We report a study of the long-term temporal and spatial dependence of the low energy (0.5 - 5 MeV/nucl) heavy ion (C, O, Fe) composition in the inner heliosphere (1.5 to 5.2 AU) from data acquired by the Wart detector in the HISCALE instrument on the Ulysses spacecraft. During the interval from 1992 to the present Ulysses has made two complete six-year orbits over the solar poles to latitudes as high as 80 deg. north and south during both solar minimum and solar maximum conditions. The heavy ion composition provides data on the solar event-produced filling of the inner heliosphere during solar active conditions as well as the abundance of low energy (order 0.5 MeV/nucl) anomalous O during solar minimum in the declining phase of solar cycle 23. The low energy anomalous O (the lowest energy anomalous O measured by any spacecraft to date) during the minimum of cycle 23 is dramatically apparent in the displays of data by time and by composition ratio. The anomalous O spectrum is basically flat over the decade energy range 0.5 to 5 MeV/nucl. The Ulysses C, O, and Fe measurements--both flux levels and composition ratios--are compared to similar measurements from the HISCALE back-up instrument (EPAM) on the ACE spacecraft at 1 AU that began after ACE launch in August 1997.

We present a multi-spacecraft analysis of the energetic particle observations during the October-November 2003 "superstorms" period. We use energetic particle measurements from the following instruments: (1) the Low-Energy Magnetospheric Measurement System (LEMMS) on board the Cassini spacecraft, (2) the Heliosphere Instrument for Spectra, Composition and Anisotropy at Low Energies (HISCALE) and the Cosmic Ray and Solar Particle Investigation (COSPIN) telescopes on board Ulysses, (3) the Electron, Proton and Alpha Monitor (EPAM) on board ACE, and (4) the Energetic Particle Sensor (EPS) on board the GOES spacecraft. We combine energetic particle data with solar wind and magnetic field observations from the magnetometers and plasma instruments on board the respective spacecraft. The Cassini spacecraft was en route to Saturn, close to the ecliptic plane, at 8.7 AU from the Sun and less than 70 degrees west in longitude with respect to the Sun-Earth line. The Ulysses spacecraft was at 5.2 AU from the Sun, very close to the ecliptic plane, and 54 degrees to the west with respect to the Sun-Cassini line. Prior to the occurrence of these series of events, the structure of the inner heliosphere was well-organized by recurrent corotating high-speed streams. The intense solar events of October-November 2003 disturbed this stable structure, filling the inner heliosphere with energetic particles and sending a sequence of fast CMEs past the three spacecraft. In this paper we characterize the particle intensity enhancements seen at the three spacecraft and associate them with the solar wind disturbances traveling between the Sun and the spacecraft.

Using measurements of energetic electrons (>38 keV) by the EPAM experiment on the ACE spacecraft, we examine the dependence of the characteristic decay time scales of solar electron events on the large-scale structure of the Interplanetary Magnetic Field (IMF) and the resulting implications for particle containment and the formation of particle reservoirs in the heliosphere. The technique of mapping the solar wind and extrapolating the frozen-in magnetic field is used to obtain the large-scale IMF structure within and beyond the location of the spacecraft. Colliding slow and fast solar wind streams originating at different locations in the solar corona give rise to extended regions with compressed magnetic field which can serve as reflecting magnetic mirrors along the path of the injected energetic electrons. From the study of a number of events we find that electron events observed within a converging IMF structure exhibit a remarkably longer decay phase compared to electron events that propagate inside diverging configurations of the IMF. Our results provide strong evidence for the physical mechanisms that determine the establishment and maintenance of particle reservoirs in the heliosphere based upon the inferred locations of magnetic "barriers" in space beyond 1 AU. We use these understandings to interpret measurements of electron and heavy ion reservoirs that are observed simultaneously in the ecliptic by EPAM and out of the ecliptic, at high heliolatitudes, by the HISCALE instrument on the ULYSSES spacecraft.

