Persistent EMIC Wave Activity Across the Nightside Inner Magnetosphere

2020 ◽  
Vol 47 (6) ◽  
Author(s):  
L. W. Blum ◽  
B. Remya ◽  
M. H. Denton ◽  
Q. Schiller
Keyword(s):  
Wave Activity ◽  
Inner Magnetosphere ◽  
Emic Wave

The Impacts of Substorms on the Ring Current

2020 ◽  
Author(s):  
Jasmine Sandhu ◽  
Jonathan Rae ◽  
Maria-Theresia Walach ◽  
Clare Watt ◽  
Mervyn Freeman ◽  
...  
Keyword(s):  
Ring Current ◽  
Energy Content ◽  
Wave Activity ◽  
Time Asymmetry ◽  
Inner Magnetosphere ◽  
H Index ◽  
Current Population ◽  
Emic Wave ◽  
The Impact ◽  
Current Energy

<p>Substorms are a highly dynamic process that results in the global redistribution of energy within the magnetosphere. The occurrence of a substorm can provide the inner magnetosphere with hot ions and consequently intensify the ring current population. However, substorms are a highly variable phenomenon that can occur as an isolated event or as part of a sequence. In this study we investigate how substorms shape the energy content, anisotropy, and storm time behaviour of the ring current population.</p><p>Using ion observations (H+, O+, and He+) from the RBSPICE and HOPE instruments onboard the Van Allen Probes, we quantify how the total ring current energy content and ring current anisotropy changes during the substorm process. A statistical analysis demonstrates the impact of a typical substorm energises the ring current by 12% on average. The features of the energy enhancement correlate well with the expected properties of particle injections into the inner magnetosphere, and large enhancements in the O+ contribution to the energy content suggest important compositional variations.</p><p>Analysis also shows that the ring current ions experience significant isotropisation following substorm onset. Although previously attributed to enhanced EMIC wave activity, a consideration of different drivers of the isotropisation identifies that although EMIC wave activity plays a role, the properties of the injected and convected population is the dominant driver.</p><p>Finally, we explore the storm time variations of the ring current, revealing important information on the role of substorms in storm dynamics. A superposed epoch analysis of ring current energy content shows large enhancements particularly in the premidnight sector during the main phase, and a reduction in both local time asymmetry and intensity during the recovery phase. A comparison with estimated energy content using the Sym-H index was conducted. In agreement with previous results, the Sym-H index significantly overestimates energy content. A new finding is an observed temporal discrepancy, where estimates maximise ~ 12 hours earlier than the in-situ observations. We assert that an observed enhancement in substorm activity coincident with the Sym-H recovery is responsible. The results highlight the drawbacks of ring current indices and emphasise the impacts of substorms on the ring current population.</p>

Direct measurements of cold and hot plasma composition and EMIC waves in the outer magnetosphere: Implications for inner magnetosphere wave-particle interactions

2021 ◽  
Author(s):  
Justin Lee ◽  
Drew Turner ◽  
Sarah Vines ◽  
Robert Allen ◽  
Sergio Toledo-Redondo
Keyword(s):  
Unstable Wave ◽  
Linear Wave ◽  
Plasma Composition ◽  
Inner Magnetosphere ◽  
Hot Plasma ◽  
Emic Wave ◽  
Direct Measurements ◽  
Wave Numbers ◽  
Emic Waves

