Tracking heliospheric disturbances by interplanetary scintillation

Tokumaru, M.; Kojima, M.; Fujiki, K.; Yamashita, Masahiro

doi:10.5194/npg-13-329-2006

Cited by 17 publications

(9 citation statements)

References 33 publications

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“…In this analysis, a kinematic model of an ICME is fit to IPS observations by calculating simulated g-values from LOS integration. 49,50) The 3D reconstructions of the ICME have been compared with in situ and white-light measurements. 51,52) An interesting feature revealed from this analysis is a loop-shaped high-Δ N e structure, which is often observed in Earth-directed (so-called “halo” 53) ) CME events.…”

Section: D Properties Of Interplanetary Disturbances Associated Withmentioning

confidence: 99%

Three-dimensional exploration of the solar wind using observations of interplanetary scintillation

Tokumaru

2013

Proc. Jpn. Acad., Ser. B

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The solar wind, a supersonic plasma flow continuously emanating from the Sun, governs the space environment in a vast region extending to the boundary of the heliosphere (∼100 AU). Precise understanding of the solar wind is of importance not only because it will satisfy scientific interest in an enigmatic astrophysical phenomenon, but because it has broad impacts on relevant fields. Interplanetary scintillation (IPS) of compact radio sources at meter to centimeter wavelengths serves as a useful ground-based method for investigating the solar wind. IPS measurements of the solar wind at a frequency of 327 MHz have been carried out regularly since the 1980s using the multi-station system of the Solar-Terrestrial Environment Laboratory (STEL) of Nagoya University. This paper reviews new aspects of the solar wind revealed from our IPS observations.

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Section: D Properties Of Interplanetary Disturbances Associated Withmentioning

confidence: 99%

Three-dimensional exploration of the solar wind using observations of interplanetary scintillation

Tokumaru

2013

Proc. Jpn. Acad., Ser. B

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“…∆S m (ε) varies with the solar elongation angle [ε] for a line-of-sight (LOS) from an observed radio source to a telescope. When a radio signal is weakly scattered, the g-value is given by the following equation (Tokumaru et al, 2003(Tokumaru et al, , 2006:…”

Section: Stel Ips Observationmentioning

confidence: 99%

Radial Speed Evolution of Interplanetary Coronal Mass Ejections During Solar Cycle 23

2013

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We report radial-speed evolution of interplanetary coronal mass ejections (ICMEs) detected by the Large Angle and Spectrometric Coronagraph onboard the Solar and heliospheric Observatory (SOHO/LASCO), interplanetary scintillation (IPS) at 327 MHz,and in-situ observations. We analyzed solar-wind disturbance factor (g-value) data derived from IPS observations during 1997 -2009 covering nearly whole period of Solar Cycle 23. By comparing observations from SOHO/LASCO, IPS, and in situ, we identified 39 ICMEs that could be analyzed carefully. Here, we defined two speeds [V SOHO and V bg ], which are initial speed of the ICME and the speed of the background solar wind, respectively. Examination of these speeds yield the following results: i) Fast ICMEs (with V SOHO − V bg > 500 km s −1 ) rapidly decelerate, moderate ICMEs (with 0 km s −1 ≤ V SOHO −V bg ≤ 500 km s −1 ) show either gradually decelerating or uniform motion, and slow ICMEs (with V SOHO − V bg < 0 km s −1 ) accelerate. The radial speeds converge on the speed of the background solar wind during their outward propagation. We subsequently find; ii) both the acceleration and deceleration are nearly complete by 0.79 ± 0.04 AU, and those are ended when the ICMEs reach a 489 ± 21 km s −1 . iii) For ICMEs with V SOHO − V bg ≥ 0 km s −1 , i.e. fast and moderate ICMEs, a linear equation a = −γ 1 (V − V bg ) with γ 1 = 6.58 ± 0.23 × 10 −6 s −1 is more appropriate than a quadratic equation a = −γ 2 (V − V bg )|V − V bg | to describe their kinematics, where γ 1 and γ 2 are coefficients, and a and V are the acceleration and ICME speed, respectively, because the χ 2 for the linear equation satisfies the statistical significance level of 0.05, while the quadratic one does not. These results support the assumption that the radial motion of ICMEs is governed by a drag force due to interaction with the background solar wind. These findings also suggest that ICMEs propagating faster than the background solar wind are controlled mainly by the hydrodynamic Stokes drag.

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“…This analysis maps the heliosphere using all available data covering an interesting period of observation, including data both prior to and well after the ejected solar material moves past 1 AU. These compare favorably with other techniques used to invert the IPS data to show the extent of CME structures (e.g., Tokumaru et al, 2005Tokumaru et al, , 2007 using archival data sets. The program can be operated in two different modes.…”

Section: D Reconstructions Using In-situ Density Measurementsmentioning

confidence: 59%

Inclusion of Real-Time In-Situ Measurements into the UCSD Time-Dependent Tomography and Its Use as a Forecast Algorithm

et al. 2012

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The University of California, San Diego (UCSD) three-dimensional (3D) timedependent tomography program, used for over a decade to reconstruct and forecast coronal mass ejections (CMEs), does so from observations of interplanetary scintillation (IPS) taken using the Solar-Terrestrial Environment Laboratory (STELab) radio arrays in Japan. An earlier article (Jackson et al. in Solar Phys. 265, 245, 2010) tion can be used in addition to remote-sensing data to constrain a time-dependent tomographic velocity solution. Here we extend this in-situ inclusion to density measurements, and show how this constrains the tomographic density solution. Supplementing remote-sensing observations with in-situ measurements provides additional information to construct an iterated solar-wind parameter that is propagated outward from near the solar surface past the measurement location, and throughout the volume. As in the case of velocity when this is done, the largest changes within the volume are close to the radial directions around Earth that incorporate the in-situ measurements; the inclusion significantly reduces the uncertainty in extending these measurements to global 3D reconstructions that are distant in time and space from the spacecraft. At Earth, this analysis provides a finely tuned real-time result up to the latest time for which in-situ measurements are available, and enables more-accurate extension of these results near Earth to those remotely sensed. We show examples of this new algorithm using real-time STELab IPS data that were used in our forecasts throughout Carrington rotations 2010 through 2016, and we provide one metric prescription that we have used to determine the forecasting accuracy one, two, and three days in advance of the time data become available to analyze from STELab. We show that the accuracy is considerably better than assuming persistence of the same signal over one to two days in advance of when the data are available.

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Tracking heliospheric disturbances by interplanetary scintillation

Cited by 17 publications

References 33 publications

Three-dimensional exploration of the solar wind using observations of interplanetary scintillation

Three-dimensional exploration of the solar wind using observations of interplanetary scintillation

Radial Speed Evolution of Interplanetary Coronal Mass Ejections During Solar Cycle 23

Inclusion of Real-Time In-Situ Measurements into the UCSD Time-Dependent Tomography and Its Use as a Forecast Algorithm

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