Zhang et al. [Astrophys. J., 595, 493-499, 2003; J. Geophys. Res., 108, A4, 1154, SSH 4-1, 4-13, 2003] report strong anisotropies of 40-90 MeV protons transverse to the local magnetic field in two solar energetic particle events (2000:196 and 2000:256) observed by Ulysses/COSPIN/HET. They interpret their results in the context of diffusive transport and consequently conclude these events constitute strong evidence for the existence of transverse diffusion in the heliosphere. We see three difficulties with this interpretation. 1) The magnetic field was unusually well ordered during the periods of transverse anisotropies. Theories of transverse diffusion require the presence of irregularities in the magnetic field. 2) Fourier analysis of the angular distribution reveals a second harmonic whose amplitude is comparable to that of the first harmonic. This is inconsistent with diffusive transport (Fick's law) that predicts a dominant first harmonic. 3) Only two such intervals have been identified in a search of the mission-long Ulysses COSPIN data set. The paucity of such intervals is inconsistent with this being a pervasive mode of transport. We have independently analyzed the COSPIN/HET channel H45 data and we confirm the data analysis of Zhang et al. for both events. However, we find that the data are much more consistent with a quantitative interpretation in terms of weak scattering with an evolving field-aligned streaming and a bi-directional anisotropy component in the presence of a gradient anisotropy. The scale of the gradient extracted from the pitch-angle distributions is comparable to that of the flux-rope-like magnetic structures in which it occurs. The above-mentioned three points are thus explained as follows. 1) Weak-scattering is expected in regions of quiet fields. 2) The pitch-angle distribution in both events eventually becomes predominantly bi-directional, indicating a mirroring within the structure. Consequently the significant second harmonic is immediately explained. 3) The conditions for observing a strong gradient anisotropy at these energies is restricted to a special class of structures, and hence should be a relatively rare occurrence.

The structure of the inner heliosphere that was delineated by the energetic charged particle populations (electrons and ions) during the recent Ulysses fast latitude scan during solar maximum conditions is found to be very different from that measured during a similar latitudinal transit in solar minimum conditions. Measurements made by the Heliosphere Instrument for Spectra, Composition and Anisotropy at Low Energies (HISCALE; electrons ~50-1000 keV and ions ~50 keV-10000 keV/nucl) during solar maximum show that the inner heliosphere was populated at all latitudes, and with varying spatial scales, by particles largely originating from active solar regions. During solar minimum the major particle populations were confined to the near equatorial solar current sheet. The relative energetic ion (Z>2) abundances throughout the inner heliosphere were also substantially different, a result of the dominance in the inner heliosphere of solar-produced particles during solar maximum and the dominance of anomalous cosmic ray ions (especially O) and interplanetary accelerated particles during solar minimum. The H/He abundance ratios are nearly a factor of ten larger during solar maximum conditions at all heliolatitudes, showing the importance of a dominant solar source during this epoch. The ratios of the HISCALE ion abundances in the fast latitude scan during solar maximum are compared to measurements of ions made during the same time interval with a similar instrument (EPAM) on the ACE spacecraft in the ecliptic plane near 1 AU and show significant variations with time and spatial location. However, there are several intervals of time following solar maximum activity, including at latitudes as high as 80 degrees, during which the ion abundances and the electron fluxes at both locations are nearly identical. These intervals demonstrate that at times particle reservoirs (which are found to persist for nearly a solar rotation), can be established in the inner heliosphere and have volumes ranging from ~40 to ~150 AU3.

We present the results of the analysis of the heliographic latitude variation of the background counting rates (MFSA channels) in the HISCALE instrument on board the Ulysses spacecraft during the first Ulysses fast latitude scan (day 257 of 1994 to day 212 of 1995). The background rates are found to decrease between the heliographic latitudes of 20-60 degrees on both sides of the heliospheric equator, and to increase at heliolatitudes between 0 and +/-20 degrees to values approximately as measured over the solar poles, >60 degrees. The modulation of 0.3-2.1 GeV protons and helium is seen clearly by the COSPIN:KET detector at heliographic latitudes <60 degrees, but these ion rates remain low during Ulysses' passage through perihelion. We conclude that the systematic decrease in the background at heliographic latitudes <60 degrees is likely the result of the modulation of relativistic galactic electrons and ions, and that the recovery of the background rates during the Ulysses ecliptic crossing is due to relativistic electrons, probably of Jovian origin. The result of this analysis may also be used to better understand the propagation of electrons perpendicular to the ecliptic.

