A multi-periodic oscillatory event in a solar flare

Centre for Fusion, Space and Astrophysics, Physics Department, University of Warwick, Coventry, CV4 7AL, UK e-mail: a.inglis@warwick.ac.uk

Received: 27 June 2008
Accepted: 14 November 2008

Abstract

Aims. Ratios of different significant periods found in the light curves of a solar flare exhibiting quasi-periodic pulsations (QPP) are used to distinguish between the possible physical mechanisms responsible for such periodic behaviour.

Methods. Time series data of the flaring event of 2002 July 3, observed via the Nobeyama Radioheliograph, Nobeyama Radiopolarimeters, and the RHESSI satellite, are investigated with the use of the Lomb-Scargle periodogram technique. Images of the event are also recovered via the RHESSI, SOHO, and Nobeyama Radioheliograph instruments.

Results. Statistical analysis of the Lomb-Scargle periodogram results indicates three distinct periods above the 99% confidence level in Nobeyama Radioheliograph and Radiopolarimeter data, at 28 s, 18 s, and 12 s, respectively. The two longest of these periods were also observed in the RHESSI data at the same confidence level. Wavelet analysis demonstrated that multiple periods occurred simultaneously without any significant frequency shift over time. Reconstructed images of the event reveal a very compact flare structure unsuitable for spatially resolved analysis. Consideration of the period ratios leads to the conclusion that the cause of this multi-periodic event is likely to be a kink mode periodically triggering magnetic reconnection.