Estudo dos efeitos de explosões solares na região D ionosférica por meio de ondas em VLF

Abstract

The D Region is the lowest portion of Ionosphere and its formation depends on the solar radiation, mainly of Lyman-α. Because of this, the D Region only exists during the day. A solar flare releases X-Rays, which are able to penetrate into the D Region and increase the ionization level, consequently inducing its lowering. Once the D Region act as a boundary of Earth-Ionosphere Waveguide, any modification produces important variations both in Very Low Frequency (VLF) radio signals amplitude and in phase. For this research was used X- Rays flow measurements obtained from the Geostationary Operational Environmental Satellite and VLF data during the period of March (2011) and July (2012), obtained by South America VLF Network. These chosen VLF signal paths correspond to the NAA Transmitter Station in Cutler, USA, and from two Receptor Stations in South America: ATI Station in Atibaia, Brazil, and the PLO Station at Punta Lobos, Peru. The VLF data allows through alterations, both in signal amplitude and in phase, alongside with X-Rays flows data to identify Ionospheric events caused by solar flares. The results of this study indicate alterations occurred in analyzed signals; this happened because of the D Region lowering caused by ionization, which came from X-Rays released through Solar Flares. One of these analyzed events started at 6:08 p.m. UTC on March 8th, 2011, and peak X-Ray release at 6:28 p.m. UTC. The signal’s amplitude increments on the pre-event state was until 11.43% to the route: NAA–ATI, and until 12.13% to the route: NAA–PLO during the mentioned Solar Flare.