Microwave Quasi-periodic Pulsations in Multi-timescales Associated with a Solar Flare/CME Event

TL;DR

This study confirms microwave quasi-periodic pulsations across multiple timescales during a solar flare/CME event, revealing two distinct groups with different generation mechanisms linked to MHD oscillations and tearing-mode oscillations.

Contribution

It classifies QPPs into two groups based on their timescales and proposes different physical mechanisms for each, enhancing understanding of solar flare dynamics.

Findings

QPPs span from hecto-second to centi-second timescales.

Two distinct groups of QPPs are identified with different origins.

Group I likely related to MHD oscillations; Group II to tearing-mode oscillations.

Abstract

Microwave observations of quasi-periodic pulsations (QPP) in multi-timescales are confirmed to be associated with an X3.4 flare/CME event at Solar Broadband Radio Spectrometer in Huairou (SBRS/Huairou) on 13 December 2006. It is most remarkable that the timescales of QPPs are distributed in a broad range from hecto-second (very long period pulsation, VLP, the period P>100 s), deca-second (long period pulsation, LPP, 10<P<100 s), few seconds (short period pulsation, SPP, 1<P<10 s), deci-second (slow-very short period pulsation, slow-VSP, 0.1<P<1.0 s), to centi-second (fast-very short period pulsation, fast-VSP, P<0.1 s), and forms a broad hierarchy of timescales. The statistical distribution in logarithmic period-duration space indicates that QPPs can be classified into two groups: group I includes VLP, LPP, SPP and part of slow-VSPs distributed around a line approximately; group II includes fast-VSP and most of slow-VSP dispersively distributed away from the above line. This feature implies that the generation mechanism of group I is different from group II. Group I is possibly related with some MHD oscillations in magnetized plasma loops in the active region, e.g., VLP may be generated by standing slow sausage mode coupling and resonating with the underlying photospheric 5-min oscillation, the modulation is amplified and forms the main framework of the whole flare/CME process; LPP, SPP, and part of slow-VSPs are most likely to be caused by standing fast modes or LRC-circuit resonance in current-carrying plasma loops. Group II is possibly generated by modulations of resistive tearing-mode oscillations in electric current-carrying flaring loops.