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This page describes the steps necessary to create and edit your own article.  This information is generally valid for creating any kind of article on this wiki but may be particularly useful to new Nugget authors.
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== Solar Hard X-ray Albedo ==
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== Creating an Article ==
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In the early days (1972) of solar hard X-ray flare observations,
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All pages on this wiki are articles including the RHESSI science nuggets. In order to create a new article a title must first be chosen. The title of an article cannot be changed so choose your article title carefully!  It is possible to move the content from one article to another with a different title but this is not a recommended practice. There are two main ways to create an article.
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<a href="http://adsabs.harvard.edu/abs/1972ApJ...171..377T">Fred
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Tomblin</a> published theoretical arguments
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that the hard X-ray spectrum of solar flares in the 5-40 keV
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range must have an albedo component  due to Compton back-scattering
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in the photosphere of those primary bremsstrahlung
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photons that are emitted downward. In a more complete
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analysis,  <a href="http://adsabs.harvard.edu/abs/1978ApJ...219..705B">
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Taeil Bai & Reuven Ramaty</a>
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showed that this albedo component would be polarized and
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its size must depend on the height of the primary source.
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<p>
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The "reflected" photons form what is called an albedo patch.
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For sufficiently high primary source altitudes, the albedo would
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be much larger in extent than the primary source, with a size
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scale that increases with source height. (See Fig. 1 below.)
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Furthermore, the albedo source would be displaced toward
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disk center by a distance h sin &theta;,
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where &theta; is the heliocentric angle.
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<p>
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*Simply search for the title of the article you wish to create using the search bar on the left. The wiki should confirm that no other articles have this title by not finding it and will give a choice to create this article. Click the link (at "you searched for") and your new article will open in edit mode.
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== Why albedo has not been imaged before ==
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A significant fraction (possibly as high as 40%) of the X-ray flux from solar flares
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comes from X-rays
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that propagate back to the solar surface from coronal sources and "reflect" off
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the photosphere. This component of flares is called the <i>albedo</i>, and it is remarkably
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difficult to observe because it is very diffuse with an intensity that is one or two
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orders of magnitude smaller than the primary flare sources themselves.
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Its importance for flare physics is that it both distorts the spectral interpretation of X-ray
 +
emission and offers a potentially powerful diagnostic of electrons accelerated in
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solar flares. Our study uses the unique capabilities of the Ramaty High Energy
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Spectroscopic Imager (RHESSI) to isolate this albedo component, determine its
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properties such as size, shape and centroid location as a function of energy.  
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We have focused on single-component flares in the 12-30 keV range that appear a
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within 45&deg; of disk center. Using standard techniques, we have obtained the X-ray
 +
visibilities
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(<a href="http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/RHESSI_Visibilities">RHESSI Nugget # 39</a>) of a number of such flares and applied Forward-Fitting methods
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to determine the parameters of the primary component (position, flux, and size) and
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the albedo-related parameters (primary source height and albedo flux).
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*Articles are organized through categories.  An article is added to a category by adding meta-data into the article text.  The next method for creating an article is to navigate to the category page and use the Form to create a new article in that category.  The RHESSI Science Nugget category page can be found [[:Category:Nugget|here]].  The category meta-data will then automatically be included in the article text.
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<p>
== Writing your article ==
== Writing your article ==

Revision as of 22:05, 12 January 2010

Contents

Solar Hard X-ray Albedo

In the early days (1972) of solar hard X-ray flare observations, <a href="http://adsabs.harvard.edu/abs/1972ApJ...171..377T">Fred Tomblin</a> published theoretical arguments that the hard X-ray spectrum of solar flares in the 5-40 keV range must have an albedo component due to Compton back-scattering in the photosphere of those primary bremsstrahlung photons that are emitted downward. In a more complete analysis, <a href="http://adsabs.harvard.edu/abs/1978ApJ...219..705B"> Taeil Bai & Reuven Ramaty</a> showed that this albedo component would be polarized and its size must depend on the height of the primary source.

The "reflected" photons form what is called an albedo patch. For sufficiently high primary source altitudes, the albedo would be much larger in extent than the primary source, with a size scale that increases with source height. (See Fig. 1 below.) Furthermore, the albedo source would be displaced toward disk center by a distance h sin θ, where θ is the heliocentric angle. <p>

Why albedo has not been imaged before

A significant fraction (possibly as high as 40%) of the X-ray flux from solar flares comes from X-rays that propagate back to the solar surface from coronal sources and "reflect" off the photosphere. This component of flares is called the albedo, and it is remarkably difficult to observe because it is very diffuse with an intensity that is one or two orders of magnitude smaller than the primary flare sources themselves. Its importance for flare physics is that it both distorts the spectral interpretation of X-ray emission and offers a potentially powerful diagnostic of electrons accelerated in solar flares. Our study uses the unique capabilities of the Ramaty High Energy Spectroscopic Imager (RHESSI) to isolate this albedo component, determine its properties such as size, shape and centroid location as a function of energy. We have focused on single-component flares in the 12-30 keV range that appear a within 45° of disk center. Using standard techniques, we have obtained the X-ray visibilities (<a href="http://sprg.ssl.berkeley.edu/~tohban/wiki/index.php/RHESSI_Visibilities">RHESSI Nugget # 39</a>) of a number of such flares and applied Forward-Fitting methods to determine the parameters of the primary component (position, flux, and size) and the albedo-related parameters (primary source height and albedo flux).

<p>

Writing your article

Writing a wiki article is very straightforward. Every article has an "edit" tab above it. Clicking that will open in the article in an editable window. Many formatting shortcuts can be found above the editing window. Since each article on this wiki can be edited, it is easy to learn by example. For more basic help with editing read the following article.

Adding Figures

In order to add a figure it is first necessary to upload the image to the wiki. This can be done by using the link on the left titled "Upload File". Please use a descriptive name for the file and add a description of its contents. Once uploaded the file can be added to articles using the following command

[[Image:POF.jpg|200px|thumb|right|'''Figure 1''': This is the figure caption.]]

whose results can be seen to the right. Most of these parameters should be self explanatory. The "thumb" parameters tells the wiki that this is a figure and therefore displays the figure caption. The float parameters (in this case set to "right") tells the wiki where to float the image. Possibilities include "left", "center", or "right".

Figure 1: This is the figure caption. Note that the figure has properlyy appeared on the right, but that you can't really control how the text will wrap around it - that depends on the browser.

If you'd like to experiment with more advanced methods read this article on Wikipedia's website.

Style and content

We try to write the Nuggets so that a technically literate reader won't be baffled. That means that the text should appear in plain English, and that jargon is a no-no. Many scientists don't realize they are writing gibberish so please be careful about this. On the plus side, you can freely use cgs units if you wish. Also please be aware that many of the audience are not native English speakers, so phrases like "X must have been a gutsy operator to have diagonalized those macrospicules" would not do so well. Writing as though for a newspaper, rather than as for a boring archival journal, would be best - there is no need really to have complete literature

citation, since those really knowledgeable about the field will certainly know where to go (ADS).

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