NoRH%20Observations%20of%20Prominence%20Eruption

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NoRH Observations of Prominence Eruption

• Masumi Shimojo
• Nobeyama Solar Radio Observatory
• NAOJ/NINS

2004/10/28 Nobeyama Symposium 2004 _at_ SeiSenRyo
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Todays Topic

• Introduction
• What are advantages of prominence eruption
  observations using Nobeyama Radioheliograph?
• 12 years NoRH Observations of Prominence
  Activities
• Automatic Detection of Prominence Activities
• Solar Cycle and Prominence Activities

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Introduction

• NoRH observes the thermal microwave (17/34GHz)
  emission from prominences.
• The typical brightness temperature of a
  prominence before the eruption is about 10,000K.
• The prominence is usually optically thick plasma.
  Hence, the filament is also the dark feature in
  radio images.

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Advantages of NoRH Observation 1

• The influence of the weather is small.
• NoRH can observe the Sun on cloudy and rainy days
  !!
• Ex. The transit of Venus
• But, snow and heavy rain influence the image
  quality.

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Advantages of NoRH Observation 2

• Large Field of View
• 1 Rsun
• High Time Resolution
• Flare Observation 100 msec
• Normal Observation 1 sec

Courtesy of Y. Hanaoka
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Advantages of NoRH Observation 3

• The effect of the Doppler shift is very small for
  NoRH Observations, since NoRH observe the thermal
  microwave emission.
• The brightness temperature of prominence is
  depend only temperature and emission measure of
  prominence plasma.
• NoRH can observe the high-speed prominence
  eruption.

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Disadvantages of NoRH Observation

• It is difficult to resolve the fine structures in
  the prominence.
• Usually, we can find moving features in the
  prominence. But, the features are made from the
  side-lobes.

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Advantages of NoRH Observation
ltltSummarygtgt

• The influence of the weather is small.
• Large Field of View
• High time resolution
• The effect from Doppler shift is small.

We try to develop the automatic detection
system for the prominence eruption.
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Todays Topic

• Introduction
• What are advantages of prominence eruption
  observations using Nobeyama Radioheliograph?
• 12 years NoRH Observations of Prominence
  Activities
• Automatic Detection of Prominence Activities
• Solar Cycle and Prominence Activities

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Automatic Detection Method Step 1

• NoRH makes 44 17GHz images, everyday.
• The time resolution of the images is 10mins.
• The images are made in quasi real-time.
• The automatic detection program runs after the
  daily observation.

28 Aug, 2000 004626 UT Original Image
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Automatic Detection Method Step 2

• Erase faint features and disk.
• Tb of faint features is smaller than 2000K.
• Tb of faint features is smaller than 1/100 of the
  maximum Tb in each image.
• We delete the major side-lobe effect on the
  method through the process.

After deleted faint features and disk
Original Image
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Automatic Detection Method Step 3

• Make a daily average image.
• We use all 17GHz images on the day.
• Before calculate the average, we delete disk.

average
daily average image
44 images
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Automatic Detection Method Step 4

• Find enhanced pixels in each image.
• The criterion of enhancements is 6 times larger
  than the daily average image at each pixel.

After deleted faint features
Daily average image
gt 6
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Automatic Detection Method Step 5

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

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Automatic Detection Method Step 6

• Define the structure as the limb events, if the
  structure satisfies the following criterions.
• The center of gravity of enhanced pixels is not
  in the disk
• The lifetime of the structure in the NoRH's FoV
  is over 30 min.
• The number of enhance pixels is larger than 400.

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The method catches these phenomena

• Prominence activities
• Eruptive Prominence
• Disappearance of Prominence (not Eruption)
• Morphology changing of Prominence
• Limb flare
• Flare Loop on the Limb

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The undetectable events using the method

• Very fast eruptive events (v gt 300km/s)
• Because we use 10 min resolution
• Very long duration events
• Because we use the daily average as the quiet
  state.
• Simultaneous eruptive events.
• Because we use the center of gravity for the
  identification.
• Weak brightness event
• The NoRH dynamic range is 1/100.

