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