scholarly journals Association of radiation belt electron enhancements with earthward penetration of Pc5 ULF waves: a case study of intense 2001 magnetic storms

2015 ◽  
Vol 33 (11) ◽  
pp. 1431-1442 ◽  
Author(s):  
M. Georgiou ◽  
I. A. Daglis ◽  
E. Zesta ◽  
G. Balasis ◽  
I. R. Mann ◽  
...  
Keyword(s):  
Radiation Belt ◽  
Low Frequency ◽  
Recovery Phase ◽  
Wave Activity ◽  
Magnetic Storms ◽  
Ulf Waves ◽  
Relativistic Electrons ◽  
Outer Radiation Belt ◽  
Magnetometer Arrays ◽  
The One

Abstract. Geospace magnetic storms, driven by the solar wind, are associated with increases or decreases in the fluxes of relativistic electrons in the outer radiation belt. We examine the response of relativistic electrons to four intense magnetic storms, during which the minimum of the Dst index ranged from −105 to −387 nT, and compare these with concurrent observations of ultra-low-frequency (ULF) waves from the trans-Scandinavian IMAGE magnetometer network and stations from multiple magnetometer arrays available through the worldwide SuperMAG collaboration. The latitudinal and global distribution of Pc5 wave power is examined to determine how deep into the magnetosphere these waves penetrate. We then investigate the role of Pc5 wave activity deep in the magnetosphere in enhancements of radiation belt electrons population observed in the recovery phase of the magnetic storms. We show that, during magnetic storms characterized by increased post-storm electron fluxes as compared to their pre-storm values, the earthward shift of peak and inner boundary of the outer electron radiation belt follows the Pc5 wave activity, reaching L shells as low as 3–4. In contrast, the one magnetic storm characterized by irreversible loss of electrons was related to limited Pc5 wave activity that was not intensified at low L shells. These observations demonstrate that enhanced Pc5 ULF wave activity penetrating deep into the magnetosphere during the main and recovery phase of magnetic storms can, for the cases examined, distinguish storms that resulted in increases in relativistic electron fluxes in the outer radiation belts from those that did not.

On the effect of ULF waves on the outer radiation belt during geomagnetic storms

2021 ◽  
Author(s):  
Christopher Lara ◽  
Pablo S. Moya ◽  
Victor Pinto ◽  
Javier Silva ◽  
Beatriz Zenteno
Keyword(s):  
Relativistic Electron ◽  
Radiation Belt ◽  
Geomagnetic Storms ◽  
Cumulative Effect ◽  
Radiation Belts ◽  
Ulf Waves ◽  
Relativistic Electrons ◽  
Relative Role ◽  
Outer Radiation Belt ◽  
Ulf Wave

<p>The inner magnetosphere is a very important region to study, as with satellite-based communications increasing day after day, possible disruptions are especially relevant due to the possible consequences in our daily life. It is becoming very important to know how the radiation belts behave, especially during strong geomagnetic activity. The radiation belts response to geomagnetic storms and solar wind conditions is still not fully understood, as relativistic electron fluxes in the outer radiation belt can be depleted, enhanced or not affected following intense activity. Different studies show how these results vary in the face of different events. As one of the main mechanisms affecting the dynamics of the radiation belt are wave-particle interactions between relativistic electrons and ULF waves. In this work we perform a statistical study of the relationship between ULF wave power and relativistic electron fluxes in the outer radiation belt during several geomagnetic storms, by using magnetic field and particle fluxes data measured by the Van Allen Probes between 2012 and 2017. We evaluate the correlation between the changes in flux and the cumulative effect of ULF wave activity during the main and recovery phases of the storms for different position in the outer radiation belt and energy channels. Our results show that there is a good correlation between the presence of ULF waves and the changes in flux during the recovery phase of the storm and that correlations vary as a function of energy. Also, we can see in detail how the ULF power change for the electron flux at different L-shell We expect these results to be relevant for the understanding of the relative role of ULF waves in the enhancements and depletions of energetic electrons in the radiation belts for condition described.</p>

scholarly journals The relativistic electron response in the outer radiation belt during magnetic storms

2002 ◽  
Vol 20 (7) ◽  
pp. 957-965 ◽  
Author(s):  
R. H. A. Iles ◽  
A. N. Fazakerley ◽  
A. D. Johnstone ◽  
N. P. Meredith ◽  
P. Bühler
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Wind Speed ◽  
Interplanetary Magnetic Field ◽  
Relativistic Electron ◽  
Radiation Belt ◽  
Solar Wind Speed ◽  
Recovery Phase ◽  
Magnetic Storms ◽  
Outer Radiation Belt

