Very long period activity at the base of solar wind streams
نویسندگان
چکیده
Using time series data of spectral lines originating from a wide range of temperatures in the solar transition region, above a polar coronal hole, from SUMER (Solar Ultraviolet Measurements of Emitted Radiation) on SoHO (Solar and Heliospheric Observatory), we report on the detection of very long (≈170 min) periodic intensity fluctuations, above the limb. Our data also reveal long periodicities (10-90 min), previously observed with other SoHO instruments. With the acoustic cut-off frequency implying a maximum allowable period of ≈ 90 min, it is unclear whether these intensity fluctuations are due to waves or are the result of a recurrent magnetic reconnection process.
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