Geomagnetic cutoff rigidity!

Geomagnetic rigidity is the minimum energy a primary proton must have to create a cascade which can reach sea level at that location.

The shielding effect of the Earth's magnetic field is usually described by the concept of cutoff rigidities since the magnetosphere imposes a lower limit on the energy of primary cosmic ray particles to enter the atmosphere.

The unit of rigidity is volts or as in the graphic, GV (giga-volts). The higher the rigidity, the lower the probability that primary particles will hit the atmosphere in order to produce secondary particles at a specific location.

Fig.1 Global geomagnetic cutoff rigidity (Epoch 2000)
Click on the image for a large view!

Dipolar Approximation!

If we assume Earth's magnetic field as a simple dipole field, we can calculate the cutoff rigidity. Enter your latitude (northern latitudes are positive) and your longitude (eastern longitudes are positive) in the form and press calculate. The javascript will calculate the magnetic coordinates for your location, aswell as the approximate cutoff rigidity.

Fig. 2 Plotted cutoff rigidity from the calculation above.
Longitude/latitude grid as in Fig. 1
Rigidities in steps of 1,3,5 ... 17 GeV

Be very careful when handling high voltages!
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