Dissertation- Alex Kelly

Alex Kelly
ABERYSTWYTH UNIVERSITY 130000169
SOLAR CHROMOSPHERIC
DYNAMICS
ANALYSING CHROMOSPHERIC SPICULES TO SOLVE THE
CORONAL HEATING PROBLEM
Abstract
Type II chromospheric spicules are analysed using data obtained from the
Swedish Solar Telescope CRISP instrument. Analysis is carried out using the SSW
IDL widget and the CRISPEX IDL based software. Using arbitrary and comparative
analysis, analytical techniques are established that could be used in tandem with
parallel data analysis to establish type II spicules as a definite cause of observed
and unexplained coronal heating mechanisms.

P a g e | 1
Solar Chromospheric Dynamics Alex Kelly
Contents
Abstract...................................................................................................................................................0
1. Risk Assessment..................................................................................................................................2
2. Introduction ........................................................................................................................................3
Background information.....................................................................................................................3
The Sun............................................................................................................................................3
The Chromosphere .........................................................................................................................3
Spicules ...........................................................................................................................................5
The Corona and the problem..........................................................................................................6
Project introduction............................................................................................................................6
Literature Review................................................................................................................................7
Introduction ....................................................................................................................................7
The Swedish Solar Telescope..........................................................................................................7
CRISP and CRISPEX ..........................................................................................................................8
Chromosphere ................................................................................................................................9
Spicules .........................................................................................................................................10
Alfvén waves .................................................................................................................................10
The corona ....................................................................................................................................11
References (for literature review) ................................................................................................11
3. Analysis .............................................................................................................................................13
1. Spicule lifetime..............................................................................................................................13
2. Doppler shift .................................................................................................................................18
4. Discussion..........................................................................................................................................24
5. Conclusions .......................................................................................................................................26
6. Acknowledgements...........................................................................................................................26
7. Appendices........................................................................................................................................27
1. Figure 1.2...................................................................................................................................27
2. Spectral Positions......................................................................................................................27
3. Raw data ...................................................................................................................................28
4. IDL code.....................................................................................................................................30
8. Bibliography ......................................................................................................................................31

P a g e | 2
1. Risk Assessment
This is an extremely low risk project, conducted almost exclusively in front of computer screens. The
only slight risks are of repetitive strain injuries (RSIs) from continuous typing and posture issues born
from being sat in front of the computer monitor. These can be easily avoided by ensuring regular
breaks are taken to move around and rest wrists and hands, and to make sure chairs used are
providing good support to the lower back.

P a g e | 3
2. Introduction
Background information
The Sun
The sun is a G class (Zombeck, 1990), main sequence star at the centre of the solar system. It is
around 4.6 billion years old (Bonanno, et al., 2008), with equatorial radius of 695700km, equivalent
to 109 times the radius of Earth (Mamajek, 2015) and an estimated mass of almost 2 x 1030
kg
(Williams, 2013). The sun is composed largely of hydrogen and helium, with small amounts of
heavier elements present, data on the chemical composition is obtained through spectroscopic
techniques (Asplund, et al., 2006). A ball of predominantly ionised plasma (Zombeck, 1990), it is in
equilibrium, with the gravity from its mass being balanced with thermal pressure radiating from the
proton-proton nuclear fusion occurring in the solar core (Park, et al., 2001).
The Sun has a very complex structure, in a layered form, as shown in Figure 1.1. The bulk of nuclear
fusion processes happen in the core, and the energy and light travels outwards via different
mechanisms. The area of interest of this project are the outermost regions, the chromosphere and
corona.
The Chromosphere
The chromosphere lies just above the photosphere (the region that is visible to us) and for this
reason it can be very difficult to observe. In the spectrum of visible light, the photosphere creates far
too much background light, rendering the chromosphere invisible. To observe it, other wavelengths
such as Infrared light, or different techniques like spectroscopy, must be used. The chromosphere
has a temperature range between 6000 and 20000 Kelvin (Athay, 1976), making it one of the coolest
regions of the star. The chromosphere is extremely interesting because of how dynamic it is;
structures in the chromosphere form and collapse on a minute to minute basis. The images in Figure
1.2 demonstrate this very nicely, with each image taken less than eighty seconds after its
predecessor. These images were generated in the course of this project using data from the Swedish
Solar Telescope’s CRISP instrument. More information about these images is in Appendix 1.
Figure 1.1:
Diagram showing depth layered structure of
the sun (Hillyard & Hillyard, n.d.)

P a g e | 4
Much of the dynamism in the chromosphere is driven by wave propagation. Density and Alfvén
waves are both extremely common (De Pontieu, et al., 2007). Alfvén waves are waves that
propagate along magnetic fields while causing no density fluctuations in the surrounding plasma
(Alfvén, 1942). Different types of structures can be seen on the chromosphere. Loops such as the
one in figure 1.3 extend out into the corona, before reconnecting with the chromosphere. The
structure is maintained by localised magnetic fields, and often associated with sunspots on the
photosphere (De Moortel, et al., 2000). These structures, or more specifically the collapse of these
structures, has been linked to the creation of solar flares and coronal mass ejections (CME’s) (Hood
& Priest, 1979).
Figure 1.2
Series of images of the chromosphere. Each image, left to right, is taken 77 seconds after
its predecessor. Although the formatting is not ideal, as this sort of thing is much better
illustrated by animations, it should be apparent how much chromospheric structure varies
with time.

