Energetic solar particle events in a stream-structured solar wind

AbstractNew developments in the understanding of the interplanetary transport of solar cosmic rays are reviewed. Based on carefully analyzed solar particle events observed on the Helios and ISEE 3 spacecraft, the relation of transport parameters to the structure of the interplanetary magnetic field is discussed. Special emphasis is given to a comparison of particle mean free paths determined from fits to intensity and anisotropy profiles with theoretical predictions derived from magnetic field spectra measured at the time of the solar particle event. Different aspects of the turbulence and wave models for the magnetic fluctuations are considered, including the effects resulting from the finite temperature of the plasma and of resonance broadening. It is found that a modified quasi-linear theory of particle scattering taking into account the effects of plasma waves propagating with respect to the average solar wind flow and the proper treatment of the dispersion relation at high wavenumber gives results which are in several cases in good agreement with particle observations in the interplanetary medium between 0.3 and 1 AU, indicating that quasi-linear theory is probably a good approximation to a full theory of solar particle transport. This has important implications for other astrophysical problems where quasi-linear theory is often used, such as the propagation and acceleration of Galactic cosmic rays and particle acceleration at shock waves.Subject headings: acceleration of particles — cosmic rays — interplanetary medium — MHD — solar wind — Sun: particle emission

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Comparison of Radiation Transport Codes for Solar Particle Events Space Environment: II

AIAA SPACE 2009 Conference & Exposition ◽

10.2514/6.2009-6573 ◽

2009 ◽

Author(s):

Ram Tripathi ◽

Lawrence Townsend ◽

Tony Gabriel ◽

Lawrence PIinsky ◽

Tony Slaba

Keyword(s):

Radiation Transport ◽

Space Environment ◽

Solar Particle Events ◽

Solar Particle

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Radiation Risks in Cis-Lunar Space for a Solar Particle Event Similar to the February 1956 Event

Aerospace ◽

10.3390/aerospace8040107 ◽

2021 ◽

Vol 8 (4) ◽

pp. 107

Author(s):

Fahad A. Zaman ◽

Lawrence W. Townsend

Keyword(s):

Effective Dose ◽

Energy Transport ◽

Radiation Transport ◽

Organ Doses ◽

Solar Particle Events ◽

Solar Particle ◽

Transport Code ◽

On Line ◽

Critical Organ ◽

In Cis

Solar particle events (SPEs) can pose serious threats for future crewed missions to the Moon. Historically, there have been several extreme SPEs that could have been dangerous for astronauts, and thus analyzing their potential risk on humans is an important step towards space exploration. In this work, we study the effects of a well-known SPE that occurred on 23 February 1956 on a mission in cis-Lunar space. Estimates of the proton fluence spectra of the February 1956 event were obtained from three different parameterized models published within the past 12 years. The studied geometry consists of a female phantom in the center of spherical spacecraft shielded by aluminum area densities ranging from 0.4 to 40 g cm−2. The effective dose, along with lens, skin, blood forming organs, heart, and central nervous system doses, were tallied using the On Line Tool for the Assessment of Radiation In Space (OLTARIS), which utilizes the High Z and Energy TRansport code (HZETRN), a deterministic radiation transport code. Based on the parameterized models, the results herein show that thicknesses comparable to a spacesuit might not protect against severe health consequences from a February 1956 category event. They also show that a minimum aluminum shielding of around 20 g cm−2 is sufficient to keep the effective dose and critical organ doses below NASA’s permissible limits for such event. In addition, except for very thin shielding, the input models produced results that were within good agreement, where the doses obtained from the three proton fluence spectra tended to converge with slight differences as the shielding thickness increases.

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