Ulysses Observations of the Polar Solar Wind--the Outer Boundary Condition for the Interpretation of Coronal Data
Explore the source record for details and available documents.
polar corona Spartan 201 SOHO Yohkoh polar coronal↗
Engineering topics
Smith, E. J.
Publications and source records attributed to Smith, E. J..
(abstract) Ulysses Solar Wind Ion Temperatures: Radial, Latitudinal, and Dynamical Dependencies
Observations of the Ulysses SWOOPS plasma experiment are used to determine the dependencies of solar wind ion temperatures upon radial distance, speed, and other parameters, and to estimate solar wind heating. Comparisons with three dimensional temperature estimates determined from the ion spectra by a least squares fitting program will be provided (only small samples of data have been reduced with this program).
Ulysses solar wind ions magnetic field plasmas↗
Ulysses at high latitudes: An overview of recent results
After its fly-by of the planet Jupiter in February 1992, the Ulysses spacecraft is now in a highly inclined heliocentric orbit that will bring it above the south polar regions of the Sun in September 1994. The high-latitude phenomena observed to date have been strongly influenced by the near-minimum solar activity conditions encountered during this phase of the mission. In late April 1993, when Ulysses was at approximately 29 deg S heliographic latitude, the recurrent high speed solar wind stream that had been observed at the location of the spacecraft for 11 consecutive solar rotation underwent a dramatic change. The wind speed in the valleys between successive peaks increased in a single step from approximately 420 km/s to aopproximately 560 km/s. This change in solar wind flow was accompanied by the disappearance at the spacecraft of the magnetic sector structure that had been observed until then. Both these finding are consistent with Ulysses having climbed beyond the latitude of the coronal streamer belt in which is embedded the heliospheric current sheet (HCS). In its subsequent poleward journey, no further evidence for an encounter with the HCS has been seen at Ulysses. Other phenomena observed include the evolution with latitude of corotating interaction region (CIRs) and their influence on the acceleration of energetic particles, and the characteristics of the solar wind flows emanating from the south polar coronal hole. In this paper, we present details of the above observations. Finally, while the polar passes of the prime mission will take place near solar minimum, an extended mission will bring Ulysses back over the poles near the maximum of the next cycle. A summary of scientific goals for Ulysses at solar maximum is given.
Marsden, R. G.↗
Hourly Variances of Fluctuations in the Heliospheric Magnetic Field out of the Ecliptic Plane
Magnetic field fluctuations at high heliographic latitudes are discussed in terms of the latitude and radial dependence of their variances, as observed by the Ulysses spacecraft.
Magnetic field fluctuations Ulysses heliographic l↗
Properties of Slow-Mode Shocks in the Distant (>200 R(sub e)) Geomagnetic Tail
Two distant ISEE-3 geomagnetic tail passes have been examined to identify all slow-mode shocks present in the data. We find a total of 86 events from 439 plasmasheet/lobe crossings, using five criteria based on relations between the upstream lobe and the downstream plasmasheet magnetic field and plasma measurements. The statistical results of slow-mode shock parameters such as the angle between magnetic field and shock normal, Theta(sub bn), Alfven Mach number along the normal direction, M(sub an), and electron beta, Beta(sub e), are calculated and reported.
magnothermodynamic theory MHD geomagnetic tails sl↗
Radial Component of the Magnetic Field: Ulysses
Explore the source record for details and available documents.
deficit↗
Ulysses OUt-of-ecleptic Observations of Interplanetary Shocks
Interplanetary shocks observed at the Ulysses spacecraft as it traveled from the ecliptic plane to the southern solar pole have been identified and analyzed using both magnetic field and plasma measurements.
Interplanetary shocks Ulysses magnetic field plasm↗
Solar Cycle Dependence of the Solar Wind Dynamics: Pioneer, Voyager, and Ulysses from 1 to 5 AU
Significant differences between Pioneer and Voyager observations were found in solar wind structure between 1 to 6 AU. These disagreements were attributed to temporal effects related to the solar cycle, but no unifying study of Pioneer-Voyager observations was performed.
solar wind interplanetary shocks interaction regio↗
Pasma Wave Characteristics of the Jovian Magnetopause Boundary Layer: Can Wave-Particle Interactions Cause the Jovian Aurora?
The full Jovian magnetopause boundary layer (BL) plasma wave spectra from 10(sup -3) to 10(sup 3) Hz, have been measured for the first time...The B'/E' ration does not have a f(sup -1) dependency, so it was suggested that the waves are a mixture of whistler mode electromagnetic emissions and electrostatic waves.
jovian magnetosphere Jupiter Jovian magnetopause E↗
Ulysses
Within the last two years, in 1994-95, a spacecraft called Ulysses transited the Sun's polar regions for the first time. This accomplishment is comparable to the reaching of the Earth's poles within this century which brought the exploration of the Earth's surface to its conclusion.
Ulysses Sun solar polar regions↗
The Three-Dimensional Nature of Interaction Regions: Pioneer, Voyager, and Ulysses fro 1 to 5 AU: Solar Cycle Variations
We investigated diverse aspects of the interaction regions detected by four spacecraft that travelled from Earth to Jupiter at different phases of the solar cycle: Pioneer 11 (declining phase of cycle 20); voyagers 1 and 2 (ascending phase of cycle 21); and Ulysses (just after solar maximum 22). From the analysis of 38 stream interfaces we found that the interaction regions detected by the three missions have different geometries.
stream interfaces solar winds solar wind streams↗
The Sources of Bz Fluctuations within CIRs: Magnetic Storms During the Descending Phase of the Solar Cycle
This presentation examines the magnetic field fluctuations within Corotating Interaction Regions (CIRs) detected by Ulysses at mid- and low-latitudes. CIRs are formed by the interaction of high-speed streams flowing from the polar coronal hole with slow-speed streams. Several wave modes are identified, and the effectiveness of these waves causing magnetic storms at Earth will be discussed.