P a g e | 5
Spicules
The other main type of structure found in the chromosphere are known as spicules. These are
plumes of plasma that erupt from the solar surface, exist for only a short time before either
dispersing the material into the solar atmosphere or collapsing back to the surface. There are two
types of spicules, type I and type II. Type I spicules are caused by magnetic and density shock waves
in the chromosphere (De Pontieu, et al., 2007). These are the spicules that linger longest,
occasionally up to 10 minutes or so, before collapsing back towards the chromosphere. During the
lifetime of the spicule, plasma will flow both up and down the spicule in a convective system related
to the local magnetic field, giving it a fair amount of stability.
Type II spicules are much more dynamic and interesting, and are the subject of this project. Thin,
and forming very quickly, they show only upward motion (although occasionally rotational lateral
motion is observed (De Pontieu, et al., 2012)), and extremely high velocities, sometimes as high as
150km/s (De Pontieu, et al., 2007), before expiring after a couple of minutes at most. It is unknown
what mechanism drives these spicules to such high speeds, although magnetic reconnection is a
suspected candidate. Interestingly, they are also heated to temperatures ordinarily found below the
photosphere. The spicules tend to reach heights of over 5 million metres above the solar surface
before dispersing.
Figure 1.3
Coronal loops extending out from the
chromosphere (Jenner, 2008).

P a g e | 6
The Corona and the problem
The corona is generally thought of as the “atmosphere” of the sun, and the metaphor works well
enough for picturing its scale. The corona is comprised of plasma extending out beyond a solar
radius from the photosphere (Aschwanden, 2006). It is very difficult to observe the corona visually as
the disk of the sun is so much brighter. There are two main elements to the corona. Within two solar
radii of the disk centre, the k corona is dominant. This is the brightest area of the corona, mostly
featureless, and with scattered photospheric light getting sharply dimmer toward the outer edge.
Further out from the sun, the F corona becomes more dominant. This is much dimmer, in which the
light is mostly scattered off of interplanetary dust (Cravens, 1997).
By far the most interesting feature of the corona is the temperature. While the photosphere is
around 6000K, and the chromosphere up to 20000K, the corona can reach temperature beyond 106
K
(Aller, 1953). One of the greatest unknowns in astrophysics is the mechanism which causes this
increase in temperature in the corona. Several different theories exist as suggestions. But it is agreed
one of the most likely sources is from type II spicules in the chromosphere (De Pontieu, et al., 2007).
Project introduction
This project aims to establish a method for the investigation of type II spicules as potential
driving mechanisms for coronal heating. Data collected by the Swedish Solar Telescope’s
CRISP (CRisp Imaging SpectroPolarimeter) is analysed using CRISPEX IDL-based software. The
data used consists of intensity values taken on 21st June 2012, between the times 07:18 and
07:48 UT. The data collected was focused on sunspot AR1054, which at the time of
observation was very close to the solar limb. Crucially to this project however, the images
generated show a number of spicules visible off the solar disk. These spicules are studied in
different ways for a number of purposes, ultimately to determine whether this type of
observation could lead to establishing whether or not type II spicules are the drivers of
coronal heating.
Figure 1.4
A type II spicule is traced by the white line. The
white line, in real distance, stretches to around
3600km.

P a g e | 7
Literature Review
Introduction
Small-scale structures existing within the Sun’s Chromosphere have been observed through
use of the Swedish 1m Solar Telescope, in the H-α wavelength. These structures, known as
spicules, are jets of cool, dense plasma (when compared with background temperatures)
that extend out and into the corona.
The literature review covers previous and ongoing research with a view to guide the analysis
within this project, which uses data and images obtained from the Crisp Spectral Explorer
(Crispex) Instrument on the Swedish Solar Telescope in order to produce animations of the
evolution of spicules in time with an aim to help with determining their physical properties
and lay the foundations for investigations into their relationship with coronal heating.
The Swedish Solar Telescope
Currently the largest optical solar telescope in Europe, with a clear aperture of 97cm[1], the
Swedish Solar Telescope offers unparalleled resolution in its images with a resolution factor
R of up to 230000 (on its TRIPPEL instrument). It became operational in May 2002[2] and its
adaptive optics also allow the generation of diffraction-limited images[3] (through cross-
correlation of sub-images, with each correction being made in about 0.1ms). It replaces the
50cm Swedish Vacuum Solar Telescope.
As the images produced are near diffraction-limited only, there are no improvements that
are needed for image quality[4].
SST has two operational modes: a spectrographic and an imaging mode. For the purpose of
this project, the imaging mode, using the CRisp Imaging SpectroPolarimeter Instrument
(CRISP Instrument)[5], which collects data with 3 1kx1k CCDs[5], is the only mode necessary to
understand. These three CCDs are split into 3 categories: Wide-Band, which obtains images
that have yet to be passed into CRISP, Narrow-Band Transmitted, which collects polarised
light that passes through the Polarising Beam-Splitter located after CRISP, and Narrow-Band
Reflected, collecting light reflected by the PBS and polarised perpendicular to that collected
by the NBT. The output image is a combination of the light received from these three
cameras[6].
Figure 1.5: Path taken by light
through the SST, courtesy of
http://www.solarphysics.kva.se/Natu
reNov2002/telescope_eng.html

