A magnetospheric disturbance typically defined by variations in the horizontal component of the Earth's surface magnetic field. The variation typically starts with a field enhancement associated with
a solar wind pressure pulse and continues with a field depression associated with an enhancement of the diamagnetic magnetospheric ring current. (spase)
A measure of the gathering power of aparticle detector. The geometric factor can be used to correct particlemeasurements by accounting for the fact that only a fraction of sourceparticles are able to
gain entry through the aperture of a detector. For anisotopic source distribution, the geometric factor corresponds to the solidangle subtended by the aperture. In practice, determination of the geometricfactor requires numerical modeling and depends on detector design and thecharacteristics of the source.