Comparison of atmospheric inoziation models

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David Dickerson
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1 Comparison of atmospheric inoziation models

2 Models: basic information Responsible person: Dr. Laurent Desorgher Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-312 Bern, Switzerland Also: Prof. Erwin Flückiger Dr. Fan Lei, QinetiQ, ESA/ESTEC Program basis: GEANT 4 application Physics behind: Monte-Carlo, all included (cascade + thin target) Particles: protons (factor 1.31 to account for α-particles). Energy range: max. energy (currently 1 GeV/nucleon, potentially higher) Claimed validity: the whole range Responsible person: Dr. Ilya Usoskin Sodankylä Geophysical Observatory (Oulu unit), P.O.Box 3, FIN-914 University of Oulu, Finland Also: Dr. Gennady Kovaltsov Ioffe Phys-Tech. Institute, St. Petersburg, Russia Program basis: CORSIKA package Physics behind: Monte- Carlo, the program starts only in the first interaction. Particles: protons and α- particles explicitly Energy range: from 1 MeV - 5 GeV/nucleon Claimed validity: g/cm 2 (-1 km) Responsible person: Dr. Lachezar Mateev, Marussia Bucharova Space Res. Institute, Bulgarian Academy of Sciences, Sofia, Bulgaria Also: Prof. Peter Velinov Program basis: Theoretical model, spherical atmosphere Physics behind: Direct ionization (Thin target), no cascade Particles: protons, α, L, M, H, VH Energy range: 1 MeV 1 GeV Claimed validity: > 16 km (<1 g/cm 2 ) - minimum > 12 km (<18 g/cm 2 ) - maximum

Energy range: max. energy (currently 1 GeV/nucleon, potentially higher) Claimed validity: the whole range Responsible person: Dr. Ilya Usoskin Sodankylä Geophysical Ob

3 Comparison: Polar regions (Pc<1.5 GV) 35 Solar maximum 6 Solar minimum 3 5 Ion. rate (cm 3 sec) Oulu, 1 MV Bern, 1 MV Sofia (max) Ermakov,97 Yu, 22 Neher, 1971 Rosen,85 Ion. rate (cm 3 sec) Bern, 3 MV Oulu, 3 MV Sofia (min) Rosen, 1985 Neher, h (g/cm2) h (g/cm2) Comparison of Bern, Oulu and Sofia models with observations (fragmentary, short balloon flights). Similar for low atmosphere (h>5 g/cm 2 ); Oulu model seems to underestimate ionization, while Bern model seems to overestimate; Sofia model is consistent with observations above 1 g/cm 2

rate (cm 3 sec) -1 4 3 2 Bern, 3 MV Oulu, 3 MV Sofia (min) Rosen, 1985 Neher, 1971 5 1 2 4 6 8 1 h (g/cm2) 2 4 6 8 1 h (g/cm2) Comparison of Bern,

4 Comparison: Equatorial regions (Pc=14-15 GV) Ion. rate (cm 3 sec) Bern, 3 MV Oulu, 3 MV Sofia (min) Neher, 1967 Neher, h (g/cm2) Comparison of Bern, Oulu and Sofia models with balloon-borne observations. Oulu model seems to overestimate with respect to the Bern model; Sofia model underestimates the ionization;

Neher, 1971 2 4 6 8 1 h (g/cm2) Comparison of Bern, Oulu and Sofia models with

5 Comparison: Ionization at 3 g/cm 2 4 Ionization at 3 g/cm 2 (cm 3 sec) MV 3 MV Neher, 1971 Bern oulu Measur. Neher (1971) Bern model Oulu model max min ratio Measurements were done in Thule (polar region) Oulu model systematically underestimate the ionization and the cycle variation; Bern model seems to overestimate the cycle variation;

2 1955 1957 1959 1961 1963 1965 1967 1969 Measurements were done in Thule (polar region) Oulu model

6 Comparison: Q-vs-Φ (Pc=7 GV) 25 2 Bern Oulu Ion. rate (cm 3 sec) (MV) The models agree for 7 g/cm 2, more or less agree for 5 g/cm 2, and disagree for 3 g/cm 2

7 Atmospheric profile 25 2 h (km) h (g/cm 2 )

8 Summary Polar Equator Solar max. Bern (whole range) Oulu (>3 g/cm2) Bern (whole range, but > 3 g/cm2) Oulu (>3 g/cm2) Solar min Bern (>5 g/cm2) Oulu (>3 g/cm2) Sofia (< 5 g/cm2) Sofia underestimate Conservative validity range (models agree with each other and with observations): > 5 g/cm 2 (< 7 km) Acceptable validity range : Bern model: the whole range (some questions for polar regions around solar minima) Oulu model: > 3 g/cm 2 (< 1 km) for all conditions Sofia model: < 1 g/cm 2 (> 16 km) (questions for equatorial regions) < 15 g/cm 2 (>12 km) for solar maximum

g/cm2) Sofia underestimate Conservative validity range (models agree with each other and with observations): > 5 g/cm 2 (< 7 km) Acceptable

9 Questions and solutions Questions Oulu model: The program starts only after the first interaction neglect direct ionization (thin target) This leads to underestimate ionization at high altitude (< 3 g/cm 2 ) and underestimate of the Φ-dependence; Bern model: Does the model account for CR (>1 GeV)? can be essential contribution; Indirect account for α-particles (by a constant factor of 1.31) This may lead to overestimate of the Φ-dependence and underestimate of the flux at the equator. Sofia model: Contribution of CR (>1 GeV); heavier species. Recommendations: Oulu: ionization during the first nuclear path length; Bern: Direct account for α-paticles and increase the max energy. Sofia: Increase the energy range and account for heavier species

can be essential contribution; Indirect account for α-particles (by a constant factor of 1.

10 α-particles Flux (GeV/nucleon m 2 sr s) AMS, June E (Gev/nucleon).2.15 AMS, June, CAPRICE, August E (Gev/nucleon) CAPRICE, August 1994 He/p Ratio E (GeV/nucleon) E (GeV/nucleon)

1 1 1 1 E (Gev/nucleon) CAPRICE, August 1994 He/p Ratio.1.1.5.

Establishing and Using the real-time Neutron Monitor Database (NMDB)

**FULL TITLE** ASP Conference Series, Vol. **VOLUME**, **YEAR OF PUBLICATION** **NAMES OF EDITORS** Establishing and Using the real-time Neutron Monitor Database (NMDB) H. Mavromichalaki, A. Papaioannou,