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

Tokumaru, M.

doi:10.2183/pjab.89.67

Cited by 40 publications

(35 citation statements)

References 63 publications

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“…[]). UCSD reconstruction analyses of IPS data compare favorably with ISEE results [ Tokumaru , ; Jackson et al ., ]. For mathematical details about the UCSD CAT program, see Hick and Jackson [] and Jackson et al [].…”

Section: Tomographic Analysis and Field Extrapolation Using A Sample mentioning

confidence: 99%

Exploration of solar photospheric magnetic field data sets using the UCSD tomography

Jackson

Buffington

et al. 2016

Space Weather

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This article investigates the use of two different types of National Solar Observatory magnetograms and two different coronal field modeling techniques over 10 years. Both the “open‐field” Current Sheet Source Surface (CSSS) and a “closed‐field” technique using CSSS modeling are compared. The University of California, San Diego, tomographic modeling, using interplanetary scintillation data from Japan, provides the global velocities to extrapolate these fields outward, which are then compared with fields measured in situ near Earth. Although the open‐field technique generally gives a better result for radial and tangential fields, we find that a portion of the closed extrapolated fields measured in situ near Earth comes from the direct outward mapping of these fields in the low solar corona. All three closed‐field components are nonzero at 1 AU and are compared with the appropriate magnetometer values. A significant positive correlation exists between these closed‐field components and the in situ measurements over the last 10 years. We determine that a small fraction of the static low‐coronal component flux, which includes the Bn (north‐south) component, regularly escapes from closed‐field regions. The closed‐field flux fraction varies by about a factor of 3 from a mean value during this period, relative to the magnitude of the field components measured in situ near Earth, and maximizes in 2014. This implies that a relatively more efficient process for closed‐flux escape occurs near solar maximum. We also compare and find that the popular Potential Field Source Surface and CSSS model closed fields are nearly identical in sign and strength.

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Section: Tomographic Analysis and Field Extrapolation Using A Sample mentioning

confidence: 99%

Exploration of solar photospheric magnetic field data sets using the UCSD tomography

Jackson

Buffington

et al. 2016

Space Weather

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“…IPS observations have been regularly conducted since the 1980s at the Institute for Space‐Earth Environmental Research (ISEE; formerly Solar‐Terrestrial Environment Laboratory) of Nagoya University using the 327‐MHz multistation system (Kojima & Kakinuma, ; Tokumaru, ). The solar wind speeds are derived from the cross‐correlation analysis of multistation IPS data.…”

Section: Observationsmentioning

confidence: 99%

Rarefaction of the Very Slow (<350 km/s) Solar Wind in Cycle 24 Compared With Cycle 23

et al. 2018

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We investigate long‐term variation of the very slow solar wind (VSSW), whose speed is less than 350 km/s, during the period between 1997 and 2015, that is, Cycles 23 and 24, using interplanetary scintillation measurements, which enable determination of the global distribution of the flow speed and the electron density fluctuation level ΔNe. We find that the occurrence rate of VSSW increases in the maximum phase of the solar cycle, and it was mostly associated with high ΔNe in Cycle 23. However, the VSSW is found to be more associated with low ΔNe in Cycle 24. This fact is consistent with an increased occurrence of the low‐density VSSW observed in situ in Cycle 24. These facts, which are considered to be a manifestation of weak solar activity in this cycle, suggest that the VSSW has become significantly rarefied in recent years. We identify the source region of the VSSW on the photosphere using a potential field analysis and examine the magnetic field properties of the VSSW source. We find that the low‐ΔNe VSSW is associated with a smaller expansion factor and possibly a slightly weaker photospheric field strength than the high‐ΔNe VSSW. The results obtained here may suggest that more open magnetic field areas producing the VSSW in Cycle 24 are formed in the quiet Sun region, which is associated with a lower mass flux supply into the corona, than those in Cycle 23.

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“…Interplanetary scintillation (IPS) observations at 327 MHz have been carried out regularly using the multi-station system of the Solar-Terrestrial Environment Laboratory (STEL) of Nagoya University to elucidate 3D structure of the solar wind and its time evolution (Tokumaru, 2013). The multi-station system was upgraded in the period between 2013 and 2014 to improve its sensitivity.…”

Section: Interplanetary Scintillation and Radio Spectro-polarimeter Omentioning

confidence: 99%

Division E Commission 49: Interplanetary Plasma and Heliosphere

Mann¹,

Manoharan²,

Gopalswamy³

et al. 2015

Proc. IAU

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Abstract. After a little more than forty years of work related to the interplanetary plasma and the heliosphere the IAU's Commission 49 was formally discontinued in 2015. The commission started its work when the first spacecraft were launched to measure the solar wind in-situ away from Earth orbit, both inward and outward from 1 AU. It now hands over its activities to a new commission during an era of space research when Voyager 1 measures in-situ the parameters of the local interstellar medium at the edge of the heliosphere. The commission will be succeeded by C.E3 with a similar area of responsibility but with more focused specific tasks that the community intends to address during the coming several years. This report includes a short description of the motivation for this commission and of the historical context. It then describes work from 2012 to 2015 during the present solar cycle 24 that has been the weakest in the space era so far. It gave rise to a large number of studies on solar energetic particles and cosmic rays. Other studies addressed e.g. the variation of the solar wind structure and energetic particle fluxes on long time scales, the detection of dust in the solar wind and the Voyager measurements at the edge of the heliosphere. The research is based on measurements from spacecraft that are at present operational and motivated by the upcoming Solar Probe + and Solar Orbiter missions to explore the vicinity of the Sun. We also report here the progress on new and planned radio instruments and their importance for heliospheric studies. Contributors to this report are

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

Cited by 40 publications

References 63 publications

Exploration of solar photospheric magnetic field data sets using the UCSD tomography

Exploration of solar photospheric magnetic field data sets using the UCSD tomography

Rarefaction of the Very Slow (<350 km/s) Solar Wind in Cycle 24 Compared With Cycle 23

Division E Commission 49: Interplanetary Plasma and Heliosphere

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