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89 results on '"Lakhina Gurbax S."'

52. Helicon Modes Driven by Ionosheric 0+ Ions in the Plasma Sheet Region

Author

Lakhina, Gurbax S and Tsurutani, Bruce T

Subjects
Plasma Physics
Abstract

It is shown that the precence of ionospheric-origin oxygen ion beams with anisotropic pressure can excite helicon modes in the near-Earth plasma shet region provided their Alfvenic Mach numbers lie in a certain range.

Published
1996

53. Preface: Nonlinear waves and chaos

Author

Lakhina, Gurbax S., primary, Tsurutani, Bruce T., additional, Morales, George J., additional, Pouquet, Annick, additional, Hoshino, Masahiro, additional, Valdivia, Juan Alejandro, additional, Narita, Yasuhito, additional, and Grimshaw, Roger, additional

Published
2018
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59. Space Weather Forecasting: What We Know Now and What Are the Current and Future Challenges?

Author

Tsurutani, Bruce T., Lakhina, Gurbax S., and Hajra, Rajkumar

Subjects
MAGNETOSPHERE, SPACE environment, WEATHER forecasting, SOLAR energetic particles, SOLAR spectra, MAGNETIC storms, SOLAR wind, SOLAR radiation
Abstract

Geomagnetic storms are caused by solar wind southward magnetic fields that impinge upon the Earth's magnetosphere (Dungey, 1961). How can we forecast the occurrence of these interplanetary events? We view this as the most important challenge in Space Weather. We discuss the case for magnetic clouds (MCs), interplanetary sheaths upstream of ICMEs, corotating interaction regions (CIRs) and high speed streams (HSSs). The sheath- and CIR-related magnetic storms will be difficult to predict and will require better knowledge of the slow solar wind and modeling to solve. There are challenges for forecasting the fluences and spectra of solar energetic particles. This will require better knowledge of interplanetary shock properties from the Sun to 1 AU (and beyond), the upstream slow solar wind and energetic "seed" particles. Dayside aurora, triggering of nightside substorms, and formation of new radiation belts can all be caused by shock and interplanetary ram pressure impingements onto the Earth's magnetosphere. The acceleration and loss of relativistic magnetospheric "killer" electrons and penetrating electric fields in terms of causing positive and negative ionospheric storms are currently reasonable well understood, but refinements can still be made. The forecasting of extreme events (extreme shocks, extreme solar energetic particle events, and extreme geomagnetic storms ( "Carrington" events or greater)) are also discussed. Energetic particle precipitation and ozone destruction is briefly discussed. For many of the studies, the Parker Solar Probe, Solar Orbiter, Magnetospheric Multiscale Mission (MMS), Arase, and SWARM data will be useful. [ABSTRACT FROM AUTHOR]

Published
2019
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77. Polar cap boundary layer waves: An auroral zone phenomenon

Author

Tsurutani, Bruce T., primary, Arballo, John K., additional, Galvan, Carlos, additional, Zhang, Liwei Dennis, additional, Zhou, Xiao-Yan, additional, Lakhina, Gurbax S., additional, Hada, Tohru, additional, Pickett, Jolene S., additional, and Gurnett, Donald A., additional

Published
2001
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79. CROSS-FIELD DIFFUSION OF ENERGETIC (100 keV to 2 MeV) PROTONS IN INTERPLANETARY SPACE.

Author

Jr., Edio da Costa, Tsurutani, Bruce T., Alves, Maria Virgínia, Echer, Ezequiel, and Lakhina, Gurbax S.

Subjects
MAGNETIC fields, SOLAR radiation, PROTONS, SPACE vehicles, STAR observations
Abstract

Magnetic field magnitude decreases (MDs) are observed in several regions of the interplanetary medium. In this paper, we characterize MDs observed by the Ulysses spacecraft instrumentation over the solar south pole by using magnetic field data to obtain the empirical size, magnetic field MD, and frequency of occurrence distribution functions. The interaction of energetic (100 keV to 2 MeV) protons with these MDs is investigated. Charged particle and MD interactions can be described by a geometrical model allowing the calculation of the guiding center shift after each interaction. Using the distribution functions for the MD characteristics, Monte Carlo simulations are used to obtain the cross-field diffusion coefficients as a function of particle kinetic energy. It is found that the protons under consideration cross-field diffuse at a rate of up to ≈11% of the Bohm rate. The same method used in this paper can be applied to other space regions where MDs are observed, once their local features are well known. [ABSTRACT FROM AUTHOR]

Published
2013
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84. Plasma wave characteristics of the Jovian magnetopause boundary layer: Relationship to the Jovian aurora?

