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- Title
The 27-Day Cosmic Ray Intensity Variations During Solar Minimum 23/24.
- Authors
Modzelewska, R.; Alania, M.
- Abstract
We have studied the 27-day variations and their harmonics in Galactic cosmic ray (GCR) intensity, solar wind velocity, and interplanetary magnetic field (IMF) components during the recent prolonged solar minimum 23/24. The time evolution of the quasi-periodicity in these parameters connected with the Sun's rotation reveals that the synodic period of these variations is ≈ 26 - 27 days and is stable. This means that the changes in the solar wind speed and the IMF are related to the Sun's near-equatorial regions in considering the differential rotation of the Sun. However, the solar wind parameters observed near the Earth's orbit provide only the conditions in the limited local vicinity of the equatorial region in the heliosphere (within ± 7 in latitude). We also demonstrate that the observed period of the GCR intensity connected with the Sun's rotation increased up to ≈ 33 - 36 days in 2009. This means that the process that drives the 27-day GCR intensity variations takes place not only in the limited local surroundings of the equatorial region but in the global 3-D space of the heliosphere, covering also higher latitude regions. A relatively long period (≈ 34 days) found for 2009 in the GCR intensity gives possible evidence of the onset of cycle 24 due to active regions at higher latitudes and rotating slowly because of the Sun's differential rotation. We also discuss the effect of differential rotation on the theoretical model of the 27-day GCR intensity variations.
- Subjects
GALAXIES; GALACTIC cosmic rays; INTERPLANETARY magnetic fields; SOLAR wind; HELIOSPHERE; EARTH (Planet); ROTATION of the Sun; EARTH'S orbit; SUN
- Publication
Solar Physics, 2013, Vol 286, Issue 2, p593
- ISSN
0038-0938
- Publication type
Article
- DOI
10.1007/s11207-013-0261-4