CNA pulsations accompanying hydromagnetic waves at conjugate stations

Higuchi, Yoshinori; Shibuya, Senkichi; Sato, Natsuo

doi:10.1016/0032-0633(88)90077-3

Cited by 6 publications

(4 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In Sect. 2, we recap the main results of Fouchard et al (2020) and the relevant theoretical analysis in Higuchi (2020). In Sect.…”

Section: Introductionmentioning

confidence: 94%

“…In Fouchard et al (2020), three distinct categories of longterm dynamical evolution typical of the disk model were able to carry such a memory: (i) B1 group comets, whose orbits remain largely unchanged during the entire propagation except at the very end, when a rapid increase in the orbital energy induces a rapid decrease in the perihelion distance under the action of the Galactic tides; (ii) B2 group comets, with a single large perihelion distance oscillation caused by Galactic tides, with the other elements remaining nearly constant; and (iii) B3 group comets, for which the perihelion distance and argument of perihelion performed a single period, whereas the longitude of the ascending node performed half a period. Such comets returned to the planetary region with an orbital plane close to the empty ecliptic (EE) plane (Higuchi 2020), which was obtained by rotating the ecliptic plane around the Galactic pole by 180 • . An example of each behavior is shown in Fig.…”

Section: Transport and Detection Of The Memory Of A Disk-like Proto-o...mentioning

confidence: 99%

See 1 more Smart Citation

What long-period comets tell us about the Oort Cloud

Fouchard¹,

Higuchi²,

Itô³

2023

A&A

View full text Add to dashboard Cite

Context. The Oort Cloud is located in the farthest outskirts of the Solar System, extending to a heliocentric distance of several tens of thousands of au, and remains the last region of the Solar System where no object has been detected. Thus, all our knowledge of the Oort Cloud has been deduced from the observed long-period comets that are thought to originate from it. Aims. We aimed to retrieve valuable information that might be hidden in the orbital distributions of the observed long-period comets. Such information will allow us to impose constraints not only on the present shape of the Oort Cloud but also on its initial shape 4.5 Gyr ago. This has direct implications for the scenario proposed for its formation. Methods. We used two different databases of long-period comets. First, we calculated the distribution of orbital elements that might carry valuable information about the shape of the Oort Cloud. Then, we compared the distribution with that obtained from two synthetic samples of observable comets. These samples correspond to two considerably different initial configurations: one is a disk model, where we consider a swarm of comets with orbits aligned to the ecliptic plane and with a cometary perihelion close to the giant planets. The other is an isotropic model, where we consider a fully isotropic and thermalized initial distribution of comets. Results. The comparison revealed that the databases contained several features that were in better agreement with the disk model than with the isotropic model. The Oort Cloud contained an initial disk of objects with perihelia close to the planetary region of the Solar System and aphelia extending out to roughly 20 000 au. Some parts of this disk likely remain in the present Solar System. However, the fit to the disk model is poor. The discrepancy between the observational and synthetic results indicates that some dynamical processes in the current Oort Cloud were not included in either model. Conclusions. This initial shape of the Oort Cloud implies that planetary scattering was crucial during its formation. In addition, the fact that some dynamical features are still detec table 4.5 Gyr after the cloud formation imposes constraints on the role of exosolar effects, such as giant molecular clouds, Galactic tides, and the stellar cluster surrounding the Solar System at the time of its formation.

show abstract

“…In Sect. 2, we recap the main results of Fouchard et al (2020) and the relevant theoretical analysis in Higuchi (2020). In Sect.…”

Section: Introductionmentioning

confidence: 94%

Section: Transport and Detection Of The Memory Of A Disk-like Proto-o...mentioning

confidence: 99%

What long-period comets tell us about the Oort Cloud

Fouchard¹,

Higuchi²,

Itô³

2023

A&A

View full text Add to dashboard Cite

show abstract

“…Kokubun et al, 1977;Higuchi et al, 1988;Kleimenova et al, 1997;Nosé et al, 1998). The riometer data on 21 November 2003 showed that only the Pc5 pulsations in the interval of 06:00-07:00 UT were accompanied by pulsating electron precipitation.…”

Section: Discussionmentioning

confidence: 99%

Unusual strong quasi-monochromatic ground Pc5 geomagnetic pulsations in the recovery phase of November 2003 superstorm

Клейменова

Козырева

Manninen³

et al. 2005

Ann. Geophys.

