Global Properties of Heliospheric Disturbances Observed by Interplanetary Scintillation M. Tokumaru,...
Transcript of Global Properties of Heliospheric Disturbances Observed by Interplanetary Scintillation M. Tokumaru,...
Global Properties of Global Properties of Heliospheric Heliospheric Disturbances Disturbances Observed by Observed by
Interplanetary Interplanetary ScintillationScintillationM. TokumaruM. Tokumaru, M. Kojima, K. , M. Kojima, K. Fujiki, and M. YamashitaFujiki, and M. Yamashita
(Solar-Terrestrial Environment (Solar-Terrestrial Environment Laboratory, Nagoya University) Laboratory, Nagoya University)
Interplanetary Scintillation (IPS) Measurements as Interplanetary Scintillation (IPS) Measurements as a Tool for Studying Global Properties of CME in the a Tool for Studying Global Properties of CME in the
Solar Wind Solar Wind
Sun
Earth
CME
Radio Source
Shock
IPS observations enable to probe multiple points in the solar wind in a relatively short time.
(SOHO/LASCO)
3D structure and propagation dynamics of CMEs between the Sun and the Earth orbit are mostly obscure.Propagation direction?, Angular Extent?, Speed evolution?
Sun
White Light Image of Solar Corona
Coronal Mass Ejection (CME)
STEL 327-MHz Four-Station IPS STEL 327-MHz Four-Station IPS SystemSystem
SWIFT
Kiso antenna
Fuji antenna
Sugadaira antenna
Toyokawa antenna
Aperture Size:A ~ 2,000 ㎡N~40 sources/day
Measurements•Solar wind speed •Scintillation disturbance factor (g-value)
SOHO/LASCO Projection map of g-values between2000/7/11:22h UT and 7/12:7h UT
Interplanetary CME identified from STEL IPS Measurements
g>1 → Excess of ΔNe
The g-value represents the relative variation of scintillation level ΔS ; i.e. solar wind density fluctuations ΔNe (Gapper et al., 1982).
STEL IPS observations:Frequency: 327 MHz No. Sources: ~40 sources (ε<90 deg) in a day
G-value enhancements are ascribed to interplanetary CMEs.
IPS Observations of an Earth-Directed CMEIPS Observations of an Earth-Directed CME(the 2000 Jun 6 halo CME event)(the 2000 Jun 6 halo CME event)
Observed g-value mapLASCO CME ImageEarth-directed CME
Retrieval of 3D Structure of Interplanetary CME by Retrieval of 3D Structure of Interplanetary CME by Model Fitting AnalysisModel Fitting Analysis
2 1 2( ) ( )cal eg K N w z dz
Earth
Sun
2 2
1
| | / minN
obs cal cali
g g g
ΔNe ModelObserved g-map
Line-of-Sight
ΔNe: Density fluctuationsK: Normalizing factorw(z): IPS weightening functionz: Distance along los
q: Spectral indexΨ: Apparent source sizeλRF: Observing wavelength
Search for the best-fit parameters
dkzkzk
kzw RFq
2exp
4sin)(
222
0
221
Sun
Earth
(Cf. Tappin, 1987)
ΔNe model ΔNe model – Enhancement Component -– Enhancement Component -
lapseSpeak TVR )2/(cos0
Ecliptic Plane
Enhanced ΔNe region (ICME)
EarthSun
Radial Distance
ΔNee-folding thickness D
θ : Separation AngleTlapse: Lapse Time after Lift-OffVS0 : Ave. Transit Speed
C0( 1)≒
C1
Radial Expansion (Const. Speed)Solar Rotation
(Cf. α =2 Smart & Shea, 1985)
ΔNe of the ambient solar wind is assumed to distribute as R-2.
Global Feature of CMEs in the Global Feature of CMEs in the Solar WindSolar Wind
1999 Sep 20 event 2000 Jul 10 event 2000 Jun 2 event
1999 Aug 17 event 2000 Jul 14 event1999 Apr 13 event2001 Aug 25 event
3D Reconstruction from IPS and 3D Reconstruction from IPS and White-light Observations for 2003 White-light Observations for 2003
October 28 CME EventOctober 28 CME Event
Propagation Speed Estimated from IPS: 1,083 km/s @0.42 AU Cf. Shock Transit Speed: 2,186 km/s @1AU
STEL IPS Solar Mass Ejection Imager (SMEI)SMEI-IPS Correlation(by B.V. Jackson)
Correlation Coefficient
Radial Variation of CME Radial Variation of CME SpeedsSpeeds
Coronagraph IPS
In Situ
(M. Yamashita, D. thesis)
Propagation speeds of ICME were derived by fitting a shell-shape model to IPS data.
Deceleration of Fast Deceleration of Fast CMEsCMEs
We fit a power law functioWe fit a power law function n RRaa to the deceleration pr to the deceleration profile of CME speeds in thofile of CME speeds in the solar wind frame.e solar wind frame.
The slope of radial fall deThe slope of radial fall depends on pends on difference betwdifference between initial CME speed and een initial CME speed and ambient flow speedambient flow speed..
Interaction between CME Interaction between CME and the ambient SW plays and the ambient SW plays an important rolean important role Cf. Drag force model (VrsnaCf. Drag force model (Vrsna
k & Gopalswamy, 2002).k & Gopalswamy, 2002).
aSWCME RVV
M. Yamashita, D. thesis
Pow
er-
law
In
dex
a
Summary Summary STEL IPS observations were used to study global feSTEL IPS observations were used to study global fe
ature and propagation dynamics of CMEs in the solature and propagation dynamics of CMEs in the solar wind.ar wind.
Our results suggest thatOur results suggest that Some CMEs observed in the solar wind exhibited loop-shSome CMEs observed in the solar wind exhibited loop-sh
ape distribution, and some had shell-shape distribution.ape distribution, and some had shell-shape distribution. There are two possible origins for g-value enhancements.There are two possible origins for g-value enhancements. Shock compression region and coronal ejecta Shock compression region and coronal ejecta
Shell-shape events associated with halo CMEsShell-shape events associated with halo CMEs Fast (slow) CMEs were decelerated (accelerated) during propagaFast (slow) CMEs were decelerated (accelerated) during propaga
tion.tion. Deceleration rates of fast CMEs correlated with speed difference Deceleration rates of fast CMEs correlated with speed difference
to the ambient solar wind. to the ambient solar wind. Interaction with the ambient SW plays an important role in evoluInteraction with the ambient SW plays an important role in evolu
tion of interplanetary CMEs.tion of interplanetary CMEs.
Future Subject: New IPS AntennaFuture Subject: New IPS Antenna
Aperture Size: Ae ~ 3520×cosθ×η( ㎡ )
Efficiency η ~ 90%
•Meridian Transit Observations•Antenna Beam: 1 (Steerable in NS-direction)•327 MHz
SWFT (Solar Wind Imaging Facility of Toyokawa)SWFT (Solar Wind Imaging Facility of Toyokawa)
To improve spatial resolution
Increase No. of Radio Sources
Large Aperture Antenna