Glendale App - Aurora Alerts UK

Glendale App

WARNING : You have prevented the app from using your location, so all times and forecasts will be inaccurate. You will be unable to report sightings and may be seeing a version of the app for the wrong country.

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A status report will normally be posted by 7pm each evening, with further updates as things develop.

Last night:

Live Reports

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What's On Your Camera Now?

Register to activate the full features of the app. Pro bono. No SPAM. No advertisements. No mailshots. No cost.

Glendale App is the world's only accurate aurora alerting and forecasting app.

You are seeing only sample data at the moment. You need to register to see real-time updates.

Who's Shouted Tonight?

Noctilucent Clouds

Sun Position
Max Height

Noctilucent Clouds

Noctilucent clouds are lit by sunlight in an area of the night sky called the Twilight Arc.

My twilight-arc tracker is constantly monitoring the position of the sun at your location and calculating the position and height of the twilight arc.

The centre of the twilight arc is at the sun's azimuth. The sun's elevation is its angle above (or below, if -ve) the horizon.

The 'Max Heights' are the maximum angles above the horizon that Noctilucent Clouds and Cirrus can be lit directly by sunlight.

NLCs are only visible when the sun is between 6° and 16° below the horizon and the times when you are best able to see them are shown.

They are much rarer than auroras, typically seen fewer than 15 nights per year. They are clearly visible by eye, even in towns and cities. There is no way to predict them, you just have to look at the optimum time and hope.



Substorm Tracker

The headline figure (with 'nT' beside it) is the substorm strength. It equates to the strength of the aurora in the sky right now. It is the single most important number on the app and overrides all others. This is the number you need to follow closely. You want it negative. The more negative it is, the stronger the aurora is at that minute. Falling is good, rising is bad. It tracks the strength of the actual aurora in the sky in real-time.

When it says 'growth', the substorm is charging up like a battery. When it says 'expansion' that energy is being released as aurora. When it says 'recovery', the aurora will slowly begin to fade.

The trendline shows the changes in strength over the last hour. The line dropping sharply downwards is good. Rising is bad. The green shaded area indicates the ambient level.

I am indebted to the kindness and generosity of the Tromsø Geophysical Observatory, Swedish Institute of Space Physics and the US Geological Survey for letting me access their live data feeds. I am also indebted to I.R. Mann, D.K. Milling and the rest of the CARISMA team for use of data from the Canadian magnetometer array. CARISMA is operated by the University of Alberta, funded by the Canadian Space Agency.

IMF (at Earth)



The table shows an analysis of the interplanetary magnetic field in the 30 minute window that is currently arriving at Earth, together with the 30 minute windows either side of it. The 'percentage' figure indicates how negative the Bz was, the ideal is 100% negative.

If the 'now' and 'next' rows are both lit up, the substorm will continue if one is active or will start in about an hour if one isn't active.

If the 'next' row is not lit up, the activity will start to wane if a substorm is active but there can be an extra burst of activity, so wait an hour.

"Turns bad" is "good" because it triggers expansion in an active substorm. It is "bad" for future substorms.

When a substorm is in its expansion phase all of these values are irrelevant to that substorm. Substorm strength overrides all other metrics.

The trendline shows the Bz and Bt that is arriving at Earth now and as far into the future as it is possible to see. You want the bottom line to be below the green shaded (ambient) area.

Solar Wind (at Earth)


Solar Wind Analysis

How do I use the Wind Analysis?

Solar Wind

This the the mean velocity, density, pressure and power of the solar wind that is currently arriving at the Earth. The higher the pressure (density & speed) of the solar wind the better.

The trendline shows the changes in the solar wind speed over the last 24 hours, with the density shown behind. When both of these are rising it normally indicates arrival of a co-rotating interaction region. When speed rises and density falls this indicates a coronal hole stream. The green shaded area indicates the ambient level.

When a substorm is active, all of these values are irrelevant. Substorm strength overrides all other metrics.

