Properties of high heliolatitude solar energetic particle events and constraints on models of acceleration and propagation

Dalla, S.; Balogh, A.; Krucker, S.; Posner, A.; Müller‐Mellin, R.; Anglin, J. D.; Hofer, M. Y.; Marsden, R. G.; Sanderson, T. R.; Tranquille, C.; Heber, B.; Zhang, M.; McKibben, R. B.

doi:10.1029/2003gl017139

Cited by 67 publications

(48 citation statements)

References 10 publications

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“…Dalla et al (2003a, b) studied the differences between SEP onset times and times-to-maximum as a function of latitude and found that the delays at Ulysses were best organized by the difference in latitude between the associated flare and the s/c. Dalla et al (2003b) concluded that the presence of a shock is not necessary for creating the near-equal intensities observed at Ulysses and near Earth during decay phases; these observations are better explained by diffusion across the main IMF. Figure 53 shows intensity-time profiles of ∼1-200 MeV protons and ∼3-8 MeV electrons during the January 1, 1978 SEP event as observed at four different s/c.…”

Section: Sep Observations At Helios and Ulyssesmentioning

confidence: 88%

Large gradual solar energetic particle events

Desai

Giacalone

2016

Living Rev. Sol. Phys.

419

305

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Solar energetic particles, or SEPs, from suprathermal (few keV) up to relativistic (∼few GeV) energies are accelerated near the Sun in at least two ways: (1) by magnetic reconnection-driven processes during solar flares resulting in impulsive SEPs, and (2) at fast coronal-mass-ejection-driven shock waves that produce large gradual SEP events. Large gradual SEP events are of particular interest because the accompanying high-energy (>10s MeV) protons pose serious radiation threats to human explorers living and working beyond low-Earth orbit and to technological assets such as communications and scientific satellites in space. However, a complete understanding of these large SEP events has eluded us primarily because their properties, as observed in Earth orbit, are smeared due to mixing and contributions from many important physical effects. This paper provides a comprehensive review of the current state of knowledge of these important phenomena, and summarizes some of the key questions that will be addressed by two upcoming missions-NASA's Solar Probe Plus and ESA's Solar Orbiter. Both of these missions are designed to directly and repeatedly sample the near-Sun environments where interplanetary scattering and transport effects are significantly reduced, allowing us to discriminate between different acceleration sites and mechanisms and to isolate the contributions of numerous physical processes occurring during large SEP events.

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Section: Sep Observations At Helios and Ulyssesmentioning

confidence: 88%

Large gradual solar energetic particle events

Desai

Giacalone

2016

Living Rev. Sol. Phys.

419

305

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“…In Figure 2 we show summary plots of the events number 2, 3 and 4 of Sanderson et al (2003b). These events have also been studied in detail by Dalla et al (2003aDalla et al ( , 2003b, Lario et al (2004) and McKibben at al. (2003).…”

Section: The Second Northern Polar Passmentioning

confidence: 85%

“…Larger than expected delays in onset times were observed for most of these highlatitude events (Dalla et al, 2003a, corresponding typically to 120 to 350 minutes from the flare onset. These delay times and the path lengths were correlated by Dalla et al (2003aDalla et al ( , 2003b) against several variables. The best correlation was found with difference in latitude between the flare site and the latitude of Ulysses, this correlation being surprisingly better than the correlation with the angular separation between the site and Ulysses.…”

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confidence: 99%

Propagation of Energetic Particles to High Heliographic Latitudes

Sanderson¹

2004

Proc. IAU

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Abstract. The Ulysses spacecraft has now completed its second orbit over the poles of the Sun. Energetic particles associated with CMEs were observed at the highest latitudes over both poles, quite unlike the first polar pass when virtually no CME or CIR accelerated particles were observed at the very highest latitudes. We present observations of solar energetic particle events observed in the energy range ∼1 MeV to ∼100 MeV made by the COSPIN instrument, when the spacecraft was at high heliographic latitude over the northern pole, above the current sheet, and immersed in high-speed solar-wind flow coming from the northern polar coronal hole. We discuss the rise to maximum, the onset time and the anisotropy of the energetic particles. We find that, unlike the events observed at mid and low latitudes, the particle angular distributions were almost isotropic, but with a net outward flow along the magnetic field lines. We compare these events with other events observed at lower latitudes.

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“…Whether or not an SEP event will be detected, for example near Earth, depends on the location at the Sun of the parent event: eruptions at Western locations on the solar disk have a much higher likelihood of resulting in an SEP event at Earth, due to the curvature of the Parker spiral interplanetary magnetic field. However, in many events particles can be detected at locations widely separated, either in longitude (e.g., [124]) or in latitude (e.g., [25]), from the parent region. While this was thought initially to apply only to gradual events, it has been shown that impulsive events can also be detected over wide longitudinal ranges [147].…”

Section: Location Of Parent Active Regionmentioning

confidence: 99%

The acceleration and propagation of solar energetic particles

Dalla

2004

AIP Conference Proceedings

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Solar Energetic Particles (SEPs) are an important component of Space Weather, including radiation hazard to humans and electronic equipment, and the ionisation of the Earth's atmosphere. We review the key observations of SEPs, our current understanding of their acceleration and transport, and discuss how this knowledge is incorporated within Space Weather forecasting tools. Mechanisms for acceleration during solar flares and at shocks driven by Coronal Mass Ejections are discussed, as well as the timing relationships between signatures of solar eruptive events and the detection of SEPs in interplanetary space. Evidence on how the parameters of SEP events are related to those of the parent solar activity is reviewed and transport effects influencing SEP propagation to near-Earth locations are examined. Finally, the approaches to forecasting Space Weather SEP effects are discussed. We conclude that both flare and CME shock acceleration contribute to Space Weather relevant SEP populations and need to be considered within forecasting tools.

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Properties of high heliolatitude solar energetic particle events and constraints on models of acceleration and propagation

Cited by 67 publications

References 10 publications

Large gradual solar energetic particle events

Large gradual solar energetic particle events

Propagation of Energetic Particles to High Heliographic Latitudes

The acceleration and propagation of solar energetic particles

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