Research Topics
Introduction
- Figure 1: Victor Hess and his balloon
Cosmic ray research began in 1912 when Victor Hess measured the intensity of the ionizing radiation with an electroscope in a balloon to an altitude of about 5000 m. He discovered evidence of a very penetrating radiation (cosmic rays) coming from outside our atmosphere.
At energies below a few GeV the influence of solar modulation on the galactic cosmic ray energy spectra becomes important. Measurements by particle detectors showed that their intensity varies on different time scales. The short term variations observed at Earth are mostly correlated with disturbances originating at the Sun e.g. Coronal Mass Ejections Cane (2000) and interaction of solar wind streams with different speeds forming Corotating Interaction Regions beyond the Earth's orbit Richardson (2004). On longer time scales the cosmic ray flux is varying in anti-correlation with the 11-year and 22-year solar activity cycle. Therefore galactic cosmic rays entering the regions close to the Sun are modulated as they traverse the region controlled by the Sun, called the heliosphere.
Problems, wich can be addressed by cosmic rays at high latitudes Of the many interesting problems waiting to be solved within the heliospheric physics, only those concerned with propagation and modulation of cosmic rays at high latitudes are selected here. The main question to pose, is: How do energetic charged particles propagate through the three-dimensional heliosphere and how does propagation vary with the solar cycle? Problems related to this main question are:
- Source spectra: Can we determine the local interstellar particle spectra from high latitude observations?
What can we learn from in-situ particle observations about the source spectra of anomalous cosmic rays? - The propagation parameter: What does the spatial diffusion tensor look like? What is the importance of global drifts?
- The solar cycle dependence: What can we learn from high latitude observations about the solar cycle dependence of the above parameters?
