Are drivers of northern lights in the ionosphere?

Mapping Intimacies ◽

10.5194/angeo-2021-66 ◽

2021 ◽

Author(s):

Osuke Saka

Keyword(s):

Field Line ◽

Large Scale ◽

Rotational Symmetry ◽

Polar Ionosphere ◽

Physical Processes ◽

Distinct Features ◽

General Dynamic

Abstract. Known as northern lights, auroral spirals are distinct features of substorm auroras composed of large-scale spirals (100s km Surges) mixed with smaller scale ones (10s km Folds, and 1 km Rays). Spiral patterns are generally interpreted in terms of the field line mapping of the upward field-aligned currents produced in the magnetosphere during the field line dipolarization. The field line mapping results in opposing spiral rotations of small- and large-scale auroras. Because of a rotational symmetry deformation and similarity in deformation speeds (6~8 km/s) of small- and large-scale spirals, it has been suggested that common physical processes may underlie the deforming processes. Internal processes in the polar ionosphere (ionospheric driver) will be proposed as the general dynamic for spiral auroras. The ionospheric driver rotated in the ionosphere to produce spirals that characteristically differ from the field line mapping scenario.

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Evolution of Large-Scale Coronal Structures

International Astronomical Union Colloquium ◽

10.1017/s0252921100024945 ◽

1994 ◽

Vol 144 ◽

pp. 29-33

Author(s):

P. Ambrož

Keyword(s):

Magnetic Field ◽

Field Line ◽

Large Scale ◽

Coronal Magnetic Field ◽

Source Surface ◽

Solar Cycles ◽

Characteristic Relationship ◽

The Magnetic Field ◽

Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

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The development of magnetic field line wander by plasma turbulence

Journal of Plasma Physics ◽

10.1017/s0022377817000617 ◽

2017 ◽

Vol 83 (4) ◽

Cited By ~ 5

Author(s):

Gregory G. Howes ◽

Sofiane Bourouaine

Keyword(s):

Magnetic Field ◽

Field Line ◽

Magnetic Field Line ◽

Large Scale ◽

Magnetic Energy ◽

Plasma Turbulence ◽

Alfven Wave ◽

Astrophysical Plasmas ◽

Field Lines ◽

The Magnetic Field

Plasma turbulence occurs ubiquitously in space and astrophysical plasmas, mediating the nonlinear transfer of energy from large-scale electromagnetic fields and plasma flows to small scales at which the energy may be ultimately converted to plasma heat. But plasma turbulence also generically leads to a tangling of the magnetic field that threads through the plasma. The resulting wander of the magnetic field lines may significantly impact a number of important physical processes, including the propagation of cosmic rays and energetic particles, confinement in magnetic fusion devices and the fundamental processes of turbulence, magnetic reconnection and particle acceleration. The various potential impacts of magnetic field line wander are reviewed in detail, and a number of important theoretical considerations are identified that may influence the development and saturation of magnetic field line wander in astrophysical plasma turbulence. The results of nonlinear gyrokinetic simulations of kinetic Alfvén wave turbulence of sub-ion length scales are evaluated to understand the development and saturation of the turbulent magnetic energy spectrum and of the magnetic field line wander. It is found that turbulent space and astrophysical plasmas are generally expected to contain a stochastic magnetic field due to the tangling of the field by strong plasma turbulence. Future work will explore how the saturated magnetic field line wander varies as a function of the amplitude of the plasma turbulence and the ratio of the thermal to magnetic pressure, known as the plasma beta.

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Observations of diverging field-aligned ion flow with the ESR

Annales Geophysicae ◽

10.5194/angeo-22-889-2004 ◽

2004 ◽

Vol 22 (3) ◽

pp. 889-899 ◽

Cited By ~ 11

Author(s):

S. C. Buchert ◽

Y. Ogawa ◽

R. Fujii ◽

A. P. van Eyken

Keyword(s):

Field Line ◽

Geomagnetic Field ◽

Plasma Temperature ◽

Ionization Mechanism ◽

Soft Particle ◽

Polar Ionosphere ◽

Ion Composition ◽

Ion Flow ◽

F Region ◽

Ionization Balance

Abstract. We report on observations of a diverging ion flow along the geomagnetic field that is often seen at the EISCAT Svalbard radar. The flow is upward above the peak of the electron density in the F-region and downward below the peak. We estimate that in such events mass transport along the field line is important for the ionization balance, and that the shape of the F-layer and its ion composition should be strongly influenced by it. Diverging flow typically occurs when there are signatures of direct entry of sheath plasma to the ionosphere in the form of intense soft particle precipitation, and we suggest that it is caused by the ionization and ionospheric electron heating associated with this precipitation. On average, 30% of all events with ion upflow also show significant ion downflow below. Key words.Ionosphere (polar ionosphere; ionization mechanism; plasma temperature and density)

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Random Walk and Trapping of Interplanetary Magnetic Field Lines: Global Simulation, Magnetic Connectivity, and Implications for Solar Energetic Particles

10.5194/egusphere-egu21-3719 ◽

2021 ◽

Author(s):

David Ruffolo ◽

Rohit Chhiber ◽

William H. Matthaeus ◽

Arcadi V. Usmanov ◽

Paisan Tooprakai ◽

...

