Ultra–Low‐Frequency Solar Heii30.4 nm Pulsations

Solar EUV and X-ray measurements from the Charge, Element and Isotope Analysis System/Solar EUV Monitor (CELIAS/SEM) on board Solar and Heliospheric Observatory (SOHO) and the Geostationary Operational Environmental Satellites (GOES) have been studied for four time periods. Two ultra-low-frequency CELIAS/SEM He II 30.4 nm pulsations were observed with frequencies of 0: 02316 +/- 0: 00232 and 0: 00926 +/- 0: 00232 mHz during days 244-248 of 1999 and 89-93 of 2003, respectively. The He II 30.4 nm pulsation lifetimes were found to be of the order of a few days. The frequencies of the observed EUV pulsations are in the frequency range of the solar g-modes. The short lifetimes of these He II 30.4 nm pulsations, however, do not match the expected long lifetimes of solar g-modes. No statistically significant peak was found in the GOES X-ray data.