<p>Although thorough characterization of magnetospheric ion composition is rare for EMIC wave studies, convective processes that occur more frequently in Earth’s outer magnetosphere have allowed the Magnetospheric Multiscale (MMS) satellites to make direct measurements of the cold and hot plasma composition during EMIC wave activity. We will present an observation and linear wave modeling case study conducted on EMIC waves observed during a perturbed activity period in the outer dusk-side magnetosphere. During the two intervals investigated for the case study, the MMS satellites made direct measurements of cold plasmaspheric plasma in addition to multiple hot ion components at the same time as EMIC wave emissions were observed. Applying the in-situ plasma composition data to wave modeling, we find that wave growth rate is impacted by the complex interactions between the cold as well as the hot ion components and ambient plasma conditions. In addition, we observe that linear wave properties (unstable wave numbers and band structure) can significantly evolve with changes in cold and hot ion composition. Although the modeling showed the presence of dense cold ions can broaden the range of unstable wave numbers, consistent with previous work, the hot heavy ions that were more abundant nearer storm main phase could limit the growth of EMIC waves to smaller wave numbers. In the inner magnetosphere, where higher cold ion density is expected, the ring current heavy ions could also be more intense near storm-time, possibly resulting in conditions that limit the interactions of EMIC waves with trapped radiation belt electrons to multi-MeV energies. Additional investigation when direct measurements of cold and hot plasma composition are available could improve understanding of EMIC waves and their interactions with trapped energetic particles in the inner magnetosphere.</p>

scholarly journals EMIC wave activity during geomagnetic storm and nonstorm periods: CRRES results

2010 ◽  
Vol 115 (A12) ◽  
pp. n/a-n/a ◽  
Author(s):  
A. J. Halford ◽  
B. J. Fraser ◽  
S. K. Morley
Keyword(s):  
Geomagnetic Storm ◽  
Wave Activity ◽  
Emic Wave

scholarly journals Solar wind influence on Pc4 and Pc5 ULF wave activity in the inner magnetosphere

2010 ◽  
Vol 115 (A12) ◽  
pp. n/a-n/a ◽  
Author(s):  
W. Liu ◽  
T. E. Sarris ◽  
X. Li ◽  
R. Ergun ◽  
V. Angelopoulos ◽  
...  
Keyword(s):  
Solar Wind ◽  
Wave Activity ◽  
Inner Magnetosphere ◽  
Ulf Wave ◽  
Wind Influence

Correlations Between Dispersive Alfvén Wave Activity, Electron Energization, and Ion Outflow in the Inner Magnetosphere

2020 ◽  
Vol 47 (17) ◽  
Author(s):  
A. J. Hull ◽  
C. C. Chaston ◽  
J. W. Bonnell ◽  
P. A. Damiano ◽  
J. R. Wygant ◽  
...  
Keyword(s):  
Wave Activity ◽  
Alfven Wave ◽  
Ion Outflow ◽  
Inner Magnetosphere ◽  
Dispersive Alfvén Wave

Cold ion dynamics and interaction with EMIC waves near the Earth's magnetopause

2020 ◽  
Author(s):  
Sergio Toledo-Redondo ◽  
Justin Lee ◽  
Sarah Vines ◽  
Drew Turner ◽  
Robert Allen ◽  
...  
Keyword(s):  
Wave Packet ◽  
Coupling Mechanism ◽  
Ion Dynamics ◽  
Dispersion Theory ◽  
Linear Dispersion ◽  
Inner Magnetosphere ◽  
Emic Wave ◽  
Wave Normal ◽  
Normal Angle ◽  
Emic Waves

<p>The Earth’s magnetosphere is constantly supplied by plasma coming from the solar wind and from the ionosphere. The ionospheric supply is typically cold and contains heavy ions, which can be often found in most parts of the magnetosphere.</p><p>Electromagnetic Ion Cyclotron (EMIC) waves occur in the outer magnetosphere, often in association with ionospheric ions, and serve as a coupling mechanism to the ionosphere and inner magnetosphere. Using the MMS spacecraft, we investigate the dynamics of these waves when ionospheric ions are present, and resolve their motion and energy exchange with the electromagnetic fields below the ion scale. We find that ring current ions and ionospheric ions have different dynamics inside an EMIC wave packet near the magnetopause, affecting the dispersion relation of the wave. We compare the observations to linear dispersion theory, and find excellent agreement between both. Cold ions are accelerated and drain energy from the wave packet, and modify the intrinsic properties such as the wave normal angle and the polarization of the wave.</p><p> </p><p> </p><p> </p><p> </p>

Differences in inner magnetospheric wave activity, outer Van Allen belt electron dynamics and atmospheric precipitation during CME sheaths and flux ropes