P a g e | 8
CRISP and CRISPEX
The CRISP Instrument’s primary component is a dual Fabry-Pérot Interferometer[5]
comprised of two sets of parallel reflective plates (also known as Etalons) positioned in
tandem, as demonstrated in the figure below:
Figure 1.6[6]
: Showing the CRISP Instrument and the path taken by a beam of light within the telescope. Note:
FL=Field Lens of the telescope, PCO=Polarization Calibration Optics, TM=Tip-Tilt mirror, used to ensure the
image contains minimal smearing from movement, DM=Deformable mirror, used to calibrate against phase
aberrations and controlled by a Shack-Hartmann Wave=Front Sensor, DC=Dichromatic Beamsplitter, that
separates out blue and red light (with the separation occurring at 500nm) and allows red light through to
CRISP, AO WFS=Adaptive Optics Wave-Front Sensor, Shutter= Instrument that synchronises the three CCDs
within the system, Prefilter=Instrument that controls the spectral range of light that reaches CRISP, WB= Wide-
Band, LC=Liquid Crystal Modulators, PBS=Polarising Beamsplitter, used to separate the horizontally and
vertically polarised components of the wave, NBR=Narrow-Band Reflected and NBT=Narrow-Band
Transmitted.
Any light that reaches the Etalon is partially transmitted and partially reflected. This process
repeats multiple times as the light reflects continuously between the two plates. The
multiple transmitted waves interfere with each other, which, at points of constructive
interference (when the waves are in phase), produces extremely high resolution akin to
diffraction gratings. This interference is based upon the phase difference, which can be
written as 𝛿 =
2𝜋
𝜆
2𝑛𝑙𝐶𝑜𝑠𝜃[7], where λ is wavelength, n is the refractive index of the material
between the plates, l is the distance between the two plates and θ is the angle of reflection;
when the path length difference (2nlCosθ) is equal to an integer multiple of the wavelength
(mλ, where m is known as the order of interference), this produces a phase difference 𝛿 =
2𝜋𝑚; since 2m will always be an even number and a phase difference of an even multiple of
π always equates to 0, this means δ=0. A phase difference of 0 means that the waves are
completely in phase and hence constructively interfere.
These Etalons are tuneable (the spacing between each pair of plates can be adjusted) to
allow different spectral resolutions to be obtained. For CRISP, the first Etalon is at High
Spectral Resolution and the second at Low Spectral Resolution. The HRE enhances the
desired wavelength whilst the LRE subdues the first few orders of interference of any
secondary transmission peaks obtained from the HRE.

P a g e | 9
Based upon the following graph[6] demonstrating the prefilters available for CRISP, and its
high resolution (0.071 arcseconds per pixel[5]), it is clear that the data obtained from this
instrument is of great importance for the experiment, which looks at Spicules within the H-α
spectrum (656.30nm[8]).
Figure 1.7: Showing prefilters used by CRISP, at 500nm and above. The 656.3 line, for H-α, is circled.
Chromosphere
The chromosphere is a layer of the solar surface just above the photosphere, shown in
figure 1.8[12]. The temperature of the chromosphere varies greatly, ranging from 6000-
20000K[13]. The chromosphere is impossible to observe in visible light due to the background
noise from the photosphere[14].The chromosphere can be observed in higher energy
wavelengths of light, or at specific wavelengths for the purposes of spectroscopy. Observing
at wavelengths known to be found in spectra of specific elements and compounds can
reveal the composition of the chromosphere[15]. However, there are not enough
observations to determine the composition, nor why the temperature increases with
radius[16] .
When the chromosphere is visibly observed, it is red in colour due to Hα emission lines[17].
Many other spectra have been observed on the solar surface, but the photospheric
background radiation makes it difficult to define the composition of the chromosphere.
Figure 1.8: Diagram showing layers
of the sun. The chromosphere is just
above the photosphere.

P a g e | 10
There are many interesting processes that occur in the chromosphere, for example the
varying magnetic field, Alfvén wave propagation along the surface and spicules.
Spicules
As described by Martinez-Sykora[9], two types of Spicules, Type I and Type II, are known to
exist. Type I Spicules follow a parabolic path with alternating upward and downward
motions, reaching 2 to 9Mm above the photosphere and existing between 3 and 10
minutes. Magneto-acoustic shockwaves propagating through the chromosphere are the
cause of these. As of yet, whilst their formation is well known, little research has gone into
understanding how many processes related to Chromospheric dynamics affect their
evolutions in time.
Type II Spicules contrastingly have relatively unknown origin. They only last for up to
approximately 100s, but reach an average height of 6.5Mm. Apart from only having an
upward velocity (appearing to be 50-100kms-1), motion tangential to the solar surface (10-
30kms-1) – possibly implying Alfvén waves – and torsional motion (25-30kms-1) also occur.
Determining the cause of Type II Spicules brings the potential to further develop knowledge
on Coronal Heating and can be done through analysis of time-evolving animations of
spicules within the H-α spectrum, including measurement of the Doppler shifts of each
spicule.
Alfvén waves
Alfvén waves are waves occurring in plasma that produce no density or pressure
fluctuations with propagation[18]. They vary in velocity as the magnetic field changes, shown
by Bagenal[19]. The equations below demonstrate this, with v being the phase speed of the
waves in plasma and va being the Alfvén speed. Θ represents the angle between the
direction of propagation and the magnetic field it is travelling through, explaining why
velocity changes.
𝑣 = 𝑣 𝑎 cos 𝜃
Where
𝑣 𝑎 =
𝐵
√ 𝜇𝜌
The waves carry energy along the magnetic field lines in the plasma[20]. These waves are
produced by the interaction between magnetic fields and the electrical currents they
generate[21]. Correlations have been found between wave activity by spectroscopic
techniques and solar activity, suggesting waves on the solar surface could be responsible for
misunderstood mechanisms, such as the coronal heating problem[22]. Another paper
discovered what appeared to be damped standing waves in the chromosphere in a perfect
90° phase shift with the intensity variation of activity in the corona[23], supporting this
assertion. The idea that Alfvén waves can produce spicules was also first suggested a long
time previously, evidenced by Haerendel[24].

