Energetic particle observations by Ulysses during the declining phase of solar cycle 23

Malandraki, O.; Marsden, R. G.; Tranquille, C.; Forsyth, R. J.; Elliott, H. A.; Lanzerotti, L. J.; Geranios, A.

doi:10.1029/2006ja011876

Cited by 18 publications

(26 citation statements)

References 36 publications

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“…The observations by Malandraki et al (2007Malandraki et al ( , 2008 during the periods of CIR/SEP combinations similarly show CIR abundance of the He/O ratio whereas C/O was consistent with SEP values. They suggested that since there is not much C production beyond 3 AU the CIR might have re-accelerated C ions from the SEP population.…”

Section: He/o Ratiosupporting

confidence: 65%

“…However, more recent observations (Sanderson et al, 1995;Torsti, Anttila, and Sahla, 1999;Malandraki et al, 2007Malandraki et al, , 2008, and statistical (Desai et al, 1998;Mason et al, 2008a) studies of corotating energetic particle phenomena suggest that sub-MeV particles from SEP events may provide a seed population for CIR acceleration. Such a sub-MeV particle population appears to be an attractive source since it can supply ions with energies above the threshold energy which is required for the ion acceleration by the CIR shocks.…”

Section: Introductionmentioning

confidence: 99%

“…They proposed a re-acceleration of SEPs, injected two days earlier, by the CIR. Malandraki et al (2007Malandraki et al ( , 2008 examined elemental composition of the energetic particle fluxes recorded at Ulysses at 5 AU during the periods of SEP/CIR combinations. They found the C/O ratio consistent with SEP values and suggest as one possibility that the CIR reverse shocks re-accelerated particles of this species from the SEP events themselves.…”

Section: Introductionmentioning

confidence: 99%

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STEREO Observations of Energetic Ions in Corotating Interaction Regions During the May 2007 Solar Events

et al. 2009

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Elemental composition and energy spectra of ∼ 0.1 -1.0 MeV/n heavy ions were analyzed in two corotating interaction region (CIR) events starting on 18 May (CIR1), and 24 May (CIR2), 2007, that occurred during two weak solar energetic particle (SEP) events. The data were taken by the Suprathermal Ion Telescope (SIT) instruments onboard STEREO-A and B. The ion intensity increases related to the CIR2 were much more pronounced compared to those associated with the CIR1, although the total pressure, the magnetic field magnitude and the speed difference between high and slow solar wind were less enhanced. We found that the ratio of CIR2 to CIR1 helium fluence decreases with energy as a power -law below ∼ 1 MeV/n. The energy spectra of hydrogen and helium inside the CIR2 region are much softer compared to the spectra observed in the CIR1 region. Based on these findings, we argue that the larger intensities in the CIR2 event could be due to an additional source population. The elemental abundances in CIR2 and the high-speed stream of the CIR1 region have a SEP-like composition. The energy spectra of hydrogen and helium inside the CIR2 were close to the preceding SEP event spectra. The similarity in the elemental abundances and in the spectral slopes suggests that the seed population of CIR2 are ions from the preceding SEP event. For the CIR1 event the ions seem to be contaminated by SEPs.

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Section: He/o Ratiosupporting

confidence: 65%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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STEREO Observations of Energetic Ions in Corotating Interaction Regions During the May 2007 Solar Events

et al. 2009

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“…3. They are correlated with periods of larger solar activity in January, August, September 2005, and December 2006 (Struminsky, 2007;Malandraki et al, 2007) and several ICMEs and solar energetic particle (SEP) events Lario and Roelof (2007) that have been observed in particular up to 2005.6, i.e. during C23/P1.…”

Section: Amplitudesmentioning

confidence: 87%

Observations of recurrent cosmic ray decreases during solar cycles 22 and 23

et al. 2008

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Abstract. 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<0) neither such a pronounced maximum nor significant decreases above 40 • . In other words: the periodicity in the cosmic ray intensity, which can be clearly seen in the slow solar wind, appears to vanish there. Theoretical models for drift effects, however, predict quite the opposite behaviour for the two solar cycles. To closer investigate this apparent contradiction, we first put the visual inspection of the data onto a more solid basis by performing a detailed Lomb (spectral) analysis. The next step consists of an analysis of the resulting periodicities at 1 AU in order to distinguish between spatial and temporal variations, so that we can obtain statements about the question in how far there is a correlation between the in-situ data at 1 AU and those measured by Ulysses at larger latitudes. We find a good correlation being present during cycle 22, but not for cycle 23. As one potential explanation for this behaviour, we suggest the difference in the coronal hole structures between the cycles 22 and 23 due to a large, stable coronal hole structure, which is present during cycle 22, Correspondence to: P. Dunzlaff (dunzlaff@physik.uni-kiel.de) but not in cycle 23. We support this possibility by comparing Yohkoh SXT and SOHO EIT maps.

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“…The SPE's association with type III solar radio bursts also need to be examined in future works with information on the magnetic condition around the flaring site from the type III burst [Klein et al, 2010[Klein et al, , 2011. The small values of |T H − T L | might be observed when an interplanetary structure is crossing over the spacecraft that can greatly modulate the energetic particle profiles and influence the particle propagation [Malandraki et al, 2007;Lario et al, 2008]. More detailed examinations of this effect should be performed for those events with simultaneous onset times in all energy channels.…”

Section: Summary and Discussionmentioning

confidence: 99%

Characteristics of four SPE groups with different origins and acceleration processes

et al. 2015

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Solar proton events (SPEs) can be categorized into four groups based on their associations with flare or CME inferred from onset timings as well as acceleration patterns using multienergy observations. In this study, we have investigated whether there are any typical characteristics of associated events and acceleration sites in each group using 42 SPEs from 1997 to 2012. We find the following: (i) if the proton acceleration starts from a lower energy, a SPE has a higher chance to be a strong event (> 5000 particle flux per unit (pfu)) even if its associated flare and/or CME are not so strong. The only difference between the SPEs associated with flare and CME is the location of the acceleration site. (ii) For the former (Group A), the sites are very low (∼ 1 Rs) and close to the western limb, while the latter (Group C) have relatively higher (mean = 6.05 Rs) and wider acceleration sites. (iii) When the proton acceleration starts from the higher energy (Group B), a SPE tends to be a relatively weak event (< 1000 pfu), although its associated CME is relatively stronger than previous groups. (iv) The SPEs categorized by the simultaneous acceleration in whole energy range within 10 min (Group D) tend to show the weakest proton flux (mean = 327 pfu) in spite of strong associated eruptions. Based on those results, we suggest that the different characteristics of SPEs are mainly due to the different conditions of magnetic connectivity and particle density, which are changed with longitude and height as well as their origin.

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Energetic particle observations by Ulysses during the declining phase of solar cycle 23

Cited by 18 publications

References 36 publications

STEREO Observations of Energetic Ions in Corotating Interaction Regions During the May 2007 Solar Events

STEREO Observations of Energetic Ions in Corotating Interaction Regions During the May 2007 Solar Events

Observations of recurrent cosmic ray decreases during solar cycles 22 and 23

Characteristics of four SPE groups with different origins and acceleration processes

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