Coronal Holes


Coronal Holes

Coronal holes cause most of our auroras and they are regular, repeating on a 27 day cycle. Plasma from an Earth-facing coronal hole typically takes 3 to 4 days to reach us and spark auroras.

Flipping between the 'now' and '-27 days' tabs allows you to see how coronal holes have changed since their last rotation 27 days ago.

The '-4 days' tab allows you to see how the coronal hole looked when it was in the earth-facing position 4 days ago.

Solar imagery courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.

Coronal Mass Ejections

Recent CMEs


Coronal Mass Ejections

How do I use CMEs?


Coronal Mass Ejections are bursts of plasma that sometimes erupt from sunspots during a solar flare. They can trigger the strongest auroras if they hit Earth.

You are looking for plasma surrounding more than 50% of the solar disk in this graphic (a partial halo). The ideal is a 'full halo', where plasma appears to surround the entire solar disk. It then takes 2 to 3 days for the CME to reach Earth.

CME data derived by Glendale App from solar imagery kindly provided by SOHO.

Solar Flares

5-Day Maxima


Last 3 Flares



Solar flares from sunspots sometimes produce a CME which, if directed earthward, can cause strong substorms between two and four days after the eruption.

Flares are classed A, B, C, M or X with A being weakest and X being strongest. The number indicates how strong the flare was within its class.

After a flare, it can take several hours before imagery becomes available that enables us to determine whether there was a CME and whether that CME was Earth-directed. After a flare, keep checking the Coronal Mass Ejections panel for the latest updates as imagery arrives.

Twilight & Moon Times


Cloud Coverage (Infrared)

Satellite Image of Europe & Iceland

How do I use cloud data?

Cloud Coverage

The infrared satellite imagery shows you where the weather fronts are moving. This will indicate whether you have a chance of getting clear sky.

Satellite imagery very kindly provided by

Long-Range Forecast


Long-Range Forecast

How do I use long-range data?

Long-Range Forecast

These are the dates when solar wind streams that gave us good auroras will rotate around again. There is no guarantee that the coronal holes that caused the substorms on the previous rotation won't have closed but they also may have got larger. You can only use these as a guide but this is the most accurate long-range forecast for the UK, Ireland, Iceland, Scandinavia, North America and Australasia that you will find anywhere in the world.

Check the coronal holes panel, as we get closer to the dates that interest you, to confirm the current status of the hole that caused the activity.

This forecast is based on my own data collected in the UK and is valid worldwide. The more negative the figure, the stronger the aurora could be.

Dates that are coloured black are uncertain. Dates shown in colour are more likely.

* You need to register to view the full 28-day forecast.

Manage Settings & Alerts

Your Details

Registered User Details
Optional Password Protect

Your Details

Entering your details here will allow you to make instant, live, aurora reports to let others know what the current situation is where you are. You will also be able to see reports from other users, access all features of the app and see the live data in real-time.

Enter the exact same details on all devices where you use the app to synchronise your history and reports across them all.

If you work as an aurora tour guide, researcher, scientist or are an admin on an aurora facebook site you can enter those details and they may be shown to other users.

Privacy Policy

This app collects sighting reports you make for purposes of scientific research, to improve the accuracy of aurora forecasting and for alerting users when the aurora is active.

Your personal data is not shared with any other organisations or third parties.

You will not be spammed. You may be contacted about interesting reports you have made, problems you are having with the app or security/authentication issues.

This app only uses essential cookies.

Your History

Your Annual Totals

Your Reported Dates

Add Late Reports



Your phone is android and is capable of receiving alerts but you need to install the Chrome app and make it your default web browser.

