The norlys model is an experimental model that aims to transcribe global magnetometer data into a dynamic map displaying the probable, near-real-time auroral activity. This is the first-ever public northern lights map of its kind featuring near real-time magnetometer data across such an extensive area.

The norlys model is derived from global magnetometer data, which are converted into a back-end ionospheric current map. This map works in the background and is updated every minute. It calculates the intensity and direction of equivalent ionospheric currents above an area of the world covering Europe, Iceland, Greenland and north America. The ionospheric current vectors are assessed thanks to magnetometer stations (provided by TGO, UAF, USGS, Carisma, IRF, FMI and DTU ; See Credits and acknowledgements), and derived from associated magnetic field displacements in the horizontal components (raw x and y), in nanoTeslas. This intermediary map enables us to locate the position of the real-time auroral oval, as well as to determine the flowing direction and intensity of the auroral electrojet current.

Some of these currents have been widely demonstrated to be closely assimilated to the auroral oval (specifically, the Auroral Electrojet current) and their direction / intensity correlated with atmospheric electron precipitation creating the aurora. Based on these scientific assumptions, our norlys model can give us a foundation to work out a relatively precise location and intensity for the auroral oval.

With these ionospheric current data, we are able to compute and then reveal a naturally realistic map of the tentative auroral oval, which evolves in latitude, longitude and intensity in near real-time. This is extremely useful for aurora chasing because users can literally locate where the oval is and where the maximum activity can be found along the oval. This is especially true when users monitor the evolution of the oval on our map over several minutes, as discrepancies may arise at times (see disclaimer below). With this in mind, users can easily identify how far from the oval they are and the sector of the oval they are crossing in order to anticipate the type of auroral activity they will face.

Please note that our model does not precisely determine the different types of auroral behaviors along the oval (e.g. quiet arcs, substorms, pulsating auroras…) because it is not (yet) possible to use magnetometer / current data to do so in a very scientifically accurate way. If it was, such models would likely have already been produced. With that being said, our model can still help greatly to anticipate the major types of behavior using the relative intensity and location of this activity.

As an example, early magnetic evening auroras are often quiet arcs and so the geographical locations passing under this sector of the auroral oval should on average only experience a thinner, dimmer activity in our model. In the same way, closer to magnetic midnight, the nightside of the Earth experiences more explosive auroras (substorms) that work in a dim build-up (growth), then bright explosion (expansion), followed by a diffuse phase (recovery). Our model does show the real-time development of these spectacular substorms by sudden changes in intensity and location of the oval. The growth phase will display a low intensity aurora slowly migrating equatorward, typically over several hours. The substorm oval will likely remain dim and thin just like during early evening. The expansion phase will typically feature a sudden, quick (minutes), intense brightening (highest values) of the aurora traveling from the equatorward oval towards a much more poleward location. The recovery phase will generally show a moderate intensity but over a much larger oval in latitude span.

The model has been designed with the utmost care for user utilization. It is pasted onto a 3-D globe that can be smoothly rotated, zoomed and moved. Use your mouse (desktop) or fingers (mobile) to drag and rotate the globe. Scroll forward (desktop) or pinch out (mobile) to zoom in. Scroll back or pinch in to zoom out.

The map also shows cities where we have online webcams, as well as your location (provided you turn on location services). On the desktop version, hover over the city to reveal the webcam. On mobile devices, click on the city to reveal the webcam. Click again to close it down.

As the sunlight is the major obstacle that prevents one from seeing the aurora, our model displays where the sunset / sunrise terminator is. It is the line that marks the transition between the lightest gray area of the map and a band of darker gray. This band of darker gray corresponds to a time after sunset or before sunrise where it is yet too bright for aurora (the Sun is between 0 and 8 degrees of elevation under the horizon). The darkest color (very dark gray) corresponds to the area of the Earth where it should be dark enough to see the aurora. In this zone, the Sun is below 8 degrees of elevation under the horizon. Please note that from 8 to 18 degrees under the horizon, it is not fully dark (twilight), Consequently, it can affect aurora viewing by washing out the fainter auroras.

The scale of aurora probability goes from low to high. Very low to moderate activity would correspond to faint aurora, often encountered when the geomagnetic activity is generally quiet, or during substorm growth. This type of aurora is often seen in the daytime oval (dayside aurora), in the afternoon oval (discrete quiet arcs), the early evening oval (discrete quiet arcs), the late evening and nighttime oval (substorm growth arcs or substorm recovery pulsating aurora). Moderate probability often describes situations like more intense evening auroras, more intense substorm growth and substorm recovery. High and very high intensities typically correspond to the most active auroras, occurring generally during substorm expansion in the nighttime oval, during other types of explosive auroral activity (convection bay), at the beginning of the recovery phase or anywhere along the oval under a unusually active magnetosphere ( called geomagnetic storming, where all the different sectors of the oval intensify).

