Intensity oscillations and heating of the coronal X-ray bright points from Hinode/XRT

Indian Institute of Astrophysics, Bangalore 560 034, India e-mail: rkari@iiap.res.in

Received: 23 November 2007
Accepted: 16 April 2008

Abstract

Aims. Our aim is to investigate the intensity oscillations in coronal X-ray Bright Points (XBPs).

Methods. We analysed a 7 h long time sequence of the soft X-ray images obtained on April 14, 2007 with a 2 min cadence using the X-Ray Telescope (XRT) on-board the Hinode mission. We use SSW in IDL to derive the time series of 14 XBPs and 2 background regions. For the first time, we have tried to use power spectrum analysis on XBP data to determine the periods of intensity oscillations.

Results. The power spectra of XBPs show several significant peaks at different frequencies corresponding to time scales that range from a few minutes to hours. The light curves of all the XBPs give the impression that the XBPs can be grouped into three classes depending on emission levels: (i) weak XBPs; (ii) bright XBPs; and (iii) very strong XBPs. The periods of intensity oscillation are consistent in all the XBPs and are independent of their brightness level, suggesting that the heating mechanisms in all the three groups of XBPs are similar. The different classes of XBPs may be related to the different strengths of the magnetic field with which they have been associated.