A1 Vertaisarvioitu alkuperäisartikkeli tieteellisessä lehdessä
Time delay effect between long quasi-periodic oscillations of 37 GHz radio sources and the magnetic field of the nearest sunspots
Tekijät: V. V. Smirnova, A. Riehokainen, A. A. Solov’ev, J. Kallunki
Kustantaja: SPRINGER
Julkaisuvuosi: 2015
Journal: Astrophysics and Space Science
Tietokannassa oleva lehden nimi: ASTROPHYSICS AND SPACE SCIENCE
Lehden akronyymi: ASTROPHYS SPACE SCI
Artikkelin numero: 149
Vuosikerta: 357
Numero: 2
Sivujen määrä: 7
ISSN: 0004-640X
eISSN: 1572-946X
DOI: https://doi.org/10.1007/s10509-015-2382-8
Measurements and the interpretation of the time delay effect between long quasi-periodic oscillations of sunspot magnetic fields and nearby millimeter radio sources observed at 37 GHz were the main goals of this work. Ground-based radio telescope operated by Metsahovi Radio Observatory, Aalto University, Finland was used to obtain time series variations of radio intensity at 37 GHz frequency, as well as, the Helioseismic and Magnetic Imager instrument on-board the Solar Dynamics Observatory spacecraft was used to obtain the magnetic field time series variations. Lags (time delays) in the interval of 15-35 minutes were obtained by cross-correlation analysis of time series and by direct geometrical measurements of distances between the radio sources and nearby sunspots. These distances were in the interval of 11-24 Mm. Corresponding time delays were defined as the relation of these distances to the sound speed. Time delays obtained by two different independent methods turned to be very close. This fact confirms the interpretation of the phenomenon under the study as a process of propagation of disturbances from the slowly oscillating sunspot to the radio source with the sound speed.