Latitudinal distribution of &gt;106 MeV protons and its relation to the ambient solar wind in the inner southern and northern heliosphere: Ulysses Cosmic and Solar Particle Investigation Kiel Electron Telescope Results

Heber, B.; Bothmer, V.; Dröge, W.; Kunow, H.; Müller‐Mellin, R.; Sierks, H.; Wibberenz, G.; Ferrando, P.; Raviart, A.; Paizis, C.; Potgieter, M. S.; Burger, R. A.; Hattingh, M.; Haasbroek, L. J.; McComas, D. J.

doi:10.1029/97ja01984

Cited by 24 publications

(29 citation statements)

References 21 publications

(7 reference statements)

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“…Spatial variations can be separated in a latitudinal and a radial component. We have shown in previous studies [Heber et al, 1996[Heber et al, , 1998] that we can determine both the (e.g., [Evenson, 1998]) allows us to conclude that for periods around solar minimum (a* <25 ø) the response of cosmic rays varies with the product qA (q = particle charge), with a stronger (weaker) response for qA < 0 (qA > 0), in qualitative agreement with the prediction from drift models.…”

Section: Discussionsupporting

confidence: 72%

Differences in the temporal variations of galactic cosmic ray electrons and protons: Implications from Ulysses at solar minimum

Heber

Ferrando

Raviart

et al. 1999

Geophysical Research Letters

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Section: Discussionsupporting

confidence: 72%

Differences in the temporal variations of galactic cosmic ray electrons and protons: Implications from Ulysses at solar minimum

Heber

Ferrando

Raviart

et al. 1999

Geophysical Research Letters

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“…From mid 1999, when Ulysses was above 30 • S to mid 2001, a highly variable and slow solar wind has been observed by Ulysses only (McComas et al, 2001b). In Heber et al (1998) and Belov et al (1999) we showed that latitudinal gradients are small in the streamer belt dominated region. Therefore, we argue here that the expansion described by the tilt angle and structure of the streamer belt to high heliographic latitudes leads to a strong increase in modulation and the form of the cosmic ray spatial distribution in the inner heliosphere.…”

Section: Discussionmentioning

confidence: 62%

“…It is important to keep in mind that Ulysses was below 20 • S before 1999 and around 30 • , when this latitudinal gradient has been observed. In Heber et al (1997Heber et al ( , 1998 it was shown that latitudinal gradients are significantly smaller close to the heliographic equator than at higher latitudes, so that a significant contribution of the latitudinal gradient is not expected to occur before 1999. If we attribute the excess of the observations in mid 1999 in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…In that case drift models predict that positively charged cosmic rays drift predominantly inward through the solar polar regions and then outward through the equatorial regions along the heliospheric current sheet (Jokipii et al, 1977). (3) The latitudinal distribution of high energy cosmic rays measured by Ulysses showed the expected behavior (Paizis et al, 1995;Heber et al, 1998): The count rate of >2 GeV/n protons and helium increased towards high latitudes, and was nearly symmetric with respect to the equator Belov et al, 1999). The observed time profile at these rigidities during Ulysses' first fast latitude scan in 1994/1995 is dominated by the latitudinal gradient (Belov et al, 1999 Smith et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

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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

et al. 2003

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Abstract. Ulysses, launched in October 1990, began its second out-of-ecliptic orbit in September 1997. In 2000/2001 the spacecraft passed from the south to the north polar regions of the Sun in the inner heliosphere. In contrast to the first rapid pole to pole passage in 1994/1995 close to solar minimum, Ulysses experiences now solar maximum conditions. The Kiel Electron Telescope (KET) measures also protons and alpha-particles in the energy range from 5 MeV/n to >2 GeV/n. To derive radial and latitudinal gradients for >2 GeV/n protons and alpha-particles, data from the Chicago instrument on board IMP-8 and the neutron monitor network have been used to determine the corresponding time profiles at Earth. We obtain a spatial distribution at solar maximum which differs greatly from the solar minimum distribution. A steady-state approximation, which was characterized by a small radial and significant latitudinal gradient at solar minimum, was interchanged with a highly variable one with a large radial and a small -consistent with zero -latitudinal gradient. A significant deviation from a spherically symmetric cosmic ray distribution following the reversal of the solar magnetic field in 2000/2001 has not been observed yet. A small deviation has only been observed at northern polar regions, showing an excess of particles instead of the expected depression. This indicates that the reconfiguration of the heliospheric magnetic field, caused by the reappearance of the northern polar coronal hole, starts dominating the modulation of galactic cosmic rays already at solar maximum.

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“…Thus, the particle transport in the inner heliosphere is very different at solar minimum, with coexisting different solar wind regimes. In this context it is interesting to note that Heber et al (1998) found only significant latitudinal gradients at solar minimum when Ulysses was embedded in the fast solar wind stream.…”

Section: Mev Electronsmentioning

confidence: 99%

The Ulysses fast latitude scans: COSPIN/KET results

Heber¹,

Sarri²,

Wibberenz

et al. 2003

Ann. Geophys.

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Abstract. 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 A<0-solar magnetic modulation epoch will establish itself once both polar coronal holes have developed.

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Latitudinal distribution of >106 MeV protons and its relation to the ambient solar wind in the inner southern and northern heliosphere: Ulysses Cosmic and Solar Particle Investigation Kiel Electron Telescope Results

Cited by 24 publications

References 21 publications

Differences in the temporal variations of galactic cosmic ray electrons and protons: Implications from Ulysses at solar minimum

Differences in the temporal variations of galactic cosmic ray electrons and protons: Implications from Ulysses at solar minimum

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

The Ulysses fast latitude scans: COSPIN/KET results

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Latitudinal distribution of >106 MeV protons and its relation to the ambient solar wind in the inner southern and northern heliosphere: Ulysses Cosmic and Solar Particle Investigation Kiel Electron Telescope Results

Cited by 24 publications

References 21 publications

Differences in the temporal variations of galactic cosmic ray electrons and protons: Implications from Ulysses at solar minimum

Differences in the temporal variations of galactic cosmic ray electrons and protons: Implications from Ulysses at solar minimum

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

The Ulysses fast latitude scans: COSPIN/KET results

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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