Details

Autor(en) / Beteiligte

• Koldobskiy, Sergey A.
• Kovaltsov, Gennady A.
• Usoskin, Ilya G.

Titel

A Solar Cycle of Cosmic Ray Fluxes for 2006–2014: Comparison between PAMELA and Neutron Monitors

Ist Teil von

• Journal of geophysical research. Space physics, 2018-06, Vol.123 (6), p.4479-4487

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2018

Quelle

Wiley Online Library

Beschreibungen/Notizen

• A comparison of cosmic proton spectra directly measured by the Payload for Antimatter Matter Exploration and Light‐nuclei Astrophysics (PAMELA) experiment during 2006–2014 with data of polar neutron monitors for the same time interval is presented. It is shown that the measured spectra are well described by the force‐field model for the modulation potential range 350–750 MV. The obtained modulation potential agrees with that calculated from the data of the world neutron monitor network for low solar activity between 2006 and 2012 but diverges during the maximum of solar cycle. The empirical relation between the modulation potential and the (inverted) neutron monitor count rate appears somewhat steeper than the modeled one, as confirmed also by data from fragmentary balloon‐borne measurements. A reason for the discrepancy is unclear and calls for additional study using independent data sets. Plain Language Summary A global network of ground‐based neutron monitors is the main tool to monitor cosmic ray variability since the 1950s, but its absolute calibration to the cosmic ray flux in the open space is somewhat uncertain and based on models. Here we performed a comparison of cosmic proton spectra directly measured in space by the Payload for Antimatter Matter Exploration and Light‐nuclei Astrophysics experiment during 2006–2014 with data of polar neutron monitors for the same time intervals. We have shown that the measured spectra are well described by the existing models for the period of weak/moderate solar activity but diverges during the maximum of solar cycle, suggesting that the models may be not precise. A reason for the discrepancy is unclear and calls for additional study using independent data sets. Key Points The GCR proton spectra measured by PAMELA are well described by the force‐field model PAMELA data are in good agreement with neutron monitors for low solar activity in 2006–2012 but diverge for higher activity in 2013–2014 The systematic discrepancy is possibly related to an underestimate of the neutron monitor yield function in the high‐energy range