Solar energetic particle access to distant longitudes through turbulent field-line meandering

Laitinen, Timo; Kopp, A.; Effenberger, Frederic; Dalla, S.; Marsh, Michael

doi:10.1051/0004-6361/201527801

Cited by 75 publications

(94 citation statements)

References 65 publications

(139 reference statements)

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“…The mean free paths presented in Figure 1 are consistent with those obtained using interplanetary turbulence properties (e.g. Pei et al 2010;Laitinen et al 2016;Strauss, Dresing & Engelbrecht 2017) and SEP observation analysis (e.g. Palmer 1982;Torsti, Riihonen & Kocharov 2004).…”

Section: Modelsupporting

confidence: 82%

“…While such a model is easy to implement and can be used as the first approach, as in, e.g., Laitinen et al (2016), we will consider here an improvement to the modelling of the transition, based on the work by Laitinen & Dalla (2017). In Appendix A, we derive a model with timedependent diffusion coefficient, which will justify fitting the variance with functional forms such as Equation (A6).…”

Section: Resultsmentioning

confidence: 99%

“…Simple models, such as the one applied in Laitinen et al (2016), which model the particle distribution evolution as cross-field diffusion of particles from meandering field lines provide a significant improvement as compared to the earlier models diffusing particles with respect to the mean magnetic field. Future fully consistent cross-field propagation models should also include the timescales related to the decoupling of the particles from the meandering field lines (Laitinen & Dalla 2017).…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Early propagation of energetic particles across the mean field in turbulent plasmas

Laitinen

Dalla

Marriott

2017

Monthly Notices of the Royal Astronomical Society

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Propagation of energetic particles across the mean field direction in turbulent magnetic fields is often described as spatial diffusion. Recently, it has been suggested that initially the particles propagate systematically along meandering field lines, and only later reach the time-asymptotic diffusive cross-field propagation. In this paper, we analyse cross-field propagation of 1-100 MeV protons in composite 2D-slab turbulence superposed on a constant background magnetic field, using full-orbit particle simulations, to study the non-diffusive phase of particle propagation with a wide range of turbulence parameters. We show that the early-time non-diffusive propagation of the particles is consistent with particle propagation along turbulently meandering field lines. This results in a wide cross-field extent of the particles already at the initial arrival of particles to a given distance along the mean field direction, unlike when using spatial diffusion particle transport models. The cross-field extent of the particle distribution remains constant for up to tens of hours in turbulence environment consistent with the inner heliosphere during solar energetic particle events. Subsequently, the particles escape from their initial meandering field lines, and the particle propagation across the mean field reaches time-asymptotic diffusion. Our analysis shows that in order to understand solar energetic particle event origins, particle transport modelling must include non-diffusive particle propagation along meandering field lines.

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Section: Modelsupporting

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Early propagation of energetic particles across the mean field in turbulent plasmas

Laitinen

Dalla

Marriott

2017

Monthly Notices of the Royal Astronomical Society

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“…Klein et al, 2008), or very high levels of lateral diffusion in a turbulent solar wind (e.g. Laitinen et al, 2016). The large spatial extent of global waves and their ability to accelerate particles far from the erupting active region therefore suggests that more SEP events should have been identified.…”

Section: Relationship With Solar Energetic Particle Eventsmentioning

confidence: 99%

A Statistical Analysis of the Solar Phenomena Associated with Global EUV Waves

et al. 2017

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Solar eruptions are the most spectacular events in our solar system and are associated with many different signatures of energy release including solar flares, coronal mass ejections, global waves, radio emission and accelerated particles. Here, we apply the Coronal Pulse Identification and Tracking Algorithm (CorPITA) to the high-cadence synoptic data provided by the Solar Dynamics Observatory (SDO) to identify and track global waves observed by SDO. 164 of the 362 solar flare events studied (45%) were found to have associated global waves with no waves found for the remaining 198 (55%). A clear linear relationship was found between the median initial velocity and the acceleration of the waves, with faster waves exhibiting a stronger deceleration (consistent with previous results). No clear relationship was found between global waves and type II radio bursts, electrons or protons detected in situ near Earth. While no relationship was found between the wave properties and the associated flare size (with waves produced by flares from B to X-class), more than a quarter of the active regions studied were found to produce more than one wave event. These results suggest that the presence of a global wave in a solar eruption is most likely determined by the structure and connectivity of the erupting active region and the surrounding quiet solar corona rather than by the amount of free energy available within the active region.

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“…Using the novel modelling approach introduced in L2013, Laitinen et al (2016) developed a particle transport model in the heliospheric Parker Spiral magnetic field configuration. They demonstrated that in moderate turbulence conditions, parametrised by the parallel scattering mean free path l k = 0.3 AU, fast spreading of SEPs across the field to a wide range of longitudes, as found by multi-spacecraft observations of SEP events (e.g.…”

Section: Introductionmentioning

confidence: 99%

The effect of turbulence strength on meandering field lines and Solar Energetic Particle event extents

Laitinen

Effenberger

Kopp

et al. 2018

J. Space Weather Space Clim.

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-Insights into the processes of Solar Energetic Particle (SEP) propagation are essential for understanding how solar eruptions affect the radiation environment of near-Earth space. SEP propagation is influenced by turbulent magnetic fields in the solar wind, resulting in stochastic transport of the particles from their acceleration site to Earth. While the conventional approach for SEP modelling focuses mainly on the transport of particles along the mean Parker spiral magnetic field, multi-spacecraft observations suggest that the cross-field propagation shapes the SEP fluxes at Earth strongly. However, adding cross-field transport of SEPs as spatial diffusion has been shown to be insufficient in modelling the SEP events without use of unrealistically large cross-field diffusion coefficients. Recently, Laitinen et al. [ApJL 773 (2013b); A&A 591 (2016)] demonstrated that the early-time propagation of energetic particles across the mean field direction in turbulent fields is not diffusive, with the particles propagating along meandering field lines. This early-time transport mode results in fast access of the particles across the mean field direction, in agreement with the SEP observations. In this work, we study the propagation of SEPs within the new transport paradigm, and demonstrate the significance of turbulence strength on the evolution of the SEP radiation environment near Earth. We calculate the transport parameters consistently using a turbulence transport model, parametrised by the SEP parallel scattering mean free path at 1 AU, l Ã k , and show that the parallel and cross-field transport are connected, with conditions resulting in slow parallel transport corresponding to wider events. We find a scaling s ';max ∝ð1=l Ã k Þ 1=4 for the Gaussian fitting of the longitudinal distribution of maximum intensities. The longitudes with highest intensities are shifted towards the west for strong scattering conditions. Our results emphasise the importance of understanding both the SEP transport and the interplanetary turbulence conditions for modelling and predicting the SEP radiation environment at Earth.

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Solar energetic particle access to distant longitudes through turbulent field-line meandering

Cited by 75 publications

References 65 publications

Early propagation of energetic particles across the mean field in turbulent plasmas

Early propagation of energetic particles across the mean field in turbulent plasmas

A Statistical Analysis of the Solar Phenomena Associated with Global EUV Waves

The effect of turbulence strength on meandering field lines and Solar Energetic Particle event extents

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