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Global Properties of Heliospheric Disturbances Observed by Interplanetary Scintillation

Global Properties of Heliospheric Disturbances Observed by Interplanetary Scintillation. M. Tokumaru , M. Kojima, K. Fujiki, and M. Yamashita (Solar-Terrestrial Environment Laboratory, Nagoya University) .

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Global Properties of Heliospheric Disturbances Observed by Interplanetary Scintillation

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  1. Global Properties of Heliospheric Disturbances Observed by Interplanetary Scintillation M. Tokumaru, M. Kojima, K. Fujiki, and M. Yamashita (Solar-Terrestrial Environment Laboratory, Nagoya University)

  2. Interplanetary Scintillation (IPS) Measurements as a Tool for Studying Global Properties of CME in the Solar Wind White Light Image of Solar Corona Shock (SOHO/LASCO) Radio Source Sun Sun Earth Coronal Mass Ejection (CME) CME 3D structure and propagation dynamics of CMEs between the Sun and the Earth orbit are mostly obscure. Propagation direction?, Angular Extent?, Speed evolution? IPS observations enable to probe multiple points in the solar wind in a relatively short time.

  3. STEL 327-MHz Four-Station IPS System Kiso antenna Sugadaira antenna • Measurements • Solar wind speed • Scintillation disturbance factor (g-value) Aperture Size: A～2,000㎡ N~40 sources/day Fuji antenna Toyokawa antenna SWIFT

  4. Interplanetary CME identified from STEL IPS Measurements The g-value represents the relative variation of scintillation level ΔＳ; i.e. solar wind density fluctuations ΔNe (Gapper et al., 1982). g>1 → Excess of ΔNe STEL IPS observations: Frequency: 327 MHz No. Sources: ~40 sources (ε<90 deg) in a day SOHO/LASCO Projection map of g-values between 2000/7/11:22h UT and 7/12:7h UT G-value enhancements are ascribed to interplanetary CMEs.

  5. IPS Observations of an Earth-Directed CME(the 2000 Jun 6 halo CME event) LASCO CME Image Earth-directed CME Observed g-value map

  6. Retrieval of 3D Structure of Interplanetary CME by Model Fitting Analysis Observedg-map ΔNe Model ΔNe: Density fluctuations K: Normalizing factor w(z): IPS weightening function z: Distance along los q: Spectral index Ψ: Apparent source size λRF: Observing wavelength Sun Sun Earth Earth Line-of-Sight Search for the best-fit parameters (Cf. Tappin, 1987)

  7. ΔNe model – Enhancement Component - C1 Ecliptic Plane ΔNe e-folding thickness D Sun Earth C0(≒1) Enhanced ΔNe region (ICME) Radial Distance • Radial Expansion (Const. Speed) • Solar Rotation θ : Separation Angle Tlapse: Lapse Time after Lift-Off VS0 : Ave. Transit Speed ΔNe of the ambient solar wind is assumed to distribute as R-2. (Cf. α＝２ Smart & Shea, 1985)

  8. 1999 Sep 20 event 2000 Jun 2 event 2000 Jul 10 event Global Feature of CMEs in the Solar Wind 1999 Apr 13 event 1999 Aug 17 event 2001 Aug 25 event 2000 Jul 14 event

  9. 3D Reconstruction from IPS and White-light Observations for 2003 October 28 CME Event STEL IPS Solar Mass Ejection Imager (SMEI) SMEI-IPS Correlation (by B.V. Jackson) Correlation Coefficient Propagation Speed Estimated from IPS: 1,083 km/s @0.42 AU Cf. Shock Transit Speed: 2,186 km/s @1AU

  10. Radial Variation of CME Speeds Propagation speeds of ICME were derived by fitting a shell-shape model to IPS data. Coronagraph IPS In Situ (M. Yamashita, D. thesis)

  11. Deceleration of Fast CMEs • We fit a power law function Ra to the deceleration profile of CME speeds in the solar wind frame. • The slope of radial fall depends on difference between initial CME speed and ambient flow speed. • Interaction between CME and the ambient SW plays an important role • Cf. Drag force model (Vrsnak & Gopalswamy, 2002). Power-law Index M. Yamashita, D. thesis

  12. Summary • STEL IPS observations were used to study global feature and propagation dynamics of CMEs in the solar wind. • Our results suggest that • Some CMEs observed in the solar wind exhibited loop-shape distribution, and some had shell-shape distribution. • There are two possible origins for g-value enhancements. • Shock compression region and coronal ejecta • Shell-shape events associated with halo CMEs • Fast (slow) CMEs were decelerated (accelerated) during propagation. • Deceleration rates of fast CMEs correlated with speed difference to the ambient solar wind. • Interaction with the ambient SW plays an important role in evolution of interplanetary CMEs.

  13. To improve spatial resolution Increase No. of Radio Sources Large Aperture Antenna Future Subject: New IPS Antenna SWFT (Solar Wind Imaging Facility of Toyokawa) Aperture Size: Ae～3520×cosθ×η(㎡) Efficiency η～90% • Meridian Transit Observations • Antenna Beam: 1 (Steerable in NS-direction) • 327 MHz

  14. Improved Resolution of IPS Mapping Observations Existing STEL IPS Antenna SWIFT(New IPS Antenna)

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