arXiv subjects

D. Ruffolo

Publications and source records attributed to D. Ruffolo.

22 records · Page 2Linked to original sources

arXiv1997

Charge States of Solar Cosmic Rays and Constraints on Acceleration Times and Coronal Transport

We examine effects on the charge states of energetic ions associated with gradual solar flares due to shock heating and stripping at high ion velocities. Recent measurements of the mean charges of various elements after the flares of 1992 Oct 30 and 1992 Nov 2 allow one to place limits on the product of the electron density times the acceleration or coronal residence time. In particular, any residence in coronal loops must be for < 0.03 s, which rules out models of coronal transport in loops, such as the bird cage model. The results do not contradict models of shock acceleration of energetic ions from coronal plasma at various solar longitudes.

astro-ph↗

arXiv1996

Observations of Electrons from the Decay of Solar Flare Neutrons

We have found evidence for fluxes of energetic electrons in interplanetary space on board the ISEE-3 spacecraft which we interpret as the decay products of neutrons generated in a solar flare on 1980 June 21. The decay electrons arrived at the s/c shortly before the electrons from the flare and can be distinguished from the latter by their distinctive energy spectrum. The time profile of the decay electrons is in good agreement with the results from a simulation based on a scattering mean free path derived from a fit to the flare electron data. The comparison with simultaneously observed decay protons and a published direct measurement of high-energy neutrons places important constraints on the parent neutron spectrum.

astro-ph↗

arXiv1995

Formation, Propagation, and Decay of Coherent Pulses of Solar Cosmic Rays

We have performed numerical simulations of the interplanetary transport of solar cosmic rays. The particles form a coherent pulse within $\sim0.01$ AU after their injection. The gradual decrease of a pulse's speed and anisotropy can be understood in terms of an equilibrium between pitch-angle scattering and focusing. The results should be useful for estimating times of particle injection.

astro-ph↗

arXiv1994

Effect of Adiabatic Deceleration on the Focused Transport of Solar Cosmic Rays

In the framework of focused transport theory, adiabatic deceleration arises from adiabatic focusing in the solar wind frame and from differential solar wind convection. An explicit formula is given for the deceleration of individual particles as a function of the pitch angle. Deceleration and other first-order effects of the solar wind, including convection, are incorporated into a numerical code for simulating the transport of energetic particles along the interplanetary magnetic field. We use this code to model the transport of solar flare protons. We find that including deceleration can increase the decay rate of the near-Earth intensity by 75\% more than would be expected based on advection from higher momenta, due to an interplay with diffusive processes. Improved response functions are derived for the impulsive injection of particles near the Sun, and it is found that neglecting deceleration leads to incorrect estimates of the scattering mean free path based on the intensity decay alone, especially for lower-energy particles.

astro-ph↗