Discovery of Relativistic Positrons in Solar Flares with Microwave Imaging and Polarimetry

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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
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HAPPY BIRTHDAY, DALE!
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Dale Gary, Research HighlightsI. 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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Dale Gary, Research HighlightsII. Research
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Dale Gary, Research HighlightsII. Research
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Dale Gary, Research HighlightsII. Research
276 Citations
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HAPPY BIRTHDAY, DALE!
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BEST WISHES, DALE!
60 Million NSF Grant Will Upgrade EOVSA to FASR
NEWARK, Nov 5 2013
60
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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
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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

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Origin of Relativistic Positrons in Flares
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Acceleration of Ions
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Polarimetry a key to positron detection
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Nobeyama Radioheliograph (NoRH) is well suited
for our study
NoRH produces images of intensity (I RL) 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

1. single, spatially coinciding, sources at both 17
   and 34 GHz
2. 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
3. the total power V must have opposite signs at 17
   and 34 GHz.

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13 Mar 2000
Yohkoh
NoRP
Gan et al (2001).
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Gan et al (2001).
Bz, photosphere
V, 17 GHz, RCP
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Spectra
X-ray
Gan et al (2001).
MW
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Polarization
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24 Aug 2002
gt90 MeV
70-150 keV
0.7-2 MeV
V.Kurt. Pr. Com.
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17 May 1999
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15 Jul 2004
Kawate et al. 2012
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03 Mar 2000
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02 Sep 2001
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23 Apr 1998
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24 Oct 2003
?
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9 Jul 2012
NO
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Summary

• 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.