摘要

Direct measurements of cosmic-ray electrons and positrons were first made in the early 1960s and since then a number of instruments were built to study this component of the cosmic radiation. The precise measurement of the intensities of cosmic-ray electrons and positrons are key to our understanding of origin and propagation of cosmic rays. In addition the locally observed abundance of cosmic ray electrons and/or positrons may exhibit interesting spectral features. Observations confirm the almost exclusive secondary nature of positrons up to a few GeV, yet as early as 1995, measurements by the HEAT instrument suggested a possible primary positron component. The FERMI satellite and ground based Cherenkov telescopes have provided new electron measurements and recent reports by the PAMELA team of a continued rise in the cosmic-ray positron fraction above about 10 GeV have stirred excitement beyond the cosmic ray community. This has resulted in a flurry of publications discussing these observations either as a possible dark matter signature or as a contribution from isolated astrophysical sources. This presentation will give a critical assessment of cosmic ray electron and positron measurements and discuss upcoming observations that will extend the cosmic-ray electron observations into the 10 TeV region where local sources may dominate the spectrum.

报告人简介

Dr. Schubnell received his PhD in 1990 from the University of Wuppertal in Germany. He is currently a research scientist in the Physics Department at the University of Michigan. Most of his research has been in the general area of experimental astrophysics and has involved balloon-borne, spacecraft, and ground-based detector systems investigating galactic and extragalactic radiation and particles. One of his research interests is the measurement of cosmic ray electrons and positrons to study origin of cosmic radiation and possible primary contributions to the observed flux due to dark matter or isolated pulsars. His research efforts also target the experimental investigation of dark energy and how it can best be characterized using existing ground-based facilities. He has been a member of the Joint Dark Energy Mission instrument team and is currently involved in the Dark Energy Survey.