Latitudinal and radial variation of &amp;gt;2 GeV/n protons and alpha-particles at solar maximum: ULYSSES COSPIN/KET and neutron monitor network observations

Белов, А. В.; Eroshenko, E. A.; Heber, B.; Yanke, V. G.; Raviart, A.; Müller‐Mellin, R.; Kunow, H.

doi:10.5194/angeo-21-1295-2003

Cited by 14 publications

(7 citation statements)

References 13 publications

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“…We will assume, therefore, that the radial gradient increases during period 'B'. Such an increase is consistent with the analysis of Belov et al [2001]. They studied Ulysses >2 GeV/nucleon proton and a-particles from 1998 to 2001.…”

Section: Proton Spatial Gradients In the Inner Heliospheresupporting

confidence: 87%

Ulysses Cosmic Ray and Solar Particle Investigation/Kiel Electron Telescope observations: Charge sign dependence and spatial gradients during the 1990–2000 A > 0 solar magnetic cycle

Heber¹

2002

J. Geophys. Res.

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Ulysses, launched in October 1990, began its second out‐of‐ecliptic orbit in September 1997. From 1991 to mid‐2000, solar polar magnetic field observations indicate a magnetic field pointing outward over the northern polar region (A > 0 epoch). While the first fast latitude scan in 1994/1995 was performed around solar minimum, the second Ulysses orbit covering high latitudes is being performed around solar maximum. We present data of ∼2.5 GV electrons and protons from the Kiel Electron Telescope up to southern heliographic latitudes of 80°, reached by Ulysses in November 2000. Spatial gradients are determined by comparison with a near‐Earth baseline. The radial gradient for an integral proton channel is found to be 2.2 ± 0.6%/AU before early 1998 and 3.5%/AU thereafter. Until mid‐1999 the latitudinal variation is consistent with a zero gradient at low latitudes and an average gradient of about 0.25%/degree for latitudes above about ±25°. In contrast, the latitudinal gradient decreases markedly after mid‐1999, leading to a spherically symmetric intensity distribution with the approach to solar maximum conditions. The electron to proton (e/p) ratio is used to study charge sign dependent modulation. According to drift‐dominated modulation models, galactic cosmic ray protons and electrons respond differently to the global heliospheric magnetic field. Comparison of the e/p ratio over the period 1991 to 2000 with model predictions indicates that drift effects are important over a large part of an 11‐year period with A > 0. With the approach to solar maximum the e/p ratio increases, indicative for the fading out of drift effects and the transition to a diffusion‐dominated modulation.

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Section: Proton Spatial Gradients In the Inner Heliospheresupporting

confidence: 87%

Ulysses Cosmic Ray and Solar Particle Investigation/Kiel Electron Telescope observations: Charge sign dependence and spatial gradients during the 1990–2000 A > 0 solar magnetic cycle

Heber¹

2002

J. Geophys. Res.

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“…Meridional cut of the >2 GeV protons spatial distribution in a sphere of ∼2 AU radius during solar minimum (a) and solar maximum (b). Thus the two panels show the reconfiguration of the cosmic ray distribution towards spherical symmetry at solar maximum (Belov et al, 2003). Such structures are confirmed by model calculations by Haasbroek and Potgieter (1995b) and Langner and Potgieter (2005).…”

Section: Latitudinal Distribution Of Galactic Cosmic Rayssupporting

confidence: 73%

“…Heber et al (2002b), Belov et al (1999), andMcDonald et al (2001) showed that the radial gradient was increasing in 1997 to 1998. Thus Belov et al (2003) and Heber et al (2002b) suggested that the transformation from the minimum to the maximum distribution must have occurred around mid-1999, when the spacecraft was well below the heliographic equator, allowing for a good determination of latitudinal effects.…”