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The results of the Automatic Detection
System

• Survey period 1992/07/01 2004/10/12
• Over one Solar Cycle
• Observation time 0800 1530 (JST)
• The number of detected events 389
• The percentage of limb flares is less than 5 .
• You can see the list on our web.
• http//solar.nro.nao.ac.jp/norh/html/prominence
  /

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Solar Cycle and Prominence Activities1Number
Variation during One Solar Cycle

• The number variation of prominence activities is
  similar to that of sunspots.
• The raise phase of prominence activities is
  shorter than that of sunspot.

Cross Prominence Activities Red line Sun
spot Number
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Solar Cycle and Prominence Activities2The
distribution of prominence activities of Cycle
21/22
Background KP Magnetogram limb event Size
of Size of Activities 1992 1999
1993 2000 1994 2001 1995 2002
1996 2003 1997 2004 1998
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Solar Cycle and Prominence Activities3Filament
bands and Prominence Activities
Contour Standard deviation of coronal green
line Thick Line the migration trajectories of
neutral filament bands for cycle 20 (Makarov
and Sivaraman, 1989 Solar Phys. 123, 367)

• The distribution of the activities is similar to
  the neutral filament bands.

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Solar Cycle and Prominence Activities4The
distribution of filaments and prominence
activities
Background The distribution of neutral lines
The distribution of filaments of Cycle 21 and
22 Aa Active Region Filaments, Aq Quiescent
Filaments Ap Polar Filaments (Mouradian and
Soru-Escaut, 1994, AA, 290, 279)

• Prominence activities occurred on the neutral
  filament bands.

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Solar Cycle and Prominence Activities5When a
polar-crown prominence erupt? 1

• The polar crown prominences erupted, when the
  polarity of the polar magnetic field reverse.
• (Gopalswamy, et al.,
• 2003, ApJ. 598, L63)

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Solar Cycle and Prominence Activities5 When a
polar-crown prominence erupt? 2

• The polar-crown prominences erupted when some
  magnetic poles appeared near the polar-crown
  neutral line.
• Prominence/filament eruptions need magnetic
  activities, like an emerging flux (Feynman and
  Martin, 1995, JGR, 100, A3,3355) , the intrusion
  of opposite polarity magnetic fields.

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Solar Cycle and Prominence Activities 6 Size of
Active Prominences

• The frequency distribution of size of active
  prominences show the power-law (like)
  distribution.
• The correlation between the latitude and size is
  weak.

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Solar Cycle and Prominence Activities 7 Size of
Active Prominence and Solar Cycle
Neutral lines at Solar Minimum
Neutral lines at Solar Maximum
The scatter plot of date and size of prominence
eruption The diamond marks indicate the average
prominence size of the year.

• The variation of average active prominence size
  similar to the solar cycle.
• The size of active prominence seems to relate the
  complexity of the neutral line on photosphere.

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Summary 1

• We developed the automatic detection system for
  limb events, mainly prominence activities.
• The system found 398 events from July, 1992 to
  Oct, 2004.
• The number variation during solar cycle of
  prominence activities is similar to that of
  sunspots.

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Summary 2

• Prominence activities occurred on the neutral
  filament bands.
• The frequency distribution of size of active
  prominences show the power-law (like)
  distribution.
• The size of active prominence seems to relate the
  complexity of the neutral line on photosphere.

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The undetectable events using the method

• Very fast eruptive events (v gt 300km/s)
• Because we use 10 min resolution
• Very long duration events
• Because we use the daily average as the quiet
  state.
• Simultaneous eruptive events.
• Because we use the center of gravity for the
  identification.
• Weak brightness event
• The NoRH dynamic range is 1/100.

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Automatic detection using 3 minuets
time resolution images
Coming soon!!
Using 10 min time resolution images
Using 3min time resolution images