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Gyroresonance emission in FORWARD & Developments in radio telescopes. Stephen White. Free-Free Opacity. Two different “modes,” or circular polarizations ( s =+1 o-mode, s = - 1 x-mode)

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Stephen White

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Gyroresonance emission in



Developments in radio telescopes

Stephen White

free free opacity
Free-Free Opacity
  • Two different “modes,” or circular polarizations (s=+1 o-mode, s=-1 x-mode)
  • X-mode has higher opacity, so becomes optically thick slightly higher in the chromosphere, while o-mode is optically thick slightly lower
  • Polarization P = (TR-TL)/(TR+TL) = 0 for isothermal atmosphere because temperature is same in both layers
  • In “real” atmosphere get polarization due to temperature gradient
gyroresonance emission
Gyroresonance emission
  • Opacity results from electrons gyrating in coronal magnetic fields at fB = 2.8 106 B Hz: linear scaling of B with frequency.
  • In the non-flare (non-relativistic) corona this produces narrow resonances, i.e. physically very thin layers (tens of km).
  • Opacity  n B/(B/l) (T/mc2 sin2)s-1 where s = 1, 2, 3, … is the harmonic
  • Because T/mc2 is 1/3000, opacity drops by 3 orders of magnitude from one layer to the next
  • Big difference in opacity of two polarizations of electromagnetic waves: extraordinary mode interacts more with electrons than ordinary mode
ovsa expansion project

OVSA Expansion Project

Dale E. Gary

Professor, Physics, Center for Solar-Terrestrial Research

New Jersey Institute of Technology

Prototype Review Meeting

magnetic and plasma structure of active regions

murchison widefield array
Murchison Widefield Array

Joint US/Australian project located at the candidate SKA site in Western Australia (miles and miles from anywhere)

US players are Haystack, Harvard/CfA, MIT

Australian players are CSIRO/ATNF, Curtin University (WA) with a lot of support from Australian (federal) and West Australian (state) governments

Covering the high-frequency end of the LOFAR range, same technique, same science goals.

Using GPU units to do their data processing!


The Long Wavelength Array

US project involving Naval Research Laboratory, U. New Mexico, Los Alamos, Virginia Tech, U. Texas, NRAO, AFRL, …


ATA solar image

LOFAR’s first solar image


ALMA can observe the Sun! Will be wonderful for flares (but small FOV) and chromosphere studies IF we can get observing time …