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Radio Physics and Radio Astronomy

ISSN Imprimer: 2152-274X
ISSN En ligne: 2152-2758

Archives: Volume 1, 2010 to Volume 3, 2012

Radio Physics and Radio Astronomy

DOI: 10.1615/RadioPhysicsRadioAstronomy.v1.i3.10
pages 181-188

DECAMETRIC SOLAR U- AND J-TYPE BURSTS

V. V. Dorovsky
Institute of Radio Astronomy, National Academy of Sciences of Ukraine
V. N. Melnik
Institute of Radio Astronomy, National Academy of Sciences of Ukraine
Alexandr A. Konovalenko
Institute of Radio Astronomy of the National Academy of Sciences of Ukraine
H. O. Rucker
Institut für Weltraumforschung der Österreichischen Akademie der Wissenschaften, 6, Schmiedlstrasse, Graz, 8042, Austria
E. P. Abranin
Institute of Radio Astronomy, National Academy of Sciences of Ukraine
A. Lecacheux
Ovservatoire Paris-Meudon, Paris, CNRS UMR 8644, France

RÉSUMÉ

The first solar decameter wavelength U- and J-bursts observed with the UTR-2 radiotelescope in 2003-2004 are reported. During that period, more than 50 J-bursts and only 7 U-bursts had been recorded. It is the first case of the J- and U-bursts ground-observed with the turning frequencies ranging between 10 and 25 MHz. A harmonic structure of J-bursts in the form of Jb-J pairs similar to well known type IIIb-III pairs was first found. The average ratio of harmonic frequencies appeared to be 1.8. A group of J-bursts was recorded with an unusual Turning Frequency Drift (TFD) of –2 kHz/s. Such a TFD corresponds to the coronal loop elevation velocity of about 60 km/s. Coronal loops with similar elevation velocities were also detected with the SOHO/LASCO coronagraph in visible light. The dynamic spectra of unusual U- and J-bursts are shown. A simplified model of a semicircle-shaped coronal loop was constructed on basis of the U-burst dynamic spectrum and the Newkirk coronal density model. With this loop model, the source linear traverse speed along the loop, height of the turning frequency point and loop geometry were calculated.