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