Keyword(s):

Magnetic Field ◽

Random Walk ◽

Field Line ◽

Large Scale ◽

Transport Model ◽

Source Region ◽

Science Research ◽

Energetic Particles ◽

Solar Energetic Particles ◽

Field Lines

<p>The random walk of magnetic field lines is an important ingredient in understanding how the connectivity of the magnetic field affects the spatial transport and diffusion of charged particles. As solar energetic particles (SEPs) propagate away from near-solar sources, they interact with the fluctuating magnetic field, which modifies their distributions. We develop a formalism in which the differential equation describing the field line random walk contains both effects due to localized magnetic displacements and a non-stochastic contribution from the large-scale expansion. We use this formalism together with a global magnetohydrodynamic simulation of the inner-heliospheric solar wind, which includes a turbulence transport model, to estimate the diffusive spreading of magnetic field lines that originate in different regions of the solar atmosphere. We first use this model to quantify field line spreading at 1 au, starting from a localized solar source region, and find rms angular spreads of about 20 &#8211; 60 degrees. In the second instance, we use the model to estimate the size of the source regions from which field lines observed at 1 au may have originated, thus quantifying the uncertainty in calculations of magnetic connectivity; the angular uncertainty is estimated to be about 20 degrees. Finally, we estimate the filamentation distance, i.e., the heliocentric distance up to which field lines originating in magnetic islands can remain strongly trapped in filamentary structures. We emphasize the key role of slab-like fluctuations in the transition from filamentary to more diffusive transport at greater heliocentric distances. This research has been supported in part by grant RTA6280002 from Thailand Science Research and Innovation and the Parker Solar Probe mission under the ISOIS project (contract NNN06AA01C) and a subcontract to University of Delaware from Princeton University (SUB0000165). &#160;MLG acknowledges support from the Parker Solar Probe FIELDS MAG team. &#160;Additional support is acknowledged from the&#160; NASA LWS program&#160; (NNX17AB79G) and the HSR program (80NSSC18K1210 & 80NSSC18K1648).</p>

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Physical Transport Processes that Affect the Distribution of Oil in the Gulf of Mexico: Observations and Modeling

Oceanography ◽

10.5670/oceanog.2021.117 ◽

2021 ◽

Vol 34 (1) ◽

pp. 58-75

Author(s):

Michel Boufadel ◽

◽

Annalisa Bracco ◽

Eric Chassignet ◽

Shuyi Chen ◽

...

Keyword(s):

Gulf Of Mexico ◽

Physical Environment ◽

Large Scale ◽

Transport Processes ◽

Small Scale ◽

Surface Mixed Layer ◽

Physical Processes ◽

Mixing Processes ◽

Near Surface ◽

Wide Range

Physical transport processes such as the circulation and mixing of waters largely determine the spatial distribution of materials in the ocean. They also establish the physical environment within which biogeochemical and other processes transform materials, including naturally occurring nutrients and human-made contaminants that may sustain or harm the region’s living resources. Thus, understanding and modeling the transport and distribution of materials provides a crucial substrate for determining the effects of biological, geological, and chemical processes. The wide range of scales in which these physical processes operate includes microscale droplets and bubbles; small-scale turbulence in buoyant plumes and the near-surface “mixed” layer; submesoscale fronts, convergent and divergent flows, and small eddies; larger mesoscale quasi-geostrophic eddies; and the overall large-scale circulation of the Gulf of Mexico and its interaction with the Atlantic Ocean and the Caribbean Sea; along with air-sea interaction on longer timescales. The circulation and mixing processes that operate near the Gulf of Mexico coasts, where most human activities occur, are strongly affected by wind- and river-induced currents and are further modified by the area’s complex topography. Gulf of Mexico physical processes are also characterized by strong linkages between coastal/shelf and deeper offshore waters that determine connectivity to the basin’s interior. This physical connectivity influences the transport of materials among different coastal areas within the Gulf of Mexico and can extend to adjacent basins. Major advances enabled by the Gulf of Mexico Research Initiative in the observation, understanding, and modeling of all of these aspects of the Gulf’s physical environment are summarized in this article, and key priorities for future work are also identified.

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The Dynamic and Thermodynamic Structures Associated with a Series of Heavy Precipitation Events over China during January 2008

Weather and Forecasting ◽

10.1175/2010waf2222335.1 ◽

2010 ◽

Vol 25 (4) ◽

pp. 1124-1141 ◽

Cited By ~ 16

Author(s):

Xiaohui Shi ◽

Xiangde Xu ◽

Chungu Lu

Keyword(s):

Large Scale ◽

East Coast ◽

Heavy Precipitation ◽

Chinese History ◽

Physical Processes ◽

Ice Storms ◽

Upper Level ◽

Upper Level Jet ◽

The Western Pacific ◽

Precipitation Events

Abstract In the winter of 2008, China experienced once-in-50-yr (or once in 100 yr for some regions) snow and ice storms. These storms brought huge socio economical impacts upon the Chinese people and government. Although the storms had been predicted, their severity and persistence were largely underestimated. In this study, these cases were revisited and comprehensive analyses of the storms’ dynamic and thermodynamic structures were conducted. These snowstorms were also compared with U.S. east coast snowstorms. The results from this study will provide insights on how to improve forecasts for these kinds of snowstorms. The analyses demonstrated that the storms exhibited classic patterns of large-scale circulation common to these types of snowstorms. However, several physical processes were found to be unique and thought to have played crucial roles in intensifying and prolonging China’s great snowstorms of 2008. These include a subtropical high over the western Pacific, an upper-level jet stream, and temperature and moisture inversions. The combined effects of these dynamic and thermodynamic structures are responsible for the development of the storms into one of the most disastrous events in Chinese history.

