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Ulysses, launched in October 1990, began its second out-of-ecliptic orbit in December 1997, and its second fast latitude scan in September 2000. In contrast to the first fast latitude scan in 1994/1995, during the second fast latitude scan solar activity was close to maximum. The solar magnetic field reversed its polarity around July 2000. While the first latitude scan mainly gave a snapshot of the spatial distribution of galactic cosmic rays, the second one is dominated by temporal variations. Solar particle increases are observed at all heliographic latitudes, including events that produce >250 MeV protons and 50 MeV electrons. Using observations from the University of Chicago’s instrument on board IMP8 at Earth, we find that most solar particle events are observed at both high and low latitudes, indicating either acceleration of these particles over a broad latitude range or an efficient latitudinal transport. The latter is supported by "quiet time" variations in the MeV electron background, if interpreted as Jovian electrons. No latitudinal gradient was found for >106 MeV galactic cosmic ray protons, during the solar maximum fast latitude scan. The electron to proton ratio remains constant and has practically the same value as in the previous solar maximum. Both results indicate that drift is of minor importance. It was expected that, with the reversal of the solar magnetic field and in the declining phase of the solar cycle, this ratio should increase. This was, however, not observed, probably because the transition to the new magnetic cycle was not completely terminated within the heliosphere, as indicated by the Ulysses magnetic field and solar wind measurements. We argue that the new AKey words. Interplanetary physics (cosmic rays; energetic particles; interplanetary magnetic fields)

The Solar Electron and Proton Telescope (SEPT) aboard the Solar Terrestrial Relations Observatory (STEREO) is designed to provide the three-dimensional distribution of energetic electrons and protons with good energy and time resolution. Each SEPT instrument consists of two double-ended magnet–foil particle telescopes which cleanly separate and measure electrons in the energy range from 30 keV to 400 keV and protons from 60 keV to 7000 keV. Anisotropy information on a non-spinning spacecraft is provided by two separate but identical instruments: SEPT-E aligned along the Parker spiral magnetic field in the ecliptic plane looking both towards and away from the Sun, and SEPT-NS aligned vertical to the ecliptic plane looking towards North and South. The dual set-up refers to two adjacent sensor apertures for each of the four viewing directions SUN, ANTISUN, NORTH, and SOUTH: one for protons, one for electrons. In this contribution a simulation of SEPT utilizing the GEANT4 toolkit has been set up with an extended instrument model in order to calculate improved response functions of the four different telescopes. Here we applied these response functions to quiet-time periods during the minimum between Solar Cycles 23 and 24 (SC-23 and SC-24) when the flux of ions above 10 MeV is dominated by galactic cosmic rays (GCRs). The corresponding spectra are determined by a force-field approximation and used as input for our calculation, leading to good agreement of the computed ion count rates with measurements of SEPT above 400 keV.

Context. Interplanetary (IP) shocks are known to be accelerators of energetic charged particles observed in-situ in the heliosphere. However, the acceleration of near-relativistic electrons by shocks in the interplanetary medium is often questioned. On 9 August 2011 a corotating interaction region (CIR) passed STEREO B (STB), which resulted in a flux increase in the electron and ion channels of the Solar Electron and Proton Telescope (SEPT). Because electron measurements in the few keV to several 100 keV range rely on the so-called magnet foil technique, which is utilized by SEPT, ions can contribute to the electron channels. Aim. We aim to investigate whether the flux increase in the electron channels of SEPT during the CIR event on 9 August 2011 is caused by ion contamination only. Methods. We compute the SEPT response functions for protons and helium utilizing an updated GEANT4 model of SEPT. The CIR energetic particle ion spectra for protons and helium are assumed to follow a Band function in energy per nucleon with a constant helium to proton ratio. Results. Our analysis leads to a helium to proton ratio of 16.9% and a proton flux following a Band function with the parameters I0 = 1.24 × 104 (cm2 s sr MeV nuc−1)−1, Ec = 79 keV nuc−1, and spectral indices of γ1 = −0.94 and γ2 = −3.80, which are in good agreement with measurements by the Suprathermal Ion Telescope (SIT) aboard STB. Conclusions. Since our results explain the SEPT measurements, we conclude that no significant amount of electrons were accelerated between 55 and 425 keV by the CIR.

We show that a spacecraft launched from Earth towards Mars following a Hohmann minimum energy transfer trajectory has a strong tendency to remain well-connected magnetically to Earth, in the early phase of the transfer, or to Mars in the late phase, via the Parker spiral magnetic field. On the return trip, the spacecraft would remain reasonably well-connected magnetically first to Mars and later to Earth. Moreover, good magnetic connectivity occurs on all Hohmann transfers between neighboring planets in the inner solar system out to Mars. We call this hitherto unnamed circumstance the Hohmann–Parker effect. We show consequences of the effect by means of simultaneous cosmic radiation proxy observations made near Earth, near Mars, and at the Mars Science Laboratory on the transfer from Earth to Mars in 2011/2012. We support the observations with simulations of the large-scale magnetic field of the inner heliosphere during this period and compare the results with our predictions. The implications of the Hohmann–Parker effect are discussed. & 2013 Published by Elsevier Ltd.

In the absence of solar activity, Co-rotating Interaction Regions (CIRs) are a prevailing source of energetic ions observed near 1 AU. The combination of observations by near-Earth space observatories and the twin STEREO spacecraft offers an excellent platform for multi-point studies of CIRs. The analysis of CIR events during Carrington rotations 2067–2082 provides evidence that CIR-associated energetic ions frequently show significant differences, particularly at sub-MeV energies. We found discrepancies in the structures observed by different spacecraft which cannot always be attributed to the latitudinal separation or to changes in the coronal hole which generates the high-speed stream. We present several cases where these differences are linked to the presence of Interplanetary Coronal Mass Ejections (ICMEs) or small-scale interplanetary transients in the vicinity of or embedded within the CIR. Evidence of the possible role of ICME-CIR interactions as sources of temporal variations in the CIR-associated ion increases are presented and discussed.