Author

Tsurutani, Bruce T., primary, Arballo, John K., additional, Goldstein, Bruce E., additional, Ho, Christian M., additional, Lakhina, Gurbax S., additional, Smith, Edward J., additional, Cornilleau-Wehrlin, Nicole, additional, Prangé, Renée, additional, Lin, Naiguo, additional, Kellogg, Paul, additional, Phillips, John L., additional, Balogh, Andre, additional, Krupp, Norbert, additional, and Kane, Mark, additional

Published
1997
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85. The Structure and Microstructure of Rising‐Tone Chorus With Frequencies Crossing at f∼ 0.5 fce

Author

Chen, Rui, Tsurutani, Bruce T., Gao, Xinliang, Lu, Quanming, Chen, Huayue, Lakhina, Gurbax S., and Hajra, Rajkumar

Abstract

Intense, midnight‐to‐dawn sector, near‐equatorial, chorus rising tones which cross frequencies of ∼0.5fce$\sim 0.5{f}_{\text{ce}}$have been analyzed to determine their structures and possible substructures. Upper band (f≥0.5fce$f\ge 0.5{f}_{\text{ce}}$) chorus and “gap” (f∼0.5fce$f\sim 0.5{f}_{\text{ce}}$) chorus are examined in detail for the first time. It is found that upper band chorus and gap chorus are composed of the same structure as lower band (f≤0.5fce$f\le 0.5{f}_{\text{ce}}$) chorus: they are composed of short‐duration subelements, which are monochromatic with σ≤1%$\sigma \le 1\%$. These findings have strong implications for the chorus element generation mechanism. Following Kennel and Petschek (1966, https://doi.org/10.1029/JZ071i001p00001) the overall chorus riser is most likely generated by anisotropic (T⊥/T∥${T}_{\perp }/{T}_{{\Vert} }$> 1) ∼10–100 keV substorm‐injected electrons. Assuming cyclotron resonance, the upper band chorus is generated by the low energy portion of the electron spectrum. The often‐present gap at ∼0.5fce$\sim 0.5{f}_{\text{ce}}$is related to Landau/cyclotron damping. This however is not the end of the story. There is another type of two‐frequency chorus (called Type 2) for which the lower band is not well connected to the upper band. A Type 2 chorus reported previously by Fu et al. (2014, https://doi.org/10.1002/2014JA020364) has also been studied in detail. Both the lower band and upper band are composed of subelements which are monochromatic. Such a similar fine structure for the different type of chorus may imply a similar generation mechanism, for which the difference between them is just the energy range of resonant energetic electrons. One mechanism discussed here, generation by phase bunched electrons, will be tested in the near future. Understanding chorus structure and microstructure is essential toward understanding the wave generation mechanisms and wave‐particle interaction consequences. In this paper we show that upper band (f≥0.5fce$f\ge 0.5{f}_{\text{ce}}$) chorus and gap chorus (f∼0.5fce$f\sim 0.5{f}_{\text{ce}}$) are composed of substructures (subelements) which are monochromatic with σ≤1%$\sigma \le 1\%$. These are the same features of lower band (f≤0.5fce$f\le 0.5{f}_{\text{ce}}$) chorus. The Kennel‐Petschek theory therefore needs to be enlarged such that phase‐bunching of ∼10–100 keV substorm injected anisotropic electrons occur, which then “lase” to yield the monochromatic wave subelements. Coherent and monochromatic chorus can explain the rapid burstiness of ionospheric microburst X‐ray structures. There is another type of upper band chorus, called Type 2 upper band chorus, where the lower band chorus elements are not clearly connected to the upper band chorus. A Type 2 chorus reported previously by Fu et al. (2014, https://doi.org/10.1002/2014JA020364) has been examined in this paper. The apparently unrelated upper band has been found to be composed of subelements which are monochromatic in nature. Thus the different type of chorus may be excited by a similar generation mechanism, for which the difference between them is only the energy interval of the resonant energetic electrons. Type 1 upper band chorus and gap chorus are found to be composed of short duration subelements which are monochromatic (σ≤1%$\sigma \le 1\%$)Since all parts of chorus risers have similar constructions, it is most probable that they are generated by anisotropic narrow energy‐range phase‐bunched electronsA Type 2 chorus (no connection between the lower band and upper band) was studied. The upper band was composed of monochromatic subelements Type 1 upper band chorus and gap chorus are found to be composed of short duration subelements which are monochromatic (σ≤1%$\sigma \le 1\%$) Since all parts of chorus risers have similar constructions, it is most probable that they are generated by anisotropic narrow energy‐range phase‐bunched electrons A Type 2 chorus (no connection between the lower band and upper band) was studied. The upper band was composed of monochromatic subelements

Published
2022
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