Space Physics Magnetic Storms Solar Cycles Sun↗
Ulyssis Observations of Differential Streaming Between Protons and Alphas at High Latitudes
Reported are observations from the Ulysses SWOOPS experiment which provided measurements of the differential streaming between protons and alphas as a function of heliocentric distance and latitude. The data reported are of observations for those periods when Ulysses sampled only the flows from the solar polar coronal holes. All of the high-latitude results differ from the outbound, in-ecliptic data.
Ulyssis SWOOPS sun solar corona geophysics↗
Magnetic Merging Locations Deduced from: Slow-Mode Shock Orientation Determinations, Boundary Layer Wave Intensities and Energetic Ion Velocity Dispersion in the Distant Geomagnetic Tail
Several techniques will be used to determine the location of the magnetic reconnection in the distant geomagnetic tail using the ISEE-3. Techniques to be used are calculated wave-particle scattering time, plasmoid source location (if a plasmoid is found), analysis of the magnetic field geometry and slow-mode shock orientation, and examination of the magnetic field Bz components and plasma bulk speeds.
geomagnetic tail ISEE-3 magnetic fields↗
High Heliographic Latitude Tangential Discontinuities Ulysses Observations
Data from the Ulysses spacecraft was used for studying solar tangential discontinuities (TDs) at high latitudes. Significant numbers of TDs seem to exist at these latitudes.
tangential discontinuities Sun Ulysses↗
Variances of the components and magnitude of the polar heliospheric magnetic field
The heliolatitude dependences of the variances in the components and the magnitude of the heliospheric magnetic field have been analysed, using the Ulysses magnetic field observations from close to the ecliptic plane to 80 southern solar latitude. The normalized variances in the components of the field increased significantly (by a factor about 5) as Ulysses entered the purely polar flows from the southern coronal hole. At the same time, there was at most a small increase in the variance of the field magnitude. The analysis of the different components indicates that the power in the fluctuations is not isotropically distributed: most of the power is in the components of the field transverse to the radial direction. Examining the variances calculated over different time scales from minutes to hours shows that the anisotropy of the field variances is different on different scales, indicating the influence of the two distinct populations of fluctuations in the polar solar wind which have been previously identified. We discuss these results in terms of evolutionary, dynamic processes as a function of heliocentric distance and as a function of the large scale geometry of the magnetic field associated with the polar coronal hole.
Balogh, A.↗
On the origin of 1/f spectrum of magnetic fluctuations in the solar wind
Spacecraft measurements show that the spectrum of magnetic fluctuations in the solar wind can be divided into low- and high frequency parts. The low and high frequency parts are approximately self-similar (follow a power-law) but with different spectral exponents. (There is, in addition, a very low frequency range in which the spectrum is dominated by structures coming directly from the Sun and it is not self-similar.) For the wind coming from the south polar hole the boundary between the low- and high frequency parts is at about 1 hour near 1 AU. The observed exponent of the low-frequency part is approximately -1 . The high frequency spectrum is steeper with an exponent of about -5/3 . The high frequency spectrum is commonly believed to be the result of non-linear interactions of magnetic and velocity perturbations which lead to a turbulent cascade. However, for the low frequency fluctuations, the site of origin (on the Sun, in the solar corona or in the solar wind?) and mechanism of generation remain basically unknown. In this paper we consider the origin of the 1/f spectrum. The analysis of Ulysses data is compared with analysis of Helios data and the results are used to confront possible models of origin of the spectrum.
Ruzmaikin, A.↗
The underlying magnetic field direction in Ulysses observations of the southern polar heliosphere
Between May 1993 and January 1995, the Ulysses spacecraft has probed the southern polar heliosphere at latitudes greater than 30 deg S, reaching a maximum latitude of 80.2 deg S in September 1994. Using hourly averages of the data obtained by the magnetometer experiment on Ulysses we have studied the underlying direction of the magnetic field threading this region of the heliosphere, away from the influence of the magnetic sector structure which complicates similar analyses in the ecliptic plane. We have constructed histograms of the measured magnetic field direction using the simple Parker spiral model field direction as a reference. We find that throughout this region the meridional angle between the field vector and the Parker model direction has a distribution which is symmetric and has a most probable value consistent with the model. At latitudes below about 60 deg S the azimuthal angle distribution also has a most probable value consistent with the model but this distribution is highly asymmetric with a greater number of observations of field lines less tightly wound than the expected spiral direction. At latitudes greater than 60 deg S the most probable value of the azimuthal angle is found to have become nearly 30 more tightly wound than the expected direction, but due to the asymmetric distribution still with a greater number of observations less tightly wound than expected. We consider possible causes of both the asymmetry in the distributions and the shift in the most probable value at the highest latitudes, one of which may be the presence of large amplitude, long period Alfven waves in the magnetic field originating from the Sun's southern polar coronal hole.
Forsyth, R. J.↗