We compare estimates of the power spectrum from three sections of Ulysses data: 20-40 deg. S, (Nov. 1992- Sept 1993, Orbit 1), 40-20 deg. N, (March - Dec, 1996, Orbit 1), and 20-40 deg. S, (Jan.- Dec. 1999, Orbit 2). In all cases multitaper spectrum estimates are computed from logarithms of low-energy ( ~50 - 200 keV) electron fluxes from three independent channels of the HISCALE instrument. In addition, three overlapping data sections with 8 Slepian sequences on each section are used, so that the average spectra used in the comparisons have over 100 degrees-of-freedom each. The spectra from solar minimum in 1996 have the lowest power over a wide range of frequencies. The power spectra estimated from the 1993 data during the declining phase of the solar cycle, when co-rotating interaction regions were ubiquitous, is somewhat higher than that from the 1999 data during the increase to solar maximum. (Both are from 20 to 40 deg. South). As solar activity, as measured by sunspot numbers, was lower, 54.6, in 1993 than in 1993, 93.3, this provides yet another example where the falling edge of a solar cycle is more variable than the rising edge. Many of the peaks in the spectra of the three time series appear as common features in all spectra. Further, the spectra contain peaks at the frequencies reported in TML 95. Detailed comparisons of the frequencies of the peaks in the different spectra suggest that the frequencies may be slightly dependent on solar activity.

The Ulysses spacecraft has nearly completed two full polar orbits around the Sun. We can now examine the variations of energetic electron and ion spectra as functions of heliolatitude, radial distance, and phase of the solar activity cycle. The key instrumental capability is that of the MF Spectrum analyzer (MFSA) of the Heliosphere Instrument for Spectral, Composition, and Anisotropy at Low Energies (HISCALE). Reporting on this for the first time, we show 25-point energy spectra for protons and Z > 1 particles, and 12-point energy spectra for electrons. We have also determined the separately time-varying contributions to the instrumental background from the omni-directional penetrating galactic cosmic rays and from the gamma rays emanating from the spacecraft radioisotope thermoelectric generators. All four of the HISCALE detector heads are used to form a complete set of electron and ion spectra in the solar wind frame in four or eight spin sectors and at four angles to the spacecraft spin axis. Using these spectra, we present the large-scale variations in the energetic particle spectra as functions of latitude, radial distance, and time for both impulsive flare events and recurring co-rotating events (CIRs). The variation of the MFSA observed background rates as Ulysses passed through the streamer belt at ~1 AU as an indication of strong GCR modulation is a secondary result that we will present.

The rise to maximum of the 23rd solar cycle finds the Ulysses (ULS) spacecraft on its trajectory to the south pole of the sun while the ACE spacecraft continues to monitor the interplanetary medium sunward of Earth. Low energy interplanetary ions (~0.5 to ~8 MeV/nucl) are measured by the composition aperture telescope in each of the twin instruments HISCALE and EPAM on ULS and ACE, respectively. For ULS within ~30 deg. of the heliosphere equator, we found that the statistical distributions of the relative abundances of the ions at the two locations were similar (Maclennan et al., Proc. ACE 2000, in press). We also found that, on a statistical basis, the ion flux times the radial distance at ULS is proportional to the flux as measured at ACE. These results were interpreted in terms of a large parallel diffusion coefficient in the heliosphere inside ~5 AU. Here, we report on an extension of this study to higher heliographic latitudes as the solar cycle increases in intensity and as ULS approaches the southern solar pole. We remark on implications for the mechanisms for ion propagation to high heliolatitudes during more disturbed interplanetary conditions.

Voyager data in the outer heliosphere is not continuous because of the absence of continuous coverage by the Deep Space Net (DSN). Hence the data are characterized by substantial (order eight hour) data gaps each day. We have been investigating different analysis techniques on the time series of Voyager magnetic field data (magnitude) in the outer heliosphere using several modern statistical techniques. The purpose is to investigate possible long period (many day) variations in the data series. These studies include investigations of possible procedures for data gap-filling, of power spectral techniques with various data tapers (windows), and of statistical tests for robustness of any results. We report here an overview of the analysis procedures and some present conclusions. In addition, we report some comparisons with time series analysis of interplanetary particle and magnetic field data from the Ulysses spacecraft in the inner heliosphere where the data coverage is close to 100%.