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   \title{MANDATORY ASSIGNMENT I}

   \author{Candidate \# X} % Please fill in your candidate number. 
 
	\date{}

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   \maketitle
   \notemandatory
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%\input{cheeseipsum}
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\section{Preparatory exercises} 
\instructions{The exercises in this section will help you getting started with tasks that are essential for working with the next mandatory and the final project assignments. }

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\subsection{Literature search and bibliography}
\instructions{Use the \textbf{Astrophysics Data System (ADS) Science Explorer} to find the right references. You should retrieve the \bibtex items from ADS and build up a bibliography file (.bib). Please answer the questions below by specifying the \textbf{bibcode}\footnote{A correct bibcode is similar to  \texttt{1999xxxxx.123.....A}.} and using the \textbf{cite command}.} 


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\subsubsection{\textbf{Which is the most cited paper that contains the word "Sun" in the title?}}\label{sec:prep_lit_ex1}

Answer: \citet{} - title of the paper --- Bibcode: 

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\subsubsection{\textbf{Which of the papers that do cite the paper referred to above in exercise 
\ref{sec:prep_lit_ex1} \underline{and} was published after the year 2000 has itself received the most citations?}}
%Correction for next year: Look at the reference list for the paper asked for in exercise \ref{sec:prep_lit_ex1} (i.e. the papers cited). Which of those cited papers that has been published before the year 2000 has itself received the most citations?}

Answer: \citet{} - title of the paper --- Bibcode: 

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\subsubsection{\textbf{Which is the most cited paper of the author Parker, E that contains the word "solar" in the title?}}

Answer: \citet{} - title of the paper --- Bibcode: 

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\subsubsection{\textbf{In their paper on simulations of solar granulation, which the authors Stein, R. F. \& Nordlund, \AA\ published in the Astrophysical Journal (ApJ) in 1998, they refer to another paper on magnetic elements. Which is that paper?}}

Answer: \citet{} - title of the paper --- Bibcode: 

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\subsubsection{\textbf{Which is the most cited paper that contains the words
"solar metallicity low-mass stars" in the title and/or abstract?}}

Answer: \citet{} - title of the paper --- Bibcode: 

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\subsection{A first look at relevant data sets and tools} 

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\subsubsection{\textbf{Plotting and analysing a reference atmosphere model}}
\instructions{Load the data file \texttt{val81c.h5}, which contains the model atmosphere VAL~C \citep{1981ApJS...45..635V}. Reproduce the plot in Fig.~\ref{fig:val}, save it to a file (e.g., PNG), and replace the file name in the includegraphics command with your own file. In addition, please answer the questions below using the same data.}


\begin{figure}[h!]
\sidecaption
\includegraphics[width=11cm]{ast5770ma1_val81c.png}
\caption{The plot shows the semi-empirical atmosphere model~C by \citet{1981ApJS...45..635V}. \textit{Top:}~Gas temperature as function of height. \textit{Bottom:}~Logarithmic gas density as function of height. The vertical dashed line marks the height at which the optical depth $\tau_{500\,\mathrm{nm}}$ is unity, marking the bottom of the photosphere.} 
\label{fig:val}
\end{figure}
 
The VAL~C model (see Fig.~\ref{fig:val}) shows that the gas temperature $T$ decreases with height $h$ in the photosphere until it reaches a minimum and then increases again with height. 
\begin{enumerate} 
\item At what height $h$ do you find the temperature minimum and what value has the temperature there? 
\item At what height $h$ in the upper atmosphere does the temperature suddenly jump to temperatures $T > 10^4$\,K? 
\end{enumerate} 


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\subsubsection{Context data for the Sun.}
\instructions{Use the interactive helioviewer tool (either the web-based version at \url{https://helioviewer.org/} or as downloadable application at \url{https://www.jhelioviewer.org/}). The latter may have more functions. Provide context images for an observation that was carried out on January 10, 2022, at 08:57:42 UTC. The target is the trailing sunspot of an Active Region in the southern hemisphere with the (helioprojective) coordinates  $[x,y]=[+180",-480"]$. 
Generate figure files (e.g., via helioviewer's screenshot function) for the SDO/HMI Continuum, SDO/HMI Magnetogram, and SDO/AIA~171 and show them in Fig.~\ref{fig:helioviewer}. The shown field of view should include both magnetic polarities.}  

\begin{figure}[h!]
\begin{center}
\includegraphics[width=6cm]{example-image-a} % Replace file name - SDO/HMI continuum
\includegraphics[width=6cm]{example-image-b} % Replace file name - SDO/HMI magnetogram
\includegraphics[width=6cm]{example-image-c} % Replace file name - SDO/AIA 171 
\caption{ 
%Add a caption here describing the figure obtained with helioviewer as instructed above.
} 
\label{fig:helioviewer}
\end{center}
\end{figure}



