Relations Between Bursty Bulk Flows in the Magnetotail and Substorms

2006 ◽  
Vol 49 (3) ◽  
pp. 531-538 ◽  
Author(s):  
Yu-Duan MA ◽  
Jin-Bin CAO ◽  
Guo-Cheng ZHOU ◽  
Zhen-Xing LIU ◽  
H. Reme ◽  
...  
Keyword(s):  
Bursty Bulk Flows

Intense dB/dt variations driven by near-Earth Bursty Bulk Flows (BBFs): A case study

2021 ◽  
Author(s):  
Dong Wei ◽  
Malcolm Dunlop ◽  
Junying Yang ◽  
Xiangcheng Dong ◽  
Yiqun Yu ◽  
...  
Keyword(s):  
Large Scale ◽  
Current System ◽  
Geomagnetically Induced Currents ◽  
Inner Magnetosphere ◽  
Wide Range ◽  
Ground System ◽  
Induced Currents ◽  
Ground Magnetic ◽  
Bursty Bulk Flows

<p>During geomagnetically disturbed times the surface geomagnetic field often changes abruptly, producing geomagnetically induced currents (GICs) in a number of ground based systems. There are, however, few studies reporting GIC effects which are driven directly by bursty bulk flows (BBFs) in the inner magnetosphere. In this study, we investigate the characteristics and responses of the magnetosphere-ionosphere-ground system during the 7 January 2015 storm by using a multi-point approach which combines space-borne measurements and ground magnetic observations. During the event, multiple BBFs are detected in the inner magnetosphere while the magnetic footprints of both magnetospheric and ionospheric satellites map to the same conjugate region surrounded by a group of magnetometer ground stations. It is suggested that the observed, localized substorm currents are caused by the observed magnetospheric BBFs, giving rise to intense geomagnetic perturbations. Our results provide direct evidence that the wide-range of intense dB/dt<strong> </strong>(and dH/dt) variations are associated with a large-scale, substorm current system, driven by multiple BBFs.</p>

scholarly journals The Acceleration of Outer-Belt Electrons by Localized Electric Fields

2021 ◽  
Vol 61 (4) ◽  
pp. 477-482
Author(s):  
A. P. Kropotkin
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Relativistic Electrons ◽  
Strong Component ◽  
Short Term ◽  
Energetic Electrons ◽  
Geomagnetic Tail ◽  
Night Side ◽  
Bursty Bulk Flows

Abstract To explain the populations of the outer-belt energetic electrons, including relativistic electrons, that sporadically appear in the magnetosphere, a mechanism was proposed long ago for the acceleration of those electrons by short-term bursts of the electric field, which appear on the night side during substorm disturbances (Kropotkin, 1996). This mechanism can be substantially specified if the modern concepts of bursty bulk flows in the geomagnetic tail, the occurrence of dipolarization fronts, and the excitation of localized field-aligned-resonant poloidal Alfvén oscillations involving a strong component of the electric field in the dawn-dusk direction are taken into account.

scholarly journals The dependence of Pi2 waveforms on periodic velocity enhancements within bursty bulk flows

2011 ◽  
Vol 29 (3) ◽  
pp. 493-509 ◽  
Author(s):  
K. R. Murphy ◽  
I. J. Rae ◽  
I. R. Mann ◽  
A. P. Walsh ◽  
D. K. Milling ◽  
...  
Keyword(s):  
Causal Relation ◽  
Low Frequency ◽  
Temporal Variations ◽  
Magnetic Activity ◽  
Common Source ◽  
Magnetometer Array ◽  
Frequency Domains ◽  
Bulk Plasma ◽  
Bursty Bulk Flows

Abstract. Pi2s are a category of Ultra Low Frequency (ULF) waves associated with the onset of magnetic substorms. Recent work has suggested that the deceleration of bulk plasma flows in the central plasmasheet, known as bursty bulk flows (BBFs), are able to directly-drive Pi2 oscillations. Some of these studies have further shown evidence that there is a one-to-one correlation between Pi2 magnetic waveforms observed on the ground and periodic peaks in flow velocity within the BBF, known as flow bursts. Utilising a favourable conjunction between the Geotail spacecraft and the Canadian Array for Real-time Investigations of Magnetic Activity (CARISMA) magnetometer array on 31 May 1998, we examine the causality of the link between BBF flow bursts and Pi2 waveforms. Using a series of analytical tests in both the time and frequency domains, we find that while the Pi2 and BBF waveforms are very similar, the ground response for this event occurs prior to the observed flow enhancements in the magnetotail. We conclude that during this specific case study the temporal variations of the flow bursts within the BBF are not directly-driving the observed ground-based Pi2 waveforms, despite the fact that a visual inspection of both time-series might initially suggest that there is a causal relationship. We postulate that rather than there being a direct causal relation, the similar waveforms observed in both Pi2s and BBFs may result from temporal variations in a common source for both the BBFs and the Pi2s, such as magnetic reconnection in the tail, this source modulating both the Pi2 and BBF at the same frequency.

scholarly journals Contribution of Bursty Bulk Flows to the Global Dipolarization of the Magnetotail During an Isolated Substorm

