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Astronomy & Astrophysics manuscript no. (will be inserted by hand later)

Summary: Astronomy & Astrophysics manuscript no.
(will be inserted by hand later)
The Nature of Network Oscillations
D. Banerjee 1 , E. O'Shea 2 , J.G. Doyle 3 , and M. Goossens 1
1 Centre for Plasma Astrophysics, Katholieke Universiteit Leuven, Celestijnenlaan 200B, 3001 Heverlee, Belgium
2 ESA Space Science Department, ESTEC Solar System Division, Keplerlaan 1, NL-2201 AZ, Noordwijk, The
3 Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland
e-mail: eoshea@so.estec.esa.nl, jgd@star.arm.ac.uk, marcel.goossens@wis.kuleuven.ac.be
Received 10 January 2001 / 21 March 2001
Abstract. We examine time-series of spectral data obtained from the Coronal Diagnostic Spectrometer (CDS) and
the Solar Ultraviolet Measurements of Emitted Radiation instrument (SUMER) onboard the Solar Heliospheric
Observatory (SOHO) spacecraft, in the period 30{31 July 1996. The observations were obtained in lines, ranging
in temperature from 12,000 K to 10 6 K, covering the low chromosphere to the corona. We report here on a
time series analysis, using wavelet methods, of small individual network regions in the quiet Sun. The wavelet
analysis allows us to derive the duration as well as the periods of the oscillations. The statistical signi cance of
the oscillations was estimated by using a randomisation method. The oscillations are considered to be due to
waves, which are produced in short bursts with coherence times of about 10-20 minutes. The low chromospheric
and transition region lines show intensity and velocity power in the 2-4 mHz range. The coronal line Mg x does
not show any statistically signi cant power in this range. In general, it is thought likely that the chromosphere


Source: Armagh Observatory


Collections: Physics