During the latestUlyssesout-of-ecliptic orbit the solar wind density, pressure, and magneticfield strength have been the lowest ever observed in the history of space exploration. Since cosmic-ray particles respond to the heliospheric magnetic field in the expanding solar wind and its turbulence, the weak heliospheric magnetic field as well as the low plasma density and pressure are expected to cause the smallest modulation since the 1970s. In contrast to this expectation, the galactic cosmic-ray (GCR) proton flux at 2.5 GV measured by Ulysses in 2008 does not exceed the one observed in the 1990s significantly, while the 2.5 GV GCR electron intensity exceeds the one measured during the 1990s by 30%‐40%. At true solar minimum conditions, however, the intensities of both electrons and protons are expected to be the same. In contrast to the 1987 solar minimum, the tilt angle of the solar magnetic field has remained at about 30 " in 2008. In order to compare the Ulysses measurements during the 2000 solar magnetic epoch with those obtained 20 years ago, the former have been corrected for the spacecraft trajectory using latitudinal gradients of 0.25% deg # 1 and 0.19% deg # 1 for protons and electrons, respectively, and a radial gradient of 3% AU # 1 . In 2008 and 1987, solar activity, as indicated by the sunspot number, was low. Thus, our observations confirm the prediction of modulation models that current sheet and gradient drifts prevent the GCR flux to rise to typical solar minimum values. In addition, measurements of electrons and protons allow us to predict that the 2.5 GV GCR proton intensity will increase by a factor of 1.3 if the tilt angle reaches values below 10 " .

The period between 21 June and 8 October, 2007 (Carrington rotations 2058 to 2061), comprising the Ulysses ecliptic plane crossing, was characterized by low solar activity. Excluding the small solar energetic particle events observed during July, the ion increases observed in the inner heliosphere between 100 keV/n and 10 MeV/n were associated with Corotating Interaction Regions (CIRs). In this work, we investigate CIR-related ion increases using multipoint observations from Ulysses, ACE, and the twin STEREO spacecraft. The ballistic backmapping technique has been used to correlate in situ observations of these spacecraft and remote-sensing observations of coronal holes. Although the radial, longitudinal and latitudinal separation of the spacecraft (except Ulysses) are relatively small, we find discrepancies when a detailed comparison of narrow structures like stream interfaces and CIR-associated shocks is performed. Therefore we concentrate on the two CIR events from day 5 to day 10 of August 2007 and from day 25 to day 31 of August 2007, which lend themselves to a more undisturbed comparison. Using the multi-spacecraft measurements we could determine a radial gradient of 230±30% AU−1, which is consistent with previous results by van Hollebeke et al. (J. Geophys. Res.83, 4723, 1978) of ∼ 350% AU−1 using Helios and Pioneer data.

The biggest halo coronal mass ejection (CME) since the Halloween storm in 2003, which occurred on 2006 December 13, is studied in terms of its solar source and heliospheric consequences. The CME is accompanied by an X3.4 flare, EUV dimmings and coronal waves. It generated significant space weather effects such as an interplanetary shock, radio bursts, major solar energetic particle (SEP) events, and a magnetic cloud (MC) detected by a fleet of spacecraft including STEREO, ACE, Wind and Ulysses. Reconstruction of the MC with the Grad-Shafranov (GS) method yields an axis orientation oblique to the flare ribbons. Observations of the SEP intensities and anisotropies show that the particles can be trapped, deflected and reaccelerated by the large-scale transient structures. The CME-driven shock is observed at both the Earth and Ulysses when they are separated by 74$^{\circ}$ in latitude and 117$^{\circ}$ in longitude, the largest shock extent ever detected. The ejecta seems missed at Ulysses. The shock arrival time at Ulysses is well predicted by an MHD model which can propagate the 1 AU data outward. The CME/shock is tracked remarkably well from the Sun all the way to Ulysses by coronagraph images, type II frequency drift, in situ measurements and the MHD model. These results reveal a technique which combines MHD propagation of the solar wind and type II emissions to predict the shock arrival time at the Earth, a significant advance for space weather forecasting especially when in situ data are available from the Solar Orbiter and Sentinels., 26 pages, 10 figures. 2008, ApJ, in press

During solar cycle 22, the modulation of several hundred MeV galactic cosmic rays (GCRs) by recurrent and transient cosmic ray decreases was observed by the Ulysses spacecraft on its descent towards the solar south pole. In solar cycle 23, Ulysses repeated this trajectory segment during a similar phase of the solar cycle, but with opposite heliospheric magnetic field polarity. Since cosmic ray propagation in the heliosphere should depend on drift effects, we determine in this study the latitudinal distribution of the amplitude of recurrent cosmic ray decreases in solar cycles 22 and 23. As long as we measure the recurrent plasma structures in situ, we find that these decreases behave nearly the same in both cycles. Measurements in the fast solar wind, however, show differences: in cycle 22 (A>0) the recurrent cosmic ray decreases show a clear maximum near 25° and are still present beyond 40°, whereas we see in cycle 23 (A

The Solar Electron and Proton Telescope (SEPT), one of four instruments of the Solar Energetic Particle (SEP) suite for the IMPACT investigation, is designed to provide the three-dimensional distribution of energetic electrons and protons with good energy and time resolution. This knowledge is essential for characterizing the dynamic behaviour of CME associated and solar flare associated events. SEPT consists of two dual double-ended magnet/foil particle telescopes which cleanly separate and measure electrons in the energy range from 30–400 keV and protons from 60–7 000 keV. Anisotropy information on a non-spinning spacecraft is provided by the two separate telescopes: SEPT-E looking in the ecliptic plane along the Parker spiral magnetic field both towards and away from the Sun, and SEPT-NS looking vertical to the ecliptic plane towards North and South. The dual set-up refers to two adjacent sensor apertures for each of the four view directions: one for protons, one for electrons. The double-ended set-up refers to the detector stack with view cones in two opposite directions: one side (electron side) is covered by a thin foil, the other side (proton side) is surrounded by a magnet. The thin foil leaves the electron spectrum essentially unchanged but stops low energy protons. The magnet sweeps away electrons but lets ions pass. The total geometry factor for electrons and protons is 0.52 cm2 sr and 0.68 cm2 sr, respectively. This paper describes the design and calibration of SEPT as well as the scientific objectives that the instrument will address.