Abstract. The relativistic electron response in the outer radiation belt during magnetic storms has been studied in relation to solar wind and geomagnetic parameters during the first six months of 1995, a period in which there were a number of recurrent fast solar wind streams. The relativistic electron population was measured by instruments on board the two microsatellites, STRV-1a and STRV-1b, which traversed the radiation belt four times per day from L ~ 1 out to L ~ 7 on highly elliptical, near-equatorial orbits. Variations in the E > 750 keV and E > 1 MeV electrons during the main phase and recovery phase of 17 magnetic storms have been compared with the solar wind speed, interplanetary magnetic field z-component, Bz , the solar wind dynamic pressure and Dst *. Three different types of electron responses are identified, with outcomes that strongly depend on the solar wind speed and interplanetary magnetic field orientation during the magnetic storm recovery phase. Observations also confirm that the L-shell, at which the peak enhancement in the electron count rate occurs has a dependence on Dst *.Key words. Magnetospheric physics (energetic particles, trapped; storms and substorms) – Space plasma physics (charged particle motion and accelerations)

ULF waves and their influence on radiation belt dynamics in Earth's magnetosphere

2020 ◽  
Author(s):  
Robert Rankin ◽  
Alexander Degeling
Keyword(s):  
Radiation Belt ◽  
Geomagnetic Storms ◽  
Low Frequency ◽  
Recovery Phase ◽  
Ulf Waves ◽  
Wave Source ◽  
Initial Plasma ◽  
Plasma State ◽  
Van Allen Probes ◽  
Geomagnetic Fields

<p>Recent observations from the Van Allen Probes mission have established that Pc3-5 ultra-low-frequency (ULF) waves can energize ions and electrons via drift-resonance and drift-bounce resonance. The extent to which these waves contribute to the space weather of the belts is relatively poorly understood and requires sophisticated modelling and characterization of the dominant wave modes that arise in the development and recovery phase of geomagnetic storms. Despite more than four decades of observations and theoretical analysis of ULF waves, there is no framework for accurately assessing the global distribution of ULF waves and their influence on the ring current. <br>In this presentation, we describe a new global model of ULF waves that incorporates non-dipolar geomagnetic fields. The model is constrained using the GCPM of cold plasma density model and a specification of the ionosphere using the IRI and MSIS models. An algorithm is applied to adjust the initial plasma state to a quasi-static equilibrium that is then driven by a global convection electric field and ULF wave source. For specific observations by the Van Allen Probes and ARASE mission, the effect of these ULF waves on radiation belt ions and electrons is evaluated utilizing test-particle methodology and Liouville's theorem, which enables the phase space density to be followed and compared one-for-one with the satellite observations.  </p>

Generation of magnetic and particle Pc5 pulsations during the recovery phase of strong magnetic storms

2010 ◽  
Vol 466 (2123) ◽  
pp. 3363-3390 ◽  
Author(s):  
V. Pilipenko ◽  
O. Kozyreva ◽  
V. Belakhovsky ◽  
M. J. Engebretson ◽  
S. Samsonov
Keyword(s):  
Solar Wind ◽  
Spatial Structure ◽  
Stable State ◽  
Low Frequency ◽  
Solar Wind Plasma ◽  
Recovery Phase ◽  
Magnetic Storms ◽  
Relativistic Electrons ◽  
Oscillatory Systems ◽  
Using Data

The dynamics of intense ultra-low-frequency (ULF) activity during three successive strong magnetic storms during 29–31 October 2003 are considered in detail. The spatial structure of Pc5 waves during the recovery phases of these storms is considered not only from the perspective of possible physical mechanisms, but as an important parameter of the ULF driver of relativistic electrons. The global structure of these disturbances is studied using data from a worldwide array of magnetometers and riometers augmented with data from particle detectors and magnetometers on board magnetospheric satellites (GOES, LANL). The local spatial structure is examined using the IMAGE magnetometers and Finnish riometer array. Though a general similarity between the quasi-periodic magnetic and riometer variations is observed, their local propagation patterns turn out to be different. To interpret the observations, we suggest a hypothesis of coupling between two oscillatory systems—a magnetospheric magnetohydrodynamic (MHD) waveguide/resonator and a system consisting of turbulence + electrons. We propose that the observed Pc5 oscillations are the result of MHD waveguide excitation along the dawn and dusk flanks of the magnetosphere. The magnetospheric waveguide turns out to be in a meta-stable state under high solar wind velocities, and quasi-periodic fluctuations of the solar wind plasma density stimulate the waveguide excitation.

