بررسی تغییرات شدت در تاج خورشید طی خورشیدگرفتگی 20 مرداد 1378

  An experiment to search for short-period intensity oscillations in the solar corona was conducted during the total solar eclipse of August 11, 1999 in Esfahan, Iran. The intensity in the continuum, centered about 4700 Å and with a passband having a half-width of 190 Å, was recorded at a counting rate of 5 Hz using six low-noise Hamamatsu R647 photomultiplier tubes. We recorded intensity values from 6 different regions on the image of the solar corona from 1.2 R ° to 1.5 R ° . The power spectrum analysis of all channels, except for a channel that failed to receive any coronal light, shows excess power in the frequency range 0.02-0.2 Hz. The results of analyzing all channels demonstrate various waves with some degree of coherence and amplitudes from 0.3 to 0.7 percent of the mean coronal brightness. There are some similarities between waves in various channels and it may show that these waves exist in a large region of the corona, of the order of a few hundred thousand kilometers, much larger than the fiber optic diaphragms. The energy flux of each wave was calculated by assuming them as the slow or fast mode waves for the active and quiet regions of the solar corona. The energy flux of the fast mode waves in the active regions is comparable with the required energy flux for heating up the solar corona. The intensity oscillations observed in this experiment are similar to those detected during the 1995 and 1997 eclipses.