Solar Particle Radiation Storms Forecasting and Analysis by Olga E. Malandraki & Norma B. Crosby

Author:Olga E. Malandraki & Norma B. Crosby
Language: eng
Format: epub, pdf
Publisher: Springer International Publishing, Cham

6.4 Neutron Monitor Detector

Neutron monitors cover the energy range of primary cosmic ray particles from ∼ 0.5 to 100 GeV per nucleon. This energy range includes the solar modulation of the galactic cosmic rays, Forbush decreases, sporadic GLEs or relativistic SEP (Solar Energetic Particle) events, and geomagnetic effects. The longterm stability of neutron monitors is generally excellent so that the cosmic ray effects of the 11-year solar activity cycle can be investigated over several solar cycles. The longest time series of single neutron monitor stations are available over a period of ∼ 60 years, i.e. during a time range over more than five solar activity cycles. The comparison of the measurements of different neutron monitor stations have however shown that some neutron monitors may show a degrading of the detector efficiency (Bieber et al. 2007).

As the name suggests, neutron monitors record predominantly the secondary neutrons from the atmospheric cascades. The contribution to the total neutron monitor counting rate of an NM64 are neutrons ∼ 85%, protons ∼ 7%, μs ∼ 6%, πs ∼ 1% (Hatton 1971).

The functionality, construction and other properties of a neutron monitor are described in Sect. 6.4.1. The response of the neutron monitor to primary cosmic ray particles at the top of the Earth’s atmosphere is explained in Sect. 6.4.2. The influence of the atmospheric effects on the neutron monitor measurements are addressed in Sect. 6.4.3.

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