Section: Latitudinal Distribution Of Galactic Cosmic Raysmentioning

confidence: 98%

“…Belov et al (2003) derived radial and latitudinal gradients for >2 GeV/nucleon protons and alpha-particles by using data from the Kiel Electron Telescope, the Chicago instrument on board IMP 8 and the neutron monitor network. To visualize the differences between the mean cosmic ray distribution at solar minimum in 1994 to 1996 and around solar maximum from mid-1999 to mid-2001, Figure 41 displays these distributions within a sphere of 5 AU radius, respectively.…”

Section: Latitudinal Distribution Of Galactic Cosmic Raysmentioning

confidence: 99%

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Cosmic Rays at High Heliolatitudes

2007

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The Ulysses spacecraft has been the first to orbit the Sun over its poles and to explore the heliosphere at these high heliolatitudes. It has now completed two fast latitude scans, one at solar minimum and one at solar maximum. Since its launch in October 1990, this mission has led to several surprising discoveries concerning energetic particles, cosmic rays, Jovian electrons, the solar wind, the heliospheric magnetic field and the global features of the heliosphere. This review addresses mainly the propagation and modulation of cosmic rays and other charged particles, from both an observational and theoretical point of view, with emphasis on what has been learned from exploring the inner heliosphere to high heliolatitudes. This is done for solar minimum and maximum conditions. The review is concluded with a summary of the main scientific discoveries and insights gained so far from the Ulysses mission.

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“…Six years later when Ulysses performed another fast latitude scan Belov et al (2003), Heber et al (2003), andMcKibben et al (2003) reported a spherical symmetric cosmic ray distribution indicating that drifts are of minor importance around solar maximum. Ndiitwani et al (2005) analyzed the e/p-ratio time profile during solar maximum and found that the no drift solution explains very well the solar maximum observations, but fails shortly before and after, indicating that the particle drift is an important factor for understanding solar modulation and that modulation models have to include all components used in Parker's transport Equation (1).…”

Section: Solar Cycle Variationmentioning

confidence: 97%

Solar and Heliospheric Modulation of Galactic Cosmic Rays

2007

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The significance of external influences on the environment of Earth and its atmosphere has become evident during recent years. Especially, on time scales of several hundred years, the cosmogenic isotope concentration during the Wolf-, Spoerer-, Maunder-and Dalton-Minimum indicates an increased cosmic ray flux. Because these grand minima of solar activity coincide with cold periods, a correlation of the Earth climate with the cosmic ray intensities is plausible. Any quantitative study of the effects of energetic particles on the atmosphere and environment of the Earth must address their transport to Earth and their interactions with the Earth's atmosphere including their filtering by the terrestrial magnetosphere. The first problem is one of the fundamental problems in modern cosmic ray astrophysics, and corresponding studies began in the 1960s based on Parker's cosmic ray modulation theory taking into account diffusion, convection, adiabatic deceleration, and (later) the drift of energetic particles in the global heliospheric magnetic field. It is well established that all of these processes determining the modulation of cosmic rays are depending on parameters that are varying with the solar magnetic cycle. Therefore, the galactic cosmic ray intensities close to Earth is the result of a complex modulation of the interstellar galactic spectrum within the heliosphere. The modern view of this cosmic ray modulation is summarized in our contribution.

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Latitudinal and radial variation of >2 GeV/n protons and alpha-particles at solar maximum: ULYSSES COSPIN/KET and neutron monitor network observations

Cited by 14 publications

References 13 publications

Ulysses Cosmic Ray and Solar Particle Investigation/Kiel Electron Telescope observations: Charge sign dependence and spatial gradients during the 1990–2000 A > 0 solar magnetic cycle

Ulysses Cosmic Ray and Solar Particle Investigation/Kiel Electron Telescope observations: Charge sign dependence and spatial gradients during the 1990–2000 A > 0 solar magnetic cycle

Cosmic Rays at High Heliolatitudes

Solar and Heliospheric Modulation of Galactic Cosmic Rays

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