P a g e | 11
The corona
Visible stretching out until about 2 Solar Radii, the Corona is a source of decades of interest
due to its extreme temperatures (in excess of 106K) despite the much cooler photosphere
(~5800K). The closest, most visible section of the Corona is the K-Corona, where Doppler
Broadening causes the absorption lines from free-electron scattering to completely smear,
forming an apparent continuous spectrum. It is a highly active area, containing such regions
as Coronal Loops, Coronal Mass Ejections and also Coronal Holes where open magnetic field
lines exist (the cause of high solar winds).
Spicules are thought to be part of the heating process because according to the Second Law
of Thermodynamics, any thermal energy would be forbidden from travelling from the cooler
Photosphere to the hotter Corona. Spicules carry high kinetic energy, therefore this energy
transfer is allowed. A paper[9] found that small-scale heating events could translate to large-
scale overall heating, but did not link dynamic process taking place in the Chromosphere or
Transition Region to these simulated events. A second paper[10] simulated small-scale
heating events for a quiet corona and found that they could sustain the coronal balance,
and that the majority of the heating was ~2Mm above the surface. The model ran over an
hour and the energy transfers were considered instantaneous. The events again need to be
identified observationally and conditions other than the quiet Sun need to be simulated.
Also, Joule Heating was the main focus, which is based upon heat produced by electrical
currents, rather than Kinetic energy.
References (for literature review)
[1]: Scharmer, G.B. et al., The New Swedish Solar Telescope, High Resolution Solar Physics:
Theory, Observation and Techniques Vol. 183, 1999.
[2]:Scharmer, G.B. et al., The 1-meter Swedish Solar Telescope, Innovative Telescopes and
Instrumentation for Solar Astrophysics, Proceedings of SPIE, February 2003.
[3]: Scharmer, G.B. et al., Adaptive Optics System for the new Swedish Solar Telescope,
Innovative Telescopes and Instrumentation for Solar Astrophysics, Proceedings of SPIE,
February 2003.
[4]: Born, M., Wolf, E., Principles of Optics, Cambridge University Press, 1997, [NO PAGE
GIVEN], ISBN 0-521-63921-2.
[5]: Scharmer, G.B. et al., CRISP SpectroPolarimetric Imaging of Penumbral Fine Structure, The
Astrophysical Journal Vol. 689 No. 1, December 2008.
[6]: de la Cruz Rodríguez, J. et al., CRISPRED: A Data Pipeline for the CRISP Imaging
SpectroPolarimeter, Astronomy & Astrophysics Vol. 573, January 2015.
[7]: Lipson, S.G., Lipson, H., Tannhauser, D.S., Optical Physics (3rd Edition), Cambridge
University Press, London, 1995, page 248, ISBN 0-521-06926-2.
[8]: Bertello, L. et al., Solar Cycle Dependency of Sun-as-a-Star Photospheric Spectral Line
Profiles, 18th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (Conference)
June 2014, Published January 2015.

P a g e | 12
[9]: Martínez-Sykora, J. et al., A Detailed Comparison between the Observed and Synthesized
Properties of a Simulated Type II Spicule, The Astrophysical Journal Vol. 771 No. 1, June
2013.
[10]: Hansteen. V. et al., Numerical Simulations of Coronal Heating through Footpoint
Braiding, The Astrophysical Journal Vol. 811 No. 2, October 2015.
[11]:Guerreiro, N. et al., Small-Scale Heating Events in the Solar Atmosphere. I. Identification,
Selection, and Implications for Coronal Heating, The Astrophysical Journal Vol. 813 No. 1,
November 2015.
[12]: Brooke Boen, Hinode mission, NASA, 2010
[13]: R Grant Athay, The solar chromosphere and corona, D Reidol Publishing company, 1976
[14]: L Macdonald, How to Observe the Sun Safely, Springer New York, 2012
[15]: D T Woods & L E Cram, High Resolution Spectroscopy of the Disk Spectroscopy, Solar
Physics, 1980
[16]: R O Milligan, Extreme Ultra-Violet Spectroscopy of the Lower Solar Atmosphere During
Solar Flares, Solar Physics, 2015
[17]: P Marmet, Redshift of spectral lines in the sun’s chromosphere, IEEE Transactions on
Plasma Science, 1989
[18]: H J Singer et al., Alfvén wave resonances in a realistic magnetospheric magnetic field
geometry, Journal of Geophysical Research, 1981
[19]: F Bagenal, Alfvén wave propagation in the Io plasma torus, Journal of Geophysical
Research, 1983
[20]: B N Dwivedi & A K Srivastava, Coronal heating by Alfvén waves, Current Science, 2010
[21]: S Vincena et al., Production of Alfvén Waves by a Rapidly Expanding Dense Plasma,
Physical Review Letters, 2001
[22]: B De Pontieu et al., Chromospheric Alfvén Waves Strong Enough to Power the Solar
Wind, Science, 2007
[23]: T Wang et al., Doppler shift Oscillations of Hot Solar Coronal Plasma Seen by SUMER: A
Signature of Loop Oscillations?, The Astrophysical Journal Letters, 2002
[24]: G Haerendel, Weakly damped Alfvén waves as drivers of solar chromospheric spicules,
Nature, 1992

