AuroraTonight

Besides a high probability local forecast, you need *dark* and *clear* sky! The forecast page shows the hours of darkness based on nautical twighlight (when the sun is 6 degrees below the horizon) and indicates cloud cover. Click on the "weather" box to see the detailed cloud cover forecast. Make sure that the horizon is not blocked by trees or buildings. Get away from bright city lights, but remember that the aurora is large, so a few small light sources, including the moon, are no problem.

One of the easiest ways to see the aurora is using your phone's camera! Take a picture in night mode of the sky towards north (or south in the Southern hemisphere) and look at the recorded image. Our phones are much more sensitive to the colors of the aurora than our eyes, so you may take beautiful photos even when your eyes see only subtle hues. If you are lucky, you may see the aurora in other directions too, even directly above you!

The Aurora Alert is based on cutting-edge research at the University of Michigan resulting in the state-of-the-art GeoDGP machine learning model to predict the global storm time disturbance (Dst) index and local magnetic perturbations around the world. These magnetic disturbances are caused by charged particles that also cause the aurora. The alerts are based on the solar wind measurements one million miles away from Earth, which provides about one hour forecast window for the Alerts.

The aurora is only visible in darkness and can only be predicted reliably about an hour ahead, so you may need to get an alert at night to catch it. Subscribe to notifications to receive app notification, text message or a phone call when the aurora is visible near your location. The alerts are only sent if all your preferred conditions are met, including a time period.

Remember to allow the app to notify you even when the do-not-disturb mode is on. This works if you are awake, but the app notification will not wake you up. Text messages and phone calls are much more likely to work at night. Remember to add the AuroraTonight phone number as a contact and make phone calls and texts audible from this number even at night.

The aurora forecast is uncertain just like weather forecast. Setting a 25% limit means you will be alerted for even a small chance, while with a 75% limit you will only be alerted for very high-probability events.

We check the local forecast for cloud cover to make sure the aurora is visible from your location. Setting a "Clear Sky" limit means you will be only alerted when the sky is mostly clear, while the "Partly Cloudy" limit allows for some clouds. If you want an alert no matter what, choose the "Cloudy" limit value.

Michigan researchers developed in 2024 a machine learning model trained on 28 years of observations of the solar wind, the Dst index and hundreds of ground based magnetometers. The GeoDGP model uses the observed time series of solar wind, magnetic field and Dst index as input to predict magnetic perturbations at any location on Earth with unprecedented accuracy. This is then used to forecast the aurora one hour ahead.

NOAA uses the Ovation 2020 empirical model based on historical satellite observations of the aurora. Ovation 2020 relies on the latest measurements of the solar wind and magnetic field without looking at the time series or the Dst or Kp indexes. As a result, the Ovation model predictions have limited validity for substorms and extreme geomagnetic storms. The SWPC aurora model provides a 30-minute forecast window.

Aurora Watch is based on the predicted space storm activity from solar observations. It takes from 1 to 3 days for a coronal mass ejection (CME) to arrive at Earth. The G scale is based on the maximum Kp index value in the forecast issued by NOAA Space Weather Prediction Center (SWPC). These long-term forecasts are highly uncertain, this is why it is called an Aurora Watch. You can get a free app notification if the forecast exceeds a certain G scale.

The G scale goes from 0 (quiet) to 5 (extreme) and it is obtained from the planetary K (Kp) index by subtracting 4, rounded to a non-negative integer. The Kp index measures the rate at which global magnetic perturbations evolve and goes up to 9.

The D scale goes from 0 (quiet) to 5 (extreme) and it is obtained from the magnitude of the storm time disturbance (Dst) index divided by 50. The Dst index measures the global magnetic field disturbance in nanotesla (nT) units. The more negative Dst, the stronger the geomagnetic storm. Peak Dst magnitudes can reach 500 nT in some very rare cases, but the scale is limited to D5.

The Aurora Borealis, or Northern Lights, is a natural light display in the sky, usually seen in high-latitude regions. It is caused by collisions between energetic particles from the solar wind and atoms in Earth's upper atmosphere. The Aurora Australis, or Southern Lights, occurs on the southern hemisphere.

The sun constantly releases a stream of charged particles called the solar wind. When the solar wind hits Earth's magnetic field, it is funneled towards the poles. These particles then excite oxygen (which glows green or red) and nitrogen (which glows blue or purple) atoms causing them to light up. The most important properties of the solar wind are its speed, density, and the magnetic field it carries. The solar wind changes dramatically during geomagnetic storms caused by space weather.

The typical speed of the solar wind is about 400 km/s (or 250 miles per second), and the typical density is about 5 particles per cubic centimeter. While this speed is already enormous by our standards, it can increase up to 2000 km/s during geomagnetic storms! The density can also increase to more than 50 particles per cubic centimeter. The speed and density combine to dynamic pressure that compresses Earth's magnetosphere, and this can create beautiful aurora.

The typical magnitude of magnetic field carried by the solar wind is about 5 nT (nanotesla). When it points southward (negative Bz), it reconnects with Earth's magnetic field that points northward, allowing solar wind energy to enter Earth's magnetosphere. This creates the best conditions for aurora. During geomagnetic storms Bz can reach -20 nT or even -50 nT for several hours causing huge events.

Geomagnetic storms are typically caused by increased solar wind speed and density, and a sustained strong southward magnetic field. The severity of a geomagnetic storm is often characterized by the storm-time disturbance (Dst) index. The aurora is brighter and visible at lower latitudes during geomagnetic storms.

Auroral activity is strongest during geomagnetic storms. The most intense storms happen when a coronal mass ejection (CME) from the sun sends a massive burst of energy toward Earth. These space storms have many impacts besides producing beautiful aurora: they can cause radio outage, GPS errors, satellite mafunctions or even power grid blackouts. This is why accurate space weather forecasts are so important.

The top panel contains the logo that opens the University of Michigan Aurora page, the app name AuroraTonight that returns you to the top of the main page, and the share button that lets you share the app with others. The bottom panel contains the icon that opens the information page, the icon that returns you to the top of the main page, and the that opens the settings.

The main page shows the chance of seeing the aurora at the selected location in the next 60 minutes, the hours of darkness and the cloud cover at the top. You will also see the global aurora activity and the multi-day aurora watch prediction. Scroll down to see the regional map, polar activity movie, NOAA aurora prediction map, solar wind observations and the observed and predicted Dst indexes. To get the latest data (and restart the polar activity movie), refresh the page by pulling down on the screen.

You can change the location by tapping/clicking on the location box at the top of the page or in the settings. To check the surrounding area, set the distance limit. The distance units can be set in the settings. Clicking on the weather/cloud info opens a window with the cloud cover forecast for the night. Click outside the window to close it. Clicking on other items opens the relevant FAQ section.

The settings page lets you set your location, distance limit for local forecast, the distance unit (miles or kilometers) and notification preferences. All settings are saved automatically into your browser's local storage. See the data security FAQ for details.

If you do not subscribe to notifications, we do not store any information about you on our servers. All your settings are saved locally in your browser's local storage. If you clear your browser data or open the web page/app on another device or with a different browser, you will need to set them again.

If you subscribe to notifications, your user ID, email address and notification preferences will be saved on our server. If you choose to receive notifications via text messages or phone calls, we will also need your phone number. We store this information securely and do not share it with anyone. This information is only used to send you aurora notifications and reminders for subscription renewal. You can suspend or cancel your subscription any time with a couple of clicks in the app. When you suspend your subscription, we will keep your information on our server, so you can easily resume your subscription later. When you cancel your subscription, we will delete all your information from our server.