Examination of broadband coherent synchrotron radiation to describe THz and sub-THz solar flare spectral emissions

Conference · Sat May 01 04:00:00 EDT 2010

OSTI ID:1997385

Klopf, John; Kaufmann, Pierre; Raulin, Jean-Pierre

Over the past decade, interest in terrestrial applications for THz radiation has grown. In particular, much effort has been directed toward development of new higher power sources. One method for producing very high power coherent broadband microwave to THz radiation has been demonstrated in laboratory accelerators, where relativistic bunches of electrons are compressed and accelerated using specially designed magnetic structures. The resulting synchrotron emission from suitably compressed electron bunches exhibits a coherent enhancement for wavelengths approximately equal to or longer than the bunch length. This produces a modified synchrotron spectrum with a second peak at lower frequency associated with the coherent synchrotron radiation (CSR), with power proportional to the square of the number electrons undergoing the process. The CSR spectrum can also be produced from microbunching that is self-induced in larger bunches as a result from the interaction of the high energy electrons with the coherent component of their own radiation field. In either case, the CSR peak occurs at a frequency related to the spatial charge density of the high energy electrons. Here, we propose how the CSR mechanism may operate as a source to explain certain anomalous spectral features recently identified in the microwave to sub-THz emission of solar flare events. We outline the methods used in laboratory accelerators to produce CSR emission from high energy electron bunches, and how these methods may be related to magneto-active plasma medium where solar flare electron beams are accelerated. Utilizing estimates for active region magnetic field structures and solar flare plasma parameters, we have calculated the CSR and the ISR spectral components and compare these results to the anomalous spectrum observed from microwaves to sub-THz frequencies during the solar flare event of November 4, 2003.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• DOE Contract Number: AC05-06OR23177
• OSTI ID: 1997385
• Report Number(s): JLAB-FEL-10-1294; DOE/OR/23177-7092
• Country of Publication: United States
• Language: English