Since the 1970's interplanetary electrons in the MeV energy range, of Jovian origin, have been extensively studied from close to the Sun to beyond the Kronian orbit, near the ecliptic. The Ulysses trajectory allowed to study the propagation of these particles, in a wide range of heliographic latitudes. The location of Jupiter with respect to the structure of the heliospheric magnetic field is precisely determined and non-central. This makes Jovian electrons an ideal opportunity for studying the particle propagation parallel and perpendicular to the heliospheric magnetic field. 12 years after its first encounter in February 1992, the Ulysses mission encountered Jupiter for a second time in February 2004 at a distance of 1684 Jovian radii. The first flyby took place at a distance of closest approach of 6 Jupiter radii ( R J ) and changed the inclination of the Ulysses trajectory so that it would pass above the Sun's polar regions. During the 2004 encounter, in contrast to 1992, Ulysses did not enter the Jovian magnetosphere but remained upstream of it. In mid 2002, the MeV electron flux started increasing and displaying large short term variations. These features lasted throughout the encounter, making the electron intensities less obviously correlated with the proximity to Jupiter compared with the first Jovian encounter. In previous studies it has been shown that the diffusion coefficient κ ⊥ , ϑ perpendicular to the heliospheric magnetic field in polar direction increased in 1998 during the transition from solar minimum to solar maximum close to the ecliptic plane. Although the distant Ulysses encounter took place during the declining phase of the solar cycle the absence of an intensity variation with latitude indicate an unexpected further increase of κ ⊥ , ϑ . Thus the diffusion coefficients, and in particular perpendicular diffusion in the polar direction, are highly time-dependent. In this paper, we present the corresponding data and discuss the implication for particle propagation in the three-dimensional heliospheric magnetic field.

The Ulysses spacecraft at high heliographic latitudes has detected eight large solar energetic particle events during the recent solar maximum in 2000 and 2001 years. These events are easily identified with famous episodes of the solar activity and the corresponding SEP events near the Earth. Analyzing the absolute intensities of ∼40–100 MeV proton time profiles from the Ulysses COSPIN/KET and the GOES detector near Earth we find that for these eight events the intensities vary only within a factor of 2–3 from event to event at high latitudes during the first 30 h. In contrast the intensities at Earth differ from one event to another by several orders of magnitude. Thus, the time history during these 30 h has only a weak dependence on the relative position of Ulysses to the possible flare location. This implies: (1) a nearly isotropic injection of protons with comparable intensities to high heliolatitudes, and (2) a similar propagation process during the first 30 h of the events. We attribute the fact that the decay phases of these events are nearly the same at Ulysses and in the ecliptic rather to cross-field diffusion than to the presence of a shock.

Temporal profiles of energetic ions and electrons observed at 1 AU during solar energetic particle events are mainly determined by particle injection features, the observer location relative to the source region at the Sun, and the interplanetary space plasma and field conditions during particle transport. In this work, temporal profiles of 18 solar energetic particle events have been analyzed by fitting a pulse function to them in order to find a set of parameters which can be used to characterize the events.

The electron spectrum in the energy range 150 keV to 10 MeV, measured by EPHIN sensor on board SOHO observatory during 1996 quiet time periods, is presented. The results show that the dominant electron population is of jovian origin. The spectral indexes obtained range from 1.5 to 1.8. In this work an estimation of the emission intensity of electrons from the jovian magnetosphere is also obtained. Unexpected recurrence of jovian electrons at the middle of 1996 during poor Earth–Jupiter magnetic connection has been observed.

Ulysses observations have shown that solar energetic particles (SEPs) can easily reach high heliographic latitudes. To obtain information on the release and propagation of SEPs prior to their arrival at Ulysses, we analyse the onsets of nine large high-latitude particle events. We measure the onset times in several energy channels, and plot them versus inverse particle speed. This allows us to derive an experimental path length and time of release from the solar atmosphere. We repeat the procedure for near-Earth observations by Wind and SOHO. We find that the derived path lengths at Ulysses are 1.06 to 2.45 times the length of a Parker spiral magnetic field line connecting the spacecraft to the Sun. The time of particle release from the Sun is between 100 and 350 min later than the release time derived from in-ecliptic measurements. We find no evidence of correlation between the delay in release and the inverse of the speed of the CME associated with the event, or the inverse of the speed of the corresponding interplanetary shock. The main parameter determining the magnitude of the delay appears to be the difference in latitude between the flare and the footpoint of the spacecraft.Key words. Interplanetary physics (energetic particles) – Solar physics, astrophysics and astronomy (energetic particles, flares and mass ejections)

The Ulysses trajectory provides a unique opportunity to study the propagation of MeV electrons in a wide range of heliographic latitudes and during varying conditions in the inner heliosphere. From the Ulysses launch up to the beginning of 1998, the 3-10 MeV electron count rate of the COSPIN/KET instrument has been consistently described by modulation models taking into account Galactic cosmic rays as well as Jovian electrons. In this paper we focus on the MeV electron observations from 1998 onward, covering Ulysses' second out-of-ecliptic path, which was performed under solar maximum conditions. In contrast to our expectations, the electron intensity stayed at approximately the same level as the one observed in 1991 when Ulysses was magnetically well connected to Jupiter. In this paper we report on the discovery of short-term 3-10 MeV and 7-20 MeV electron intensity increases at the highest southern heliographic latitudes, which are not correlated with solar particle events.

