using the scintillation of extended objects...

USING THE SCINTILLATION OF

EXTENDED OBJECTS TO PROBE

LOWER ATMOSPHERIC TURBULENCE

Concept & First Results Published in: Experimental Astronomy 12, 1, 2001

Jacques M. BeckersUS National Solar Observatory

“SHADOW BANDS” DURING SOLAR ECLIPSE

~ 60 cmCLOSE TO “TOTALITY” AT A TOTAL ECLIPSE OF THE SUN RAPIDLY VARYING, LOW CONTRAST LIGHT PATTERNS ARE SEEN ON THE GROUND OR BUILDINGS.THESE AREREFERRED TO AS “SHADOW BANDS”. IT IS THE SAME AS SOLAR SCINTILLATION.

SHADOW BAND PATTERN IS ELONGATED IN THE DIRECTION OF THE CRESCENT

CONTRAST APPEARS TO VARY FROM ECLIPSE TO ECLIPSE AND PROBABLY WITH LOCATION

IT IS CLEARLY A PHENOMENON ASSOCIATED WITH ATMOSPHERIC TURBULENCE

ED SEYKORA DETERMINED IN 1993 THAT PHENOMENON IS ALSO PRESENT OUTSIDE SOLARECLIPSE BUT WITH MUCH LOWER CONTRAST ( ≤ 0.1 % RMS)

HE ALSO FOUND AT SAC PEAK A STRONG CORRELATION BETWEEN CONTRAST AND SEEING

Images taken by Franz Kerschbaum (Vienna) during 2006 eclipse

Seykora

Rimmele

CORRELATION OF

SOLAR SCINTILLATION&

SOLAR LIMB MOTION

CORRELATION OF

SOLAR SCINTILLATION&

GRANULATION CONTRAST

NOTE: AT SAC PEAK SEEING IS DOMINATED BY BOUNDARY LAYER TURBULENCE

ATMOSPHERIC OPTICS(using Roddier, Progress in Optics XIX, 283, 1981)

Notations: σI

2 = (ΔIRMS/I)2 = Scintillation Indexr0 = Fried Parameter at 500 nmζ = Zenith DistanceCn

2(h) = Refractive Index Structure Constant

σI2 (for Stars) = 19.2*λ-7/6*cos-11/6ζ* h+5/6*Cn

2(h)dhLOOKING AT THE SUN ONE RECEIVES A CONE OF LIGHT ~ 0.01 RADIAN IN WIDTH ONEAVERAGES THE ATMOSPHERIC EFFECTS OVER AN AREA WHICH INCREASES WITH INCREASING DISTANCE HIGHER LAYERS CONTRIBUTE LESS TO SCINTILLATION INDEX

σI2 (for Sun) = 0.955x106*cos-2/3ζ* h-1/3*Cn

2(h)dh (independent of λ!)

ALSO:

r0-5/3 = 0.060*λ2*cosζ* Cn

2(h)dh (:) FWHMseeing5/3

⇒ σI(Sun)2/FWHM5/3 = const.* h-1/3*Cn2(h)dh/ Cn

2(h)dh

THIS RATIO IS DOMINATED BY BOUNDARY LAYER OPTICAL TURBULENCE. WHEN IT DOMINATES (as it does in daytime) THIS RATIO DOES NOT VARY MUCH WITH TIME AND LOCATION EXPLAINS SEYKORA RELATION

Used Single Scintillometers Pointedat Meridional Transit of Sun

Sites Tested: Big Bear Lake,CALake Heron,NMLa Palma/ORMMauna Loa,HISac Peak,NM

“lakeshine”

EARLY “ADVANCED TECHNOLOGY SOLAR TELESCOPE” SITE SURVEY

SHABAR = SHAdow BAnd Ranger

Correlation of ►SHABAR pairs

SHABAR Pair Light Path

CorrelationCoefficient vs Separation

2 cm

4 cm

6 cm

16 cm 20 cm

100 cm 200 cmSHABAR

Yunnan’s Fuxian Hu Seeing Monitor

NON-REDUNDANT SOLAR SCINTILLOMETER ARRAY

DIMM

S-DI

MM

PAN

EL

CCD IMAGEOF SLITSACROSS

SOLAR LIMB

SHAB

AR P

ANEL

S

INTERPRETATION OF THE ATST SHABAR DATADEVELOPED BY P. HICKSON, F. HILL, M. COLLADAS & H. SOCAS-NAVARRO

USE: H. Socas-Navarro, J. Beckers, et al. PASP 117, 1296, 2005

d=12mm h-1/3 curved=12mm

d=468mm

d=0 mm

16 curves corresponding to 16 spacings

CVobs(d)

constant*CVtheory(h,d)

“missing scintillation”(due to L0 & time filtering)

Inversion of Equation ⇒ Cn2(h)

Inclusion of DIMM Results (r0)⇒ ∆s

Since 10 mm < d < 500 mm Height Range is Limited to~ 0.2m< h < 500m

TEST OF SHABAR Cn2(h)

DETERMINATIONS USING

100+ METER DASH TOWER

IN ERIE, COLORADO

NEXT TO AN ATST

SEEING MONITOR

FINAL ATST SITE SURVEY INCLUDED 6 SITES IN USA, MEXICO AND EUROPE

Big Bear, CAHaleakala, HILa Palma, SpainPanguitch Lake (UT)Sacramento Peak, NMSan Pedro Martir, MX

LAKE SITES

LAND SITES

HEIGHT VARIATION OF Cn2 AND SEEING (r0)

Collados

Socas-Navarro

STATISTICAL RESULTS OF TWO INVERSION PROGRAMS(full: Collados analysis; dashed: Socas-Navarro analysis)

CONCLUSIONS:

• Place Telescopeat h > 25m

• Haleakala isbest site

• Conclusion basedalso on numberof periods withcontinuous verygood seeing

THE SCINTILLATION OF MOON AND PLANETS

FULL MOON ONLY (= like Sun)

PLANETS AT OPPOSITION ONLY

DO NOT INCLUDE SATURN BECAUSE OF ITS RINGS

PLANETS: URANUS (dia 3.60 arcsec,; mV = 5.5) MARS (dia 17.9 arcsec.; mV = -2.0) JUPITER (dia 46.9 arcsec.: mV = -2.6)

h+5/6

h-1/3

0 arcsec.

3.6 arcsec.

17.9 arcsec.

46.9 arcsec.

1920 arcsec.

• SCINTILLATION OF MARS IS ALMOST PROPORTIONAL TO THE SEEING • L0 ( “missing scintlillation ∆s”) IS OF NO CONCERN FOR STARS & PLANETS

h = 10000m

h = 1000

m

h = 100

m

h = 10

m

SUN/MOON

STARS

JUPITER

MARS

URANUS

THANK YOU