J. K. Shi

National Space Science Center

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M. W. Dunlop

Beihang University

K. Torkar

Institute of Oncology Ljubljana

Zhengwei Cheng

Chinese Academy of Sciences

Guojun Wang

National Space Science Center

Zheng Wang

National Space Science Center

A. N. Fazakerley

University College London

X. Wang

Chinese Academy of Sciences

Zhenxing Liu

Zhejiang Sci-Tech University

Z. Y. Pu

Peking University

Tielong Zhang

Austrian Academy of Sciences

Cooperative Institutions

Chinese Academy of Sciences

157

National Space Science Center

117

University of Chinese Academy of Sciences

National Institute for Space Research

State Key Laboratory of Space Weather

Peking University

University of Science and Technology of China

Chinese Academy of Meteorological Sciences

Space Research Institute

Austrian Academy of Sciences

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Response of Hainan GPS ionospheric scintillations to the different strong magnetic storm conditions

Advances in Space Research (2007)

S. P. Shang J. K. Shi P. M. Kintner Weimin Zhen Xiaoqing Luo

Interplanetary scintillation

Midnight

Sunset

10.1016/j.asr.2007.05.020

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Citations (26)

Properties of Spread-F in High and Low Latitude Ionospheres

J. K. Shi Tao Wei G. J. Wang G. Zherebotsov O. M. Pirog

The ionospheric spread-F has many significant effects on radio waves that propagation through the Earth's atmosphere, such as refraction, reflection, absorption, time delay, phase change, amplitude change, Doppler shifts, and so on. In this paper, we used the data from DPS-4 Digisondes at low latitude station Hainan (19.4 degrees N, 109.0 degrees E), China, and high altitude stations Yakutsk (62 degrees N, 129 degrees E) and Zhigansk (66 degrees N, 123 degrees E), Russia to study the ionospheric Spread-F (SF) properties during geo-magnetic storm time. Some new results are obtained by data analysis. In Hainan and Yakutsk, SF was observed only in night time, but in Zhigansk it was also observed in day time. The SF seems more activity over Yakutsk. The SSF concerned with equatorial plasma bubble is only observed at low latitude station Hainan and the branch SF is only observed at high latitude stations Yakutsk and Zhigansk. For most cases start time of SF is later if the station latitude is lower. This implies that plasma instability caused ionospheric irregularity is propagation from high latitude to low latitude ionosphere.

Low latitude

Middle latitudes

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Citations (1)

South‐north asymmetry of field‐aligned currents in the magnetotail observed by Cluster

Journal of Geophysical Research Atmospheres (2010)

J. K. Shi Zhengwei Cheng Tielong Zhang M. W. Dunlop Z. X. Liu

We statistically investigated features of the field‐aligned current (FAC) distribution in plasma sheet boundary layers between 17 and 19 R E in the magnetotail using the curlometer technique to calculate the current from four‐point magnetic field measurements taken in 2001. The results show that the FAC distribution in the plasma sheet boundary layers in the magnetotail has dusk‐dawn asymmetry, earthward‐tailward (polarity) asymmetry, and north‐south asymmetry. The occurrence and polarities of FACs in the Northern Hemisphere are different from those in the Southern Hemisphere. The average density and the standard deviation of the FACs that are most likely to be connected to the Earth are 4.90 nA m −2 and 2.55 nA m −2 in the Northern Hemisphere and 4.21 nA m −2 and 1.80 nA m −2 in the Southern Hemisphere, respectively. For investigating the mechanism of the north‐south asymmetry, we mapped the FACs along the field line into the polar region. The footprints of the FACs also show a difference between the Southern and Northern hemispheres (as a function of mapped latitude). These characteristics suggest a north‐south asymmetry of the FACs in the magnetosphere. Further investigation is needed to identify the causes of this asymmetry, although the configuration of the magnetosphere, the polar cap boundary, the conductivity in the ionosphere, or the various solar wind‐magnetosphere interaction processes all may be contributors. That the FAC densities are different between the hemispheres suggests that an important source of these currents must be a voltage generator.

