Planetary Clarity’s guide to SDO for beginners

Solar Dynamics Observatory has the best and most important website for anyone who wants to see solar flares. This is a brief tutorial of some basic features that can help get you started using the SDO website. – The Main Page

At the top of the main page you can scroll through the latest images from all AIA/HMI channels and composites. Below, you will see a button that says “More Images” this will take you to the url

The “More Images” button brings you to this site which is labeled by a tab that says “The Sun Now.” Any time you see this menu, clicking on “The Sun Now” will bring you back to this data page.

Here you can scroll down to see thumbnails of all AIA channels, the HMI magnetograms, intensitygrams, & dopplergram, and the solar projection maps.

On the right it says “Browse Daily Images” there is a bar with a pop up calendar where you can choose any date and it will show you a thumbnail of every channel’s image from around midnight UTC on that date.

Below each thumbnail is a button that says “Data Links” this gives you a menu with the option to see the image in four different sizes, followed by the same four sizes with the acronym PFSS. What does PFSS stand for? I forgot, but it’s the same images with spaghetti lines added on top showing the direction of the Sun’s coronal magnetic field. At the bottom of this menu is the option to view a video showing the previous 48 hours of solar images sped up to less than 30 seconds. These videos are a great way to get acquainted with the Sun’s behavior.

On the menu below where it says “The Sun Now” the next tab says “AIA/HMI Browse Data” this takes you to the url This is where you can control your search for all SDO images.
It is very straightforward where you choose your start and end dates, and pick a channel. “Browser Display” shows you a movie. The browser display always resets itself to 1024 pixel resolution, but it gives you the option to set it to 512 pixels for faster image loading. I will show you how to get any high resolution single image from the 512 pixel movie browser display.

In the browser display, you can pause on the image you want, right click and open in new tab. Simply find where it says 512 in the url and replace it with any of the higher resolution sizes, hit enter and the image you want will appear.

The AIA views the Sun in several different wavelengths measured in Angstroms- each of these channels are rendered with an arbitrary color.

Read the wikipedia to learn more about the AIA/HMI instruments and the history of SDO.

94 Green
The highest vibrational channels are the best for viewing solar flares. On the green 94 angstrom channel, areas emitting X-rays above the C-class threshold appear white- this can be white flashes during low level C-flares, and/or steady white areas from active regions emitting baseline xrays near or above the C-class threshold. Large M-flares and X-flares usually appear as large white areas, very little detail can be seen of the actual flare.

131 Teal
The teal channel is best for viewing large M-flares and X-flares, which appear as white flashes relative in size to the strength of the flare. C-flares usually do not make a significant appearance on the 131 angstrom channel, it is best for seeing details of the larger flares.

171 Gold
On the gold channel, the features that stand out most prominently appear as magnetic arches or loops, connecting areas of opposing polarity within sunspots and also across vast regions of the Sun. Gold rings can often be seen protruding from the Sun’s edge when a strong magnetic region is rotating towards or away from Earth. The strongest magnetic and xray emitting points appear white at baseline- solar flare flashes often do not appear at all on the 171 angstrom channel.

193 Bronze
The 193 angstrom channel is the best over all view of everyday solar features- the latest bronze image is the first thing you see on SDO’s main page- sunspots and magnetic features appear generally white, not in the sharpest detail, but enough to be obvious. This channel also provides excellent contrast to gaps in the corona (coronal holes), which appear black. Only the strongest solar flares appear as a flash of white on the bronze channel.

211 Purple
The purple channel is similar to bronze- vague white sunspots and magnetic features, only the strongest flares make a white flash, this channel’s claim to fame is the deepest and sharpest contrast to black gaps in the corona. Plasma/CME material also appears on the 211 angstrom channel, very obviously but not in the sharpest detail.

304 Red
The 304 angstrom channel shows a highly focused view of the solar surface that lets us see “the bottom of” a solar flare. Any area of the Sun with magnetism strong enough to vary from the background will appear orange compared rest of the solar surface dappled in dark red. Small solar flares are usually unnoticeable, but the unique amount of white detail seen on the largest solar flares is always incredible. The red channel is also the best for viewing the solar material of plasma that forms surface features such as filaments/filament eruptions & CME’s.

335 Blue
The blue channel feels like the most “out of focus” channel in terms of detail, showing cloudy white wisps and smudgy dots against a dark blue background to highlight all variations in solar surface features. C-flares typically do not appear, M-flares and X-flares appear as white flash. The 335 angstrom channel is the next best channel for viewing solar flares after the 94 Green and 131 Teal.

1600 yellow/green & 1700 pink
These “lower vibrational” channels show the most stripped down possible view of the solar surface. Any area that differs from the background in any way will appear as a lighter variation on a uniform background. Sunspots appear as prominent dark spots, incredibly precise details of white appear during large solar flares. On the 1600 you can see the best detail of light. On the 1700 you can see the best detail of the sunspots. (This image shows simultaneous views of an M1.1 solar flare from sunspot 2993 on April 18th)
HMI Magnetograms

The magnetogram channels are available in black/white and colorized to show areas of positive and negative polarity. White and blue/green shows positive magnetism, black and red/yellow shows negative. (This image shows simultaneous views of sunspots 2993 and 2994 on April 19th)

SDO offers three standard AIA composites, each made by stacking images from three of the previously listed channels. There’s also a fourth standard composite made from stacking the gold channel with an HMI channel- They are all really cool to look at but don’t offer much more insights than you can get by studying the individual channels. If you want to make composites of SDO AIA/HMI channels, go to a website called Helioviewer.


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