View full text Add to dashboard Cite

Abstract. Unusually large-amplitude morning Pc5 magnetic pulsations during the recovery phase of the huge magnetic storm in November 2003 have been studied by using ground-based multi-point observations. Two main spectral Pc5 enhancements were observed: at f≈2 mHz, which featured slowly increasing frequency with decreasing latitude, and at f≈3 mHz, which was latitude independent. The Pc5 pulsations were observed at wide range of latitudes (more than 10 • ) with the same very strong amplitude (up to 500 nT) and with the same polarization. Only the 3-mHz peak was clearly seen in the spectra of pulsating auroral radio absorption, as observed by the Finnish riometer chain. Short and localized bursts of PiB (f∼50-100 mHz) magnetic pulsations and simultaneous short bursts of energetic electron precipitation were observed in the morning sector, as well. The beginning of the large-amplitude morning Pc5 activity occurred simultaneously with a substorm onset in the evening and midnight sectors. However, the spectra of pulsations in the morning and evening sectors were different. They were compared with spectra of IMF and solar wind parameters, measured by ACE spacecraft. The similarity between the spectra of morning Pc5 and IMF B y was found, but the spectra of evening Pi3 pulsations were similar to the spectra of solar wind density variations. The Pc5 and PiB pulsations, as well as bursts of the auroral radio absorption, suddenly disappeared, when the solar wind density abruptly dropped. We suppose that the ∼2-mHz Pc5 geomagnetic pulsations could be attributed to field line resonance (FLR), however, the 3-mHz oscillations were apparently non-resonance origin.

show abstract

“…There have been a number of observations using widebeam riometers and balloon-borne X-ray detectors of electron precipitation pulsations associated with magnetospheric ULF wave activity with the same periodicity (Ziauddin, 1960;Anger et al, 1963;Heacock and Hunsucker, 1977;Olson et al, 1980;Higuchi et al, 1988). One interpretation of these observations is that the electron precipitation is in some way modulated by the ULF wave.…”

Section: Introductionmentioning

confidence: 99%

Observations of the spatial structure of electron precipitation pulsations using an imaging riometer

Senior

Honary

2003

Ann. Geophys.

View full text Add to dashboard Cite

Abstract. Electron precipitation can be modulated by geomagnetic pulsation activity. This can be observed as pulsation of cosmic noise absorption as measured by riometers. Observations of such pulsations exhibiting field-line resonance and particle-driven characteristics using an imaging riometer are presented and the capability of the instrument to map their spatial structure is demonstrated. It is shown that for the events studied, the spatial variation of pulsation phase as measured by the riometer agrees with that inferred from ground-based magnetometers, whereas the spatial variation of pulsation amplitude may show a different structure. It is suggested that this is consistent with the mechanism proposed by Coroniti and Kennel (1970) where one would expect a fixed phase relationship between magnetic and absorption pulsations, but where the amplitude of the absorption pulsation can depend on several factors other than the amplitude of the magnetic pulsation.

show abstract

CNA pulsations accompanying hydromagnetic waves at conjugate stations

Cited by 6 publications

References 25 publications

What long-period comets tell us about the Oort Cloud

What long-period comets tell us about the Oort Cloud

Unusual strong quasi-monochromatic ground Pc5 geomagnetic pulsations in the recovery phase of November 2003 superstorm

Observations of the spatial structure of electron precipitation pulsations using an imaging riometer

Contact Info

Product

Resources

About