Amplitude evolution and rigidity dependence of the 26-day recurrent cosmic ray decreases: COSPIN/KET results
Abstract
In the time interval extending from July 1992 to July 1994, Ulysses climbed from 10°S heliographic latitude up to over 70°S. During this time lapse, solar minimum conditions were gradually approached, which, in turn, led to stable and long-lasting corotating interaction regions (CIRs). The corotating particle events observed during this period, associated with ~30 registered CIRs, offer a unique opportunity to probe the three-dimensional structures of the heliosphere. In this work we use data from the Cosmic Ray and Solar Particle Investigation Kiel Electron Telescope (COSPIN/KET) instrument on board Ulysses to study the amplitude evolution of the 26-day recurrent cosmic ray decreases, generated by these CIRs, at different energies and derive its rigidity dependence. We find that the amplitude has a maximum around 25°-30° heliolatitude. We also find that the rigidity dependence of both the latitudinal gradient as well as the 26-day variation amplitude show a remarkable similarity. We discuss these observations within the framework of our current understanding of heliospheric phenomena.
- Publication:
-
Journal of Geophysical Research
- Pub Date:
- 1999
- DOI:
- 10.1029/1999JA900370
- Bibcode:
- 1999JGR...10428241P
- Keywords:
-
- Interplanetary Physics: Corotating streams;
- Interplanetary Physics: Cosmic rays;
- Interplanetary Physics: Energetic particles;
- heliospheric