Center-to-Limb Variation of Microwave Emissions from Thermal-Rich and Thermal-Poor Solar Flares

Details Center-to-Limb Variation of Microwave Emissions from Thermal-Rich and Thermal-Poor Solar Flares Center-to-Limb Variation of Microwave Emissions from Thermal-Rich and Thermal-Poor Solar Flares

Dec 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufmsh41a1913k&link_type=abstract

American Geophysical Union, Fall Meeting 2011, abstract #SH41A-1913

Astronomy and Astrophysics

Astrophysics

[7514] Solar Physics, Astrophysics, And Astronomy / Energetic Particles, [7519] Solar Physics, Astrophysics, And Astronomy / Flares, [7534] Solar Physics, Astrophysics, And Astronomy / Radio Emissions

Scientific paper

Non-thermal microwave emissions observed in the impulsive phase of solar flares are produced by the gyrosynchrotron mechanism, which depends on a number of physical parameters such as electron energy spectra, their pitch angle distribution, magnetic field strength, angle between line of sight and the magnetic field (viewing angle), and the number of electrons. Therefore, it is difficult to determine those physical parameters uniquely only from the observed quantities of individual microwave burst. Statistical analysis of microwave bursts by using a number of flare events provide us a way to find mutual relationships between different quantities, and thus are useful to restrict the possible domain of those physical quantities of the microwave source. The pitch angle distribution of accelerated electrons is of a crucial importance for the problem of particle acceleration in solar flares. A clue to know the pitch angle distribution of accelerated particles could be obtained from the center-to-limb variations of observed microwave emissions, since relativistic electrons trapped in flare loops emit the microwaves to the direction of their velocity, and the viewing angle effect, i.e., center-to-limb variation of the flare emission, can be related to the pitch angle distribution of accelerated electrons. A statistical analysis of microwave flare events is performed by using the event list of Nobeyama Radioheliograph in 1996-2009. We examine center-to-limb variations of17GHz and 34GHz flux by dividing the flare events into different groups with respect to the 'thermal plasma richness' (ratio of the peak flux of soft X-ray to non-thermal microwave emissions) and the duration of microwave bursts. It is found that peak flux of 17 and 34GHz tend to be higher toward the limb for thermal-rich flares with short durations. We propose that the thermal-rich flares, which are supposed to be associated with an efficient precipitation of high energy particles into the chromosphere, have a pitch angle distribution of non-thermal electrons with a higher population along the flare loop.

Affiliated with

Also associated with

No associations

Rating

Center-to-Limb Variation of Microwave Emissions from Thermal-Rich and Thermal-Poor Solar Flares does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Center-to-Limb Variation of Microwave Emissions from Thermal-Rich and Thermal-Poor Solar Flares, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Center-to-Limb Variation of Microwave Emissions from Thermal-Rich and Thermal-Poor Solar Flares will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-879263