Discovery of Relativistic Positrons in Solar Flares with Microwave Imaging and Polarimetry Gregory D. Fleishman, Alexander T. Altyntsev, Natalia S. Meshalkina NJIT 05 Nov. 2013
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Dale Gary, Research Highlights I. Instrumentation Owens Valley Solar Array (OVSA) Korean Solar Radio Burst Locator (KSRBL) FASR Subsystem Testbed (FST) EOVSA Subsystem Testbed (EST) Expanded OVSA (EOVSA )
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Discovery of Relativistic Positrons in Solar Flares with Microwave Imaging and Polarimetry Gregory D. Fleishman, Alexander T. Altyntsev, Natalia S. Meshalkina NJIT 05 Nov. 2013
Plan of the talk Where relativistic positrons come from in flares? What is the positron contribution to the microwave emission? How emission by positrons can be distinguished from that by electrons? Can this be done with existing microwave databases? Data analysis Discussion and conclusions
Origin of Relativistic Positrons in Flares
Acceleration of Ions
Polarimetry – a key to positron detection
Nobeyama Radioheliograph (NoRH) is well suited for our study: NoRH produces images of intensity (I = R+L) and polarization (V = R – L) at 17 GHz while of the intensity only at 34 GHz. In addition, Nobeyama Polarimeters (NoRP) (Nakajima 1985) observe total power data (both I and V) at a number of single frequencies including 17 and 35 GHz. This set of observational tools suggests the following strategy of identifying properties of solar bursts with unambiguous positron contribution: (i)single, spatially coinciding, sources at both 17 and 34 GHz; (ii)the 34 GHz emission must come from an area where the 17 GHz V displays a unipolar distribution (i.e., the polarization of 17 GHz emission has a definite sense throughout the region of 34 GHz emission); and (iii) the total power V must have opposite signs at 17 and 34 GHz.
Gan et al (2001). 13 Mar 2000 YohkohNoRP
Gan et al (2001). V, 17 GHz, RCP Bz, photosphere
Gan et al (2001). X-ray MW Spectra
Polarization
24 Aug 2002 >90 MeV keV MeV V.Kurt. Pr. Com.
17 May 1999
15 Jul 2004 Kawate et al. 2012
03 Mar 2000
02 Sep 2001
23 Apr 1998
24 Oct 2003 ?
9 Jul 2012 NO
High-frequency microwave imaging spectropolarimetry offers a new way of detecting and studying relativistic positrons from solar flares. Analysis of the Nobeyama database augmented by other context data reveals around 10 events-candidates with the relativistic positron signature; a few of them unambiguously show all expected evidence, so the conclusion that the positrons dominated in producing high-frequency microwave emission in those events seems inescapable. New generation of the radio imaging instruments observing at many high frequencies, such as JVLA and ALMA, promises that the positron contribution to the GS emission can be routinely observed in many events. Being observed at many frequencies the relativistic positron energy spectrum and spatial distribution can be measured in great detail as a function of time. Summary