The method of the limb-event detection

  1. Nobeyama Radio Heliograph makes 44 17GHz images per one day. The time resolution of these images is 10 minutes.

  2. Weak-brightness features are erased from each images.
    The brightness temperature of the weak-brightness features is less than 2000 K or 1/100 of the maximum brightness temperature in each image. Because, the dynamic range of Nobeyama Radio Heliograph is about 100.

  3. The program decreases the temperature brightness in the disk to 0 K since we want to find structures on the limb only.

  4. The program find enhanced pixels in each image. The criterion of the enhanced pixels is that the enhancement of temperature brightness at the pixel is larger than 6 times of the average temperature brightness of the day at the pixel.

  5. If there are the enhance pixels in the images, the center of gravity of enhanced pixels is calculated from each images.

  6. If the center of gravity of enhanced pixels is not in the disk and the structures are found in 3 sequential images (in the other words, the lifetime of the structure in the NoRH's FoV is over 30 minutes), the program defined the structure as the limb events.

    So, the program can detect not only prominence eruption but also prominence activities and limb flares since the program does not check the direction and velocity of the motion.

The undetectable event using the method

Back to the list of limb events