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Differential Rotation of coronal BP and Source Region of their Magnetic Fields. H. Hara NAOJ 2011 Jun 29. Leverhulme – Probe the Sun 1 st Workshop at MSSL. X-ray/EUV coronal bright points. Found in the 1960’s soft X-ray imaging data of sounding rocket programs.

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differential rotation of coronal bp and source region of their magnetic fields

Differential Rotation of coronal BP andSource Region of their Magnetic Fields

H. Hara

NAOJ

2011 Jun 29

Leverhulme – Probe the Sun 1st Workshop at MSSL

x ray euv coronal bright points
X-ray/EUV coronal bright points
  • Found in the 1960’s soft X-ray imaging data of sounding rocket programs.
  • Appear almost uniformly over the solar surface.
  • Bipoles are observed at photosphere below CBPs.
  • CBP associated bipoles are mostly canceling bipoles.
  • The number density does not change much in the11-year activity cycle.
  • Differential rotation rate is quite similar to that of the quiet–Sun photospheric magnetic fields.
detection of xbp
Detection of XBP

Yohkoh soft X-ray data

X-ray Bright Point

Hara & Nakakubo-Morimoto 2003, ApJ 589, 1062

occurrence rate of xbp source of magnetic fields and depth of formation region
Occurrence rate of XBPSource of magnetic fields and Depth of Formation Region

Small amplitude change in XBP number over the 11-yr cycle

Possibly due to difference in the origin of magnetic fields

  • XBP: constancy in number & small size
  • Source region may be localized

near the surface

Much larger change in AR

XBP: Skylab+rocket

Normalized

Sunspot

number

Hara & Nakakubo-Morimoto 2003, ApJ 589, 1062

rotation rate of xbp
Rotation Rate of XBP

t1

( t2 > t1 )

t2

Yohkoh Soft X-ray data

t

XBP

detection

Position of XBP ( X, Y )  ( Longitude , Latitude  )

, : as a function of XBP height H

Longitude of XBP i

in image 1

Longitude of XBP j

in image 2

Angular velocity

Determined by

XBP i (t1) and j (t2)

Correction factor to

convert to sidereal rate

Time difference

selection of height h
Selection of Height H

d / d

H

Hara 2009, ApJ 697, 980

rotation rate from many xbp pairs
Rotation rate from many XBP pairs
  • ~4 yr Yohkoh data used
  • Shape of distribution
    • Symmetric
    • Voigt function containing Lorentz function
  • Accuracy 0.01 deg/day  1.4m/s

 (→ possible to measure

torsional oscillation

from much more data

in a shorter period )

  • Higher accuracy expected from SDO data of much more shorter period

Lat. 00-05 deg

Lat. 10-15 deg

Lat. 20-25 deg

Lat. 30-35 deg

Lat. 45-50 deg

Angular velocity (deg/day)

Bin width:0.05 deg/day

Hara 2009, ApJ 697, 980

slide9

Estimated From tracking of each BP and statistical average

EUV coronal BP (1972)

EUV coronal BP (2004; EIT)

Global corona

Dashed line:

Photospheric B

Photoshperic

Doppler

Hara 2009, ApJ 697, 980

angular rotation rate connectivity between inside and xbp

Howe et al. 2000, Sci. 287, 2456

Angular rotation rate:connectivity between inside and XBP

Angular rotation rate of XBP defined by 8 <Δt < 24 hrs coincides

with that at ~0.97Rs in latitudes between -60 and +60 deg.

Hara 2009, ApJ 697, 980

Small-scale magnetic activity localized at the top of CZ?

Equivalent depth (~0.94 Rs )

of AR surface rotation rate.

compared with another h s inversion results
Compared with another H.S. inversion results

Internal rot. data

from Sekii san

From

photospheric

magnetic fields

(Komm et al.)

From XBP

slower rotation rate for short lived xbp
Slower rotation rate for short-lived XBP

Equator only:

For samples containing

many short-lived XBPs

0 < Δt < 4 hours,

Rotation rate becomes

 (r~0.99Rs ),

approaching

surface rotation rate.

-10 < Latitude < +10 deg

Hara 2009, ApJ 697, 980

expectation from sdo data
Expectation from SDO data
  • High accuracy measurement of rotation rate from EUV data of a short period of time.
  • Examine the relation between tand .
  • Measurement of torsional oscillation
  • Measurement of meridional flow from long-lived BP
  • Detection of longitudinal rotation anomaly
  • Implication of width in the XBP histograms
    • Some information on the supergranular flows/diffusion?
slide15

SDO

211

sdo data
SDO data
  • 4096x4096 format data: 32 MB
  • 211Å band selected
  • OBS date: 2010 Oct 31
  • 12 sec cadence: 7200 images / day
  • Reduced to 1024x1024 format by pixel summing
    • ~3500 CBP detection for 6.7min run from 2Kx2K data
    • ~1600 CBP detection for 40sec run from 1Kx1K data
    • Software development needs for reducing the analysis time.
  • Data selected to reduce the process time
    • 5 min interval data; ~280 images / day
    • 1 min interval data; ~1400 images / day
test run for 5 min interval data
Test run for 5 min interval data

Height estimate not finished

0 <  t < 4 hr

S: Lat. 00-05 deg

S: Lat. 20-25 deg

S: Lat. 30-35 deg

S: Lat. 40-50 deg

Preliminary

summary
Summary
  • The rotation of small-scale magnetic fields is examined by XBP/CBP from its differential rotation profile.
  • There is a depth at which the XBP rotation rate coincide with the internal rotation rate over a wide latitude range. The depth is located at the top of the convection zone.
  • Limited examination on the rotation rate of XBP from Yohkoh SXT data can largely be improved by SDO/AIA data as expected in Hara (2009, ApJ).