NoRH Observations of Prominence Eruption

Masumi ShimojoNobeyama Solar Radio Observatory

NAOJ/NINS

2004/10/28 Nobeyama Symposium 2004 @ SeiSenRyo

2004/10/28 NoRH Observations of Prominence Eruption 2

Today’s 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 de

pend 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 <<Summary>>

The influence of the weather is small.Large Field of ViewHigh time resolutionThe effect from Doppler shift is small.

The property is very good for the monitoring observation.The properties are very good

for the eruptive prominence observation.

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

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Today’s 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, 200000:46:26 UTOriginal 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.

Original Image After deleted faint features and disk

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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 image44 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

=

> 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.

The skyblue cross indicates the center of gravity of the image.

Original Image Daily Average Image

Enhance Pixel Image Delete faint features Image Enhance Pixel Image > 6.

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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 > 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: 08:00 – 15:30 (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 Activities:1Number Variation during One Solar Cycle

Cross + : Prominence Activities Red line: Sun spot Number

The number variation of prominence activities is similar to that of sunspots.

The raise phase of prominence activities is shorter than that of sunspot.

/6m

on

th

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Solar Cycle and Prominence Activities:2The 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 Activities:3Filament bands and Prominence Activities

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

Contour: Standard deviation of coronal green lineThick Line: the migration trajectories of neutral

filament bands for cycle 20(Makarov and Sivaraman, 1989 Solar Phys. 123, 367)

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Solar Cycle and Prominence Activities:4The distribution of filaments and prominence activities

Prominence activities occurred on the neutral filament bands.

The distribution of filaments of Cycle 21 and 22Aa: Active Region Filaments, Aq: Quiescent FilamentsAp: Polar Filaments(Mouradian and Soru-Escaut, 1994, A&A, 290, 279)

Background : The distribution of neutral lines

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Solar Cycle and Prominence Activities:5When 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 Activities:5 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

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.

Neutral lines at Solar Minimum

Neutral lines at Solar MaximumThe scatter plot of date and size of prominence eruptionThe diamond marks indicate the average prominence size of the year.

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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 > 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

Using 3min time resolution images

Using 10 min time resolution images