Corotating Interaction Regions at High Latitudes
Authors: Kunow H.1; Lee M.A.2; Fisk L.A.3; Forsyth R.J.4; Heber B.5; Horbury T.S.6; Keppler E.5; Kóta J.7; Lou Y.-Q.8; McKibben R.B.9; Paizis C.8; Potgieter M.S.10; Roelof E.C.11; Sanderson T.R.12; Simnett G.M.13; Von Steiger R.14; Tsurutani B.T.15; Wimmer-Schweingruber R.F.16; Jokipii J.R.7
Source: Space Science Reviews, Volume 89, Number 1-2, 1999 , pp. 221-268(48)
Ulysses observed a stable strong CIR from early 1992 through 1994 during its first journey into the southern hemisphere. After the rapid latitude scan in early 1995, Ulysses observed a weaker CIR from early 1996 to mid-1997 in the northern hemisphere as it traveled back to the ecliptic at the orbit of Jupiter. These two CIRs are the observational basis of the investigation into the latitudinal structure of CIRs. The first CIR was caused by an extension of the northern coronal hole into the southern hemisphere during declining solar activity, whereas the second CIR near solar minimum activity was caused by small warps in the streamer belt. The latitudinal structure is described through the presentation of three 26-day periods during the southern CIR. The first at 24°S shows the full plasma interaction region including fast and slow wind streams, the compressed shocked flows with embedded stream interface and heliospheric current sheet (HCS), and the forward and reverse shocks with associated accelerated ions and electrons. The second at 40°S exhibits only the reverse shock, accelerated particles, and the 26-day modulation of cosmic rays. The third at 60°S shows only the accelerated particles and modulated cosmic rays. The possible mechanisms for the access of the accelerated particles and the CIR-modulated cosmic rays to high latitudes above the plasma interaction region are presented. They include direct magnetic field connection across latitude due to stochastic field line weaving or to systematic weaving caused by solar differential rotation combined with non-radial expansion of the fast wind. Another possible mechanism is particle diffusion across the average magnetic field, which includes stochastic field line weaving. A constraint on connection to a distant portion of the CIR is energy loss in the solar wind, which is substantial for the relatively slow-moving accelerated ions. Finally, the weaker northern CIR is compared with the southern CIR. It is weak because the inclination of the streamer belt and HCS decreased as Ulysses traveled to lower latitudes so that the spacecraft remained at about the maximum latitudinal extent of the HCS.
Document Type: Regular paper
Affiliations: 1: Extraterrestrische Physik, Universität Kiel, Kiel, Germany 10: Potchefstroom University for CHE, Potchefstroom, South Africa 11: Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland, USA 12: Space Science Dept., ESA/ESTEC, Noordwijk, The Netherlands 13: Physics and Astronomy Dept., University of Birmingham, Birmingham, United Kingdom 14: International Space Science Institute, Bern, Switzerland 15: Jet Propulsion Laboratory, Pasadena, California, USA 16: Physikalisches Institut der Universität Bern, Bern, Switzerland 2: Space Science Center, University of New Hampshire, Durham, New Hampshire, USA 3: Dept. of Atmospheric and Space Sciences, University of Michigan, Ann Arbor, Michigan, USA 4: The Blackett Laboratory, Imperial College, London, United Kingdom 5: Max-Planck-Institut für Aeronomie, Katlenburg-Lindau, Germany 6: The Blackett Laboratory, Imperial College, London, United Kingdom; Queen Mary and Westfield College, London, United Kingdom 7: Depts. of Planetary Sciences and Astronomy, University of Arizona, Tucson, Arizona, USA 8: Dipartimento di Fisica, Università di Milano, Milano, Italy 9: Enrico Fermi Institute, University of Chicago, Chicago, Illinois, USA
Publication date: 1999-01-01
- In this: publication
- By this: publisher
- In this Subject: Transportation , Astronomy
- By this author: Kunow H. ; Lee M.A. ; Fisk L.A. ; Forsyth R.J. ; Heber B. ; Horbury T.S. ; Keppler E. ; Kóta J. ; Lou Y.-Q. ; McKibben R.B. ; Paizis C. ; Potgieter M.S. ; Roelof E.C. ; Sanderson T.R. ; Simnett G.M. ; Von Steiger R. ; Tsurutani B.T. ; Wimmer-Schweingruber R.F. ; Jokipii J.R.