The Aurora Page
Aurora (or the Northern Lights) are a common sight in the polar regions and are regularly seen from scotland. but down here in the south of England, they are much rarer; but that does not mean that they never occur at all.
The magnetic fields sometimes can get unstable around sunspots and these areas can throw off huge clouds of plasma called Coronal Mass Ejections. Occasionally, this plasma heads directly for the Earth and is the trigger for the aurora. The bigger the CME, the further south the aurora can be seen. For a more detailed explanation of how the process works, please click here.
At the Newbury AS, we try to monitor solar activity and if an alert for the aurora is given, we will send a mail out to those people on the mailing list. Those people can also contact their friends to notify them, and so the process continues and as many people as possible can get to see the biggest light show in the world.
Of course, we sometimes give an alert, but the display does not occur. this does not necessarily mean it was in error. Aurorae are not predictable. Sometimes even the biggest explosions do not amount to anything, or the most visible parts of the display occur during the day and are invisible to us. Just try again next time. Even I have never seen an aurora and I am the one who sends out the mails!! But the system does work if you read Richard Fleet's tale below.
There are some links for other sites related to aurora at the bottom of this page.
Viewing the sun from Space.
A number of spacecraft are constantly monitoring the sun for signs of Coronal Mass Ejections (CMEs). The main one is the Solar and Heliospheric Observatory (SOHO) it has many cameras pointing at the Sun 24 hours a day, every day of the year.it monitors activity on the Sun at different wavelengths and keeps a constant watch for CMEs.
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| Latest image from SOHO's Lasco C3 camera |
This image is the one most used for monitoring CMEs. the central plate obsures the over-powering light from the Sun, so that the surrounding atmosphere can be seen. The white circle in the centre represents the size of the Sun itself.
SOHO also looks at the Sun in other wavelengths. Check the images below for a colourful look at our sun ans to see how diffwerent it can look in other wavelengths not normally visible to the naked eye.
All images are the latest available and automatically update if you refresh the page, providing a new image is available.
EIT images EIT (Extreme ultraviolet Imaging Telescope) images the solar atmosphere at several wavelengths, and therefore, shows solar material at different temperatures. In the images taken at 304 Angstroms the bright material is at 60,000 to 80,000 degrees Kelvin. In those taken at 171, at 1 million degrees. 195 Angstrom images correspond to about 1.5 million Kelvin. 284 Angstrom, to 2 million degrees. The hotter the temperature, the higher you look in the solar atmosphere. |
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| EIT171 | EIT 195 | EIT 284 | EIT 304 | |||
| More EIT 171 images | More EIT 195 images | More EIT 284 images | More EIT 304 images | |||
| MDI IMAGES The MDI (Michelson Doppler Imager) images shown here are taken in the continuum near the NiI 6768 Angstroms line. The most prominent features are the sunspots. This is very much how the Sun looks like in the visible range of the spectrum (for example, looking at it using special 'eclipse' glasses: Remember, do not ever look directly at the Sun! ). The magnetogram image shows the magnetic field in the solar photosphere, with black and white indicating opposite polarities. |
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| MDI Continuum | MDI Magnetogram | |||||
| More MDI Continuum images | More MDI Magnetogram images | |||||
LASCO images C2 images show the inner solar corona up to 8.4 million kilometers (5.25 million miles) away from the Sun. C3 images have a larger field of view: They encompass 32 diameters of the Sun. To put this in perspective, the diameter of the images is 45 million kilometers (about 30 million miles) at the distance of the Sun, or half of the diameter of the orbit of Mercury. Many bright stars can be seen behind the Sun. |
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| LASCO C2 image | LASCO C3 image | |||||
| more LASCO C2 images | More LASCO C3 images | |||||
VIsit the "SOHO Explore" site to learn more about the Sun.
The Aurora from Space
There are also several satellites in orbit around the earth that study the aurora. Pictures from these satellites can also be used to predict aurora and how active it is.
The image below comes from NOAA (National Oceanic and Atmospheric Administration) A US goverment group of satellites that monitor the earth's enviroment.
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| The polar view of the northern hemisphere showing the aurora band. |
Note: ignore the pale blue section in the image as this only marks the extent of the scan, not the extent of the aurora.
This plot shows the current extent and position of the auroral oval in the northern hemisphere, extrapolated from measurements taken during the most recent polar pass of the NOAA POES satellite.
The red arrow in the plot, that looks like a clock hand, points toward the noon meridian.
The statistical pattern depicting the auroral oval is appropriate to the auroral activity level determined from the power flux observed during the most recent polar satellite pass. The power fluxes in the statistical pattern are color coded on a scale from 0 to 10 ergs . cm -2 . sec -1 according to the color bar on the right. The pattern has been oriented with respect to the underlying geographic map using the current universal time, updated every ten minutes.
This presentation provides an estimate of the location, extent, and intensity of aurora on a global basis. For example, the presentation gives a guide to the possibility that the aurora is located near a given location in the northern hemisphere under the conditions that existed at the time of the most recent polar satellite pass.
Normalization factor (n)
A normalization factor of less than 2.0 indicates a reasonable level of confidence in the estimate of power. The more the value of n exceeds 2.0, the less confidence should be placed in the estimate of hemispheric power and the activity level.
The process to estimate the hemispheric power, and the level of auroral activity, involves using this normalization factor which takes into account how effective the satellite was in sampling the aurora during its transit over the polar region. A large (> 2.0) normalization factor indicates that the transit through the aurora was not very effective and the resulting estimate of auroral activity has a lower confidence. In order for users to assess the confidence in a given estimate of auroral power, we now report the numerical value of the normalization factor in our web pages.
Aurora from the Pewsey Vale
(October 2003)
By Richard Fleet
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| The CME that caused this aurora |
Thanks to Paul's e-mail alerts I kept an eye out but it was cloudy, or light rain, for most of the evening. The cloud only started to break after 10 PM, though it was obvious through the gaps that an aurora was in progress.
For a time it seemed like midsummer twilight across the entire northern horizon shining through the clouds. At one point it clouded over completely and that looked like it might be the end of the show. However around midnight most of the cloud dissipated and it stayed clear for the rest of the night. The sky was then fairly transparent with a limiting mag of 5 to 6.
Most of the time the aurora was just a quiet, slightly greenish, glow with occasional rays and red patches forming. The most active periods didn't last more than about 10 minutes or so, some of the rays came and went within a minute or two.
The display was completely over by 2am and no further activity was seen before dawn. There was a good hard frost on the car in the morning !
I didn't record the times but most of these shots were taken between midnight and 1 AM on 30th October 2003. Mostly 20-30 seconds at F3.5 on Kodak Ultra (ASA400) , which is simply what I happened to have spare at the time.
Unfortunately under these conditions film doesn't respond the same way the human eye does, so the colours were not as intense as some of the stronger images would suggest. Even so the colours were quite distinct to the naked eye, particularly the contrast between the red emission and skyglow from towns in the distance. The extent of the aurora and all the structures recorded on film were also easily visible.
Although this display wasn't as impressive as the one in April 2000 it was still well worth waiting up for.
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For more of Richard's great aurora pictures, visit the Glows, Bows & Haloes section of his own website
SOHO Explore
An educational site dedicated to the Sun and it weather and how it affects us.
SOHO main site
The main SOHO website.
NOAA (National Oceanic and Atmospheric Administration)
Providers of online data and images on solar conditions
Glows, Bows and haloes
Richard Fleet's site. Go to Glows for aurora pictures.