Automatic detection of Sfe: a proposal

Abstract

Abstract. Solar flare effects (Sfe's) are rapid magnetic variations related to the enhancement of the amount of radiation produced during solar flare events. For several minutes, the ionosphere is activated and electron densities, electrical conductivities and electric currents are enhanced. The magnetic signature of a flare is visible in the illuminated hemisphere, and sometimes it shows up as small crochet-like movements in the magnetograms. However, regarding their detection using an automatized procedure, they have been very elusive because their small amplitude, which is close to the level of noise produced by other natural phenomena, and their highly variable irregular shapes make it extremely difficult to apply predesigned patterns. In this paper, we summarize the difficulties that Sfe detection presents and explain a line of work we initiated to overcome these difficulties with the goal of achieving a system capable of performing automatic detection. Some properties of Sfe's, including spherical symmetry around the vortex and different time durations between Sfe's and other natural variations, were used to construct an index allowing us to detect Sfe's.

Analysis of the Solar Flare Effects of 6 September 2017 in the Ionosphere and in the Earth's Magnetic Field Using Spherical Elementary Current Systems

“…The SECS method is postulated as a useful tool for Sfe analysis, and it could be used to obtain complementary data for Sfe detection (Curto et al, ).…”

Automatic Detection of Sfe: A Step Forward

“…Another approach to the Sfe detection problem involves taking advantage of some of the properties of Sfe ionospheric currents, especially their spherical symmetry around the vortex [16]. A first attempt was carried out by Curto et al [5]. Their prototype algorithm calculated the derivative of the data in order to avoid contamination of the daily variation Sq, and, by means of trigonometric formulas, they computed the magnetic radial component.…”

“…First of all, the magnetic data were filtered to avoid contamination of the daily variation Sq because Sfe are high frequency phenomena with respect to Sq. We used the derivative as a high-pass filter, as in Curto et al [5], but in this case it was conducted with intervals of 8 min and not minute by minute, the option that was used in that first prototype. We used 8 min intervals because it was the average time of the Sfe events and the high frequency magnetic noise was better filtered.…”

“…The second part of our algorithm performs a change in coordinates, computing at each observatory the radial component of the variation relative to a hypothetical center where the vortex could be located; details of which can be found in Curto et al [5]. Contrary to the prototype that used a prefixed position of the vortex, here the position was varied by sweeping the space area to find the focus position.…”

“…A first attempt to construct an algorithm to automatically detect Sfe was conducted by Curto et al [5]. Their prototype was based on some of the properties of the Sfe vector configuration; in particular, a certain symmetry around the central point of the whirl of these ionospheric currents, which is called the focus.…”