scholarly journals Polarization properties of standing shear Alfvén waves in non-axisymmetric background magnetic fields

2007 ◽  
Vol 25 (3) ◽  
pp. 815-822 ◽  
Author(s):  
K. Kabin ◽  
R. Rankin ◽  
I. R. Mann ◽  
A. W. Degeling ◽  
R. Marchand
Keyword(s):  
Geomagnetic Field ◽  
Radiation Belt ◽  
Low Frequency ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Ulf Waves ◽  
Outer Radiation Belt ◽  
Simple Description ◽  
The Waves ◽  
Shear Alfven Waves

Abstract. In this paper we present results concerning periods and polarizations of cold plasma ultra-low frequency (ULF) guided Alfvén waves in a non-axisymmetric geomagnetic field. The background geomagnetic field is approximated by a compressed dipole for which we propose a simple description in terms of Euler potentials. This study is motivated by the problem of outer-radiation belt electron acceleration by ULF waves, for which the polarization of the wave is of paramount importance. We consider an approximation appropriate to decoupled Alfvénic waves and find that the polarization of the waves can change significantly with local time. Therefore, the ULF wave's contribution to the MeV electron energization process can be localized in space.

scholarly journals Average profiles of the solar wind and outer radiation belt during the extreme flux enhancement of relativistic electrons at geosynchronous orbit

2008 ◽  
Vol 26 (6) ◽  
pp. 1335-1339 ◽  
Author(s):  
R. Kataoka ◽  
Y. Miyoshi
Keyword(s):  
Solar Wind ◽  
Large Scale ◽  
Radiation Belt ◽  
Dynamic Pressure ◽  
Recovery Phase ◽  
Geosynchronous Orbit ◽  
Relativistic Electrons ◽  
Outer Radiation Belt ◽  
Flux Enhancement ◽  
Solar Wind Structure

Abstract. We report average profiles of the solar wind and outer radiation belt during the extreme flux enhancement of relativistic electrons at geosynchronous orbit (GEO). It is found that seven of top ten extreme events at GEO during solar cycle 23 are associated with the magnetosphere inflation during the storm recovery phase as caused by the large-scale solar wind structure of very low dynamic pressure (<1.0 nPa) during rapid speed decrease from very high (>650 km/s) to typical (400–500 km/s) in a few days. For the seven events, the solar wind parameters, geomagnetic activity indices, and relativistic electron flux and geomagnetic field at GEO are superposed at the local noon period of GOES satellites to investigate the physical cause. The average profiles support the "double inflation" mechanism that the rarefaction of the solar wind and subsequent magnetosphere inflation are one of the best conditions to produce the extreme flux enhancement at GEO because of the excellent magnetic confinement of relativistic electrons by reducing the drift loss of trapped electrons at dayside magnetopause.

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.

Shock-induced radiation belt dynamics: Coordinated observations of drift echoes and ULF modulations in the dayside magnetosphere 

2021 ◽  
Author(s):  
Xingran Chen ◽  
Qiugang Zong ◽  
Ying Liu ◽  
Yixin Hao ◽  
Suiyan Fu ◽  
...  
Keyword(s):  
Radiation Belt ◽  
Interplanetary Shock ◽  
Observational Evidence ◽  
Ulf Waves ◽  
Outer Radiation Belt ◽  
Particle Measurements ◽  
Van Allen Probes ◽  
Characteristic Features ◽  
The One

&lt;p&gt;We employ conjunctive observations of particle fluxes and electromagnetic fields in the solar wind, magnetosheath, and dayside magnetosphere to investigate the radiation belt dynamics in response to the impingement of a fast forward interplanetary shock on 7 September 2017. Particularly, drift echoes associated with the one-kick acceleration caused by the shock-induced magnetosonic pulse and oscillations in the Pc 4 range associated with the azimuthally localized ULF waves are identified concurrently in the in-situ particle measurements obtained by the twin Van Allen Probes in the dayside outer radiation belt. Based on this observational evidence, we demonstrate that the radiation bet can be efficiently disturbed via the two mechanisms simultaneously by the shock arrival. We also depict the characteristic features to distinguish between the two mechanisms from an observational approach.&lt;/p&gt;

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