Role of Low‐Frequency Boundary Waves in the Dynamics of the Dayside Magnetopause and the Inner Magnetosphere

Hwang, Kyoung‐Joo; Sibeck, D. G.

doi:10.1002/9781119055006.ch13

Cited by 21 publications

(35 citation statements)

References 256 publications

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“…At present the opposite motion of what we term the Alfvénic cusp and the polar cusp lacks a confirmed theoretical explanation, though possible mechanisms (e.g., review by Hwang & Sibeck, and references therein) include flux transfer events, which in the Northern Hemisphere are likewise enhanced in the dawn sector under duskward IMF conditions and vice versa (Øieroset & Sandholt, ), and the Kelvin‐Helmholtz (K‐H) instability (Fairfield et al, ; Nykyri et al, ; Nykyri, ). Primarily within the literature of ground‐based observation and theory, the occurrence of what are termed either “traveling convection vortices” (TCVs) (e.g., Murr & Hughes ) or “magnetic impulsive events” (MIEs) (Kataoka et al, ; Lanzerotti et al, ) is also favored either postnoon or prenoon under strongly dawnward or duskward B y , respectively.…”

Section: Discussionmentioning

confidence: 99%

IMF Control of Alfvénic Energy Transport and Deposition at High Latitudes

et al. 2017

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We investigate the influence of the interplanetary magnetic field (IMF) clock angle ϕIMF on high‐latitude inertial Alfvén wave (IAW) activity in the magnetosphere‐ionosphere transition region using Fast Auroral SnapshoT (FAST) satellite observations. We find evidence that negative IMF Bz coincides with nightside IAW power generation and enhanced rates of IAW‐associated electron energy deposition, while positive IMF Bz coincides with enhanced dayside wave and electron energy deposition. Large ( ≳0.3em0.3em0.3em5 nT) negative IMF By coincides with enhanced postnoon IAW power, while large positive IMF By coincides with enhanced but relatively weaker prenoon IAW power. For each ϕIMF orientation we compare IAW Poynting flux and IAW‐associated electron energy flux distributions with previously published distributions of Alfvénic Poynting flux over ∼2–22 mHz, as well as corresponding wave‐driven electron energy deposition derived from Lyon‐Fedder‐Mobarry global MHD simulations. We also compare IAW Poynting flux distributions with distributions of broad and diffuse electron number flux, categorized using an adaptation of the Newell et al. (2009) precipitation scheme for FAST. Under negative IMF Bz in the vicinity of the cusp (9.5–14.5 magnetic local time), regions of intense dayside IAW power correspond to enhanced diffuse electron number flux but relatively weaker broadband electron precipitation. Differences between cusp region IAW activity and broadband precipitation illustrate the need for additional information, such as fields or pitch angle measurements, to identify the physical mechanisms associated with electron precipitation in the vicinity of the cusp.

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Section: Discussionmentioning

confidence: 99%

IMF Control of Alfvénic Energy Transport and Deposition at High Latitudes

et al. 2017

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“…For example, while the strongest controlling factor for FTE formation is B z (Kuo et al, ; Russell et al, ) and while the separation time of FTEs appears to be independent of our causal parameters (Wang et al, 2006), the magnetic amplitude of FTEs is weakly dependent on solar wind dynamic pressure and the rate of propagation of FTEs will depend on both the magnetic curvature force on reconnected field lines and the solar wind speed. Furthermore, it has been indicated that flux transfer events and Kelvin‐Helmholtz boundary waves can interact; FTEs can provide the seed for Kelvin‐Helmholtz waves and propagating FTEs can interfere with the growth of Kelvin‐Helmholtz boundary waves (Hwang & Sibeck, , and references therein). In fact, Kavosi and Raeder () found fewer and shorter Kelvin‐Helmholtz boundary waves for southward IMF.…”

Section: Physically Interpreting External Ulf Generation Mechanismsmentioning

confidence: 99%

“…For example, narrow band oscillations have been observed in both the incident solar wind pressure and the magnetospheric magnetic field (Kepko & Spence, ; Kim et al, ). Foreshock disturbances such as hot flow anomalies can create dynamic pressure perturbations, and magnetosheath pressure anisotropies can give rise to instabilities (see, e.g., Hwang & Sibeck, , and references therein). The Kelvin‐Helmholtz instability has long been considered a potential driver of magnetospheric ULF waves (Chen & Hasegawa, ), as have magnetopause perturbations such as flux transfer events (Russell & Elphic, ).…”

