Bz and Bt are two important components of the interplanetary magnetic field (IMF). When the Bt is strong and Bz is well below zero the aurora can form easily. The nominal value of the Bz can never be higher than Bt. In this chart the Bz is thicker solid line, and Bt is thin dotted line. The color of the Bt-line is always green, but the color of the Bz will change based on its value. Values above zero are green, and values below zero are yellow, orange and red. Data comes from NOAA's SWPC. close
Speed means the velocity of the solar wind. The higher the speed is the easier it is for aurora to form. Typical speed is usually around 300 km/s, but for example the solar wind coming from coronal holes can be 800 km/s or even higher. The color in this chart changes based on the value, and red means that the speed is strong. Data comes from NOAA's SWPC. close
Density means the number of protons in one cubic centimeter of the solar wind. The higher the value is the easier it is for aurora to form. The color in this chart changes based on the value, and red means that the density is strong. Data comes from NOAA's SWPC. close
VxBz and dynamic pressure are calculated from Bz, speed and density values. Also with these the higher value means better chance for aurora to form. In this chart the VzBz is solid line, and dynamic pressure is thin dotted line. close
This chart shows by default the changes of the so called X-component of the magnetometer in Kevo of Finnish Meteorological Institute, but you can select also other stations from the drop-down menu below the chart. Data is provided by Finnish Meteorological Institute via Open data. Auroras are typically visible when the lines in this chart are going down sharp. Notice also the scale of the picture. If the Sodankylä-line drops like 700 nT in very short time, it means that there is a very good chance to see aurora very soon. Sodankylä observatory magnitude of changes in X-component compared to K-indexes of same place (K-index is kind of "local Kp-value", whereas the official Kp is global) are:
|0 - 14||0 - 7.4||0|
|15 - 29||7.5 - 14||1|
|30 - 59||15 - 29||2|
|60 - 119||30 - 59||3|
|120 - 209||60 - 104||4|
|210 - 359||105 - 179||5|
|360 - 599||180 - 299||6|
|600 - 989||300 - 494||7|
|990 - 1499||495 - 749||8|
|> 1500||> 750||9|
This chart is updated automatically as soon as there is new data available. Old values can be found from Intermagnet-site. Another good place to see real time (and also archived) values is IMAGE-site. close
Auroral oval shows NOAA's estimate of the strength of the aurora after about 30 to 90 minutes (depending on the speed of the solar wind) of the time the forecast is updated. The brighter and wider the oval is, the better chance there is for aurora to form. During the strong geomagnetic storms the picture of the oval contains also yellow, orange and red colors in addition to ordinary green.
The probability forecast is based on the speed of the solar wind. Aurora can be seen even hundreds of kilometers south from the brightest part of the oval. Data comes from NOAA's SWPC. close
Here you can see all the alerts and watches related to aurora that has been listed on NOAA's SWPC-site during previous 24 hours. The date and time on the first line of each alert is automatically converted to local time in Finland. close
Boyle Index (Φ = 10-4 * ν2 + 11.7 * B * sin3(θ/2) kV) is one of the meters used for predicting auroras. This empirically derived formula is in generally speaking most accurate, when the characters of the solar wind have been steady for a couple of hours, and the value of the index is less than 100 kV. On higher values the accurasy is not as good. When the value of the Boyle index is less than 20 kV, the magnetosphere is typically too quiet for the aurora to form outside of typical auroral oval. During very strong geomagnetic storms the value of the index can be higher than 400 kV.
Propability of reaching the level Kp 5 is higher than 95%, when Boyle index has stayed on average level of 100 kV for three hours or more. close
This map shows the locations of magnetometers in Finland, and the disturbances of the magnetic field in their location. When the local magnetic field is quiet, there's only a small dot on the map. When the disturbances in the magnetic field are high enough for auroras, you will see expanding circles around the dot. Green color means increased chance, orange remarkable increased and red very high chance for auroras. Data comes from Finnish Meteorological Institute and is updated in about every two minutes.
Thin dotted line on this chart means the value of By, and solid vertical bars/columns shows those measurements where Bz is positive and the nominal value of the By is greater than Bz. Also in those cases there is a magnetic reconnection of the solar wind and magnetosphere, and thus a change for aurora, although not as good as when Bz is negative. Data comes from NOAA's SWPC. close
Hemispheric Power Index is one of the indicators used to evaluate the activity of the aurora. Its value is typically between 5 to 150 gigawatts. When the hemispheric power is less than 20 GW, the aurora doesn’t usually show up, but when the value is 100 GW or more, the aurora can be seen far away (hundreds of kilometers) from typical auroral zone.
Readings on this chart are forecasted value of the hemispheric power based on the speed of the solar wind, and forecast is updated automatically in every 5 minutes. The rightmost value on the timeline means forecasted value at that time, usually about 30 to 90 minutes ahead. Data comes from NOAA's SWPC. close
Temperature of the solarwind. close