Modeling the propagation of solar energetic particles in corotating compression regions of solar wind

Abstract

[1] We present the first modeling of solar energetic particle (SEP) events inside corotating compression regions. We consider gradual compressions in the interplanetary magnetic field brought on by interaction of the solar wind streams of different speed. The compression model is similar to that previously suggested for the acceleration of lowenergy particles associated with corotating interaction regions (CIRs). In the framework of focused transport, we perform Monte Carlo simulations of the SEP propagation, adiabatic deceleration and reacceleration. A trap-like structure of the interplanetary magnetic field modifies the SEP intensity-time profiles, energy spectra, and anisotropy. Particle diffusion and adiabatic deceleration are typically reduced. For this reason, at a corotating vantage point the SEP event development after the intensity maximum is slower than would be expected based on the modeling in the standard, Archimedean spiral field. At the noncorotating spacecraft the magnetic tube convection past the observer becomes more important. The numerical model forms a basis on which to interpret SEP observations made by present and future spacecrafts at the longitude-dependent speed of solar wind. In particular, the modeling results are similar to the patterns observed with the ERNE particle telescope on board SOHO in August 1996. In the proton anisotropy data, we find a signature of the magnetic mirror associated with the CIR. A relation is established between the spectra observed at 1 AU and the SEP injection spectrum near the Sun.

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

“…An assumption of flatter spectrum in the SEP events is consistent with the observations. Kocharov et al (2003) showed that compression regions associated with CIRs near 1 AU could re-accelerate solar energetic particles.…”

History of cosmic ray research in Finland

“…The models are based on the Monte-Carlo simulation technique and can address practically all aspects of the solar energetic particle production and transport problem, including acceleration, propagation, charge states (e.g., Kocharov et al, 2003) and elemental abundances (Sandroos and Vainio, 2007) of solar energetic ions, as well as the low-frequency plasma turbulence generated by the accelerated particles in the corona and solar wind (Vainio and Laitinen, 2007). The results of such models are applied to space-borne observations of solar energetic particles.…”

“…State-of-the-art experiment-oriented modeling of solar energetic particle events, along with their acceleration and propagation in the interplanetary medium and magnetic fields, are successfully conducted at the Universities of Turku and Helsinki (e.g., Vainio et al, 2000;Kocharov and Torsti, 2003;Vainio and Laitinen, 2007;Sandroos and Vainio, 2007). The models are based on the Monte-Carlo simulation technique and can address practically all aspects of the solar energetic particle production and transport problem, including acceleration, propagation, charge states (e.g., Kocharov et al, 2003) and elemental abundances (Sandroos and Vainio, 2007) of solar energetic ions, as well as the low-frequency plasma turbulence generated by the accelerated particles in the corona and solar wind (Vainio and Laitinen, 2007).…”

Modeling the solar energetic particle events in closed structures of interplanetary magnetic field

“…A nonstandard interplanetary magnetic field may be associated also with corotating interaction regions (CIRs). We modeled the propagation of solar energetic particles inside a CIR [ Kocharov et al , 2003], but the SEP transport inside the CME ejecta has not yet been simulated.…”