Neutron monitors and muon detectors for solar modulation studies: Interstellar flux, yield function, and assessment of critical parameters in count rate calculations. Issue 1 (1st January 2015)

• Record Type: Journal Article
• Authors: Maurin, D.; Cheminet, A.; Derome, L.; Ghelfi, A.; Hubert, G.
• Is Part Of: Advances in space research. Volume 55:Issue 1(2015)
• Page Start: 363
• Page End: 389
• Publication Date: 2015-01-01
• Subjects: Space sciences -- Periodicals; Astronautics -- Periodicals; Geophysics -- Periodicals; 500.505
• DOI: 10.1016/j.asr.2014.06.021
• Languages: English
• ISSNs: 0273-1177

Abstract

<abstract xml:lang="en" abstract-type="author" id="ab005"> <title id="st185">Abstract</title> <sec> <p id="sp005">Particles count rates at given Earth location and altitude result from the convolution of (i) the interstellar (IS) cosmic-ray fluxes outside the solar cavity, (ii) the time-dependent modulation of IS into Top-of-Atmosphere (TOA) fluxes, (iii) the rigidity cut-off (or geomagnetic transmission function) and grammage at the counter location, (iv) the atmosphere response to incoming TOA cosmic rays (shower development), and (v) the counter response to the various particles/energies in the shower. Count rates from neutron monitors or muon counters are therefore a proxy to solar activity. In this paper, we review all ingredients, discuss how their uncertainties impact count rate calculations, and how they translate into variation/uncertainties on the level of solar modulation <inline-formula><alternatives><inline-graphic xlink:href="ark:/27927/pgh30pdfrd8" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math altimg="si276.gif" overflow="scroll" id="d13e4895" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>ϕ</mml:mi></mml:mrow></mml:math></alternatives></inline-formula> (in the simple Force-Field approximation). The main uncertainty for neutron monitors is related to the yield function. However, many other effects have a significant impact, at the 5–10% level on <inline-formula><alternatives><inline-graphic xlink:href="ark:/27927/pgh30pdbmm2" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math altimg="si277.gif" overflow="scroll" id="d13e4900" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>ϕ</mml:mi></mml:mrow></mml:math></alternatives></inline-formula> values. We find no clear ranking of the dominant effects, as some depend on the station position and/or the weather and/or the season. An abacus to translate any variation of count rates (for neutron and <inline-formula><alternatives><inline-graphic xlink:href="ark:/27927/pgh30pdc6x9" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math altimg="si278.gif" overflow="scroll" id="d13e4905" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>μ</mml:mi></mml:mrow></mml:math></alternatives></inline-formula> detectors) to a variation of the solar modulation <inline-formula><alternatives><inline-graphic xlink:href="ark:/27927/pgh30pdcjb3" xlink:type="simple" xmlns:xlink="http://www.w3.org/1999/xlink" /><mml:math altimg="si279.gif" overflow="scroll" id="d13e4910" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>ϕ</mml:mi></mml:mrow></mml:math></alternatives></inline-formula> is provided.</p> </sec> </abstract>