Plasma sheet

Polarity (international relations)

Field line

10.1029/2009ja014446

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Citations (43)

Spatial distribution of rolled up Kelvin-Helmholtz vortices at Earth's dayside and flank magnetopause

Annales Geophysicae (2012)

M. G. G. T. Taylor H. Hasegawa B. Lavraud T. D. Phan C. P. Escoubet

Abstract. The Kelvin-Helmholtz Instability (KHI) can drive waves at the magnetopause. These waves can grow to form rolled-up vortices and facilitate transfer of plasma into the magnetosphere. To investigate the persistence and frequency of such waves at the magnetopause we have carried out a survey of all Double Star 1 magnetopause crossings, using a combination of ion and magnetic field measurements. Using criteria originally used in a Geotail study made by Hasegawa et al. (2006) (forthwith referred to as H2006), 17 candidate events were identified from the entire TC-1 mission (covering ~623 orbits where the magnetopause was sampled), a majority of which were on the dayside of the terminator. The relationship between density and shear velocity was then investigated, to identify the predicted signature of a rolled up vortex from H2006 and all 17 events exhibited some level of rolled up behavior. The location of the events had a clear dawn-dusk asymmetry, with 12 (71%) on the post noon, dusk flank suggesting preferential growth in this region.

Noon

Magnetosheath

10.5194/angeo-30-1025-2012

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Citations (71)

Magnetopause reconnection across wide local time

Annales Geophysicae (2011)

M. W. Dunlop Qinghe Zhang Y. V. Bogdanova K. J. Trattner Z. Y. Pu

Abstract. During April to July 2007 a combination of 10 spacecraft provided simultaneous monitoring of the dayside magnetopause across a wide range of local times. The array of four Cluster spacecraft, separated at large distances (10 000 km), were traversing the dawn-side magnetopause at high and low latitudes; the five THEMIS spacecraft were often in a 4 + 1 grouped configuration, traversing the low latitude, dusk-side magnetosphere, and the Double star, TC-1 spacecraft was in an equatorial orbit between the local times of the THEMIS and Cluster orbits. We show here a number of near simultaneous conjunctions of all 10 spacecraft at the magnetopause. One conjunction identifies an extended magnetic reconnection X-line, tilted in the low latitude, sub-solar region, which exists together with active anti-parallel reconnection sites extending to locations on the dawn-side flank. Oppositely moving FTE's are observed on all spacecraft, consistent with the initially strong IMF By conditions and the comparative locations of the spacecraft both dusk-ward and dawn-ward of noon. Comparison with other conjunctions of magnetopause crossings, which are also distributed over wide local times, supports the result that reconnection activity may occur at many sites simultaneously across the sub-solar and flank magnetopause, but linked to the large scale (extended) configuration of the merging line; broadly depending on IMF orientation. The occurrence of MR therefore inherently follows a "component" driven scenario irrespective of the guide field conditions. Some conjunctions allow the global magnetopause response to IMF changes to be observed and the distribution of spacecraft can directly confirm its shape, motion and deformation at local noon, dawn and dusk-side, simultaneously.

Local time

Noon

Magnetosphere of Saturn

Field line

10.5194/angeo-29-1683-2011

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Citations (64)

Diurnal, seasonal, annual, and semi-annual variations of ionospheric parameters at different latitudes in East Asian sector during ascending phase of solar activity

Solar-Terrestrial Physics (2017)

Чжэн Ван Zheng Wang Цзянькуй Ши J. K. Shi Гоцзюнь Ван

We analyzed ionospheric parameters including the critical frequency of the F2 layer (foF2), the peak height of the F2 layer (hmF2), and the scale height at hmF2 (HT) from 2006 to 2012 (ascending phase of solar activity) at Hainan (19.5° N, 109.1° E, MLat. 9.7° N), Irkutsk (52.4° N, 104.3° E, MLat. 42.5° N), and Norilsk (69.2° N, 88.0° E, MLat. 59.8° N) stations (low, middle and high latitudes). We have used manual scaled digisonde ionogram data. Studies of foF2 and hmF2 di-urnal-seasonal variations continue those made earlier for East Asia. Features peculiar for the ascending phase of solar activity are mostly consistent to those for de-scending phase, except for the features of sunset and nighttime hmF2 variations. Features of annual and semi-annual variations recorded by a digisonde agree with those obtained by a satellite occultation and TEC map. We also obtained seasonal, diurnal, annual, and semi-annual variations of the ionospheric parameter HT (scale height at hmF2) from digisonde data, which differ from foF2 variations and hmF2 features.

