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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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