Auroral oval and the limits of aurora visibility

The auroral oval tool displays estimates of the equatorward and poleward boundaries of the auroral ovals around the north and south geomagnetic poles. It uses a model that predicts the location of the auroral ovals as a function of the K index. The tool also displays an estimate of the equatorward visibility line, assuming a clear night sky and an aurora height of 150 km.

The aurora oval model used by the tool is in the process of being updated since its estimate of the equatorward visibility line does not always agree with the aurora sighting reports in the ASWFC archive. These discrepancies could be due to the assumed maximum aurora height of 150 km. They could also be due to the model using Kaus instead of Kp for the K index. The model uses Kaus since it is available in near real-time. In addition, the tool will be updated to use a more accurate conversion from corrected geomagnetic coordinates (CGM) to geographic coordinates.

Parameters

The K index can be set manually. This is useful for checking observing conditions for times in the future. Click on the "Get Kaus Index" button to reset the K index to the actual value for the date and time displayed.

Changing the date or time will change the K index value to the actual value for the date and time displayed. If the date or time is in the future, the last displayed K index value will be used as the tool does not have forecasts of K indices. When entering a time, use 24-hour notation.

Click on the "Get Current Datetime" button to reset the K index and the display to the current date and time.

Aurora Sightings

The locations of aurora sightings are displayed on the map for matching date and time. The "Filter Aurora Sightings by Date" selector turns the date filter on/off, allowing sightings to be displayed for matching time and K index, and any date. Clicking on the pin displays more information about the sighting.

Animation

The tool can step forward or backward in time using the animation controls. The and buttons start the animation running automatically and can be stopped with the button when it is displayed. The and buttons step backward or forward manually.

As the animation steps through time, the tool will get the K index for that date and time, then recalculate the auroral oval. The tool does not have forecasts of K indices, so any times in the future only use the last recorded K index. If the K index has been set manually, it will not be updated as the tool is stepped through time. To reset the tool so that it automatically updates the K index, either click the "Get Kaus Index" button or the "Get Current Datetime" button.

Pan/Zoom

The map can be panned by clicking the arrow controls.

To zoom the map, click on the zoom controls.

To return the map to its default pan/zoom settings, click the • control.

Day/Night

The white background denotes the sun-lit sector, the darker grey background the night-time sector based on astronomical dawn/dusk and the lighter grey the approximate location of the day/night terminator at the Earth's surface.

The Day & Night selector just above the map on the right can be used to show/hide this feature.

Sun Position

The yellow circle represents the approximate location on the Earth where the Sun is overhead.

The Sun Position selector just above the map on the right can be used to show/hide this feature.