In November 1997, EPHIN (Electron, Proton, Helium INstrument) on board Solar and Heliospheric Observatory (SOHO 1 ) detected solar energetic particles (SEP) from a multiple large event. Composition, temporal profiles and energy spectra of electrons, hydrogen and helium have been analyzed. The SEP events show, in general, gradual characteristics related to acceleration in the shocks driven the associated coronal mass ejections (CMEs). Composition features are very similar accounting that they are associated to the same active region and with similar physical conditions of the solar corona and solar wind. Temporal profile differences can be explained in terms of the different magnetic connection in both SEP events. During the November 6 SEP event the detection of some perturbations are produced by the passage of the shock and the halo CME associated with the November 4 event. Energetic characteristics of the SEP events denote differences between the November 6 SEP event, accelerated by a very fast shock, and the November 4 SEP event accelerated in a weaker shock. The compression ratio of the shock extracted from the SEP spectral index is correlated with the shock velocity reported and it demonstrates that protons and helium are accelerated by the same acceleration mechanism.

Two versions of a method are presented to determine the background of energetic particle telescopes during low-flux periods at low energies. Traditional procedures first evaluate pulse heights of particle sensors working in coincidence then select certain areas of the ΔE/Δx versus E plane, where E is energy, and finally, accept all events falling on those areas as real particles. Such methods, however, often fail during low-flux conditions, as the background may become comparable to the genuine particle flux. The alternative methods suggested here analyze the shape of the distribution near the track of genuine particles and provide statistical estimation of its parameters to separate the background from the real particle flux. Results are presented for protons and helium during quiet activity periods of the recent solar minimum using data from energetic particle telescopes Energetic and Relativistic Nuclei and Electron (ERNE) Low Energy Detector (LED) and Comprehensive Suprathermal and Energetic Particle Analyzer (COSTEP) Electron Proton Helium Instrument (EPHIN) aboard the Solar and Heliospheric Observatory (SOHO) spacecraft. SOHO is a project of international collaboration between the European Space Agency and NASA.

In mid 1996 the Comprehensive Suprathermal and Energetic Particle Analyser (COSTEP) onboard the Solar and Heliospheric Observatory, at 1 AU in the ecliptic plane, detected recurrent periods of enhanced MeV ions in association with a corotating interaction region (CIR). Measurements of energetic ions from the Cosmic Ray and Solar Particle Instrument/Low Energy Telescope (COSPIN/LET) onboard Ulysses taken at 5 AU, at mid-northern heliographic latitudes, showed that Ulysses encountered recurrent particle events during the same time period. We used the solar wind speeds observed at both locations to estimate the corresponding solar source longitudes of the particle events. These longitudes are related to warps of the Sun's large high latitude northern coronal hole boundaries observed by SOHO's Extreme Ultraviolet Imaging Telescope (EIT). The findings are supported by threedimensional magnetohydrodynamic (MHD) calculations of the footpoint positions of the magnetic field lines at both spacecraft. The observations suggest that close to the Sun a superradial expansion of the fast solar wind from the Sun's high latitude northern coronal hole down to ecliptic latitudes is present.

An analysis of the hydrogen and helium isotopic composition from EPHIN data, during the quiet-time period from January 1 to June 1, 1996, is presented. An isotopic discrimination and background rejection have been applied and relationships between the abundances of 2H/1H, 3He/4He, and 4He/1H have been calculated. The energy spectra in the 4–50 MeV nucl−1 range have been obtained and the contribution of the different spectral components have been analysed in this energy range. We conclude that the main contribution to the 4He spectrum is of anomalous origin, while the proton and 3He spectra have contributions mainly from particles of solar origin at low energies and from the galactic cosmic radiation modulated by the heliosphere at high energies. The deuterium spectrum is mainly of galactic origin.

In the time interval extending from July 1992 to July 1994, Ulysses climbed from 10°S heliographic latitude up to over 70°S. During this time lapse, solar minimum conditions were gradually approached, which, in turn, led to stable and long-lasting corotating interaction regions (CIRs). The corotating particle events observed during this period, associated with ∼30 registered CIRs, offer a unique opportunity to probe the three-dimensional structures of the heliosphere. In this work we use data from the Cosmic Ray and Solar Particle Investigation Kiel Electron Telescope (COSPIN/KET) instrument on board Ulysses to study the amplitude evolution of the 26-day recurrent cosmic ray decreases, generated by these CIRs, at different energies and derive its rigidity dependence. We find that the amplitude has a maximum around 25°–30° heliolatitude. We also find that the rigidity dependence of both the latitudinal gradient as well as the 26-day variation amplitude show a remarkable similarity. We discuss these observations within the framework of our current understanding of heliospheric phenomena.

According to standard drift dominated modulation models the intensity variations of galactic cosmic ray protons and electrons respond differently to the latitudinal extension of the heliospheric current sheet α. In an A>0 solar cycle intensities of protons should vary weakly with the latitudinal extension, whereas electrons should show a strong response. We investigate this charge dependent variation in the 1990s (A>0) using Ulysses Kiel Electron Telescope (KET) measurements. Proton measurements at 2.5 GV corrected for latitudinal variations show the same time profile as electrons from mid 1994 until the beginning of 1996, and later from September 1997 to the end of 1997. In 1996 and 1997, when α was below ∼25°, two long lasting time periods were found when electrons had a ∼5–10% higher level. These variations are in agreement with our computations indicating that drift effects play an important role in determining the temporal variation of electrons close to solar minimum.

The Solar and Heliospheric Observatory (SOHO), in halo orbit around the L1 Lagrangian point of the Sun-Earth system, combines a unique set of instruments for studies of the Sun and the heliosphere. SOHO's Comprehensive Suprathermal and Energetic Particle Analyser measures in situ particles in the energy range 44 keV/particle to above 53 MeV/nucleon. For the time period of the Whole Sun Month Campaign in mid 1996 we have identified recurrent energetic particle intensity increases in association with corotating interaction regions (CIRs) in the energy range

Ulysses, launched in October 1990, crossed in December 1997 the heliographic equator and completed its first out of ecliptic orbit. During the time period from February 1995 to November 1997 solar activity was low and the spacecraft scanned the latitude range from 80° N to the heliographic equator. The Kiel Electron Telescope on-board Ulysses measures protons and α-particles in the energy range from 5 MeV/n to > 2 GeV/n. To separate spatial and temporal variations of > 2 GeV/n protons and α-particles along the spacecraft trajectory we used the data set from the world wide neutron monitor network. We found negligible latitudinal gradients below ∼29° N and for the radial gradient an upper limit of ≈ 0.5 %/AU for > 2 GeV/n protons and α-particles. In the latitudinal range from ≈ 25 to > 70° N the latitudinal gradient is ∼0.17 %/° and ∼0.12 %/° for > 2 GeV/n protons and α-particles, respectively, independent of spacecraft latitude and radial distance.

