NDLI: Imaging Observations of X-Ray Quasi-periodic Oscillations at 3 – 6 keV in the 26 December 2002 Solar Flare

Content Provider	Springer Nature Link
Author	Ning, Zongjun
Copyright Year	2013
Abstract	Quasi-periodic oscillations in soft X-rays (SXR) are not well known due to the instrument limitations, especially the absence of imaging observations of SXR oscillations. We explore the quasi-periodic oscillations of SXR at 3 – 6 keV in a solar flare observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) on 26 December 2002. This was a B8.1 class event and showed three X-ray sources (S$_{1}$, S$_{2}$, and S$_{3}$) at 3 – 6 keV and two sources (S$_{1}$ and S$_{2}$) at 12 – 25 keV. The light curves of the total fluxes display a two-minute oscillation at 3 – 6 keV, but not in the energy bands above 8 keV. To investigate imaging observations of the oscillations, we prepared CLEAN images at seven energy bands between 3 keV and 20 keV with an eight-second integration. The light curves of three sources were analyzed after integrating the flux of each source region. We used the Fourier method to decompose each source light curve into rapidly varying and slowly varying components. The rapidly varying components show seven individual peaks which are well fitted with a sine function. Then we used the wavelet method to analyze the periods in the rapidly varying component of each source. The results show that three sources display damped quasi-periodic oscillations with a similar two-minute period. The damped oscillations timescale varies between 2.5 to 6 minutes. Source S$_{1}$ oscillates with the same phase as S$_{3}$, but is almost in anti-phase with S$_{2}$. Analyzing the flaring images in more detail, we found that these oscillation peaks are well consistent with the appearance of S$_{3}$, which seems to split from or merge with S$_{2}$ with a period of two minutes. The flare images with a high cadence of one second at 3 – 6 keV show that source S$_{3}$ appears with a rapid period of 25 seconds. The two-minute oscillation shows the highest spectral power. Source S$_{3}$ seems to shift its position along the flare loop with a mean speed of 130 km s$^{−1}$, which is of the same order as the local sound speed. This connection between the oscillation peaks and emission enhancement appears to be an observational constraint on the emission mechanism at 3 – 6 keV.
Starting Page	1239
Ending Page	1256
Page Count	18
File Format	PDF
ISSN	00380938
Journal	Solar Physics
Volume Number	289
Issue Number	4
e-ISSN	1573093X
Language	English
Publisher	Springer Netherlands
Publisher Date	2013-10-02
Publisher Place	Dordrecht
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Flares X-ray bursts, soft Astrophysics and Astroparticles Atmospheric Sciences Extraterrestrial Physics, Space Sciences
Content Type	Text
Resource Type	Article
Subject	Astronomy and Astrophysics Space and Planetary Science

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