Substorm strength overrides all other metrics. When a substorm is in its expansion phase all of these values are irrelevant to that substorm. 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. 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 'percentage' figure indicates how negative the Bz was, the ideal is 100% negative. The table shows an analysis of the interplanetary magnetic field in the 30 minute window that is currently arriving at Earth, together with We use it to predict activity 1 to 3 hours from now. IMF tells us about the future, not the present. The trick is to look every night at the optimum times given on this app and you will get lucky. There is no way to predict noctilucent clouds. They are clearly visible by eye, even in towns They are much rarer than auroras, typically seen fewer than 15 nights per year. You have the highest chance of seeing them are shown. NLCs are only visible when the sun is in a narrow range of angles below the horizon that are dependent on your latitude. The 'Max Heights' are the maximum angles above the horizon that Noctilucent Clouds and Cirrus can be lit directly by sunlight. The sun's elevation is its angle above (or below, if -ve) the horizon. The centre of the twilight arc is at the sun's azimuth. My twilight-arc tracker is constantly monitoring the position of the sun at your location and calculating the position and height of the Noctilucent clouds are lit by sunlight in an area of the night sky called the Twilight Arc. If you are concerned about disclosing your whereabouts, you can drive a few miles away, allow the app to read your position and You can switch off your GPS to conserve battery life. It will continue to use the last position it was given. You can enable location, allow the app to read it and thenĭisable it again. The app does NOT need your location to be switched on permanently. It only reads your position once each time you start the app running, when you report a 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

To determining how far away from the aurora you are and, therefore, the probability of it being visible for you. Location is essential to calculating when it is dark enough to catch auroras where you are located.

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