P a g e | 13
3. Analysis
1. Spicule lifetime
Type II spicules can be extremely variable in lifetime. This is one of the easiest qualities to
study with intensity values, as it is very clear when spicules form and decay. The first two
spicules studied in this project (see appendix 3 for data) provide an excellent example of
this. The two spicules were observed at different times; spicule 2 appears just over 300
seconds after spicule 1 fades. Spicule 2 was also slightly closer to the solar equatorial
latitude, but the scale of the observed region relative to the scale of the sun makes this of
little consequence. Figure 3.1 (the images below) is a parallel of each frame in which both
spicules are observed. Spicule 1 is the left images, spicule 2 the right set of images. The
white lines on the images are CRISPEX’s path drawing function being used to highlight the
spicule, and to define the spicule’s central pixels.
The images serve to highlight the difference between two similar spicules in their lifetimes.
While the second spicule seems to change little during the observations (both sets of images
cover a time frame just over a minute), by the last frame the first spicule has very visibly
faded. This is represented in the data by the graphs in figure 3.2. The graphs for each frame
of spicule 2 are fairly consistent, but spicule 1 shows a trend in which the late frame graphs
generally show much lower intensities as the spicule fades.

P a g e | 14

P a g e | 15

P a g e | 16
Figure 3.1 (above):
Comparison between spicules 1 & 2 (left and right respectively). Spicule 1 frames 0
through 6, spicule 2 observed frames 45 through 52.
Figure 3.2 (below):
Graphical plot of recorded intensity values for spicules 1 (top) and 2 (bottom). Graph
colours as follows:
Frame 1- Black dotted line
Frame 2- Magenta dashed line
Frame 3- Dark blue dashed line
Frame 4- Green dash-dotted line
Frame 5- Brown line
Frame 6- Yellow solid line
Frame 7- Light blue solid line
Frame 8 (spicule 2 only)- Light pink solid line.

P a g e | 17

P a g e | 18
Another purpose these graphs serve is to support an expected result, that might seem
intuitive and obvious were it not for the coronal heating problem. Although each frame was
different due to the changing height, shape and intensity of the spicule, the “point along
spicule” x values are proportional to height above the limb. So generally speaking, further
along the x axis is proportional to higher up on the spicule. With this in mind, an obvious
trend is that generally, intensity decreases with height above the solar surface.
2. Doppler shift
Along with intensity images, CRISP can simultaneously record Doppler shift images. Type II
spicules display interesting behaviour when looked at in a Doppler spectrum. Spicule 3 was
chosen to be examined due to the Doppler shift it showed over the course of its lifetime.
Figure 3.3 is a comparison of the Doppler and intensity images of the spicule.

P a g e | 19

P a g e | 20

P a g e | 21

P a g e | 22
Throughout the 11 frames, the equivalent of over 80 seconds real time, the spicule
observed looks somewhat dim and uninteresting when looking at the intensity image. But in
some frames of the Doppler imaging, the spicule looks divided into sharply contrasted side
by side black and white areas. What this represents is in fact plasma rotation, as the entire
spicule is rotating while the plasma travels up the spicule (darker areas in the images show
blue-shifted material, meaning that if you were looking along the spicule towards the solar
surface it would be rotating anti-clockwise). The data used here does not include absolute
velocity values, but it is clear from the contrast in tone that this rotation is occurring at a
high velocity.
Figure 3.4 demonstrates more clearly the intensity vs Doppler images of the spicule. The
path drawn on the intensity image highlights the peak of the blue shift before looping back
down on the right to indicate the peak of the red shift. As would be expected, due to blue
shift indicating an object is travelling toward the observer at high speed, the blue shifted
side of the spicule is much brighter. Perhaps surprisingly, though, is how close the red
shifted part of the spicule is to the background, giving an indicator of how little is perhaps
being seen in these images.
Figure 3.3:
Parallel comparison of spicule 3, captured simultaneously in intensity and Doppler imaging.
Frames 23 through 34 are pictured. The interesting aspect of this spicule is best showcased by
the seventh set of images, frame 30. In the intensity image, the spicule looks wholly
unremarkable, and yet the Doppler image reveals parallel, very strong blue and red shifts
present in the spicule. It is important to note darker areas are blue shifted.

P a g e | 23
Also interesting in the Doppler imagery are the overall changes in the spicule. In the images
that lean towards one direction of shift or the other, these images are inconsistent.
Consider the fifth image, frame 28, and the final frame. Although the spicule has faded
slightly in frame 34, it can be argued the spicule is leaning much more towards red shift than
blue, the inverse of which is true for frame 28, in which the spicule is extremely dark. This
suggest overall motion of the spicule, not only vertically, or around the solar surface, but in
the angle of the spicule against the solar surface. An explanation for the change of overall
shift could be that in frame 28, the spicule is pointed toward the observer, and has swung
slightly away from the observer by frame 34 in a metronome-like oscillatory motion.
Figure 3.4:
Three images of spicule 3 at frame 25. Left is the Doppler image, centre the intensity image
with a path overlaid to highlight the blue and red shift on the left and right respective parts of
the spicule, and right is the intensity image without the central path drawn over.

