The evolution of energetic particles and the emitted radiation in solar flares. Ph. D. Thesis

Technical Report · Thu Jun 01 00:00:00 EDT 1989

OSTI ID:5595272

Lu, E T

The evolution of accelerated particle distributions in a magnetized plasma and the resulting radiation are calculated, and the results are applied to solar flares. To study the radiation on timescales of order the particle lifetimes, the evolution of the particle distribution is determined by the use of the Fokker-Planck equation including Coulomb collisions and magnetic mirroring. Analytic solution to the equations are obtained for limiting cases such as homogeneous injection in a homogeneous plasma, and for small pitch angle. These analytic solutions are then used to place constraints on flare parameters such as density, loop length, and the injection timescale for very short implusive solar flares. For general particle distributions in arbitrary magnetic field and background density, the equation is solved numerically. The relative timing of microwaves and X-rays during individual flares is investigated. A number of possible sources for excessive microwave flux are discussed including a flattening in the electron spectrum above hard X-ray energies, thermal synchrotron emission, and trapping of electron by converging magnetic fields. Over shorter timescales, the Fokker-Planck equation is solved numerically to calculate the temporal evolution of microwaves and X-rays from nonthermal thick target models. It is shown that magnetic trapping will not account for the observed correlation of microwaves of approximately 0.15 seconds behind X-rays in flares with rapid time variation, and thus higher energy electrons must be accelerated later than lower energy electrons.

• Research Organization: Stanford Univ., CA (USA)
• OSTI ID: 5595272
• Report Number(s): N-89-25945; NASA-CR-185389; NAS-1.26:185389; CSSA-ASTRO-89-08; TRN: 91-011019
• Resource Relation: Other Information: Thesis
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
SOLAR FLARES
ELECTROMAGNETIC RADIATION
PARTICLE PRODUCTION
DENSITY
FOKKER-PLANCK EQUATION
PLASMA
THEORETICAL DATA
DATA
DIFFERENTIAL EQUATIONS
EQUATIONS
INFORMATION
NUMERICAL DATA
PARTIAL DIFFERENTIAL EQUATIONS
PHYSICAL PROPERTIES
RADIATIONS
SOLAR ACTIVITY
640104* - Astrophysics & Cosmology- Solar Phenomena