Substorm tracking relies on data collected at magnetic observatories. I thank the national institutes that support them and INTERMAGNET for promoting high standards of magnetic observatory practice (www.intermagnet.org).

The trendlines show the solar wind speed (V), density (N), temperature (T) and IMF strength (B) that is arriving at Earth now (left) and as far into the future as it is possible to see, at L1 satellites (right). The blue shaded area indicates the ambient level.

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.

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.

The plot shows the substorm latitude over the last 24 hours, which allows you to see the periods when the substorm expanded furthest towards the equator.

The commonest reason for your account being blocked is that you have a mistake in your email address. If the account activation email bounces your account will automatically be blocked. Check your email address very carefully. It may also be due to your name failing to meet the account rules.

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

This should not be used for real-time aurora-hunting. Use the substorm panel at the top of the app instead, as it reacts faster and translates all the squiggles into a single, easy-to-use number.

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.

We use solar wind data to look for space weather events that might bring us good IMF. Primarily we look for shocks, which are simultaneous large steps on the graphs.

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.

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.

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.

The 'at-Earth' graphs allow you to see when activity was happening over the last 24 hours. These should not be used for real-time aurora-hunting, as they are deliberately delayed. They are intended to be used to correlate the timestamps on your images taken last night against the data that was being shown on Glendale App at the time. This helps you to verify how accurate the app is at tracking the actual aurora that was happening in the sky. Times are in UTC, so you will need to consider your UTC offset.

The trendlines show the Bz and Bt that is arriving at Earth now (left) and as far into the future as it is possible to see, at L1 satellites (right). Bt is at the top, Bz in the middle and the optimum Bz at the bottom (black).

If you are constantly seeing the blue loading popup, it is because you are either refreshing the screen or repeatedly closing/re-opening the app. This puts unnecessary strain on the server which can cause it to overload at peak times.

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

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

Location is essential to calculating when it is dark enough to catch auroras where you are located. It is also vital to determining how far away from the aurora you are and, therefore, the probability of it being visible for you. It is also essential to identifying which country you are in.

Your actual name, your actual email address and the name of your nearest town/village are required to use this app. Only your first and last name are required. Abuses will result in the account being de-activated. This includes nick-names, truncation, obfuscation, business names, junk, burner emails, emails that bounce, etc.

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.

The app is NOT tracking your movements. It only reads your position once each time you start the app running, when you report a sighting and when you save your details.

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.

Mann, I. R., et al. (2008), The upgraded CARISMA magnetometer array in the THEMIS era, Space Sci. Rev., 141, 413�451, doi:10.1007/s11214-008-9457-6.

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.

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.

The 'Expansion Alarm' is designed for desktop users. If you leave the app running in 'alarm mode' 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.

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

If you have forgotten what your own name is, an email can be sent to your registered email address with a reminder. Click 'Send My Name' button and a reminder will be sent to you.

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 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.

It is essential to 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, as it might have closed.

The middle line is the important one. You want it to be below the blue shaded (ambient) area and as close to the black line as possible.

Your phone is android and capable of receiving alerts but they are blocked. To fix this follow the instructions on the Technical Support Page.

'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.

Learning how to avoid this will help you have a much better experience with your device and also help me to provide a service to more people at busy times.

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.

Unverified CMEs are those automatically detected by the app that haven't been manually reviewed yet to confirm that they are valid and Earth-sided.

The plot shows the rate of change of substorm strength over the last 24 hours, which allows you to see the periods when the aurora was most dynamic.

The app does NOT need your location to be switched on permanently. You can enable location, allow the app to read it and then disable it again. It will continue to use the last position it was given. You can switch off your GPS to conserve battery life.

These are an educational tool to help you understand how the aurora you captured last night corresponds to the relevant data.

Even when there appears to be an Earth-directed component or it looks like a direct hit, the CME can still miss completely or bounce off the Earth's magnetosphere. Don't get too excited until the app alerts that a shock has been detected!

Aurora is all about magnetic fields (IMF-driven). Speed and density do NOT affect physical characteristics of the aurora such as brightness, colour or viewing latitude. Nor do they have any affect on the substorm process itself.

Location is automatically blocked by default on Apple devices. You have to fix it yourself otherwise this app will not work properly.

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.

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

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.

There is no way to predict noctilucent clouds. The trick is to look every night at the optimum times given on this app and you will get lucky.

