Kiruna magnetogram

This magnetometer gives you the values of the Kiruna station in Sweden, Europe. It is often used in Europe to see if there is a chance to see the aurora. In other places then Europe, like North America, other magnetometers should be used like the Canopus oval or another magnetometer close to your location.

But how do we read this plot? The plot displays the X, Y and Z values that are being observed at the magnetometer in Kiruna. The line of interest is the black line. It represents the X-component which shows us how far south the auroral oval reaches. When the earth's magnetic field isn't being disturbed we will see for the X-component values of about 10685 nanoTesla (nT). However, when the magnetic field is being disturbed we will see that the values on the graphic will start to fluctuate and those values are important for us to determine if there is a chance to see the aurora.

During geomagnetic storming when Kiruna is on the daylit side of the Earth the Kiruna magnetometer could deflect in an opposite way because the auroral oval is always pointed away from the Sun and the magnetometer will deflect less. This is also why it's important to look at magnetometers closer to your location.

For the Middle Latitudes, in particular the European region, you can capture photographic aurora when there is a deflection of at least 700nT and visual aurora starting from 1300nT deflection. We do understand that this is not very easy to understand but we will make a try with some examples.

In the Middle latitudes locations, like Belgium and The Netherlands, the most common forms of aurora that occur, are weak auroras low on the northern horizon. A good example of how the Kiruna magnetogram would look like in such a situation can be seen on the picture below. The deflection was about 1200nT and the predicted Kp-index at that moment was 7. We can conclude that weak visual aurora was possible for the northern parts of The Netherlands and Germany.

A second (rather extreme) example is this magnetogram from 30 October 2003. Two coronal mass ejections from a X17 and X11 solar flare arrived on earth and caused an extremely severe storm with auroras which could be seen all the way in Portugal! At all Middle latitude locations, auroras could be seen directly overhead! This was the biggest geomagnetic storm of SolarCycle 23 with a Kp-index of 9.

But how do we determine this deflection? When there is a disturbance in the Earths magnetic field, the magnetometers will react to it and thus the Kiruna magnetogram will show us minor deflections from the normal quiet level of 10650nT. The deflection is also expressed in nanoTesla units (nT). The start of the deflection is in the beginning of the storm before the measured values drop. It's difficult to explain this in words so in the graph below you'll see a good example of a deflection, measured at the Kiruna station. The deflection is shown as a yellow area in the graph; it starts shortly after the arrival of the CME before it gradualy degrades in value till it reaches it's lowest measured point. This deflection, expressed in nanoTesla, is the value we have to look at if we want to see or photograph the aurora. In this example the deflection is arround 500nT and gets a local Kiruna K-indice of 6 and thus also not enough for a chance for auroras at the Middle latitudes.

Interpreting the K-index based on values from Kiruna

De K-index is just like the Kp index: a geomagnatic storm index with a logarithmic scale from 1 to 9.
For the middle latitudes, aurora can be seen from a Kp index of 7, but considering that the Kp index is a 3 hour average of various magnetometers stations on Earth, this is not a very representive way to know if there are fair chances for auroras at Middle latitude locations. Based on the deflection from the Kiruna magnetometer we can try to determine the K-indice. We do this with the help of the table below. Be aware that, due to it's location, this magnetometer can only be helpfull for observers from Europe.

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