The geomagnetic solar flare effect identified by SIIG as an indicator of a solar flare observed by GOES satellites

Abstract

This paper studies the efficiency of geomagnetic solar flare effects (gsfe) in X solar flare detection; so during the period 1999–2007 a comparison between solar flare (sf) observed by satellites of the Geostationary Operational Environmental Satellite (GOES) programme and gsfe published by the Service International des Indices Geomagnetiques (SIIG) is made. Solar flares (sfs) are one of the most powerful manifestations of the solar activity. Because the far UV and soft and hard X-ray solar flare radiation is absorbed by the ionosphere, the ionized gas density increases (ionospheric solar flare effect, isfe) and a sudden enhancement of geomagnetic field near Earth surface (geomagnetic solar flare effect, gsfe) is produced. The solar X-ray flux is systematically recorded since 1975 by GOES satellites, and gsfe are declared by geomagnetic observatories since 1957. We corroborate that the identification of sf using gsfe is affected by several factors: – the intensity and average growth rate of solar flare radiation when quicker is it more easily the sf is detected as gsfe; – the position of the geomagnetic observatory, we found that observatories placed at summer hemisphere identify more easily the sf, so the uneven geographical distribution of observatories make the sf identification difficult; – the existing geomagnetic perturbation previous to sf, and the likeness between the gsfe and other geomagnetic variations. This work shows that gsfe recorded as associated to sf is a poor detector of sf even if it is intense. Some of these inconveniences can be avoided if the distribution of the observatories is improved and the identification of a sf is made using simultaneously gsfe, solar wind parameters and isfe.