Heliospheric tomography using interplanetary scintillation observations: 2. Latitude and heliocentric distance dependence of solar wind structure at 0.1–1 AU

Kojima, M.; Tokumaru, M.; Watanabe, Hironori; Yokobe, A.; Asai, Kikuo; Jackson, B. V.; Hick, P. P.

doi:10.1029/97ja02162

Cited by 154 publications

(135 citation statements)

References 19 publications

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“…At solar minimum the bimodal velocity structure is reproduced well, and IPS CAT results agree well with Ulysses' first fast latitude scan observations (e.g. Kojima et al, 1998Kojima et al, , 2001. The tomographic analysis requires a stable solar wind velocity structure over one solar rotation, because all of the IPS data in a given Carrington rotation are used to produce a velocity map (V-map).…”

Section: Introductionsupporting

confidence: 64%

“…IPS signals of a natural radio source are affected by a bias, which is caused by a weighted integration along the line-ofsight. Solar wind speed is derived from the IPS signals using the Computer-Assisted Tomography (CAT) technique (Kojima et al, 1998), which removes the bias and improves spatial resolution. The CAT technique has been shown to work well around solar minimum.…”

Section: Introductionmentioning

confidence: 99%

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How did the solar wind structure change around the solar maximum? From interplanetary scintillation observation

et al. 2003

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Abstract.Observations from the second Ulysses fast latitude scan show that the global structure of solar wind near solar maximum is much more complex than at solar minimum. Soon after solar maximum, Ulysses observed a polar coronal hole (high speed) plasma with magnetic polarity of the new solar cycle in the Northern Hemisphere. We analyze the solar wind structure at and near solar maximum using interplanetary scintillation (IPS) measurements. To do this, we have developed a new tomographic technique, which improves our ability to examine the complex structure of the solar wind at solar maximum. Our IPS results show that in 1999 and 2000 the total area with speed greater than 700 km s −1 is significantly reduced first in the Northern Hemisphere and then in the Southern Hemisphere. For year 2001, we find that the formation of large areas of fast solar wind around the north pole precedes the formation of large polar coronal holes around the southern pole by several months. The IPS observations show a high level agreement to the Ulysses observation, particularly in coronal holes.

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Section: Introductionsupporting

confidence: 64%

Section: Introductionmentioning

confidence: 99%

How did the solar wind structure change around the solar maximum? From interplanetary scintillation observation

et al. 2003

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“…For this analysis we have introduced a multistep CAT analysis method which has better reliability and sensitivity in the polar regions than the previous method developed by Kojima et al [1998]. …”

Section: Discussionmentioning

confidence: 99%

Latitudinal velocity structures up to the solar poles estimated from interplanetary scintillation tomography analysis

Kojima¹,

Fujiki²,

Ohmi³

et al. 2001

J. Geophys. Res.

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Abstract. The Ulysses spacecraft observed high-speed wind at high latitudes up to 80 ø and found that the high-speed solar wind increased in velocity gradually with latitude and that the velocity had asymmetry between Northern and Southern Hemispheres. We have investigated the velocity increase up to the polar regions for the Cartington rotations of 1908-1915 in the year 1996. For this purpose we have made tomographic analyses of the latitudinal structure of the solar wind speed using interplanetary scintillation data obtained at heliocentric distances of 0.1-0.9 AU and latitudes up to 90 ø. The tomographic analysis method was modified from its previous version [Kojima ½t al., 1998] so that it could obtain more reliable solutions with better sensitivity in the polar region than the previous method. The results from the observations in 1996 showed that the velocity increased with latitude and had the N-S asymmetry as observed by Ulysses. These features persisted during the period analyzed. Since the asymmetry was found in rather short period observations of several Cartington rotations and at distances within 0.9 AU, it is caused neither by temporal evolution of the solar wind structures nor by interactions in the solar wind in interplanetary space. These global latitudinal velocity structures agree qualitatively with the magnetic flux expansion factor.

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“…Thus, by inferring the level of electron density fluctuations from IPS observations, one can estimate the local speed of the SW (Hewish, Scott, and Wills, 1964;Jackson et al, 1997Jackson et al, , 2003Kojima et al, 1998). However, one needs a formula that links the electron density fluctuations δn e with the SW speed v. Usually, a relation δn e ∝ v γ is used.…”

Section: Remote-sensing Observations Of Interplanetary Scintillationsmentioning

confidence: 99%

“…Interplanetary scintillation is the phenomenon of producing diffraction patterns on an observer's plane by the interferencing radio waves from a remote compact radio source (like a quasar) that are scattered by electron density irregularities (fluctuations) in the SW (see, e.g., Hewish, Scott, and Wills, 1964;Coles and Kaufman, 1978;Kojima and Kakinuma, 1990;Kojima et al, 1998Kojima et al, , 2007. The scintillation signal is a sum of waves scattered along the line of sight (LOS) to the observed radio source.…”

Section: Remote-sensing Observations Of Interplanetary Scintillationsmentioning

confidence: 99%

Heliolatitude and Time Variations of Solar Wind Structure from in situ Measurements and Interplanetary Scintillation Observations

et al. 2012

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The 3D structure of the solar wind and its evolution in time are needed for heliospheric modeling and interpretation of energetic neutral atoms observations. We present a model to retrieve the solar wind structure in heliolatitude and time using all available and complementary data sources. We determine the heliolatitude structure of solar wind speed on a yearly time grid over the past 1.5 solar cycles based on remote-sensing observations of interplanetary scintillations, in situ out-of-ecliptic measurements from Ulysses, and in situ in-ecliptic measurements from the OMNI 2 database. Since in situ out-of-ecliptic information on the solar wind density structure is not available apart from the Ulysses data, we derive correlation formulae between the solar wind speed and density and use the information on the solar wind speed from interplanetary scintillation observations to retrieve the 3D structure of the solar wind density. With the variations of solar wind density and speed in time and heliolatitude available, we calculate variations in solar wind flux, dynamic pressure, and charge-exchange rate in the approximation of stationary H atoms.

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Heliospheric tomography using interplanetary scintillation observations: 2. Latitude and heliocentric distance dependence of solar wind structure at 0.1–1 AU

Cited by 154 publications

References 19 publications

How did the solar wind structure change around the solar maximum? From interplanetary scintillation observation

How did the solar wind structure change around the solar maximum? From interplanetary scintillation observation

Latitudinal velocity structures up to the solar poles estimated from interplanetary scintillation tomography analysis

Heliolatitude and Time Variations of Solar Wind Structure from in situ Measurements and Interplanetary Scintillation Observations

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