On the statistical detection of propagating waves in polar coronal holes
| Autor: | M. D. Popescu, E. O'Shea, Dipankar Banerjee, Girjesh R. Gupta, J. G. Doyle |
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| Rok vydání: | 2009 |
| Předmět: |
Physics
010504 meteorology & atmospheric sciences Wave propagation Phase (waves) Coronal hole FOS: Physical sciences Astronomy and Astrophysics Context (language use) Astrophysics 01 natural sciences Corona Intensity (physics) Solar wind Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science 0103 physical sciences Physics::Space Physics Astrophysics::Solar and Stellar Astrophysics Joint Astronomy Programme 010303 astronomy & astrophysics Longitudinal wave Solar and Stellar Astrophysics (astro-ph.SR) 0105 earth and related environmental sciences |
| DOI: | 10.48550/arxiv.0902.2676 |
| Popis: | Waves are important for the heating of the solar corona and the acceleration of the solar wind. We have examined a long spectral time series of a northern coronal hole observed on the 20th October 1996, with the SUMER spectrometer onboard SoHO. The observations were obtained in a transition region N IV 765 A line and in a low coronal Ne VIII 770 A line. Our observations indicate the presence of compressional waves with periods of ~25 min. Using Fourier techniques, we measured the phase delays between intensity as well as velocity oscillations in the two chosen lines. From this we are able to measure the travel time of the propagating oscillations and, hence, the propagation speeds of the waves producing the oscillations. We found that there is a difference in the nature of the propagation in bright ('network') and dark ('internetwork') regions with the latter sometimes showing evidence for downwardly propagating waves that is not seen in the former. As, in all cases, the measured propagation speeds are subsonic, we concluded that the detected waves are slow magnetoacoustic in nature. Comment: 7 pages, 7 figures |
| Databáze: | OpenAIRE |
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