Statistical analysis of interplanetary magnetic field path lengths from solar energetic electron events observed by WIND

Abstract

We calculate the interplanetary magnetic field path lengths traveled by electrons in solar electron events detected by the WIND 3DP instrument from $1994$ to $2016$. The velocity dispersion analysis method is applied for electrons at energies of $\sim$ $27$ keV to $310$ keV. Previous velocity dispersion analyses employ the onset times, which are often affected by instrumental effects and the pre-existing background flux, leading to large uncertainties. We propose a new method here. Instead of using the peak or onset time, we apply the velocity dispersion analysis to the times that correspond to the rising phase of the fluxes that are a fraction, $\eta$, of the peak flux. We perform statistical analysis on selected events whose calculated path lengths have uncertainties smaller than $0.1$ AU. The mean and standard deviation, ($\mu$, $\sigma$), of the calculated path lengths corresponding to $\eta =$ $3/4$, $1/2$, and $1/3$ of the peak flux is ($1.17$ AU, $0.17$ AU), ($1.11$ AU, $0.14$ AU), and ($1.06$ AU, $0.15$ AU). The distribution of the calculated path lengths is also well fitted by a Gaussian distribution for the $\eta =3/4$ and $1/3$ cases. These results suggest that in these electron events the interplanetary magnetic field topology is close to the nominal Parker spiral with little field line meandering. Our results have important implications for particles' perpendicular diffusion.

References in corpus (1)

• Correcting for interplanetary scattering in velocity dispersion analysis of solar energetic particles

Cited by in corpus (4)

• From Sun to interplanetary space: What is the pathlength of Solar Energetic Particles?
• A Primer on Focused Solar Energetic Particle Transport: Basic physics and recent modelling results
• The unusual widespread solar energetic particle event on 2013 August 19. Solar origin and particle longitudinal distribution
• Random Walk and Trapping of Interplanetary Magnetic Field Lines: Global Simulation, Magnetic Connectivity, and Implications for Solar Energetic Particles