PERIODICITIES IN THE X-RAY EMISSION FROM THE SOLAR CORONA

Abstract

We have studied the time series of full disk integrated soft and hard X-ray emission from the solar corona during 2004 January to 2008 December, covering the entire descending phase of solar cycle 23 from a global point of view. We employ the daily X-ray index derived from 1 s cadence X-ray observations from the Si and CZT detectors of the Solar X-ray Spectrometer mission in seven different energy bands ranging between 6 and 56 keV. X-ray data in the energy bands 6-7, 7-10, 10-20, and 4-25 keV from the Si detector are considered, while 10-20, 20-30, and 30-56 keV high energy observations are taken from the CZT detector. The daily time series is subjected to power spectrum analysis after appropriate correction for noise. The Lomb-Scargle periodogram technique has shown prominent periods of ~13.5 days, ~27 days, and a near-Rieger period of ~181 days and ~1.24 yr in all energy bands. In addition to this, other periods like ~31, ~48, ~57, ~76, ~96, ~130, ~227, and ~303 days are also detected in different energy bands. We discuss our results in light of previous observations and existing numerical models.