The spatial intensity gradients of galactic and anomalous cosmic ray helium are studied over the 1993.0–1998.0 time period using data from cosmic ray experiments on IMP 8, Ulysses, Voyagers 1 and 2 and Pioneer 10. When combined with the results of previous studies, a remarkable ordering of the radial gradients for the galactic component is found over 2 complete solar cycles and 3 successive solar minima. The latitudinal gradients for the cycle 22 solar minimum period are zero or small and positive in the inner and outer heliosphere in contrast to the much larger negative latitudinal gradients observed in the outer heliosphere in 1987 over the cycle 21 solar minimum. The changes in the intensity gradients over the 3 solar minimum periods require that at these times drift effects play an important role in the transport of cosmic rays in the heliosphere and provide further evidence for the existence of a 22-year solar modulation cycle. The Ulysses data plays a pivotal role in understanding the spatial gradients over the cycle 22 recovery and solar minimum period.

We present observations and model calculations of the modulated intensities of galactic cosmic ray protons above 106 MeV/n along the Ulysses trajectory. Data are taken by the Cosmic and Solar Particle Investigation (COSPIN) Kiel Electron Telescope (KET) from spring 1993 to fall 1996. During this time period solar activity decreased and galactic cosmic rays recovered. To separate spatial from temporal variations we used the University of Chicago measurements from IMP 8 near Earth and compare the residual spatial variation with time independent modulation models. According to standard drift dominated modulation model, one would expect a radial gradient of ≈2%/AU and a latitudinal gradient of ≈1.2%/degree in both hemispheres. The measured mean radial gradient of «3%/AU is within the uncertainties in good agreement with the model predictions. However, the measured mean latitudinal gradient has a value of (0.33 ± 0.04)%/degree in both hemispheres at intermediate latitudes and is by a factor of 4 lower than expected. In the modified models the latitudinal gradient is in agreement with the measured ones when we increase the diffusion coefficient κθθ perpendicular to the magnetic field in polar direction to a value of 15% of the diffusion coefficient parallel to the magnetic field. The latitudinal gradients >106 MeV protons calculated by modified modulation models are in very good agreement with the measured ones at intermediate latitudes. At lower latitudes, when Ulysses is embedded in the streamer belt, the models predict approximately the same latitudinal gradient than at intermediate latitudes, whereas the measured ones are significant smaller, or even vanishing. The observations support the previous conclusion from Paizis et al. [1995] that a significant latitudinal gradient is only observed when Ulysses is outside the streamer belt. Another remarkable observation is the difference of the radial gradient Gr at ∼3.5 AU in the southern (Gr≈3.5%/AU) and in the northern hemisphere (Gr≈2.3%/AU). Probable reasons for the significantly lower radial gradient in the northern hemisphere can be either a spatial asymmetry of the heliosphere or temporal variations.

The radial and latitudinal intensity gradients of 145–255 MeV/nucleon He, 34–50 MeV/nucleon He and 30–69 MeV H are studied over an extensive range of heliocentric distances and latitudes for the 1993.0–1996.0 time period using data from cosmic ray experiments on the Ulysses, IMP 8, Voyager 1 and 2, and Pioneer 10 spacecraft. The radial gradients are found to decrease rapidly with increasing heliocentric distance and agree with those measured 20 years earlier at a similar phase of the heliomagnetic cycle. The latitudinal gradients measured in the inner and outer heliosphere are in reasonable agreement and positive albeit exceedingly small. In agreement with other Ulysses energetic particle experiments it is found that a shift of heliolatitude by −7° to −10° is necessary to get reasonable symmetry in the measurements at midlatitudes. From the Ulysses data it appears there is a significantly reduced latitudinal variation in the intensity of the three energetic particle components at (magnetic) heliolatitudes above about 50° at this phase of the modulation cycle. Such a reduced entry of cosmic rays over such an extensive area above the solar poles implies a strong modification of the previously assumed cosmic ray transport processes at high latitudes, most probably a considerably increased rate of scattering combined with reduced particle gradient and curvature drifts. A significant higher intensity is observed over the north solar pole than over the south pole for the low-energy components after the corrections have been applied for the temporal changes at the 1-AU baseline.

Representative types of energetic particle phenomena recorded by the LION instrument on SOHO during its Transfer Phase to, and while in early Halo Orbit about, the L1 Lagrangian Point are presented. The data cover the period from 7 December 1995 (instrument switch on) until 9/10 July 1996 (when a particle event associated with the first Class X flare since November 1992 was recorded). Although the first new cycle spots appeared on 10 May 1996 and the Solar Weather Operations Centre in Boulder estimates that the transition from Solar Cycle 22 to 23 occurred in July 1996, the solar related particle events prominent in LION data within the interval considered were individually associated with old cycle spots. Scientific investigations that can be mounted using the already rich and progressively updating LION data set are outlined.

The basic physical processes that lead to the long-term modulation of cosmic rays in the heliosphere have been known for many years. However, our knowledge of the relative importance of the various processes is still incomplete. Observations of cosmic rays at high latitudes can be used to improve our understanding of modulation processes. In this paper we present measurements of galactic proton fluxes with energies above 106 MeV made by the Kiel Electron Telescope on board the Ulysses spacecraft during the fast scan from the South polar passage in September 1994 to the North pole in August 1995, under solar minimum conditions. Comparison of proton fluxes at high latitudes and in the ecliptic shows a 20% higher flux in polar regions. The flux increase is not symmetric with respect to the heliographic equator but rather with respect to a surface shifted by 7° South. In such a coordinate system the latitudinal gradient in both hemispheres has a value of (0.33±0.02)%/deg.

