On the detectability of solar X-ray flares using very low frequency sudden phase anomalies

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dc.contributor.authorRaulin J.-P.
dc.contributor.authorAbe Pacini A.
dc.contributor.authorKaufmann P.
dc.contributor.authorCorreia E.
dc.contributor.authorAparecida G. Martinez M.
dc.date.accessioned2024-03-13T01:42:27Z
dc.date.available2024-03-13T01:42:27Z
dc.date.issued2006
dc.description.abstractWe have studied ionization excesses produced by enhancements of X-ray emission during solar flares using the very low frequency (VLF) response of the lower edge of the ionospheric D region. We focus on whether or not the X-rays associated with a given solar flare were responsible for a sudden phase anomaly (SPA) event, independently of the characteristics of the SPA. Approximately 1300 and 200 solar events were found to cause an ionospheric event, during periods of high and low solar activity, respectively. The main results of the present work are: (i) definite spectral characteristics are required for a solar flare to produce a measurable SPA; (ii) the probability of SPA occurrence due to faint solar flares, of X-ray class C1-C2 or lower, is higher during solar minimum; (iii) the same probability for more intense solar flares (class C3 or higher) does not depend on the solar activity conditions. Our observations suggest that the low ionosphere has different sensitivities depending on the solar activity, being more sensitive when the Sun is less active. These results also constitute an observational confirmation of recent findings showing that the ionospheric reference height is lower (by about {less-than or slanted equal to}1 km) during solar maximum. © 2005 Elsevier Ltd. All rights reserved.
dc.description.firstpage1029
dc.description.issuenumber9
dc.description.lastpage1035
dc.description.volume68
dc.identifier.doi10.1016/j.jastp.2005.11.004
dc.identifier.issn1364-6826
dc.identifier.urihttps://dspace.mackenzie.br/handle/10899/37787
dc.relation.ispartofJournal of Atmospheric and Solar-Terrestrial Physics
dc.rightsAcesso Restrito
dc.subject.otherlanguageIonosphere
dc.subject.otherlanguageSolar activity cycle
dc.subject.otherlanguageSolar flares
dc.subject.otherlanguageVery low frequency propagation
dc.subject.otherlanguageX-rays
dc.titleOn the detectability of solar X-ray flares using very low frequency sudden phase anomalies
dc.typeArtigo
local.scopus.citations35
local.scopus.eid2-s2.0-33646529880
local.scopus.subjectSolar activity cycle
local.scopus.subjectSolar X-ray flares
local.scopus.subjectVery low frequency propagation
local.scopus.updated2024-05-01
local.scopus.urlhttps://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=33646529880&origin=inward
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