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Corotating Interaction Regions at High Latitudes
Simnett, G. M.; Tsurutani, B. T.; Horbury, T. S. +16 more
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 …
UVCS/SOHO Observations of Spectral Line Profiles in Polar Coronal Holes
Cranmer, S. R.; Modigliani, A.; Ciaravella, A. +6 more
Ultraviolet emission line profiles have been measured on 15-29 September 1997 for H I 1216 Å, O VI 1032, 1037 Å and Mg X 625 Å in a polar coronal hole, at heliographic heights ϱ (in solar radii) between 1.34 and 2.0. Observations of H I 1216 Å and the O VI doublet from January 1997 for ϱ = 1.5 to 3.0 are provided for comparison. Mg X 625 Å is obse…
Modulation of Galactic Cosmic Rays at Solar Minimum
Heber, B.; Burger, R. A.
Cosmic ray particles respond to the heliospheric magnetic field in the expanding solar wind and its turbulence and therefore provide a unique probe for conditions in the changing heliosphere. During the last four years, concentrated around the solar minimum period of solar cycle 22, the exploration of the solar polar regions by the joint ESA/NASA …
Spectroscopic Constraints on Models of Ion-cyclotron Resonance Heating in the Polar Solar Corona
Cranmer, S. R.; Kohl, J. L.; Field, G. B.
Using empirical velocity distributions derived from UVCS and SUMER ultraviolet spectroscopy, we construct theoretical models of anisotropic ion temperatures in the polar solar corona. The primary energy deposition mechanism we investigate is the dissipation of high frequency (10-10000 Hz) ion-cyclotron resonant Alfvén waves which can heat and acce…
Ion Temperatures as Observed in a Solar Coronal Hole
Wilhelm, K.; Tu, C. -Y.; Marsch, E.
From the widths of the extreme ultraviolet (EUV) lines measured by the SUMER instrument on SOHO, it was found previously (Tu et al. 1998) that the average temperature of Ne+7, at heights (relative to h0) above the southern solar limb from 17″ to 64″, ranges between 1.3 and 5 × 106 K and of Ne+6 between 1…
Origin, Injection, and Acceleration of CIR Particles: Theory Report of Working Group 7
Simnett, G. M.; Mann, G.; Keppler, E. +10 more
On the basis of the observational picture established in the report of Mason, von Steiger et al. (1999) the status of theoretical models on origin, injection, and acceleration of particles associated with Corotating Interaction Regions (CIRs) is reviewed. This includes diffusive or first-order Fermi acceleration at oblique shocks, adiabatic decele…
Statistical Analysis of EUV and UV Lines Inside and Outside of Solar Coronal Holes
Wilhelm, K.; Curdt, W.; Dammasch, I. E. +1 more
Two studies performed with SUMER (the Solar Ultraviolet Measurements of Emitted Radiation spectrometer on SOHO) in September 1996 are presented. Spatial scans, a long exposure time and a broad spectral window provide reliable line profiles for various regions of the Sun (off-limb corona, coronal hole, quiet Sun, bright and dark regions on disk) an…
Plasma Properties in Coronal Funnels
Mann, G.; Marsch, E.; Hackenberg, P.
A two dimensional model of the transition region and the lower corona, based on the idea that the magnetic flux is strongly concentrated at the boundaries of the supergranular convection cells, has been proposed by Gabriel in 1976. The plasma moves along the open magnetic field lines, which define the the so-called "funnel," and eventually builds …
UVCS/SOHO Observations of H I Lyman Alpha Line Profiles in Coronal Holes at Heliocentric Heights Above 3.0 R⊙
Cranmer, S. R.; Ciaravella, A.; Noci, G. +7 more
The Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO) has been used to measure spectral line profiles for H I Lyα in the south polar coronal hole at projected heliocentric heights from 3.5 to 6.0 R⊙ during 1998 January 5 11. Observations from 1.5 to 2.5 R⊙ were made for comparison. T…
UVCS/SOHO Ion Kinetics in Coronal Streamers
Raymond, J. C.; Modigliani, A.; Ciaravella, A. +9 more
We made streamer observations with the Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospheric Observatory (SOHO) during the early part of 1998, which was a time of moderate solar activity. We present an empirical study of coronal ion kinetics using the line profiles from these observations. Our first and most striking result is …