3-d evolution of solar wind streams and suprathermal particles
Zusammenfassung der Projektergebnisse
The aim of the proposal was to determine the 3-d evolution of solar wind streams and to investigate suprathermal particles. Early on in the work, it turned out that the key sensor for this work does not function as well as previously believed. It is very hard to extract solar wind composition data from PLASTIC, which meant that we could not use composition data at the positions of the two STEREO spacecraft as we had planned to use to identify streams of different origins. Nevertheless, we have PLASTIC data as well as possible to tackle the topics of the proposal, although the late start of the work (August 2008 as opposed to January 2008) meant that substantial work was already being done by our US partners. Thus we contributed to the studies which we had planned to lead and contributed to the corresponding publications. The late start of the project and the suboptimal resolution of PLATIC meant that we had to focus more on the second topic in the title, namely suprathermal particles and velocity distribution functions. This topic and the related microphysics of the solar wind plasma was receiving enhanced attention in the field as a consequence of new observations by Kasper et al. [2008] and other workers. We successfully investigated differences in the streaming velocities of heavy ions and protons in the solar wind, a key microsopic signature of the two (slow and fast) solar wind types. These studies were performed with the SWICS instrument on ACE which has a much better species resolution than PLASTIC, but a lower time resolution (due to lower counting statistics). We managed to extract only the iron velocity distribution functions from PLASTIC, but were much more successful with the SWICS data. We used the observations of Kasper et al. [2008] that the alpha particles in the solar wind stream parallel or anti-parallel along the magnetic field vector in the proton frame of reference. Together with the knowledge of the magneitc field direction, this allowed us to determine the three-dimensional velocity distribution functions of heavy ions and to determine the streaming velocity of those ions relative to protons in a highly systematic manner. Because SWICS resolves many different elements and their charge states, we were able to constrain a possible m/q-dependence of the differential streaming, vi − vp , for a much larger range in m/q than previously possible. While our work with PLASTIC did not lead to the expected results, it did pave the way for the investigations of suprathermal interstellar pickup ions. These singlycharged ions are resolved with PLASTIC due to their large m/q ratios. The high count rate achieved by PLASTC allowed us to report the first discovery of the focusing cone of interstellar Ne.
Projektbezogene Publikationen (Auswahl)
- Heber, and H. Fichtner, Open Issues in Heliospheric Physics, Earth Moon and Planets, 104, 3–9, 2009
Wimmer-Schweingruber, R. F., B
(Siehe online unter https://doi.org/10.1007/s11038-008-9266-7) - 3D velocity distribution functions of heavy ions and kinetic properties of O6+ at 1 AU, Twelfth International Solar Wind Conference, 1216, 253–256
Berger, L., R. F. Wimmer-Schweingruber, and G. Gloeckler
(Siehe online unter https://doi.org/10.1063/1.3395849) - Inner-Source Pickup Ions as Sensitive Probes to the Inner-Heliospheric Micro-State, Twelfth International Solar Wind Conference, 1216, 506–509, 2010
Wimmer-Schweingruber, R. F., and P. Bochsler
(Siehe online unter https://doi.org/10.1063/1.3395913) - Kinetic temperatures of iron ions in the solar wind observed with STEREO/PLASTIC, Twelfth International Solar Wind Conference, 1216, 257–260, 2010
Bochsler, P., et al.,
(Siehe online unter https://doi.org/10.1063/1.3395850) - Observations of interstellar neon in the helium focusing cone, Journal of Geophysical Research (Space Physics), 115 (A 14), 10,108
Drews, C., L. Berger, R. F. Wimmer-Schweingruber, A. B. Galvin, B. Klecker, and E. M¨bius,
(Siehe online unter https://doi.org/10.1029/2010JA015585) - Systematic Measurements of Ion-Proton Differential Streaming in the Solar Wind, Physical Review Letters, 106 (15), 151,103
Berger, L., R. F. Wimmer-Schweingruber, and G. Gloeckler
(Siehe online unter https://doi.org/10.1103/PhysRevLett.106.151103)
