measuring acoustic phase shifts between multiple atmospheric heights

Measuring acoustic phase shifts between multiple atmospheric heights

Ruizhu Chen1,2 & Junwei Zhao2

1. Dept. Physics, Stanford Univ., Stanford, CA 943052 Hansen Experimental Physics Laboratory, Stanford Univ.,

Stanford, CA 94305-4085

Motivation

2

ΦAB’ - ΦB’A :

•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary

• Compute acoustic phase shifts (travel-time differences) between multiple heights in quiet regions, along the same ray path but traveling in opposite directions. One purpose is to examine whether the difference is related to evanescent waves.

• Compute acoustic phase shifts (travel-time differences) between multiple heights in quiet regions, along the same ray path but traveling in opposite directions. One purpose is to examine whether the difference is related to evanescent waves.

• Investigate the orbital-velocity dependence of measured phase shifts.

• Because center-to-limb measurements are also related to different line-formation heights, the main purpose of this work is to investigate whether multi-height is one cause of center-to-limb effect.

3

Motivation

•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary

Data

•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary

4

ΦAB’ - ΦB’A :

4 sets of data: (Higher and Lower, AB and A’B’)

•I3 and I0 (original data before calibration on Vorbit)

•Line core (LC) and continuum intensity (Ic)

•Doppler proxies at line core (LC) and line wing(LW)

•AIA 1600Å and 1700Å broad lines.

Data

• 512 x 512 pixels; 0.06°/pix; 24 hrs long.

• Each set of data is divided to five 8-hour intervals:

0-8h(++), 4-12h(+-), 8-16h(--), 12-20h(--), 16-24h(+-)• I3 and I0

Line core (LC) and continuum intensity (Ic)

Doppler proxies at Line core (LC) and line wing(LW)

AIA 1600Å and 1700Å broad lines

5

Line profile influenced by Vorbit Orbital velocity for data used

calibratedoriginal

independent of Vorbit

proxy

•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary

Measurement Procedure

6

A

B’B’

B’ B’

A

B’B’

B’ B’

Corss-correlation function f (t, d)

dist

ance

time

dist

ance

frequency

phase change ΔΦ (d , w)

ΦAB’ - ΦB’A

TAB’ - TB’A

•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary

I3 and I0

7

Distance (Mm)

Freq

uenc

y (m

Hz)

ΦAB’ - ΦB’A = ΦI3 to I0 – ΦI0 to I3

• Formation height: 270 km (I3) and 20 km(I0)

• 0-8h(++), 4-12h(+-), 8-16h(--), 12-20h(--), 16-24h(+-)

K Rsun

Fre

quen

cy

(mH

z)

Phase of cross spectrum

•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary

8

ΔΦ (AB’-B’A) low freq (rad)

ΔΦ (AB’-B’A)5 mHz (rad)


ΔΦ ( Vorbit)small freq (rad)

ΔΦ ( Vorbit)large freq (rad)

I3 & I0 ~ 4 ~ 2.5 ~ 0.5 ~3-4 ~3

Phas

e sh

ift

(rad

)

ΦAB’ - ΦB’A = ΦI3 to I0 – ΦI0 to I3

Tim

e di

ffer

ence

(s

)

TAB’ - TB’A = TI3 to I0 – TI0 to I3

Distance (Mm)

I3 and I0

•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary

Line core (LC) and continuum intensity(Ic)

9

Distance (Mm)

Freq

uenc

y (m

Hz)

ΦAB’ - ΦB’A = ΦLC to Ic – ΦlC to Ic

K Rsun

Fre

quen

cy

(mH

z)


• Formation height: 270 km (LC) and 20 km(Ic)

•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary

Distance (Mm)

Phas

e sh

ift

(rad

)

ΦAB’ - ΦB’A = ΦLC to Ic – Φic to LC







LC & Ic ~2-3 ~ 1 ~ -0.5

•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary

Tim

e di

ffer

ence

(s

)

TAB’ - TB’A = TLC to Ic – TIc to LC


•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary

Phas

e sh

ift

(rad

)

ΦAB’ - ΦB’A - mean ( ΦAB’ - ΦB’A )

Tim

e di

ffer

ence

(s

)

TAB’ - TB’A – mean ( TAB’ - TB’A )

Distance (Mm)

3mHz 3.5mHz 5mHz4mHz 6mHz

3mHz 3.5mHz 5mHz4mHz 6mHz






LC & Ic ~2-3 ~ 1 ~ -0.5 0.3 ~ 0.1

12

Doppler proxy: LW=(I0-I5)/(I0+I5)

(Nagashima et al. (2014) LC=(I2-I3)/(I2+I3)

• Formation height assumed same as line core and continuum: 270 km (LC) and 20 km(LW)•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary

Doppler proxy at line core and line wing

13

Distance (Mm)

Freq

uenc

y (m

Hz)

ΦAB’ - ΦB’A = Φlc to lw – Φlw to lc

Doppler proxy at line core and line wing

Doppler proxy: LW=(I0-I5)/(I0+I5)

(Nagashima et al. (2014) LC=(I2-I3)/(I2+I3)

K Rsun

Fre

quen

cy

(mH

z)


•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary


Phas

e sh

ift

(rad

)

ΦAB’ - ΦB’A = Φlc to lw – Φlc to lw






LC & LW ~ -0.2 <0 ~ -0.5 ~ -0.8 0.2 ~ 0.5 1 ~ 2.5

Doppler proxy at Line core and line wing

•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary

Tim

e di

ffer

ence

(r

ad)

TAB’ - TB’A = Tlc to lw – Tlc to lw

Distance (Mm)

15

Distance (Mm)

Freq

uenc

y (m

Hz)

ΦAB’ - ΦB’A = Φ1600-1700 – Φ1600 to 1700


K Rsun

Fre

quen

cy

(mH

z)


•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary


ΔΦ (AB’-B’A) ΔΦ ( Vorbit)

I3 & I0 1.3 π π

Distance (Mm)

Phas

e sh

ift

(rad

)

ΦAB’ - ΦB’A = Φ1600 to 1700 – Φ1700 to 1600






AIA ~ -0.5 ~ -0.8 ~ -1.2 0 0


•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary

Tim

e di

ffer

ence

(r

ad)

TAB’ - TB’A = T1600 to 1700 – T1700 to 1600

Summary

1. Phase shifts from I3 and I0 are dominant by orbital velocity. Phase shifts from calibrated LC & Ic, and Doppler proxies at LC & LW, both have non-ignorable dependence on the orbital velocity.

2. Acoustic travel time (phase) between multiple heights is asymmetric with respect to directions.

3. ΦAB’ - ΦB’A for low frequencies are positive from line core & continuum intensity data, and negative from line core & line wing of Doppler proxy, AIA 1600Å & 1700Å data. It is unclear why is the sign different.

4. Waves of 6mHz don’t cut off, but always has a negative phase shifts. 5. Multiple formation heights will cause a phase shifts , which may be one

cause center-to-limb effect.

•Motivation

•Data

•Method

•Results

I3 & I0

LC &Ic

LC & LW

AIA

•Summary

measuring acoustic phase shifts between multiple atmospheric heights

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