article
• Language: English
• Subjects: 86 Geophysics; Classificació AMS; Flares; Fluctuations; Flux; Geofísica; Geophysica; global GPS networks; Global Positioning System; Global positioning systems; GNSS; GPS; Ionization; Ionospheric response to solar flares; Matemàtica aplicada a les ciències; Matemàtiques i estadística; Onboard; Photons; Real time; Satellite navigation systems; Solar flares; Solar physics; Spacecraft; Àrees temàtiques de la UPC
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1002/2015JA021824

In this manuscript, the authors show how the Global Navigation Satellite Systems, GNSS (exemplified in the Global Positioning System, GPS), can be efficiently used for a very different purpose from that for which it was designed as an accurate Solar observational tool, already operational from the open global GPS measurements available in real‐time, and with some advantages regarding dedicated instruments onboard spacecraft. The very high correlation of the solar extreme ultraviolet (EUV) photon flux rate in the 26–34 mm spectral band, obtained from the solar EUV monitor instrument onboard the SOHO spacecraft during Solar flares, is shown with the GNSS solar flare activity indicator (GSFLAI). The GSFLAI is defined as the gradient of the ionospheric vertical total electron content rate versus the cosine of the Solar zenith angle in the day hemisphere (which filters out nonsolar over ionization), and it is measured from data collected by a global network of dual frequency GPS receivers (giving in this way continuous coverage). GSFLAI for 60 X class flares, 320 M class flares, and 300 C class flares, occurred since 2001, were directly compared with the EUV solar flux rate data to show existing correlations. It was found that the GSFLAI and EUV flux rate present the same linear relationship for all classes of flares, not only the strong and medium intensity ones, X and M class, as in previous works, but also for the weakest C class solar flares, which is a remarkable result. Key Points It is shown how GPS can be efficiently used as an accurate solar observational tool A constant linear EUV photon flux‐GSFLAI dependence is found for all kind of solar flares GSFLAI present advantages regarding to direct EUV photons flux measurements taken from solar probes