ROSAROSA
A high-cadence synchronized multi-camera A high-cadence synchronized multi-camera solar imaging systemsolar imaging system
Dr. Mihalis MathioudakisDr. Mihalis Mathioudakis
Physics and Astronomy, Queen’s University BelfastPhysics and Astronomy, Queen’s University Belfast
ROSA : Rapid Oscillations in the Solar AtmosphereROSA : Rapid Oscillations in the Solar Atmosphere
• History (SECIS – RDI)• Science examples • Improving image quality
Post-observing correction (Speckle, PDS)• The proposed instrument – Tests• Observing modes • Associated instruments• Summary
Outline Outline
• SECIS (Solar Eclipse Coronal Imaging System)
(RAL Ken Phillips, QUB)
Fast mode impulsively generated wave in a loop (6 s) Williams, Phillips et al. MNRAS 2001
Williams, Mathioudakis et al. MNRAS 2002
• RDI (Rapid Dual Imager)
Oscillation induced along a flare ribbon (40 – 70 s)
(BBSO - NSO, Sac Peak) McAteer et al. ApJ 2005
High frequency oscillations in the lower atmosphere (15 – 30s)
Andic, Jess, Mathioudakis in preparation
SECIS - RDI SECIS - RDI
EIT/Loop imageEIT/Loop image
Williams, Mathioudakis et al. MNRAS 2002
Intensity variations along the loopIntensity variations along the loop
Williams, Mathioudakis et al. MNRAS 2002
NOAA 9591 – C9.6 in HNOAA 9591 – C9.6 in Hαα
200
arcs
ecs
McAteer et al. ApJ 2005 RDI at Big Bear Solar Observatory
C9.6 flare – Period of 52secC9.6 flare – Period of 52sec
McAteer et al. ApJ 2005
Ha blue wingHa blue wing
50 arcsec
50
arc
sec
Oscillatory power
15 – 30 sec (60 – 30mHz)
RDI at DST Sac Peak
Andic, Jess, Mathioudakis in preparation
RDI was funded by a Royal Society Instrument Grant
Multi-wavelengthMulti-wavelength
McAteer et al. ApJ (2003)
Krijger, Rutten et al A&A (2001)
The need for synchronised imagingThe need for synchronised imaging
Krijger, Rutten et al. A&A 2002
The need for high cadenceThe need for high cadence
Allred et al. ApJ (2005)
G-Band G-Band
Image credit : SST - MPS
Atmospheric turbulence • Fried’s r0 – diameter of refractive index fluctuations
r0 = 0.114 ((λ cosz) / 550))0.6 m
r0 = 11 cm (λ = 550nm , z = 0)
• Spatial resolution of a ground based telescope limited to that of a
telescope with diameter r0
The largest telescopes have the same image quality as an 11cm telescope
(if no image correction is applied)
• Choose an observing site with a large r0
• Time scale of atmospheric fluctuations : t = r0 / v
Wind speed v = 11 mph , t = 20 msec, (moves by its own diameter)
Act quickly – Exposure times of a few msec at most!
Image quality – The problemImage quality – The problem
Speckle pattern Speckle pattern
• Remember : Seeing is equivalent to many small telescopes observing the same object but affected differently by atmospheric turbulence
Speckle reconstruction Speckle reconstruction • Image of a source in an ideal telescope in the
absence of atmosphere is shaped by diffraction • The Imaging Equation
i (x) = o (x) ٭ p (x) (1)
i - observed intensity/image of the source
o - actual/true image of the source
p - PSF describing instrument and seeing
x - angular position• Following the FT of (1)
I (u) = O (u) • P (u)
P (u) – is the Optical Transfer Function (OTF)
u – spatial frequency
Speckle reconstruction Speckle reconstruction
G-bandG-band
Andic, Jess, Mathioudakis in preparation
Improving image quality Improving image quality
• For Speckle to work you need
Very short exposures. Freeze the seeing for each exposure (<20ms)
Very high cadence. A sequence of images (50-100) over timescales that solar features remain unchanged (< 10 s). Bad seeing requires more images
Great demand on camera read out speeds
Signal to noise can be very low in narrow band images
National Solar Observatory (NSO/NSF)National Solar Observatory (NSO/NSF) Sacramento PeakSacramento Peak
Altitude : 2800m
Very good seeing for short periods (morning)
Dunn Solar Telescope 0.76m
41m above ground + 67m underground
ASP/DLSP/SPINOR (vector magnetograms)
IBIS, HSG, UBF, High Order AO
PPARC approved solar facility
20 days per year for UK led proposals
• iXon+ 1004 X 1002 CCD
Andor/Texas Instruments
• Max Frames per sec : 32 (full CCD)
200 (125 x 125)
• 1.8TB/day/CCD (8 hours observing)
• Fast local disks (15K RPM)
• LTO2/3 tape autoloaders
Camera - ComputingCamera - Computing
ROSA – Hardware testsROSA – Hardware tests
Ha center before and after Ha center before and after
reconstructionreconstruction
Doppler velocities – Narrow band filtersDoppler velocities – Narrow band filters
• Construction of blue (λ – Δλ) and red (λ + Δλ) wing images.
• The intensity difference between the images provides a Doppler shift. In a symmetric profile there is no difference in intensity.
Image credit : IBIS group
Fe I velocity map Image credit : IBIS group
Magnetic Fields Magnetic Fields
Zeeman effect – Polarization Zeeman effect – Polarization
Longitudinal case
B to the line of sight
Transverse case
B to the line of sight
Splitting proportional to the magnetic field
Components are polarized
Magnetic Fields Magnetic Fields
• Δλ = 4.67 x 10-13 g λ2 B//
where B// is the line of sight component of B
• UBF (Universal Birefringent Filter) and a Wollaston prism
• Images of opposite circular polarization
Summary Summary • ROSA has been funded £450K (SRIF3 and PPARC) • Hardware tests completed (lab & telescope)• Software tests (November 2006)• Delivery in late 2008 at DST/NSO• Common user instrument
Time through TAC
The DST is a PPARC approved facility• Strong interest from the UK community• 20 days per year for UK proposals (any instrument)• The solar microscope
Advanced Technology Solar Telescope (ATST)
• Photospheric photon mean free path and pressure scale height
0.1’’ = 70 km
• Magnetoconvection coupled with atmospheric dynamics
• Small scale structures
Umbra dots – Spicules – Bright points • Flux Tubes – Buidling blocks of the magnetic photosphere• Flux Tubes and Wave Generation • Flux Tubes & Coronal Loops – How are they linked ?• Physical processes take place in very small scales (10-20 km)• Implications on stellar activity
The need for high resolutionThe need for high resolution
Advanced Technology Solar Telescope Advanced Technology Solar Telescope ATSTATST
• Aperture : 4m• FoV : 5’
• 0.35 – 35 µm • 0.03’’ @ 0.5 µm
0.08’’ @ 1.6 µm• First light in 2012 • Haleakala, Hawai• Altitude : 3,080m
• Broad-band imager - Visible & NIR spectropolarimeters - Visible tunable filter - NIR tunable filter - IR spectrograph - Vis/NIR high dispersion spectrograph
• Design challenges : Energy removal, AO, scattered light, detectors
