Aurora

How to read the aurora forecast?

The map shows where auroral activity may occur in the near future according to the NOAA OVATION model. The coloured area around the pole is called the auroral oval. This is where the aurora most often appears.

During calm space weather, the oval is located mainly at high latitudes, including over northern Scandinavia, Iceland, Greenland, and northern Canada. As geomagnetic activity increases, the oval may expand farther south. During stronger geomagnetic storms, the aurora may then also become visible from Poland and other parts of Central Europe.

The 2D map and 3D globe show the same data. Only the presentation differs, so switching to the globe does not mean a more accurate forecast.

What do the colours on the map mean?

The colours show the value calculated by the OVATION model. The higher the value, the stronger the auroral activity predicted by the model in a given area.

Green indicates weaker activity, while a shift towards yellow, orange, and red indicates an increasingly stronger model signal.

However, percentage values should not be treated as the percentage chance of seeing the aurora from a specific location. The model describes auroral activity in the atmosphere, not all the conditions needed for observation from the Earth's surface.

The aurora may be active over a given area while remaining invisible because of daylight, bright twilight, clouds, moonlight, or light pollution.

What is the potential visibility boundary?

The white line does not mark the edge of the aurora. It shows the approximate range from which the aurora may potentially be seen, even when the oval itself is farther north.

This is because the aurora forms high above the Earth's surface. A strong aurora hundreds of kilometres away from an observer may be visible low above the northern horizon.

The boundary shown in SkyLep is an estimate based on NOAA OVATION data and the Case et al. (2016) model. It is not an official boundary published by NOAA and should not be treated as a sharp line separating places where the aurora will be visible from those where it will not.

The farther south the boundary reaches, the more interesting the situation becomes for observers in Poland.

Pay attention to the forecast time

The OVATION model describes conditions for a specific moment. Below the map, we provide both the input data time and the forecast time.

This is important because the auroral oval can change its shape and extent relatively quickly. The forecast shown on the map does not describe the entire night, but rather the situation expected at the specified time.

Therefore, during rapidly changing space weather, it is worth monitoring not only a single map but also the current solar wind parameters and how they change over time.

What do current space conditions tell us?

Below the map, we show several parameters describing the state of Earth's magnetic field and the solar wind. None of them alone answers whether you will see the aurora. The most informative thing is their combined picture and how they change over time.

Kp index

Kp describes global geomagnetic activity on a scale from 0 to 9. Low values indicate a calmer Earth's magnetic field, while high values indicate increasingly stronger disturbances.

As Kp rises, the auroral oval usually expands toward lower latitudes. Therefore, a high Kp increases the possibility of observing the aurora farther from polar regions.

The Kp value displayed by SkyLep applies to a completed 3-hour period. It therefore describes recent activity rather than being an instantaneous measurement, and it is not a standalone forecast for Poland.

Bz, magnetic field direction

Bz is one of the most important parameters when assessing auroral conditions. It shows the north-south component of the interplanetary magnetic field.

For geomagnetic activity to develop, negative Bz values, meaning a southward-directed field, are particularly favourable. Under such conditions, solar wind energy can interact much more effectively with Earth's magnetosphere.

A brief drop in Bz below zero does not necessarily mean a strong aurora. What matters much more is how negative the value is and how long these conditions persist.

Bt, magnetic field strength

Bt shows the total strength of the interplanetary magnetic field.

Higher Bt may favour a stronger interaction between the solar wind and the magnetosphere, especially when Bz is also directed southward. However, high Bt alone does not mean that strong auroral activity will occur.

Therefore, Bz and Bt are best analysed together.

Solar wind speed

Solar wind is a stream of particles arriving from the Sun. Its speed can range from relatively calm values to very fast flow during periods of increased activity.

Faster solar wind can deliver more energy to the magnetosphere and favour auroral activity. However, high speed alone is not enough to produce a strong aurora. The direction and strength of the magnetic field carried by the solar wind also matter greatly.

Proton density

Proton density indicates how many solar wind particles are present in a given volume of space.

A sudden increase in density may indicate a stronger interaction of the solar wind with the magnetosphere and its compression. As with speed, an increase in the number of protons alone does not automatically mean that an aurora will occur.

How to read the charts?

A single value only indicates the conditions at a given moment. Charts allow you to see whether the situation is developing, remaining stable, or beginning to weaken.

When observing the aurora, it is especially worth paying attention to longer periods of negative Bz and simultaneous increases in Bt and solar wind speed. Short spikes may be less important than conditions that persist for several or several dozen minutes.

The Kp chart looks different because this index is a summary of successive 3-hour periods. It should therefore not be interpreted in the same way as minute-by-minute solar wind measurements.

The most important thing is to observe the trend of several parameters at the same time, rather than looking for a single value that on its own means “there will be an aurora”.

Will the aurora be visible from my location?

Even very good conditions in space do not guarantee an observation.

To see the aurora, you primarily need a dark sky and suitable weather. Cloud cover, sky brightness, moonlight, light pollution, and an unobstructed horizon all matter.

In Poland, weaker auroras often appear low above the northern horizon, so a location with an open view to the north can be very important.

The OVATION map and solar wind data therefore primarily answer the question:

Do conditions in space favour the aurora, and how is the situation developing?

Only by combining this information with the time of day and local weather conditions can the actual chance of observation be assessed.