The note of the prominence activity database
The method of the limb-event detection
- Nobeyama Radio Heliograph makes 133 17GHz images per one day.
The time resolution of these images is 3 minutes.
- 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.
- The program decreases the temperature brightness in the disk to 0 K
since we want to find structures on the limb only.
- 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.
- If there are the enhance pixels in the images, the center of gravity
of enhanced pixels is calculated from each images.
- 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 9 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
- Very fast eruptive events :
If the velocity of the eruption is over 900km/s, the program can not
detect the event since the time resolution of images is 3 minutes.
- Very slow eruptive event:
If the velocity of the eruption is less than a few km/s, the program
may not detect the event since the average temperature brightness of
the day is increased by the structure.
- Simultaneous eruptive events:
If two eruptive events occur at different hemispheres simultaneously,
the program can not detect these events since the center of gravity
of enhanced pixels of these events is in the disk.
- Weak brightness event:
If the enhancements of temperature brightness of the eruptive structure
is less than 6 times of the average temperature brightness of the day, or
if the brightness temperature of the eruptive structure is less than
2000 K or 1/100 of the maximum brightness temperature in each image,
the program can not detect the events.
The database includes the radial velocity of prominence activities.
The velocity is derived from the gravity center of the enhanced pixels, not the edge of the promience.
Instruction for using the database
Please refer the following papers when you publish the paper using the database.
- Shimojo, M.,Yokoyama, T., Asai, A., Nakajima, H., Shibasaki, K. 2006 PASJ, 58, p85
- Shimojo, M. 2013 PASJ,65,SP1,S16
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Last updated on 02 May, 2013