The COSTEP experiment on SOHO forms part of the CEPAC complex of instruments that will perform studies of the suprathermal and energetic particle populations of solar, interplanetary, and galactic origin. Specifically, the LION and EPHIN instruments are designed to use particle emissions from the Sun for several species (electrons, protons, and helium nuclei) in the energy range 44 keV/particle to > 53 MeV/n as tools to study critical problems in solar physics as well as fundamental problems in space plasma and astrophysics. Scientific goals are presented and a technical description is provided of the two sensors and the common data processing unit. Calibration results are presented which show the ability of LION to separate electrons from protons and the ability of EPHIN to obtain energy spectra and achieve isotope separation for light nuclei. A brief description of mission operations and data products is given.

We present multi-spacecraft observations of four solar electron events using measurements from the Solar Electron Proton Telescope (SEPT) and the Electron Proton Helium INstrument (EPHIN) on board the STEREO and SOHO spacecraft, respectively, occurring between 11 October 2013 and 1 August 2014, during the approaching superior conjunction period of the two STEREO spacecraft. At this time the longitudinal separation angle between STEREO-A (STA) and STEREO-B (STB) was less than 72°. The parent particle sources (flares) of the four investigated events were situated close to, in between, or to the west of the STEREO’s magnetic footpoints. The STEREO measurements revealed a strong difference in electron peak intensities (factor ≤12) showing unexpected intensity distributions at 1 AU, although the two spacecraft had nominally nearly the same angular magnetic footpoint separation from the flaring active region (AR) or their magnetic footpoints were both situated eastwards from the parent particle source. Furthermore, the events detected by the two STEREO imply a strongly unexpected onset timing with respect to each other: the spacecraft magnetically best connected to the flare detected a later arrival of electrons than the other one. This leads us to suggest the concept of a rippled peak intensity distribution at 1 AU formed by narrow peaks (fingers) superposed on a quasi-uniform Gaussian distribution. Additionally, two of the four investigated solar energetic particle (SEP) events show a so-called circumsolar distribution and their characteristics make it plausible to suggest a two-component particle injection scenario forming an unusual, non-uniform intensity distribution at 1 AU.

The cosmic ray flux observed with the Kiel Electron Telescope on board the ULYSSES spaceprobe varies with solar activity as well as with heliospheric position. Determination of spatial gradients requires a careful analysis of the influences of the current sheet tilt angle, the number of major solar flares, interplanetary shocks and interaction regions evolving in the expanding solar wind. In this paper we concentrate on nuclei with rigidity above 1 GV. We discuss the effects of the variable solar activity in the declining phase of the present solar cycle and the variation with radial distance during the in ecliptic mission period as a basis for separating latitudinal effects. We show that during this phase of the solar cycle modulation of GV nuclei is ordered by temporal evolution, radial distance and small latitudinal effects up to latitudes of 50° South. We discuss the influence on GV nuclei of a disturbance in early 1994 when ULYSSES was beyond 50° South.

We present a sample of solar energetic particle events observed between November 18 and December 31, 1982 by the HELIOS 1, the VENERA 13, and IMP 8 spacecraft. During the entire time period all three spacecraft were magnetically connected to the western hemisphere of the Sun with varying radial and angular distances from the flares. Eleven proton events, all of them associated with interplanetary shocks, were observed by the three spacecraft. These events are visible in the low-energy (about 4 MeV) as well as the high-energy (30 MeV) protons. In the largest events protons were observed up to energies of about 100 MeV. The shocks were rather fast and in some cases extended to more than 90% east of the flare site. Assuming a symmetrical configuration, this would correspond to a total angular extent of some interplanetary shocks of about 180%. In addition, due to the use of three spacecraft at different locations we find some indication for the shape of the shock front: the shocks are fastest close to the flare normal and are slower at the eastern flank. For particle acceleration we find that close to the flare normal the shock is most effective in accelerating energetic particles. This efficiency decreases for observers connected to the eastern flank of the shock. In this case, the efficiency of shock acceleration for high-energy protons decreases faster than for low-energy protons. Observation of the time-intensity profiles combined with variations of the anisotropy and of the steepness of the proton spectrum allows one in general to define two components of an event which we term ‘solar’ and ‘interplanetary’. We attempt to describe the results in terms of a radially variable efficiency of shock acceleration. Under the assumption that the shock is responsible not only for the interplanetary, but also for the solar component, we find evidence for a very efficient particle acceleration while the shock is still close to the Sun, e.g., in the corona. In addition, we discuss this series of strong flares and interplanetary shocks as a possible source for the formation of a superevent.

Since its switch-on in Oct. 90, the Kiel Electron Telescope onboard Ulysses has detected many quiet time increases of the flux of 3–30 MeV electrons, known to originate from Jupiter. We report on the long term variations of this flux for the Ulysses ecliptic journey, and at the beginning of the out of ecliptic phase. They are well accounted for by a simple convection-diffusion model, with diffusion coefficients along and perpendicular to the magnetic field of ∼ 5.10 22 and 8.10 20 cm 2 s −1 respectively. In addition to the long term flux variations, several short bursts of electrons were detected, particularly after the Jupiter fly-by at southern latitudes. Their duration is about 1 hour or less, and they show a very strong anisotropy in the general direction of Jupiter. They are more numerous and are found at larger distances after encounter (23 of them, up to 0.86 AU from Jupiter), than before (3, up to 0.40 AU).