2020 ◽  
Author(s):  
Emilia Kilpua ◽  
Milla Kalliokoski ◽  
Liisa Juusola ◽  
Maxime Grandin ◽  
Antti Kero ◽  
...  
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Dynamic Pressure ◽  
Atmospheric Precipitation ◽  
Plasma Waves ◽  
High Energy ◽  
Wave Activity ◽  
Effective Electron ◽  
Inner Magnetosphere ◽  
Magnetosphere Plasma

<p>Coronal mass ejection (CME) driven sheath regions are one of the key structures driving strong magnetospheric disturbances, in particular at high latitudes. Sheaths are turbulent and compressed regions that exhibit large-amplitude magnetic field variations and high and variable dynamic pressure. They thus put the magnetosphere under particularly strong solar wind forcing. We show here the results of our recent studies that have investigated the response of inner magnetosphere plasma waves, energy and L-shell resolved outer belt electron variations and precipitation of high-energy electrons to the upper atmosphere during sheath regions. The data come primarily from Van Allen Probes and ground-based riometers. Our results reveal that sheaths drive intense “wave storms” in the inner magnetosphere (ULF, EMIC, chorus, hiss). Lower-energy electron fluxes (source and seed populations) are typically enhanced due to frequent and strong substorms injecting fresh electrons, while relativistic electrons are effectively depleted at wide L-ranges due to scattering by wave-particle interactions and magnetopause shadowing playing in concert. We found that even non-geoeffective sheaths can drive significant wave activity and dramatic changes in the outer belt electron fluxes. The “complex ejecta”, however, that consist of multiple sheaths and distorted CME ejecta can lead to sustained chorus and ULF waves, and as a consequence, effective electron acceleration to high energies. We also report some distinct characteristics in the intensity and Magnetic Local Time distribution of precipitation during sheaths when compared to other large-scale solar wind driver structures. The different precipitation responses likely stem from driver specific characteristics in their ability to excite inner magnetosphere plasma waves.</p><p> </p>

scholarly journals Observations of coincident EMIC wave activity and duskside energetic electron precipitation on 18-19 January 2013

2015 ◽  
Vol 42 (14) ◽  
pp. 5727-5735 ◽  
Author(s):  
L. W. Blum ◽  
A. Halford ◽  
R. Millan ◽  
J. W. Bonnell ◽  
J. Goldstein ◽  
...  
Keyword(s):  
Energetic Electron ◽  
Wave Activity ◽  
Electron Precipitation ◽  
Emic Wave

High-speed stream driven inferences of global wave distributions at geosynchronous orbit: relevance to radiation-belt dynamics

2010 ◽  
Vol 466 (2123) ◽  
pp. 3351-3362 ◽  
Author(s):  
Elizabeth A. MacDonald ◽  
Lauren W. Blum ◽  
S. Peter Gary ◽  
Michelle F. Thomsen ◽  
Michael H. Denton
Keyword(s):  
High Speed ◽  
Radiation Belt ◽  
Recovery Phase ◽  
Wave Activity ◽  
Geosynchronous Orbit ◽  
Relativistic Electrons ◽  
Particle Interactions ◽  
Early Recovery ◽  
Emic Wave ◽  
Major Loss

Three superposed epoch analyses of plasma data from geosynchronous orbit are compared to infer relative distributions of electromagnetic ion cyclotron (EMIC)- and whistler-mode wave instabilities. Both local-time and storm-time behaviours are studied with respect to dynamics of relativistic electrons. Using LANL-GEO particle data and a quasi-linear approximation for the wave growth allows us to estimate the instability of the two wave modes. This simple technique can allow powerful insights into wave–particle interactions at geosynchronous orbit. Whistler-wave activity peaks on the dayside during the early recovery phase and can continue to be above normal levels for several days. The main phase of all storms exhibits the most EMIC-wave activity, whereas in the recovery phase of the most radiation-belt-effective storms, a significantly suppressed level of EMIC activity is inferred. These key results indicate new dynamics relating to plasma delivery, source and response, but support generally accepted views of whistlers as a source process and EMIC-mode waves as a major loss contributor at geosynchronous orbit.

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