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From large-scale loops to the sites of dense flaring loops: preferential conditions for long-period pulsations in solar flares View all abstracts by submitter

Claire Foullon   Submitted: 2010-06-06 07:43

Long-period quasi-periodic pulsations (QPPs) of solar flares are a class apart from shorter period events. By involving an external resonator, the mechanism they call upon differs from traditional QPP models, but has wider applications. We present a multi-wavelength analysis of spatially-resolved QPPs, with periods around 10 min, observed in the X-ray spectrum primarily at energies between 3 and 25 keV. Complementary observations obtained in Hα and radio emission in the kHz to GHz frequency range, together with an analysis of the X-ray plasma properties provide a comprehensive picture that is consistent with a dense flaring loop subject to periodic energisation and thermalisation. The QPPs obtained in Hα and Type III radio bursts, with similar periods as the QPPs in soft X-ray, have the longest periods ever reported for those types of datasets. We also report 1-2 GHz radio emission, concurrent with but unrestricted to the QPP time intervals, which is multi-structured at regularly separated narrowband frequencies and modulated with ~18-min periods. This radio emission can be attributed to the presence of multiple 'quiet' large-scale loops in the background corona. Large-scale but shorter inner loops below may act as preferential resonators for the QPPs. The observations support interpretations consistent with both inner and outer loops subject to fast kink magnetohydrodynamic waves. Finally, X-ray imaging indicates the presence of double loop-top sources in the flaring sites, which could be the particular signatures of the magnetically-linked inner loops. We discuss the preferential conditions and the driving mechanisms causing the repeated flaring.

Authors: Foullon, C., Fletcher, L., Hannah I.G., Verwichte, E., Cecconi, B., Nakariakov, V.M., Phillips K.J.H. and Tan, B.L.
Projects: RHESSI

Publication Status: ApJ (accepted)
Last Modified: 2010-06-07 08:04
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