Energetic particle increases in the energy range 4 to 130 MeV observed by the Kiel Electron Telescope (KET) during the in-ecliptic part of the ULYSSES mission between 1 and 5.4 AU differ distinctly from their appearance in the inner heliosphere inside 1 AU. Prompt events are rare, and for most of the events velocity dispersion is lacking. The observed intensity-time profiles show poor time relations with optical solar flares. The data is far better organized by the structure of the interplanetary medium with its shocks, tangential discontinuities, corotating interaction regions, heliospheric current sheet crossings (sector boundaries), and coronal mass ejections. Nine particle events are discussed in detail. Spectral information as well as composition measurements are used to determine the source of the particle increases: solar, interplanetary, and Jovian. The few prompt events can be fitted with diffusive interplanetary propagation models, yielding radial mean free paths in the range λ r = 0.05 to 0.15 AU. The shock related events are dominant at these intermediate distances, with particularly high intensities of MeV-electrons and > 30 MeV protons at merged or double shocks. A new feature are slowly-varying populations (SVP) with long time scales neither related to prompt events nor to local shock effects.

The Ulysses spacecraft made the first exploration of the region of Jupiter's magnetosphere at high Jovigraphic latitudes ( approximately 37 degrees south) on the dusk side and reached higher magnetic latitudes ( approximately 49 degrees north) on the day side than any previous mission to Jupiter. The cosmic and solar particle investigations (COSPIN) instrumentation achieved a remarkably well integrated set of observations of energetic charged particles in the energy ranges of approximately 1 to 170 megaelectron volts for electrons and 0.3 to 20 megaelectron volts for protons and heavier nuclei. The new findings include (i) an apparent polar cap region in the northern hemisphere in which energetic charged particles following Jovian magnetic field lines may have direct access to the interplanetary medium, (ii) high-energy electron bursts (rise times/= 1 minute and energies extending toapproximately 17 megaelectron volts) on the dusk side that are apparently associated with field-aligned currents and radio burst emissions, (iii) persistence of the global 10-hour relativistic electron "clock" phenomenon throughout Jupiter's magnetosphere, (iv) on the basis of charged-particle measurements, apparent dragging of magnetic field lines at large radii in the dusk sector toward the tail, and (v) consistent outflow of megaelectron volt electrons and large-scale departures from corotation for nucleons.

We present observations of solar energetic particles and shock-accelerated particles observed by the Kiel Electron Telescope (KET) on board the Ulysses spacecraft in the time interval 26 October 1990 to mid November 1991. Prompt events with diffusive propagation were observed mainly at small radial distances while at larger distances shock-related events became dominant. Particularly high intensities of high energy electrons and >30 MeV/n nuclei are observed at merged or double shocks. Slowly-varying populations (SVP) with long time scales neither related to prompt events nor to local shock effects are a new feature at these intermediate distances.

[1] Fast solar wind streams originating from coronal holes interact with the preceding slow wind, leading to the formation of corotating interaction regions (CIRs) in the interplanetary medium. Near solar minimum CIR-associated shocks become the dominant source of energetic ion increases observed near 1 AU in the energy range between some tens of keV/n and 10 MeV/n. Between March 2007 and February 2008, solar activity remained very low, and only a few minor solar energetic particle events were observed. Under these quiet conditions, recurrent CIR-accelerated ion events were regularly observed by the Solar Electron and Proton Telescope (SEPT) on board the twin STEREO spacecraft. The increasing angular separation between STEREO-A and STEREO-B and observations available from near-Earth spacecraft provide an excellent opportunity for multispacecraft analysis of the CIR-associated particle events in the inner heliosphere during an extended period of low solar activity. The ion energy spectrum in the range of 0.6–2.2 MeV is characterized by a power law with spectral indices around 2.7. Below 0.6 MeV the spectrum is flatter and shows more variability. During near-Earth periods, magnetospheric ion bursts contribute significantly to the observed intensities at low energies. Ballistic back mapping has been used to correlate multipoint in situ measurements and coronal synoptic maps. This made it possible to identify the parent coronal holes and to track the same stream for several consecutive rotations. Discrepancies in the structures and the spectra observed by different spacecraft for the same event are sometimes present. These deviations become more evident as the spatial separation between STEREO-A and STEREO-B increases. Coronal hole evolution, radial and latitudinal separation, and interactions between CIRs and interplanetary coronal mass ejections are found to be the main sources of these differences.

[1] Using simultaneous measurements of >40 keV upstream ions observed at ACE, Wind, and STEREO-A during the solar minimum period of 2007, day 1 through 2007, day 181, we investigate their spatial distributions by calculating their occurrence probabilities as a function of lateral and radial separation between L1 and STEREO-A. Our main results are given as follows: (1) STEREO-A observed upstream events even when it was separated from Earth by ∼1750 RE and ∼3800 RE in the radial and lateral directions, respectively. (2) The occurrence probability (∼20–30%) for measuring simultaneous upstream events at L1 and STEREO-A was far greater than that expected from accidental coincidences. (3) The occurrence rate of simultaneous upstream events at L1 and STEREO-A is significantly higher inside rarefaction regions of high-speed solar wind flows (>500 km s−1) that follow corotating compression regions and when there exist antisunward propagating Alfven waves. These new results confirm the global nature of the source region and place limits on the spatial size of the interplanetary structures that could either accelerate the ions in the first place or at the very least provide them with easier access by facilitating their scatter-free transport from the Earth's foreshock into the far upstream regions traversed by STEREO-A. We suggest that the existence of large amplitude Alfven waves with spatial scales of the order of 0.03 AU that are embedded in and get convected past the Earth by high-speed solar wind streams plays a critical and necessary role in the occurrence of upstream ion events near the Earth.

Ulysses, launched in 1990 October in the maximum phase of solar cycle 22, completed its third out-of-ecliptic orbit in 2008 February. This provides a unique opportunity to study the propagation of cosmic rays over a wide range of heliographic latitudes during different levels of solar activity and different polarities in the inner heliosphere. Comparison of the first and second fast latitude scans from 1994 to 1995 and from 2000 to 2001 confirmed the expectation of positive latitudinal gradients at solar minimum versus an isotropic Galactic cosmic ray distribution at solar maximum. During the second scan in mid-2000, the solar magnetic field reversed its global polarity. From 2007 to 2008, Ulysses made its third fast latitude scan during the declining phase of solar cycle 23. Therefore, the solar activity is comparable in 2007-2008 to that from 1994 to 1995, but the magnetic polarity is opposite. Thus, one would expect to compare positive with negative latitudinal gradients during these two periods for protons and electrons, respectively. In contrast, our analysis of data from the Kiel Electron Telescope aboard Ulysses results in no significant latitudinal gradients for protons. However, the electrons show, as expected, a positive latitudinal gradient of ~0.2% per degree. Although our result is surprising, the nearly isotropic distribution of protons in 2007-2008 is consistent with an isotropic distribution of electrons from 1994 to 1995.