P a g e | 24
4. Discussion
There is perhaps more to be said about the results obtained during this project than there
are results themselves, as is the nature with any research investigating a method of
research, rather than using the method itself. Firstly, this project faced many limitations
which should all be acknowledged. The bulk of the data gathered and used in this process
comprised intensity measurements. Unfortunately, no absolute definition of the intensity
counts was available, meaning they are somewhat arbitrary and only particularly in
comparing with other data self-contained in this project. The Doppler imagery generated,
while insightful, is scientifically flawed, as the CRISPEX software was unable to generate
absolute velocity values with the data used. This means that outside of seeing colour trends
in the imagery, it is impossible to draw any conclusions regarding Doppler shift. The
combination of these two issues means that mathematically there is extremely little that
can be done with this data. Knowledge of the images, for example the frames being 7.7
seconds apart, and each pixel being roughly 44km across, enables estimations but very few
meaningful calculations. To that extent, no mathematical formulae or calculations have
been included, in either the background theory or the results report, as they would be little
more than largely pointless academic exercises that would overcomplicate this report to a
reader less informed in this field of astrophysics.
In terms of errors in the data, the lack of mathematics is a positive. The Swedish Solar
Telescope and CRISP are extremely well cared for, well calibrated, accurate instruments. It is
unlikely there is noticeable, if any, error in the data used in this project; certainly none that
would impact the results and conclusions drawn.
In starting out this project, the overall aim was extremely open ended, and this was perhaps
the primary shortcoming of the project. As is seen from the literature review included in this
report that was written early on in the project, there is little focus beyond spicules and the
research on the coronal heating problem. It was found that a large portion of the eventual
focus was born out of limitations. It was discovered that the CRISPEX software had many
unexpected failings that limited what research was able to be carried out. The colleagues
working on this project also had limited experience working with IDL, which caused several
delays throughout the course of the project. There were also technical issues for some
number of weeks involving the SolarSoftWare IDL widget that is necessary to use CRISPEX
that hampered progress.
Another issue that is particularly applicable to this report is the representation of results.
This project was extremely visual, and involved a lot of time-sensitive data and imagery. On
a paper report, this is extremely difficult to represent, resulting in large swathes of
consecutive images and noisy, nigh on indecipherable graphs that would both be much
more effectively represented as animations.
In contrast to the issues with lack of focus, the timescales in which this project was set make
an expansive and comprehensive research effort difficult. Very little data was looked at, and
only three individual spicules investigated in meaningful depth. This lack of depth means

P a g e | 25
that results from this project should not be considered definitive, but at the same time still
carry weight with an insightful interpretation.
Appendix 2 discusses the meaning of the phrase “spectral position” in the context of this
project. Up to this point, every image used was taken in spectral position 5, for reasons
exemplified in figure 4.1. The comparison between spectral positions 5 and 19, in a range
that makes 19 a very central wavelength, is stark. Spectral 19 shows a huge amount of
background noise, and compared to Spectral 5, it is almost impossible to distinguish
individual spicules. Analysis was conducted in Spectral 5, as it seemed the most apt to
identifying and singling out spicules.
Figure 4.1:
Comparison of frame 25 at spectral position 5 (left) and spectral position 19 (right).

P a g e | 26
5. Conclusions
The goal of this project was to determine whether intensity and Doppler shift
measurements and analysis could make for a useful method of establishing whether or not
type II spicules could be a source of coronal heating. As mentioned previously, there are
many flaws that this project suffered that people replicating this research could easily avoid.
However, the base data being intensity and Doppler imagery has a lot of potential. With
known velocity data and defined intensity values, combining SST data with other
observations from apparatus such as Hinode and SOHO, researchers could examine spicules
in parallel with data on the corona to look for patterns and links. In that format of research,
whether or not a definite connection between spicules and coronal heating exists could be
very well established, so in that regard, it has to be said that this project has been at least
partially successful. Very few researchers have ever successfully studied type II spicules,
meaning that this project is in fact brand-new research, which should always be considered
a success.
6. Acknowledgements
I would first and foremost like to thank my project partner Elliot Vale for his role in this
project, without whom this project would have taken me a great deal longer. Playing our
skills off of each other made us both more efficient and I think taught us a great deal. I am
hugely grateful to Dr. Youra Taroyan for his patience, assistance and expertise throughout
this project, and for giving us room to see what we were capable of producing, as it led to
our best possible work. Thanks also go to the Aberystwyth University Institute of
Mathematics, Physical and Computer Sciences technical staff for their tireless work in
solving issues with IDL and SSW that could have ended this project. Finally, I wish to thank
John Kelly and Jane Kelly for their unwavering personal support and advice throughout the
course of this project and my studies as a whole.

P a g e | 27
7. Appendices
1. Figure 1.2
These images were taken at spectral position 19, every tenth frame from frame 0 to 140. This covers
a time scale of 1078 seconds.
2. Spectral Positions
Throughout this dissertation the phrase “spectral position” is used. The CRISP instrument is capable
of observing in a wide range of wavelengths, and these wavelengths are defined by the current
through the instrument. Because the data used in this project does not include defined wavelengths,
the phrase spectral position is used to describe the wavelength a particular image is using. The list of
spectral positions and the corresponding currents associated with them is given here. If needed, this
could be used with more data about the CRISP instrument to decipher the wavelengths used, but
this was unnecessary for this project.
Spectral
Position
Current
(Amperes)
1 -2.064
2 -1.892
3 -1.720
4 -1.548
5 -1.376
6 -1.290
7 -1.204
8 -1.118
9 -1.032
10 -0.946
11 -0.860
12 -0.774
13 -0.688
14 -0.602
15 -0.516
16 -0.430
17 -0.344
18 -0.258
19 -0.172
20 -0.086
21 0.000
22 0.086
23 0.172
24 0.258
25 0.344
26 0.430
27 0.516
28 0.602
29 0.688
30 0.774

