Auchere, F.

Bando, T.

Giono, G.

Ishikawa, R.

Ishikawa, S.

Kano, R.

Katsukawa, Y.

Kobayashi, K.

Kubo, Masahito

Narukage, N.

Suematsu, Y.

Trujillo-Bueno, J.

Tsuneta, S.

Winebarger, A.

NASA Technical Reports Server

Discovery of short-timescale 
oscillations in the transition region by 
CLASP at high "temporal" resolution
Masahito Kubo 
(National Astronomical Observatory of Japan)
Y. Katsukawa, R. Kano, R. Ishikawa, N. Narukage, T. Bando, 
Y. Suematsu, G. Giono, S. Tsuneta, S. Ishikawa, A. Winebarger, 
K. Kobayash, J. Trujillo Bueno, F. Auchere
1- NSO WS #30 - August 7-11, 2017
https://ntrs.nasa.gov/search.jsp?R=20170007500 2019-08-29T22:16:12+00:00Z
Lyman-alpha spectra with CLASP
2
Lyα (121.57nm): 
upper chromosphere ~ transition region
Si III (120.65nm): similar height of Lyα
O V (121.83nm)
Stokes I
- NSO WS #30 - August 7-11, 2017
Time series of Lyα Stokes I profile
3
• Cadence: 0.3s
• 1.1”/pixel
• 280s duration
• Level-1
• Channel 2
• Correction of slit 
rotation
• Correction of drift 
of line center
• Correction of 
intensity decrease
• High pass filter: 
same way as SJ
9 smoothing 
width: 30s
9 running 
average: 4.8s
High cadence & throughput Æ subtle & short-time scale changes of profiles
- NSO WS #30 - August 7-11, 2017
High pass filter
4
① Calculate a running average over 30 s (=100 images)Æ green line
② Remove the green line from a original time profile (black line) Æ blue line
③ Calculate a running average over 4.8s (=16 images) of the blue line 
Æ orange line
* The purpose of ③ is to increase S/N and to reduce intensity fluctuation 
affected by the rotating waveplate (4.8sec/rotation).
- NSO WS #30 - August 7-11, 2017
SJ Fast-propagating Intensity Disturbances
5
300km/s
Movie after removal of 
running average over 30s
Space vs. time plot along the dashed line
Kubo et al. 2016
CLASP/SJ reveals ubiquitous intensity disturbances that recurrently 
propagate in the chromosphere - transition region at a speed > 150km/s.
- NSO WS #30 - August 7-11, 2017
Short-timescale events in TR and corona
6
Network jets with IRIS
(Tian et al. 2014)
Short-timescale 
variability in moss 
region with Hi-C 
(Testa et al. 2013) 
- NSO WS #30 - August 7-11, 2017
Region of Interest
7
X
Y
Dark vertical line Æ slit
Target: bright area (=network) in QS
- NSO WS #30 - August 7-11, 2017
λ – t plots Lyα Stokes I profile
8
The intensity of the blue and red peaks 
fluctuates at time scale shorter than 30s in 
opposite phase with each other. Such 
fluctuation is visible in raw Stokes I data.
Stokes I High pass filter Intensity profile
- NSO WS #30 - August 7-11, 2017
Intensity Drop during Flight due to Water Vapor
9
Courtesy of Winebarger
The intensity degradation is corrected as make the intensity averaged 
over the slit constant, but S/N becomes worse with time. 
- NSO WS #30 - August 7-11, 2017
Doppler velocity of Lyα line center
10
• The short timescale fluctuations also can be seen in the Doppler shift 
of a central dip of the Lyα line.
• The range of Doppler velocity is ±10 km/s. 
Stokes I High pass filter Intensity profile Doppler velocity
- NSO WS #30 - August 7-11, 2017
Doppler velocity of Lyα line center
11
When the central dip of the Lyα line moves 
red-ward, the blue peak tends to be enhanced, 
and vice versa.
Stokes I High pass filter Intensity profile Doppler velocity
- NSO WS #30 - August 7-11, 2017
Bisector analysis of Lyα line
12
Line center
Center of r-b peaks
The Doppler velocities of the line center 
are different from those of the line wing.
- NSO WS #30 - August 7-11, 2017
λ – t plots Si III Stokes I profile
13
Stokes I High pass filter Doppler velocity Doppler (Lyα)
• High frequency components observed in Lyα Stokes I profile cannot 
be seen in Si III line.
• The Doppler velocity of Si III line center is similar to the Doppler 
velocity of Lyα line wing rather than the Lyα line center (?).
- NSO WS #30 - August 7-11, 2017
Fast-Propagating Intensity Disturbances in ROI
14
#1（green）: No SJ intensity disturbances
#2 (sky-blue): SJ Intensity disturbances 