Ionogram

Sunset

Critical frequency

Middle latitudes

International Reference Ionosphere

Low latitude

Radio occultation

10.12737/stp-3220177

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Citations (3)

Correlation between ionospheric strong range spread F and scintillations observed in Vanimo station

Journal of Geophysical Research Space Physics (2014)

Zheng Wang J. K. Shi K. Torkar G. J. Wang X. Wang

Abstract Data from the ionospheric scintillation monitor and ionosonde at the low‐latitude station Vanimo (2.7°S, 141.3°E; dip latitude 11°S) in the Southern Hemisphere in 2003 were statistically analyzed to study the correlation between scintillations and strong range spread F (SSF). The results showed that the observed SF had four types: frequency spread F, mixed spread F, range spread F (RSF), and strong range spread F (SSF). SSF and scintillations usually occurred simultaneously and had nearly the same periods and similar trends. Only the SSF had a high correlation (coefficient 0.7199) with the scintillation, while the other three types of SF were uncorrelated with the scintillation. This implies that the SSF has a different physical mechanism from the RSF, and both the SSF and the scintillation are caused by equatorial plasma bubbles. This is important for us to understand the physical mechanisms of the irregularities in the low‐latitude ionosphere.

Ionosonde

Low latitude

Interplanetary scintillation

Positive correlation

10.1002/2014ja020447

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Citations (18)

Nonlinear waves in a low-β plasma with cylindrical symmetry

Physics of Plasmas (2001)

J. K. Shi Birong Xu K. Torkar Z. X. Liu

The “Sagdeev potential” is derived from the magnetohydrodynamic equations in a cylindrical coordinate system, and nonlinear electrostatic density waves propagating along the magnetic field in a low-β plasma with cylindrical symmetry are studied. The results show the existence not only of periodic density waves, solitons with a density hump and solitons with a density dip, but also of density shock waves.

10.1063/1.1409959

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Citations (6)

Investigation of cubic non‐linearity‐driven electrostatic structures in the presence of double spectral index distribution function

Contributions to Plasma Physics (2019)

M. N. S. Qureshi K. H. Shah J. K. Shi W. Masood H. A. Shah

Abstract In this article, modified Korteweg‐de Vries equation (which involves cubic non‐linearity) was derived to study non‐linear ion acoustic waves in a plasma in which electrons follow the double spectral index distribution function. The double spectral index distribution successfully apes the distribution functions that have been frequently observed in space plasmas. The spectral index r moulds the distribution function at low energy and by increasing its value, flatness of the distribution enhances. The spectral index r can also have negative values due to which distribution becomes spiky at low energies. The index q , on the other hand, controls the shape of the tail of distribution function. It has been shown that propagation of the solitary structures gets significantly altered by the choice of the double spectral indices, namely, r and q . A comparison was also made, using the parameters of the auroral zone, between the quadratic and cubic non‐linearities‐driven non‐linear structures and it was shown that the solitary structures form on a much shorter scale for cubic non‐linearity compared to their quadratic counterpart.

Spectral index

Linearity

Flatness (cosmology)

10.1002/ctpp.201900065

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Citations (11)

Statistical Study on Daytime Es Observed by Ground-ionosonde and RO-COSMIC S4 Index in Magnetic Equator Region in 2010

2022 Photonics & Electromagnetics Research Symposium (PIERS) (2021)

Zheng Wang J. K. Shi Guojun Wang Zhengwei Cheng She‐Ping Shang

The previous studies show that scintillations under 150 km height shown by radio occultation (RO) of COSMIC are considered to be associated with ionospheric sporadic E (Es) layer. In this paper, we perform a statistical study on daytime Es observed by ground-ionosonde at five stations in magnetic Equator region in 2010, and make a comparison between foEs and S4 index from RO-COSMIC within 6 degree of each station. The results show that the foEs and S4 index had similar distributions. The agreement between scintillation occurrence and extreme Es cases showed that the Es had a significant contribution to the S4 index in daytime. It implies the satellite RO data could be used to study ionospheric structures/irregularities. The results also showed that the Es had more contribution at Sao Luis/Ilorin than that at Jicamarca/Kwajalein. However, the Es contribution to the S4 index during daytime need to be further studied in detail.

Ionosonde

Radio occultation

Magnetic dip

10.1109/piers53385.2021.9694798

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Citations (0)