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\subsubsection{\textbf{A first look at simulation data}}
\instructions{Load the files \texttt{simsts\_K8V/simsts\_K8V\_0G.h5} and \texttt{simsts\_K8V/simsts\_K8V\_0G\_continuumintensity.h5} and answer the  questions below.}
\begin{enumerate} 
\item What is the total extent of the computational domain in all three dimensions in units of km? 
\item What is the average gas temperature and density at the lower boundary of the model? 
\item What is the average absolute velocity amplitude ($<\,|\vec{v}|\,>_{x,y,z}$) in the model? 
\item What is the ratio of the horizontally averaged continuum intensity at $\lambda = 4.0\,\mu$m  with respect to $\lambda = 500$\,nm ($\frac{<I\,(\lambda = 4.0\,\mu\mathrm{m})>_{x,y}}{<I\,(\lambda = 500\,\mathrm{nm})>_{x,y}}$)? 
\end{enumerate} 

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\subsubsection{\textbf{A first look at observational data}}
\instructions{Load the file {\texttt{obssun\_sst3/obssun\_sst3.h5}}, which contains the observation of a sunspot in the H$\alpha$ line ($\lambda_0 =  656.28$\,nm), and answer the questions below.}

\begin{enumerate} 
\item Look at the first time step at a wavelength of 656.15\,nm. What is the horizontally averaged intensity value for that time step at that wavelength? 
\item Now look at the intensity as function of time for the pixel with the coordinates $[x,y]=[2.204'', -3.480'']$ at the central wavelength $\lambda_0$ for the observed spectral line. What is the minimum value in this time series and at what time is that value reached? 
\item Average the images for the continuum (shortest wavelength in this data set) over time and measure the extent of the sunspot umbra in arcseconds. You can measure along the $x$ and $y$ axes or, preferably, along the minor and major axis of an ellipse fitted to the umbra. 
\item What is the measured extent in units of kilometres? 
\item Look at all images for the shortest contained wavelength ($\lambda_\mathrm{min}$) and calculate a histogram for these intensity values ($I_{\lambda_\mathrm{min}}\,(x,y,t)$). Describe in a few words the distribution that you see (e.g., has a Gaussian form, several peaks, maxima etc.). Explain why the histogram looks like that by comparing it to what you would expect when looking at these images directly. 
\end{enumerate} 


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%\section{Planning your research project} 
%\subsection{Scientific question} 
%\instructions{Start with 1-3 sentences describing the context/background for your research project, motivating your 
%your tentative scientific question that you want to address in your project assignment. Continue then to explicitly state that question in 1-2 sentences. }
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%\paragraph{\textbf{Context/background.}}  % Write 1-2 sentences.  
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%\paragraph{\textbf{Scientific question.}} % Write 1-3 sentences. The more concise, the better. 
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%\subsection{Tentative work plan} 
%\instructions{Outline your tentative approach to address the chosen scientific question in bullet points. What do you plan to do first? What next? And so on. Try to briefly describe the result that you expect/hope that task will produce or the reason why you want to try it. Examples for tasks:\\ 
%$\blacksquare$~Calculate histograms of the intensity map at $\lambda = xxx$\,nm in data set obs....  for different parts of ...\\
%$\blacksquare$~Measure the size of granules in data set XX. Expected result: Obtain granule sizes.  
%}
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%\begin{itemize} 
%\item ... --- Expected result: 
%\item ... --- Expected result:  
%\item ... --- Expected result: 
%\end{itemize} 
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%\subsection{Initial reading list} 
%\instructions{For each listed paper, explain in 1-3 sentence(s) why you chose that paper. Why do you think it might be relevant for your (tentative) science case?}
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%\begin{itemize} 
%\item \citet{} --- Reason(s) for choosing this paper: 
%\item \citet{} --- Reason(s) for choosing this paper:  
%\item \citet{} --- Reason(s) for choosing this paper: 
%\end{itemize} 


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