propagating across the slit
#2
#1
- NSO WS #30 - August 7-11, 2017
Relation with Fast-Propagating Intensity Disturbances
15
SP (λ-t) SJ (x-t)
• Such alternate intensity changes of the blue and red peaks are more 
clearly observed in the bright areas but in the period without the fast 
propagating intensity disturbances with CLASP/SJ.
SP (λ-t) SJ (x-t)
#1 #2
slit
- NSO WS #30 - August 7-11, 2017
λ – t plots along the slit
16
The alternate intensity changes of the blue and red peaks are 
commonly observed in stable, bright areas in QS.
- NSO WS #30 - August 7-11, 2017
Summary from CLASP Observations
17
• We find that alternate intensity changes 
of the blue and red peaks recurrently 
appear in the short time scale. 
• The short timescale fluctuations also 
can be seen in the Doppler shift 
ranging ±10km/s.
• The Doppler shifts of the line center are related to the changes of the 
blue and red peaks.
• The short-timescale fluctuations of intensity with the Doppler shift are 
more clearly observed in the period without the intensity disturbances 
in SJ images.
Æ Oscillations or torsional motion only in the upper chromosphere –
transition region.
- NSO WS #30 - August 7-11, 2017
IRIS sit-&-stare observations
18
Item Value
Date September 22,2013
Mode Sit-and-stare
Cadence 5.1s
Duration 3.5 hour
Target Quiet Sun
Coordinate (537”, 295”)
Pixel sampling 0”.16
IRIS SJI 1400A
X
X
“Network” bright area “Internetwork” bright area
IRIS Æ many examples, long duration, 
high spatial resolution
- NSO WS #30 - August 7-11, 2017
λ – t plots Mg II k profile @ internetwork
19
• Short-timescale 
intensity fluctuations 
related to Doppler 
shifts of the line 
center are also 
observed in Mg II k 
profiles as observed 
by IRIS.
• The range of the 
Doppler shift (±10 
km/s) is similar to that 
observed by CLASP
Shock waves (~5min)
Short-timescale 
fluctuations
- NSO WS #30 - August 7-11, 2017
λ – t plots Mg II k profile @ network
20
• The short timescale 
fluctuation is less 
clearly observed in 
the region with the 
shock waves
Short-timescale 
fluctuations (?)
- NSO WS #30 - August 7-11, 2017
Power Spectrum Density of Intensity 
21
5min
internetwork
network
NT Inter-NT NT Inter-NT
height
scenario #2scenario #1
No typical time scale 
(no peak) for short-
timescale intensity 
fluctuations in PSD
- NSO WS #30 - August 7-11, 2017
RBEs? RREs?
22
Rapid Redshifted Excursions (RREs)Rapid Blueshifted Excursions (RBEs)
Δλ [km/s] Δλ [km/s]
• Our events most probably do not correspond to typical RBEs or RREs 
(weak RREs?).
• Recurrent RBEs were reported in Sekse et al. 2013 but recurrent RREs?
Rouppe van der Voort et al. 2014
- NSO WS #30 - August 7-11, 2017
Summary from IRIS observations
23
• Short-timescale intensity fluctuations related to the Doppler shifts of 
the line center are also observed in Mg II k profiles as observed by 
IRIS as well as in Lyα profiles as observed by CLASP.
• The range of the Doppler shift (±10 km/s) is also similar to that 
observed by CLASP
ÆWe can study these phenomena in more detail by using IRIS data.
• A typical time scale (no peak) for short-timescale intensity fluctuations 
is not yet obtained in the power spectrum.
- NSO WS #30 - August 7-11, 2017
24
Thanks!
- NSO WS #30 - August 7-11, 2017
Dependence of the width of smoothing window
25
Same as previous page Removal of temporal average over the whole period
Period without influence 
of the edge 
• The high frequency components of intensity fluctuations become less 
clear as the smoothing width is longer because low frequency 
components with strong power are more contaminated.
• The high frequency components can be identified at least the space-time 
plots with the smoothing time window shorter than 90 s.
- NSO WS #30 - August 7-11, 2017


Discovery of Short-Timescale Oscillations in the Transitions Region by CLASP at High Temporal Resolution

Discovery of Short-Timescale Oscillations in the Transitions Region by CLASP at High Temporal Resolution

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