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Solar Studies Using Filter Telescopes

Abstract In this experiment a range of filters and telescopes were used to define between individual sections

forming solar phenomena. Features such as filaments, solar flares, granules, were seen and their

formation evaluated.

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Table of Contents Abstract ................................................................................................................................................... 1

Table of Contents ..................................................................................... Error! Bookmark not defined.

Introduction ............................................................................................................................................ 3

Method ................................................................................................................................................... 5

Results ..................................................................................................................................................... 5

Conclusion ............................................................................................................................................... 8

Bibliography ............................................................................................................................................ 8

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Introduction The sun is a G2 type star (according to the Harvard Spectral Classification

System) at the centre of our solar system with a surface temperature of

approximately 6000K [11] [1]. The suns core which occupies only 25% of its

total radius is where nuclear fusion occurs producing the majority of its

energy [2]. Here there are constant p-p chain reactions that produce a

constant flux of neutrinos and gamma wavelength photons [3]. These

photons move through the core, having their path constantly deviated by

collisions with the electrons of the dense plasma contained within the suns

interior. The energy is eventually released from the core and moves

outwards to the top of the radiative zone, where the temperature drops to

around 2MK, where the photons are able to be absorbed by the plasma at

this temperature [4]. This absorption causes the plasma to heat up and

produce a convection current. The photons are carried by this current until

they reach the photosphere where the density of the plasma becomes low

enough for photons to be emitted and propagate through. They are

emitted at a lower energy than initially produced due to the random

motion in the radiative zone, and absorption in the convective zone [5].

The Sun when viewed through different filters produces a range of images,

with each individual wavelength analysed correlating to a wide range of

physical processes, and a range of different layers. This is scientifically

important as to understand the different phenomena of the sun, it they must be

broken down into individual processes moving through the individual layers involved [6]. The factors

effecting the wavelengths of photons being released from the sun is due to temperature, energy and

the elements involved. This produces a range of spectral lines, mainly originating from Hydrogen,

Calcium and Iron [7]. Many of the significant wavelengths look at specific spectral lines produced by

many times ionised elements, with each level of ionisation relating to specific heats. These can be

observed with different apparatus, such as ground based telescopes.

The ground based telescopes we used for our experiment were the following:

Telescope Mirror Diameter Focal Length Focal Ratio Filters

Maksutov-Cassegrain

116mm

1250mm

f/13.8 White Light

Coronado P.S.T 40mm

400mm

f/10 – with 20mm eyepiece

: <1.0 angstrom bandwidth centred on 656 nm

Big Bear Observatory (BBOS)

1.6m 83.2m f/50 H alpha

In comparison to ground based images there are satellite telescopes that remove atmospheric,

weather, and gaps in the observable times. SDO is the latest active mission from NASA to observe

solar phenomena. It was launched on the 11th February 2010, its mission aimed at studying how

solar activity is produced and how space weather results from it. Since 2010 it has been producing

images 24/7 through a range of filters studying the sun’s interior, its magnetic field, the plasma

Figure 1 Cross Sectional Diagram of Solar Interior

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confined within the corona and solar irradiance. Through a combination of these images processes

can be identified, broken down and analysed [9].

SDO AIA Imaging apparatus:

AIA Wavelength Ion(s) Region of atmosphere observed

Characteristic Log(T)

1700Å Continuum Temperature minimum,

photosphere

3.7

304Å He II Chromosphere, transition region,

4.7

1600Å C IV+cont. Transition region + upper photosphere

5.0

171Å Fe IX Quiet corona, upper transition region

5.8

193Å Fe XII, XXIV Corona and hot flare plasma

6.1, 7.3

211Å Fe XIV Active-region corona 6.3

335Å Fe XVI Active-region corona 6.4

94Å Fe XVIII Flaring regions 6.8

131Å Fe XX, XXIII Flaring regions 7.0, 7.2

Through this collection of telescopes the active atmosphere and surface of the sun can be observed

and analysed.