In most cases, this is because you have a three-button Android device and are using the 'back' button instead of the 'home' (middle) button. Try using the middle button on your phone instead of 'back' and everything will work much more efficiently.

The other graphs are all adjusted to the Earth-time frame of reference and aligned vertically so that you can easily see how the other parameters influence the substorms.

Your device will ask for permission to use your location and you must select 'allow always' when asked. If you are on a phone or tablet make sure your GPS/location is enabled before proceeding.

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

WARNING : You have prevented the app from using your location, so all local 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.

The chart shows magnetometer deflections at every station on the entire Norwegian array from north to south, in descending order of latitude, plotted over the last 24 hours.

This allows you to verify that you have enabled location services correctly in your device and confirm what lat/long your device is giving to the app. If these are wrong then all forecasts and times given on the app will be incorrect. It is vital that you resolve any issues.

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.

The 'substorm strength' graph is the main graph for retrospective use. It shows you when all of the substorm activity was happening. You will see that the times of peak activity on your images correspond to the peak drops on the graph.

The image shows the active region that was the source of the most recent solar flare, highlighted with a yellow circle. When there have been no recent flares it shows the latest image of the solar disk.

Glendale app is the world's most accurate aurora app. It needs to use your location to determine which country & timezone you are in, to provide accurate local times and aurora forecasts.

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

'Back' closes apps, instead of minimising them. This means that when you come back to the app a few minutes later it has to fully reload itself. Use the middle button and all apps will load instantly.

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

Wait patiently or come back later. Never refresh your screen. The app will automatically refresh as fast as it is able. Help

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.

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.

If you don't allow access to your location, the forecasts will be wrong, the nowcasts will be wrong and all of the displayed times will be wrong. You won't be able to report sightings.

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.

This is the mean velocity, density and pressure of the solar wind that is currently arriving at the Earth. They don't directly matter for aurora. IMF is what matters. A good IMF will lead to aurora even when speed and density are at ambient levels.

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.

I am indebted to the kindness and generosity of the Tromsø Geophysical Observatory, Swedish Institute of Space Physics, the US Geological Survey and the Finnish Meteorological Institute for letting me access their live data feeds.

The EPAM chart shows low-energy particles arriving at Earth. The protons are the thick line and electrons the thin line. The lines climbing sharply indicates that a space weather event is approaching. Proton values rise sharply in the hours before an interplanetary shock.

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

Dates that are coloured black are uncertain. Dates shown in colour are more likely. Dates that are missing have no predicted activity.

The commonest reason that you haven't received an activation code is that you have a mistake in your email address. Check your email address very carefully. If you are certain the email is correct then it is most likely your spam filter, to unblock this email me from the email account you are registering with and request a code.

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.

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. You are currently using the Samsung web browser.

If you have forgotten your password, an email will be sent to your registered email address with a link to reset it. Click 'Reset Password' button and follow the instructions in the email to log back in.

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.

Location is automatically blocked by default on Apple devices. You have to fix it yourself otherwise this app will not work properly.

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.

NLCs are only visible when the sun is in a narrow range of angles below the horizon that are dependent on your latitude. The optimum times, when you have the highest chance of seeing them are shown.

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

The world-leading 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, the Finnish Meteorological Institute and the CARISMA team in allowing me to access the live data feeds from their entire magnetometer arrays around the northern hemisphere.

The sun spins on its axis effectively every 27 days, which means that coronal holes and active regions giving us auroras today can rotate back around again in 27 days time, giving another show.

Global, real-time tracking of auroral substorms is only possible due to some incredible organisations allowing me to access the live data from their magnetometer arrays.

If you are concerned about disclosing your whereabouts, you can drive a few miles away, allow the app to read your position and then disable it again.

Your location (GPS) is turned off or blocked. If your location is on and you still see this message click 'fix it' for help.

Watch this number! 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. It is the single most important number on the app and overrides all others.

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

Only your most recent upload will be shown but you can upload as often as you like. If you abuse the system you will be blocked from uploading.

Your location in geomagnetic co-ordinates is also given, which allows you to see how much closer your effective latitude for auroras is to your true latitude.

Sharp drops correspond to substorms in their expansion phase. Ideally what you are looking for on the stackplot are drops of >200nT on the right-hand side of the graph. The scale is shown top-right.