Section: Introductionmentioning

confidence: 99%

ULF Wave Activity in the Magnetosphere: Resolving Solar Wind Interdependencies to Identify Driving Mechanisms

et al. 2018

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Ultralow frequency (ULF) waves in the magnetosphere are involved in the energization and transport of radiation belt particles and are strongly driven by the external solar wind. However, the interdependency of solar wind parameters and the variety of solar wind‐magnetosphere coupling processes make it difficult to distinguish the effect of individual processes and to predict magnetospheric wave power using solar wind properties. We examine 15 years of dayside ground‐based measurements at a single representative frequency (2.5 mHz) and a single magnetic latitude (corresponding to L ∼ 6.6RE). We determine the relative contribution to ULF wave power from instantaneous nonderived solar wind parameters, accounting for their interdependencies. The most influential parameters for ground‐based ULF wave power are solar wind speed vsw, southward interplanetary magnetic field component Bz<0, and summed power in number density perturbations δNp. Together, the subordinate parameters Bz and δNp still account for significant amounts of power. We suggest that these three parameters correspond to driving by the Kelvin‐Helmholtz instability, formation, and/or propagation of flux transfer events and density perturbations from solar wind structures sweeping past the Earth. We anticipate that this new parameter reduction will aid comparisons of ULF generation mechanisms between magnetospheric sectors and will enable more sophisticated empirical models predicting magnetospheric ULF power using external solar wind driving parameters.

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“…Ultralow frequency (ULF) magnetohydrodynamic (MHD) waves are commonly launched into the magnetosphere from the dayside magnetopause and propagate mainly in the antisunward direction (Allan & Poulter, ). The energy source of the waves is provided by oscillations of the magnetopause that can be caused by variations in the solar wind dynamic pressure (Claudepierre et al, ; Kepko & Spence, ; Kessel et al, ; Kim et al, ), shear flow (Kelvin‐Helmholtz) instability along the morning and afternoon magnetopause flanks (Chen & Hasegawa, ; Mills et al, ; Rae et al, ; Walker, ), flux transfer events at the magnetopause (Gillis et al, ; Glassmeier et al, ; Russell & Elphic, ), or hot flow anomalies in the magnetosheath (Hwang & Sibeck, ). MHD Fast mode waves, which propagate across the magnetic field as compressional waves at the Alfvén speed

v_{A} = B / \sqrt{μ_{0} ρ}

(where B and ρ are the magnetic field strength and plasma mass density, respectively), transmit wave power from the magnetopause into the magnetosphere interior.…”

Section: Introductionmentioning

confidence: 99%

Control of ULF Wave Accessibility to the Inner Magnetosphere by the Convection of Plasma Density

et al. 2018

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During periods of storm activity and enhanced convection, the plasma density in the afternoon sector of the magnetosphere is highly dynamic due to the development of plasmaspheric drainage plume (PDP) structure. This significantly affects the local Alfvén speed and alters the propagation of ULF waves launched from the magnetopause. Therefore, it can be expected that the accessibility of ULF wave power for radiation belt energization is sensitively dependent on the recent history of magnetospheric convection and the stage of development of the PDP. This is investigated using a 3‐D model for ULF waves within the magnetosphere in which the plasma density distribution is evolved using an advection model for cold plasma, driven by a (VollandStern) convection electrostatic field (resulting in PDP structure). The wave model includes magnetic field day/night asymmetry and extends to a paraboloid dayside magnetopause, from which ULF waves are launched at various stages during the PDP development. We find that the plume structure significantly alters the field line resonance location, and the turning point for MHD fast waves, introducing strong asymmetry in the ULF wave distribution across the noon meridian. Moreover, the density enhancement within the PDP creates a waveguide or local cavity for MHD fast waves, such that eigenmodes formed allow the penetration of ULF wave power to much lower L within the plume than outside, providing an avenue for electron energization.

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Role of Low‐Frequency Boundary Waves in the Dynamics of the Dayside Magnetopause and the Inner Magnetosphere

Cited by 21 publications

References 256 publications

IMF Control of Alfvénic Energy Transport and Deposition at High Latitudes

IMF Control of Alfvénic Energy Transport and Deposition at High Latitudes

ULF Wave Activity in the Magnetosphere: Resolving Solar Wind Interdependencies to Identify Driving Mechanisms

Control of ULF Wave Accessibility to the Inner Magnetosphere by the Convection of Plasma Density

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