[1] We investigate the solar origin of near-relativistic electrons and protons during the X17.2/4B flare as observed by the Comprehensive Suprathermal and Energetic Particle Analyser (COSTEP) and Three-Dimensional Plasma (3DP) analyzer experiments on board the SOHO and Wind spacecraft. These observations are combined with ground- and space-based spectral radio data obtained by the Potsdam spectrograph and the Wind/Waves instrument. Additionally, we use measurements of relativistic protons (ground-level event (GLE)) by neutron monitors (Kiel and Moscow). Timing and electron energy spectrum analysis suggest that there are three separate stages of electron injection into interplanetary space: (1) An injection of radio type III–producing electrons is observed first; (2) an impulsive injection with an almost symmetric time profile with a short duration (∼18 min) is released ∼11 min later, followed by (3) a gradual, long (>1 hour) lasting injection, with an onset ∼25 min after the first type III burst. While the first escaping type III–producing electrons are more likely related to the reconnection processes during the impulsive flare phase, the association of the two delayed electron injections with solar events is not well understood.

[1] The Ulysses orbit provides a unique opportunity to study the propagation of cosmic rays in a wide range of heliographic latitudes and during different solar activity and polarity in the inner heliosphere. Around July 2000 the solar magnetic field reversed its global polarity. In late 2000, the electron to proton ratio at the rigidities of 1.2 GV and 2.5 GV, measured by the Kiel Electron Telescope aboard Ulysses, was roughly the same as in the previous solar maximum. During 2001 the ratio profile began to flatten, however after late 2001 the ratio began to increase again, leading to the conclusion that drifts are becoming increasingly important again. Comparing the Ulysses observations with the IMP and ICE measurements in the 1980s reveals a similar time profile. If solar cycle 23 would evolve similar to solar cycle 21 then the electron intensity will increase more quickly than the helium and proton intensities in 2003/2004.

[1] We analyse 9 large solar energetic particle (SEP) events detected by the Ulysses spacecraft at high heliolatitudes during the recent solar maximum polar passes. Properties of time intensity profiles from the Ulysses/COSPIN instrument are compared with those measured by SOHO/COSTEP and Wind/3DP near Earth. We find that onset times and times to maximum at high latitude are delayed compared to in-ecliptic values. We show that the parameter which best orders these characteristics of time profiles is the difference in latitude between the associated flare and the spacecraft. We find that the presence of a shock is not necessary for the establishing of near equal intensities at Ulysses and in the ecliptic during the decay phase. The model of SEP acceleration by coronal mass ejection driven shocks does not appear to account for our observations, which would more easily be explained by particle diffusion across the interplanetary magnetic field.

Previous work on the latitudinal gradient and on the amplitude of the recurrent cosmic ray decreases, has shown that their magnitude does not decrease monotonically with the particle rigidity, but it presents a broad maximun around 1 – 2 GV. We have extended this analysis to study the behaviour of cosmic-ray particles during the modulation steps in the rising part of the solar activity of the present Solar cycle. We found that the ‘depth’ of the modulation step decreases monotonically with increasing rigidity and that the least energetic particles are the last to reach their minimum intensity value. We also considered in this analysis electrons of equal rigidity to study the influence of the charge sign on the particle behaviour during the modulation steps.

Since June 1992 the Kiel Electron Telescope on board ULYSSES measures 26-day variations of the order of 6% in the fluxes of high energy H and He. In May 1993 ULYSSES entered into the unipolar region of the southern polar coronal hole, but continued to observe similar effects: increases in the MeV proton channels due to acceleration near the shocks of the corotating interaction region and decreases in the intensity of galactic nuclei associated with the same region. Amplitude variations are presented for different magnetic rigidities and the effects are discussed in view of corotating shock development in a 3-dimensional heliospheric structure.

We describe for the first time the analysis of high energy electrons (above 240 MeV) from the COSPIN/KET experiment onboard Ulysses. The electron time profiles in four energy windows are presented from Oct. 90 to the end of March 94, up to a maximum heliographic latitude of 57 °S. The recovery rates we derived for the electrons are compared to the recovery rates of positively charged particles with the same rigidity.

The Solar Electron and Proton Telescope (SEPT) on board the twin spacecraft STEREO A and B measures electrons and ions in the energy range from 60 to above 400 keV with an energy resolution of 10%. On 19 October 2009, when STEREO-B was already 1.03 AU away from the Earth, a strong and prolonged almost monoenergetic ion event has been observed with the SEPT instrument. The event lasted 27 minutes and its energy spectrum contained a strong narrow peak at 235 keV with a relative full width at half maximum of 0.35. The event occurred during a period of slow solar wind in front of a weak ion increase associated with a distant corotating interaction region (CIR). Previously similar events containing sp ectral peaks were detected in the vicinity of the Earth’s magnetosphere using observations on Interball-1 and on both STEREO A & B spacecraft. We present evidence that the narrow spectral peak is caused by a quasi-monoenergetic ion beam and suggest that the particles were accelerated at a distant CIR or CIR shock. We discuss the possible mechanisms that could be responsible for accelerating these ions: the shock drift acceleration, the surfatron mechanism and the acceleration in a large-scale electrostatic field.

The distinction between the inner and the outer solar system is traditionally related to the planetary system, where the inner, earth-like planets, are distinguished from the outer planets by their different chemical composition and structure. In the particles and fields area a division into the “inner” and the “outer” solar system also makes sense, though for other reasons.