P a g e | 28
31 0.860
32 0.946
33 1.032
34 1.118
35 1.204
36 1.290
3. Raw data
Usually the data which the images studied were generated from would be included here. However,
the scale of this data makes this impossible. Every individual pixel in any of the images generated has
9288 intensity values associated with it, so including all of this would be ridiculous. The data for the
three spicules discussed is included, however. It should be once again be noted that the intensity
values used here are arbitrary, relative to the rest of the data. The column “pixel” refers to each
observed pixel along the spicule in the frame n, with intensity value In. Due to the changing length of
spicules, there are differing numbers of pixels
Spicule 1: Frames 0-6
Pixel I0 I1 I2 I3 I4 I5 I6
1 1764 1235 1277 961 951 1084 987
2 1632 1229 1261 952 931 1080 993
3 1668 1224 1205 950 879 1029 987
4 1689 1213 1180 920 766 1012 1076
5 1779 1183 1153 893 730 966 1076
6 1695 1146 1110 875 732 978 1073
7 1776 1095 1099 887 721 1017 1023
8 1770 1011 1083 900 714 1010 974
9 1913 975 1079 903 696 1025 923
10 1891 964 1051 901 666 1073 886
11 1835 988 1044 877 637 967 848
12 1952 990 1076 867 661 797 791
13 1205 990 1075 861 648 710
14 2001 1101 1024 865 706
15 2057 1102 1044 891 700
16 1987 986 997 887
17 1883 1031 983 820
18 1965 1070 877 757
19 1777 1129 900 701
20 1859 1164 886 675
21 1640 1156 896 686
22 1732 1108 877 770
23 1763 1032 896 832
24 1613 1008 893 831
25 1699 875 862
26 1657 856
27 1696 843
28 1606 765
29 1605 743
30 1498 731

P a g e | 29
31 1487
32 1354
33 1319
34 1264
35 1181
36 1083
37 876
Spicule 2: frames 45-52
Pixel I45 I46 I47 I48 I49 I50 I51 I52
1 2645 2759 2426 2466 2476 2506 2788 2690
2 2502 3023 2364 3195 2722 2521 2816 2833
3 2358 2874 2099 2863 2944 2205 2703 3039
4 2135 2648 1881 2905 2542 1844 2405 2528
5 1934 2518 1725 2532 2422 1595 2115 2010
6 1773 2093 1553 2001 2131 1479 2022 1897
7 1650 1946 1521 1685 1832 1469 1795 1866
8 1406 1664 1503 1509 1858 1443 1586 1772
9 1156 1446 1522 1357 1859 1366 1390 1557
10 1053 1224 1481 1123 1590 1227 1337 1455
11 980 980 1307 988 1629 1152 1302 1394
12 948 850 1038 974 1598 1192 1338 1424
13 852 851 886 947 1528 1372 1447 1577
14 783 868 810 953 1536 1508 1594 1699
15 674 935 926 957 1509 1625 1687 1590
16 640 969 1116 923 1526 1626 1771 1501
17 641 1058 1166 904 1487 1595 1782 1328
18 668 1079 1117 915 1351 1514 1768 1154
19 686 1143 1100 902 1273 1459 1701 1006
20 693 1043 1062 807 1169 1421 1460 861
21 723 993 934 1059 1333 1336 775
22 728 847 990 1248 1187 747
23 733 932 1072 954
24 737 808
25 738 722
26 693 643
27 595
Spicule 3: Frames 23-34
Pixel I23 I24 I25 I26 I27 I28 I29 I30 I31 I32 I33 I34
1 1339 731 1062 1052 984 1248 1369 1260 1027 1274 1223 922
2 887 746 946 862 895 1205 1499 1209 1018 1315 1114 803
3 819 765 865 799 873 1145 1533 1114 946 1289 1078 776
4 818 739 824 727 813 976 1483 1052 906 1106 1095 782
5 809 687 712 681 811 931 1424 1060 971 1033 919 719
6 719 602 632 628 831 927 1428 997 915 1065 678 669
7 575 699 628 790 912 1491 850 877 1029 476 598
8 572 639 816 1456 712 922 527

