Stephen White Gyroresonance emission in FORWARD & Developments in radio telescopes
Free-Free Opacity Two different “modes,” or circular polarizations ( =+1 o- mode, = 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 = (T R T L )/(T R +T L ) = 0 for isothermal atmosphere because temperature is same in both layers In “real” atmosphere get polarization due to temperature gradient
Gyroresonance emission Opacity results from electrons gyrating in coronal magnetic fields at f B = 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/mc 2 sin 2 ) s-1 where s = 1, 2, 3, … is the harmonic Because T/mc 2 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
Gyroresonance opacity at low harmonics
Model sunspot gyroresonance layers
OVSA Expansion Project Dale E. Gary Professor, Physics, Center for Solar-Terrestrial Research New Jersey Institute of Technology 7
8 09/24/2012Prototype Review Meeting
09/24/2012Prototype Review Meeting 10
LOFAR’s first solar image 11
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! 12
MWA station and 32T layout Consortium with PAPER project in the future 13
The Long Wavelength Array US project involving Naval Research Laboratory, U. New Mexico, Los Alamos, Virginia Tech, U. Texas, NRAO, AFRL, …
“Zebra” patterns more common in flares
Unexpected fine structure above 60 MHz
“Wrigglers” at 10 millisecond resolution
“Type III” burst at RSTN (3 seconds, 0.15 MHz)
At LWA1 resolution
Allen Telescope Array 21
LOFAR’s first solar image ATA solar image 22
Siberian Solar Radio Telescope (SSRT) 23
EVLA: better frequency, time coverage 24
EVLA observation of the Sun at F10.7
ALMA 26
ALMA can observe the Sun! Will be wonderful for flares (but small FOV) and chromosphere studies IF we can get observing time … 27
Solar Submillimeter Telescope (Argentina/Brazil) 28
The Sun