Time Delays in Quasi-Periodic Pulsations Observed During the X2.2 Solar Flare on 2011 February 15

Abstract

We report observations of quasi-periodic pulsations (QPPs) during the X2.2 flare of 15 February 2011, observed simultaneously in several wavebands. We focus on fluctuations on time scale 1-30 s and find different time lags between different wavebands. During the impulsive phase, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) channels in the range 25-100 keV lead all the other channels. They are followed by the Nobeyama RadioPolarimeters at 9 and 17 GHz and the Extreme Ultra-Violet (EUV) channels of the Euv SpectroPhotometer (ESP) onboard the Solar Dynamic Observatory (SDO). The Zirconium and Aluminum filter channels of the Large Yield Radiometer (LYRA) onboard the Project for On-Board Autonomy (PROBA2) satellite and the SXR channel of ESP follow. The largest lags occur in observations from the Geostationary Operational Environmental Satellite (GOES), where the channel at 1-8Å leads the 0.5-4Å channel by several seconds. The time lags between the first and last channels is up to ≈ 9 s. We identified at least two distinct time intervals during the flare impulsive phase, during which the QPPs were associated with two different sources in the Nobeyama RadioHeliograph at 17 GHz. The radio as well as the hard X-ray channels showed different lags during these two intervals. To our knowledge, this is the first time that time lags are reported between EUV and SXR fluctuations on these time scales. We discuss possible emission mechanisms and interpretations, including flare electron trapping.

Quasi-periodic Pulsations in Solar and Stellar Flares: An Overview of Recent Results (Invited Review)

“…The scenario of externally triggered QPPs can also clearly explain the time delays between QPPs in different wavelength bands (Dolla et al, 2012). In this scenario, we would have the co-temporal, periodic generation of the non-thermal particles near the X-point.…”

“…Having multiple harmonics in the loop, would then also naturally explain the multiple harmonics seen in the QPPs. In this theory, it is not very obvious how time delays between different wavelength bands may be explained (Dolla et al, 2012).…”

“…In some cases, the QPPs occur in both the rise phase and the gradual (decay) phase of the flare (e.g. Van Doorsselaere et al, 2011;Dolla et al, 2012;Simões, Hudson, and Fletcher, 2015). However, in some cases, the QPPs are restricted to only the rise phase (Jakimiec and Tomczak, 2012, and follow-up works), but in other cases, the QPPs are observed during the decay phase only (e.g.…”

“…Zimovets (2010) showed a phase shift for a long period QPP. Dolla et al (2012) performed an extensive study using all available data sources and showed that the phase shifts could reach up to a quarter or even half of the QPP period in some wavelength bands.…”

Quasi-Periodic Acceleration of Electrons in the Flare on 2012 July 19

“…This suggests that both energetic electrons and ions are accelerated in the same process. Time delays between emission peaks have also been found from observations at different wave bands, which could be caused by trap or escape processesof energetic electrons at different energy bands (Aschwanden et al 1997;Dolla et al 2012;Tsap et al 2013). Huang et al (2014) found QPPs with varying periodsin multi-wavelength observations in an X class flare.…”