P a g e | 30
9 719 1227 675
4. IDL code
The images generated, and CRISPEX software used for analysis, are based in the IDL code below.
Spicules- image generation
; Change to the directory with data
cd,'E:Spicules'
file=findfile('crispex.6563.imcube')
loadct,3
!p.multi=0
window,0,xsize=700,ysize=700
CRISPEX, 'crispex.6563.imcube', 'crispex.6563.spcube'
; Define the slits
slit1=fltarr(35,31)
slit11=fltarr(35,31)
;There are 258 frames in total. Spicule I studied appears from 168-190 frame
numbers
;7 and 30 (total 35 scans.. 0-34)corresponds to the scan number where the spicule
is
;clearly visible in red and blue wing.
start_frame=0
for i=0,30 do begin
image1=lp_get(file,7+35*(i+start_frame))
image2=lp_get(file,30+35*(i+start_frame))
image3=sqrt(sqrt(image1)) ;For more clarity in intensity image
;image4=sqrt(image1[700:825,550:775]) ;To extract Region-of-Interest
;image5=congrid(image2,375,675,/interp) ;Resize image
;image6=rot(image3,-33,/interp) ;Rotate image
;Images at blue and red wings were background subtracted before computing doppler
shift.
blue=(image1-mean(image1[690:790,670:750]))/(mean(image1[690:790,670:750]))
red=(image2-mean(image2[690:790,670:750]))/(mean(image2[690:790,670:750]))
doppler=(blue-red)/(blue+red+2)
;Define slit position for both intensity image and doppler image.
;slit1[*,i] = doppler[x1:x2,y] (for horizontal slit)
;slit1[*,i] = doppler[x,y1:y2] (for vertical slit)
;slit1[*,i]=doppler[700:780,665]
;slit11[*,i]=doppler[740,630:700]
;Plot intensity and doppler images
loadct,3
plot_image,image3[690:790,670:750],title='Intensity Image'
arrow,90,102,120,102,color=1,hsize=0,thick=2,/data ;This will show the slit
location on image
plot_image,doppler[690:790,670:750],title='Doppler Image'
arrow,90,102,120,102,color=1,hsize=0,thick=2,/data

P a g e | 31
;write_gif, 'Doppler Shift.gif', bytscl(doppler[690:790,670:750])
;To plot the scan across the slit
;plot_image,slit1,title='slit1',XTITLE='Slit (Distance)', YTITLE='Frames (time)',
FONT = 0
;plot_image,slit11,title='slit11',XTITLE='Slit (Distance)', YTITLE='Frames
(time)', FONT = 0
;Save the images with '.png' extention.
;write_png,'ScaledTest_'+string((i+start_frame),format='(I3.3)')+'.png',tvrd_24()
endfor
;This will create slit maps.. and you can plot red and blue shifts as contours and
also blend two maps.
;window,0
;map1=make_map(slit1)
;map11=make_map(slit11)
;
;blend_map,map11,map1
;plot_map,map1,/nolabels,title='slit1_middle'
;plot_map,map1,/overlay,/smooth, /contour,levels=[0.0,7],lcolor=5,cthick=2
;plot_map,map11,/overlay,/contour,levels=[-0.11,-0.1],color=100,cthick=2
;plot_map,map11,/overlay,/contour,levels=[0.1,0.11],color=450,cthick=2
;..........................................................
end
crispex- programming of CRISPEX software
Due to the complexity of a program such as CRISPEX, including the IDL code would add around sixty
thousand words and two hundred and seventy pages to this report. For the sake of ergonomics, it
will be emitted here, but the author can be contacted if it is required.
8. Bibliography
Alfvén, H., 1942. Existence of electromagnetic-hydrodynamic waves. Nature, 150(3805), pp. 405-
406.
Aller, L. H., 1953. The Atmospheres of the Sun and Stars. New York: The Ronald Press.
Aschwanden, M., 2006. Physics of the Solar Corona. s.l.:Springer Science and Business Media.
Asplund, M., Grevesse, N. & Sauval, A. J., 2006. The Solar Chemical Composition. Nuclear Physics A,
Volume 777, pp. 1-4.
Athay, R. G., 1976. The solar chromosphere and corona: Quiet sun. Boston: Reidel.
Bonanno, A., Schlattl, H. & Paterno, L., 2008. The age of the Sun and the relativistic corrections in the
EOS. Astronomy and Astrophysics, Volume 390, pp. 1115-1118.
Cravens, T. E., 1997. Physics of Solar System Plasmas. Cambridge: Cambridge University Press.
De Moortel, I., Ireland, J. & Walsh, R. W., 2000. Observation of oscillations in coronal loops.
Astronomy and Astrophysics, Volume 355.
De Pontieu, B. et al., 2012. Ubiquitous torsional motions in type II spicules. The Astrophysical Journal
Letters, Volume 752.

P a g e | 32
De Pontieu, B. et al., 2007. A Tale of Two Spicules: The Impact of Spicules on the Magnetic
Chromosphere. Publications of the Astronomical Society of Japan, Volume 59, pp. 655-652.
De Pontieu, B. et al., 2007. Chromospheric Alfvénic Waves Strong Enough to Power the Solar Wind.
Science, 318(5856).
Hillyard, W. & Hillyard, D., n.d. Solar System- The Sun. [Online]
Available at: http://www.whillyard.com/science-pages/our-solar-system/sun-structure.html
[Accessed 26 April 2016].
Hood, A. W. & Priest, E. R., 1979. Kink instability of solar coronal loops as the cause of solar flares.
Solar Physics, 64(2), pp. 303-321.
Jenner, L., 2008. NASA Goddard Space Flight Centre. [Online]
Available at: http://www.nasa.gov/centers/goddard/news/topstory/2003/0708vault.html
Mamajek, E. E. e. a., 2015. IAU 2015 Resolution B3 on Recommended Nominal Conversion Constants
for Selected Solar and Planetary Properties, s.l.: International Astronomical Union.
Park, T. S. et al., 2001. Parameter-Free Calculation of the Solar Proton Fusion Rate in Effective Field
Theory. Nuclear Theory.
Williams, D. R., 2013. NASA Goddard Space Flight Centre. [Online]
Available at: http://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html
Zombeck, M. V., 1990. Handbook of Space Astronomy and Astrophysics. Second ed. s.l.:Cambridge
University Press.

Dissertation- Alex Kelly

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Dissertation- Alex Kelly

Similar to Dissertation- Alex Kelly (20)

Dissertation- Alex Kelly