2019 ◽  
Vol 124 (11) ◽  
pp. 8647-8668 ◽  
Author(s):  
V. G. Merkin ◽  
E. V. Panov ◽  
K. A. Sorathia ◽  
A. Y. Ukhorskiy
Keyword(s):  
Bursty Bulk Flows

scholarly journals The increase of curvature radius of geomagnetic field lines preceding a classical dipolarization

2019 ◽  
Author(s):  
Osuke Saka
Keyword(s):  
Field Line ◽  
Electric Fields ◽  
Flux Tube ◽  
Slow Wave ◽  
Equatorial Plane ◽  
Curvature Radius ◽  
Flux Tubes ◽  
Ballooning Instability ◽  
Field Lines ◽  
Bursty Bulk Flows

Abstract. Downstream observations at geosynchronous altitudes of field line dipolarization exhibit fundamental component of substorms associated with high velocity magnetotail flow bursts referred to as Bursty Bulk Flows. In growth phase of substorms, we found that the magnetosphere at geosynchronous orbit are in unstable conditions for Ballooning instability due to the appreciable tailward stretching of the flux tubes, and for slow magnetoacoustic wave due to the continuing field-aligned inflows of plasma sheet plasmas towards the equatorial plane. We propose following scenario of field line dipolarization in downstream locations; (1) The slow wave was excited through Ballooning instability by the arrival of Dipolarization Front at the leading edge of Bursty Bulk Flows. (2) In the equatorial plane, slow wave stretched the flux tube in dawn-dusk directions, which resulted in the spreading plasmas in dawn-dusk directions and reducing the radial pressure gradient in the flux tube. (3) As a result, the flux tube becomes a new equilibrium geometry in which curvature radius of new field lines increased in meridian plane, suggesting an onset of field line dipolarization. (4) Increasing curvature radius induced inductive electric fields of the order of few mV/m pointing westward in the equatorial plane, as well as radial electric fields associated with stretching flux tubes in dawn-dusk directions. Westward electric fields transmitted to the ionosphere produce a dynamic ionosphere where the E layer contains both dynamo (E · J  0) processes in it for generating field-aligned current system of Bostrom type. The dipolarization processes associated with changing the curvature radius occurred in the transitional intervals lasting for about 10 minutes preceding classical dipolarization composed of reduction of cross-tail currents and pileup of the magnetic fields transported from the tail.

Near-Earth bursty bulk flows and AE index

2008 ◽  
Vol 51 (10) ◽  
pp. 1704-1712 ◽  
Author(s):  
LingQian Zhang ◽  
JianKui Shi ◽  
ZhenXing Liu ◽  
W. Baumjohann ◽  
ZhiWei Ma ◽  
...  
Keyword(s):  
Ae Index ◽  
Bursty Bulk Flows

scholarly journals Magnetic forces associated with bursty bulk flows in Earth's magnetotail

2015 ◽  
Vol 42 (9) ◽  
pp. 3122-3128 ◽  
Author(s):  
Tomas Karlsson ◽  
Maria Hamrin ◽  
Hans Nilsson ◽  
Anita Kullen ◽  
Timo Pitkänen
Keyword(s):  
Magnetic Forces ◽  
Bursty Bulk Flows

scholarly journals Transient and localized processes in the magnetotail: a review

2008 ◽  
Vol 26 (4) ◽  
pp. 955-1006 ◽  
Author(s):  
A. S. Sharma ◽  
R. Nakamura ◽  
A. Runov ◽  
E. E. Grigorenko ◽  
H. Hasegawa ◽  
...  
Keyword(s):  
Magnetic Reconnection ◽  
Current Sheet ◽  
Spatial Scales ◽  
Theoretical Models ◽  
Particle Interactions ◽  
Transient Field ◽  
Theoretical Frameworks ◽  
Flux Ropes ◽  
Night Side ◽  
Bursty Bulk Flows

Abstract. Many phenomena in the Earth's magnetotail have characteristic temporal scales of several minutes and spatial scales of a few Earth radii (RE). Examples of such transient and localized mesoscale phenomena are bursty bulk flows, beamlets, energy dispersed ion beams, flux ropes, traveling compression regions, night-side flux transfer events, and rapid flappings of the current sheet. Although most of these observations are linked to specific interpretations or theoretical models they are inter-related and can be the different aspects of a physical process or origin. Recognizing the inter-connected nature of the different transient and localized phenomena in the magnetotail, this paper reviews their observations by highlighting their important characteristics, with emphasis on the new results from Cluster multipoint observations. The multi-point Cluster measurements have provided, for the first time, the ability to distinguish between temporal and spatial variations, and to resolve spatial structures. Some examples of the new results are: flux ropes with widths of 0.3 RE, transient field aligned currents associated with bursty bulk flows and connected to the Hall current at the magnetic reconnection, flappings of the magnetotail current sheet with time scales of 100 s–10 min and thickness of few thousand km, and particle energization including velocity and time dispersed ion structures with the latter having durations of 1–3 min. The current theories of these transient and localized processes are based largely on magnetic reconnection, although the important role of the interchange and other plasma modes are now well recognized. On the kinetic scale, the energization of particles takes place near the magnetic X-point by non-adiabatic processes and wave-particle interactions. The theory, modeling and simulations of the plasma and field signatures are reviewed and the links among the different observational concepts and the theoretical frameworks are discussed. The mesoscale processes in the magnetotail and the strong coupling among them are crucial in developing a comprehensive understanding of the multiscale phenomena of the magnetosphere.

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