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Long-Term Variability of the Polytropic Index of Solar Wind Protons at 1 AU
- Source :
- Solar Physics. 289:1371-1378
- Publication Year :
- 2013
- Publisher :
- Springer Science and Business Media LLC, 2013.
-
Abstract
- Spacecraft data from the OMNI database were used to calculate the value of the polytropic index of the solar wind by fitting the logarithms of proton density and temperature in selected time intervals from 1 January 1995 to 30 June 2012. Bernoulli’s integral and the correlation coefficient were used to filter the results. An alternative method based on the maximization of the correlation coefficient was employed to confirm our results. The long-term behavior of the polytropic index we obtained is found to be virtually identical for both methods. We noticed a characteristic behavior of the estimated polytropic index values, particularly from 1995 to 2006, which tends to have a periodicity of about one year. The distribution of the polytropic index is best described by a κ-Gaussian distribution with mean ≈ 1.8 and standard deviation ≈ 2.4. We finally examined the possible correlation between the polytropic index values and solar activity.
- Subjects :
- Physics
Logarithm
Correlation coefficient
Mathematical analysis
Astronomy and Astrophysics
Polytropic process
Standard deviation
Solar cycle
Bernoulli's principle
Solar wind
Distribution (mathematics)
Classical mechanics
Space and Planetary Science
Astrophysics::Solar and Stellar Astrophysics
Astrophysics::Earth and Planetary Astrophysics
Subjects
Details
- ISSN :
- 1573093X and 00380938
- Volume :
- 289
- Database :
- OpenAIRE
- Journal :
- Solar Physics
- Accession number :
- edsair.doi...........4406b3d59b51eba7270d0d0fda6a4631