Install the App

To install this web app on your device:

  1. Open Safari.

  2. Go to

  3. Press SHARE button in Safari (NOT 'share' in the app).

  4. Scroll right.

  5. Add to Home Screen.

  6. Add (top right).

  7. Open Chrome or Firefox.

  8. Go to

  9. Click the red 'install the app' button.

  10. Open the Chrome App.

  11. Go to

  12. Click three vertical dots icon (top right).

  13. Add To Home Screen.

  14. Click 'Enable Alerts'.

  15. App installed and tile added.


How do I use alerts?


The basic alerts are push notifications that the app sends automatically when it detects that an aurora is developing. An 'onset' alert is sent first as a warning that an aurora is starting, followed by yellow, amber, red, major, severe and extreme alerts as activity develops. Your device will receive these even when the app is not running.

The 'Expansion Alarm' is designed for desktop users. If you leave the app running permanently on your PC, the app will start bleeping as soon as it detects a substorm heading into expansion phase to give you time to head out and catch it at its peak.

'Activity Alerts' are notifications that can be set to 'ping' your device only when the app is running. These occur much more frequently than the basic alerts. They alert you to all thresholds being crossed, auroras being reported by users and photos being uploaded. These are great for users of desktop PCs who want to keep constantly updated on the current aurora situation.

Graphs (At Earth in UTC Time)

Substorm Strength (24 hour)

Substorm Strength

How do I use the 24 hour graph?

Substorm Strength (24-Hour)

The plot shows the substorm strength over the last 24 hours, which allows you to see the periods when the aurora was at its best.

The more negative the figure, the stronger the aurora was.

These graphs are deliberately produced 5+ minutes behind real-time. Use the Substorm Panel above for aurora-hunting.

These graphs allow you to verify the accuracy of this app by comparing the times of your best photos against the substorm strength the following day. You will see that your best photos were taken precisely on the best drops. Remember that the graphs are in UTC time, not your local time.

IMF Clock / Theta (24 hour)

Clock / Theta

How do I use the 24 hour theta?

The plot shows the clock angle (θ) over the last 24 hours, which allows you to see the periods when the IMF was best aligned.

IMF Bt / Bz (24 hour)

IMF Bt / Bz

How do I use the 24 hour Bt & Bz?

The plot shows the IMF Bt & Bz over the last 24 hours, which allows you to see the periods when the IMF was strongest.

Speed & Density (24 hour)

Speed & Density

How do I use the 24 hour speed & density?

The plot shows the solar wind speed & density over the last 24 hours.

TGO Stackplot (24 hour)

Norwegian-Line Magnetometers

How do I use the stackplot?

Ideally what you are looking for on the stackplot are dips of >200nT on the right-hand side of the line labelled 'and' or any of the lines below it.

Stackplot courtesy of the Tromsø Geophysical Observatory.

Graphs (At Satellite in UTC Time)

Solar Wind (2 hour)

Solar Wind at ACE

How do I use the solar wind?

Ideally what we want is either a negative Bz, or a very wide separation between the Bz and Bt lines, over the course of the last hour.

A strong solar wind speed over 500 km/s over the last hour is also good.

Solar wind graphs courtesy of the NOAA SWPC.

Solar Wind (6 hour)

Solar Wind at ACE

How do I use the solar wind?



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Glendale App was created by Andy Stables of the Glendale Skye Auroras Facebook Page to make it easy for people to photograph the Aurora Borealis. It is the result of research carried out on a daily basis since September 2012 in the Isle of Skye.

The total accuracy of the app is only possible due to the generosity of the Tromsø Geophysical Observatory, the Swedish Institude of Space Physics, the US Geological Survey and the CARISMA team in allowing me to access the live data feeds from their entire magnetometer array in Norway.

The wonderful icons for the tiles, badges and logo were the work of Andrew Liley from Portree.

The Iceland Version of the App was only made possible thanks to many hours of detailed observation and recording by Caroline Weir from Reykjavik, who runs the Aurora Iceland Facebook Group.

Read the full behind-the-scenes story of Glendale App here.

Europe, Canada & Oceania Maps by

©Andy Stables