While you can use the model by spotting where the aurora activity is at a glance, we recommend that you monitor it closely over several minutes (or dozens of minutes). As magnetometer data can display very quick changes or errors, our model may therefore underestimate or overestimate the auroral activity, resulting in gaps, discrepancies or sudden drastic changes. These are almost always erased naturally in the course of several minutes, hence the need to monitor the map on a regular basis and not just punctually.

We are eternally indebted to Dr. M. G. Johnsen, head of the Tromsø Geophysical Observatory (TGO) at UiT The Arctic University of Norway, along with his team for providing us with geomagnetic data from Norway, Greenland and Svalbard, as well as helping in the construction of several aspects of the model. We would also like to thank the Finnish Meteorological Institute for providing geomagnetic data in Finland. In the same way, we thank the IRF (Swedish Institute of Space Physics) for the Swedish data, and the DTU Space (Danish Institute of Space Physics) for the Danish data. Finally, we want to extend our special thanks to the UAF (Alaska, Fairbanks), the USGS (USA) and Carisma (Canada) for providing us with the North American data.

It is of utmost importance for norlys users to be aware of the following.

The present model is merely experimental. It means that although it bases its theory and data on science literature and scientific observations, the model itself has not been peer-reviewed and is not associated with any scientific / governmental institution.

Strong ionospheric currents like the Auroral Electroject and the magnetic field variations they create are often associated with auroral activity. However, there is still a wide gap between ionospheric currents data and real-life auroral activity. When current-generated field variations are intense, the model becomes more accurate but quiet times may introduce some bias. Thus, although our model has been tested to present a thorough estimate of the auroral oval and its activity, there may be some inaccuracy and discrepancies in the intensity and location of the auroral activity at times.

To follow up on the last point, you may experience some auroral probability ‘blobs’, which are far from the oval. Please note that although we have implemented a code that limits errors, the raw magnetometer data are provided by different institutions around the world and there are often significant differences in the instrumentation used. Therefore, although we recalibrate all data following an advanced baseline calculation, there may still be data errors and discrepancies from time to time, showing you zones of aurora probability that seem out of place. They are easily identified by their ‘blobby’ look and by their distant location to the auroral oval.

The model is updated every minute by retrieving magnetometer data. The latter already presents a form of delay compared to the real-time local magnetic activity. In the field, most auroral activity is evolving slowly, over dozens of minutes, if not hours. This makes the use of magnetograms rather easy and timely. However, you may regularly experience brightenings of the aurora (substorm expansion for example), which only last for seconds or minutes. These quick intensifications tend to appear with a delay in a magnetogram array and might consequently be finished before they can be read in our model. However, there is a double silver lining to this. A) A lot of these brightenings are still slow to develop (example during solar storms), enabling our model to catch up and show you an increase in auroral brightness in time. B) By following our model regularly in the nightside oval where these intensifications happen frequently, users can put themselves in the best position to catch the brightenings by identifying the build-up process (growth), which is characterized by a thinner, dimmer oval slowly migrating equatorward.

The oval representation may be spatially inconsistent at times because some countries / land masses are simply not covered by magnetometer data or we haven’t been able to gain access to magnetometer data for such areas. Therefore, a stronger interpolation had to be implemented in such zones, leading to more spatial inaccuracy. Example: we do not yet have access to Icelandic data and so there is a large interpolation going on between Europe and Greenland, making the longitudinal resolution less accurate for iceland. In the same way, we have much fewer magnetometers at lower latitudes, so the representation of the oval will become much more uncertain when the oval really expands equatorward during extreme geomagnetic storms. In such cases, it should not be too much of an issue as other features of our app would notify you of the very intense geomagnetic conditions at mid-latitudes.

The determination of the auroral activity may cease altogether at specific times, leading to the disappearance of the oval on the map.This is the case when magnetometer traces are close to their quiet baseline and/or do not change much over time. As mentioned previously, magnetometer data can only be used as a proxy to assess the rough auroral activity. They do not depict very precisely the real-life auroral activity, especially during quieter geomagnetic periods. In such instances, auroras may still occur in the oval and the polar cap whereas our model does not display anything. The type of aurora that’s particularly affected by this issue is the quieter, dimmer aurora. For example, quiet evening arcs or substorm-growth arcs may sometimes pass under the radar. In such cases, it is important that users monitor the model continuously to spot the reappearance of the oval. We also advise users to check webcams regularly to verify the evolution of the oval when our model fails to show it. As soon as the magnetometer activity gets stronger again, the oval should reappear.