The deepest

surface visible is

through the

AIA1600, AIA1700,

and White light

filter on SDO,

observing the

photosphere [10].

These wavelengths

show the transition

region and

photosphere of the

sun. Through these

wavelengths

sunspots and granules can be seen. Sunspot phenomena can be attributed to the magnetic activity

of the sun causing an area to have magnetic flux normal to the sun, producing an area of high

magnetic force reducing the gas pressure within this area, therefore reducing the temperature.

Granules are phenomena attributed to the convection currents within the Sun and are formed by

the cooling of the plasma as it moves outwards towards the outer atmosphere of the Sun.

The next visible surface is seen through the AIA304 and H-alpha, observing the chromosphere.

Phenomena visible through this wavelength are Prominences, Filaments and Flares. Prominences are

attributed to magnetic connections between sunspots, causing magnetically confined plasma loops

to stream across the surface of the sun between magnetic North and South sunspots. Solar filaments

Figure 2 To Scale Cross Section of the Sun Showing Layers and Common Phenomena

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are areas of high magnetic density causing areas of high temperature and higher incandesce. Solar

flares are attributed to magnetic loops reconnecting in a region and cause plasma to be ejected from

the Suns surface into space.

The remaining wavelengths viewed through the SDO apparatus all view the Corona and outer

surface of the Sun, with Solar Prominences, Filaments and Flares being visible.

Method Images were obtained using our ground based telescopes. The images taken from our own

instruments we’re not of a high enough definition to be compared with the images of BBOS and SDO

and were therefore not used. However using images from each of the telescopes the images were

compared in different wavelengths which accorded to the depth and temperatures linked to known

phenomena. This allowed us to analyse the formation and features seen.

Results

Photosphere:

Figure 3 images obtained through AIA 1600 SDO.

Figure 4 Images obtained through AIA 1700 SDO.

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Chromosphere:

Corona:

Figure 6 Images obtained from BBOS through H-alpha

Figure 7 Images obtained through AIA171 SDO

Figure 5 Images obtained through AIA 304 SDO.

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All images above taken between 16:49 and 16:59 UT, 14th February 2014.

All images below taken between 06:00 and 07:00 UT, 7th June 2011

Figure 8 Images obtained through AIA131 SDO

Figure 9 Images obtained through AIA131 SDO

Figure 10 Images obtained through AIA304 SDO

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Discussion/ Conclusion As seen in figure 3 and 4 there are several dark patches, each of them signifying an area of high

magnetic density and therefore lower gaseous pressure and a lower temperature. The surrounding

area can be seen to contain long filament structures which are due to temperature differential

towards the centre of the spot. These areas are also shown to have bright marks surrounding them,

showing an area of high temperature. This shows that there is a large shift in the temperatures

which would correlate to the Solar Flare viewed in other wavelengths. The differences between the

images show more of the white marks on the AIA1600 rather than the AIA1700, which shows that

higher temperature material is rising through the photosphere as the AIA1600 looks at higher

ionised temperatures.

The chromosphere viewed through 304 and H-alpha from the big bear observatory show two

different temperatures contained within the chromosphere. These images show clear mass being

ejected from the surface at high temperatures, correlating with that of a Solar flare.

The corona is viewed through a range of wavelengths on the SDO equipment, all of them

investigating different temperatures. Figures 7-10 all show Solar Flares, with Figures 9 and 10

showing a larger event. The loops arching across the structure, this shows the temperature of the

loops to be warmer than the surface, and show that as the loops are reconnected plasma is ejected

from the surface.

To conclude different wavelengths highlight different temperatures and levels of ionisation well, and

a deeper review into these images can provide us with a better understanding of the internal and

external workings of the sun.

Bibliography

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195, no. 83, 2011.

[4] S. G. K. A. Eff-Darwich, “The Dynamics of the Solar Radiative Zone,” Solar Physics, vol. 287, no.

1, pp. 43-56, 2013.

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