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Observing the north polar ionosphere on 30 October 2003 by GPS imaging and IS radars

Annales Geophysicae ◽

10.5194/angeo-24-107-2006 ◽

2006 ◽

Vol 24 (1) ◽

pp. 107-113 ◽

Cited By ~ 16

Author(s):

C. Stolle ◽

J. Lilensten ◽

S. Schlüter ◽

Ch. Jacobi ◽

M. Rietveld ◽

...

Keyword(s):

Time Series ◽

Electron Density ◽

Large Scale ◽

Electron Content ◽

Polar Ionosphere ◽

Storm Main Phase ◽

The North ◽

F Region ◽

Longitudinal Band ◽

North Polar

Abstract. The evening of 30 October 2003 was subject to a major storm main phase. For this time, we combine large-scale electron content maps from GPS imaging with time series of electron density and temperature of two EISCAT radars in Tromsø and Svalbard and the Sondrestrom radar, for observing the north polar ionosphere. The GPS assimilations resulted in the image of the electron content trace of an anti-sunward polar Tongue Of Ionisation (TOI) consecutively to 20:00 UT. In combination with the radar observations we concluded that the TOI persisted during the whole period of continuous southward IMF Bz until about 22:40 UT while its largest extension toward the nightside auroral region was found between 21:00-22:00 UT. A typical F region electron temperature of ~2000 K and the plasma velocity of ~800 ms-1 support its convective origin from the dayside mid-latitudes. Due to the structured appearance of the electron content distribution and the radar electron density time series we believe that discrete plasma patches formed inside the anti-sunward drift pattern. After two large oscillations of the IMF Bz the nightside plasma density was observed to re-enhance after 23:00 UT along a longitudinal band below 70 N. Coinciding electron temperatures of ~2000 K suggest again the convective nature of the plasma, while a modified convection pattern is expected.

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The atomic hydrogen/molecular cloud association: an unavoidable relationship

Symposium - International Astronomical Union ◽

10.1017/s0074180900239375 ◽

1991 ◽

Vol 147 ◽

pp. 37-40

Author(s):

G. Joncas

Keyword(s):

Atomic Hydrogen ◽

Molecular Clouds ◽

Large Scale ◽

Young Stars ◽

Physical Processes ◽

Star Forming ◽

Dark Clouds ◽

Star Forming Regions ◽

The Impact

The presence of HI in the interstellar medium is ubiquitous. HI is the principal actor in the majority of the physical processes at work in our Galaxy. Restricting ourselves to the topics of this symposium, atomic hydrogen is involved with the formation of molecular clouds and is one of the byproducts of their destruction by young stars. HI has different roles during a molecular cloud's life. I will discuss here a case of coexisting HI and H2 at large scale and the origin of HI in star forming regions. For completeness' sake, it should be mentionned that there are at least three other aspects of HI involvement: HI envelopes around molecular clouds, the impact of SNRs (see work on IC 443), and the role of HI in quiescent dark clouds (see van der Werf's work).

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Heat Exchanger Design for the Process Industries

Journal of Heat Transfer ◽

10.1115/1.1833366 ◽

2004 ◽

Vol 126 (6) ◽

pp. 877-885 ◽

Cited By ~ 53

Author(s):

Kenneth J. Bell

Keyword(s):

Design Process ◽

Large Scale ◽

Environmental Control ◽

Design Method ◽

Physical Processes ◽

Process Industries ◽

Rational Representation ◽

Design Procedures ◽

Heat Exchanger Design ◽

Rating Method

The design process for heat exchangers in the process industries and for similar applications in the power and large-scale environmental control industries is described. Because of the variety of substances (frequently multicomponent, of variable and uncertain composition, and changing phase) to be processed under wide ranges of temperatures, pressures, flow rates, chemical compatibility, and fouling propensity, these exchangers are almost always custom-designed and constructed. Many different exchanger configurations are commercially available to meet special conditions, with design procedures of varying degrees of reliability. A general design logic can be applied, with detailed procedures specific to the type of exchanger. The basis of the design process is first a careful and comprehensive specification of the range of conditions to be satisfied, and second, organized use of a fundamentally valid and extrapolatable rating method. The emphasis in choosing a design method is upon rational representation of the physical processes, rather than upon high accuracy. Finally, the resultant design must be vetted in detail by the designer and the process engineer for operability, flexibility, maintainability, and safety.

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