J/A+A/618/A165ivo://CDS.VizieR/J/A+A/618/A165doi:10.26093/cds/vizier.36180165CDSZhang P.J.Wang C.B.Ye L.2019-01-07T09:21:03Z2018-10-30T06:57:26ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frthe-sunWe design an event recognition-analysis system that can automatically detect solar type III radio burst and can mine information of the burst from the dynamic spectra observed by Nancay Decameter Array (NDA). We investigate the frequency drift rate of type III bursts and the speed of electron beams responsible for the generation of the bursts. Several computer vision methods are used in this automatic analysis system. The Hough transform is performed to recognize the line segment associated with type III bursts in the dynamic spectra. A modified active contour model is used to track the backbone of the burst and estimate the frequency drift rate at different frequency channels. We run this system on the NDA data from 2012 to 2017, and give a statistical survey of the event number distribution, the starting and stopping frequencies of bursts, the frequency dependence of the drift rate, and the exciter speed using three corona density models. The median value of the average frequency drift rates is about 6.94MHz/s for 1389 simple well-isolated type III bursts detected in the frequency range 10-80MHz of NDA observation. The frequency drift rate changes with frequency as df/dt=-0.0672f^1.23^ from a least-squares fitting. The average exciter speed is about 0.2c based the density models. We do not find any significant dependence of the drift rate and the exciter speed on the solar activity cycle.2018A&A...618A.165Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/618/A165CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+AS/119/489 : Solar Type II Radio Bursts, 1990.09 - 1993.12 (Mann+ 1996)J/ApJ/710/L58 : Coronal type II radio bursts in 2002 (Lobzin+, 2010)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/618/A165https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/618/A165http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/618/A165https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/618/A165https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/618/A165http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/618/A165GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/618/A165/tableFrequency range and frequency drift rate of solar type III burstsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintObs.dateObservation date (DD-MMM-YYYY hh:mm:ss)time.epoch;obsnullablefstopStopping frequency of the eventMHzem.freqfloatfstartStarting frequency of the eventMHzem.freqfloatFDRAverage frequency drift rateMHz/sarith.rate;em.freqfloat