Magnetoacoustic Wave Trains in the 11 July 2005 Radio Event with Fiber Bursts

• Published in: Solar physics 2011-11, Vol.273 (2), p.393-402
• Main Authors: Meszarosova, H, Karlicky, M, Rybak, J
• Format: Article
• Language: English
• Subjects: Acoustics; Astrophysics and Astroparticles; Atmospheric Sciences; Bursts; Corona; Density; Emissions; Energy storage; Energy Storage and Release–Models Meet Radio Observations; Fibers; Frequency drift; Magnetic fields; Magnetoacoustic waves; Physics; Physics and Astronomy; Radio astronomy; Solar activity; Solar atmosphere; Solar flares; Solar physics; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Wave packets; Wavelet
• ISSN: 0038-0938; 1573-093X
• DOI: 10.1007/s11207-011-9794-6

A dm-radio emission with fiber bursts observed on 11 July 2005 was analyzed using wavelet filtration and spectral methods. In filtered radio spectra we found structures with different characteristic period  P and frequency drift FD: i ) fiber substructures (composed of dot emissions) with P 1 ≈ 0.5 s, FD 1 =− 87 MHz s −1 on average, ii ) fiber structures with P 2 ≈1.9 s, and iii ) drifting structures with P 3 ≈81.4 s, FD 2 =− 8.7, + 98.5, and − 21.8 MHz s −1 . In the wavelet spectra we recognized patterns having the form of tadpoles. They were detected with the same characteristic periods  P as found for the filtered structures. The frequency drift of the tadpole heads is found to be equal to the frequency drift of some groups of fibers for the long-period wavelet tadpoles ( P 3 ) and to the frequency drift of individual fibers for the short-period tadpoles ( P 2 ). Considering these wavelet tadpoles as signatures of propagating magnetoacoustic wave trains, the results indicate the presence of several wave trains in the fibers’ source. While the long-period wave trains trigger or modulate a whole group of fibers, the short-period ones look like being connected with individual fiber bursts. This result supports the model of fibers based on magnetoacoustic waves. Using a density model of the solar atmosphere we derived the velocities of the magnetoacoustic waves, 107 and 562 km s −1 , and setting them equal to the Alfvén ones we estimated the magnetic field in the source of fiber bursts as 10.7 and 47.8 G.