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

scholarly journals The Pulsating Magnetosphere at Jupiter

2020 ◽  
Author(s):  
Harry Manners ◽  
Adam Masters
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Dynamic Pressure ◽  
Wave Spectrum ◽  
Low Frequency ◽  
Global Scale ◽  
Wave Activity ◽  
Ulf Waves ◽  
Ulf Wave ◽  
Wide Range

<p>The magnetosphere of Jupiter is the largest planetary magnetosphere in the solar system, and plays host to internal dynamics that remain, in many ways, mysterious. Prominent among these mysteries are the ultra-low-frequency (<strong>ULF</strong>) pulses ubiquitous in this system. Pulsations in the electromagnetic emissions, magnetic field and flux of energetic particles have been observed for decades, with little to indicate the source mechanism. While ULF waves have been observed in the magnetospheres of all the magnetized planets, the magnetospheric environment at Jupiter seems particularly conducive to the emergence of ULF waves over a wide range of periods (1-100+ minutes). This is mainly due to the high variability of the system on a global scale: internal plasma sources and a powerful intrinsic magnetic field produce a highly-compressible magnetospheric cavity, which can be reduced to a size significantly smaller than its nominal expanded state by variations in the dynamic pressure of the solar wind. Compressive fronts in the solar wind, turbulent surface interactions on the magnetopause and internal plasma processes can also all lead to ULF wave activity inside the magnetosphere.</p><p>To gain the first comprehensive view of ULF waves in the Jovian system, we have performed a heritage survey of magnetic field data measured by six spacecraft that visited the magnetosphere (Galileo, Ulysses, Voyager 1 & 2 and Pioneer 10 & 11). We found several-hundred wave events consisting of wave packets parallel or transverse to the mean magnetic field, interpreted as fast-mode or Alfvénic MHD wave activity, respectively. Parallel and transverse events were often coincident in space and time, which may be evidence of global Alfvénic resonances of the magnetic field known as field-line-resonances. We found that 15-, 30- and 40-minute periods dominate the Jovian ULF wave spectrum, in agreement with the dominant “magic frequencies” often reported in existing literature.</p><p>We will discuss potential driving mechanisms as informed by the results of the heritage survey, how this in turn affects our understanding of energy transfer in the magnetosphere, and potential investigations to be made using data from the JUNO spacecraft. We will also discuss the potential for multiple resonant cavities, and how the resonance modes of the Jovian magnetosphere may differ from those of the other magnetized planets.</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 ULF Wave Activity in the Magnetosphere: Resolving Solar Wind Interdependencies to Identify Driving Mechanisms

2018 ◽  
Vol 123 (4) ◽  
pp. 2745-2771 ◽  
Author(s):  
S. N. Bentley ◽  
C. E. J. Watt ◽  
M. J. Owens ◽  
I. J. Rae
Keyword(s):  
Solar Wind ◽  
Wave Activity ◽  
Ulf Wave ◽  
Driving Mechanisms

Understanding the controlling factors of Ultra-Low Frequency waves and their penetration during geomagnetic storms

2020 ◽  
Author(s):  
Jonathan Rae ◽  
Kyle Murphy ◽  
Clare Watt ◽  
Jasmine Sandhu ◽  
Samuel Wharton ◽  
...  
Keyword(s):  
Solar Wind ◽  
Radiation Belt ◽  
Ring Current ◽  
Geomagnetic Storms ◽  
Particle Interaction ◽  
Low Frequency ◽  
Controlling Factors ◽  
Wave Power ◽  
Inner Magnetosphere ◽  
Ulf Wave

<p>Wave-particle interactions play a key role in radiation belt dynamics. Traditionally, Ultra-Low Frequency (ULF) wave-particle interaction is parameterised statistically by a small number of controlling factors for given solar wind driving conditions or geomagnetic activity levels. Here, we investigate solar wind driving of ultra-low frequency (ULF) wave power and the role of the magnetosphere in screening that power from penetrating deep into the inner magnetosphere. We demonstrate that, during enhanced ring current intensity, the Alfvén continuum plummets, allowing lower frequency waves to penetrate deeper into the magnetosphere than during quiet periods. With this penetration, ULF wave power is able to accumulate closer to the Earth than characterised by statistical models. During periods of enhanced solar wind driving such as coronal mass ejection driven storms, where ring current intensities maximise, the observed penetration provides a simple physics-based reason for why storm-time ULF wave power is different compared to non-storm time waves. We demonstrate statistically that the ring current plays a pivotal role in allowing ULF wave energy to access the inner magnetosphere and show a new parameterisation of ULF wave power for radiation belt research purposes that is specifically tuned for geomagnetic storms.</p>

scholarly journals Intermediate-<I>m</I> ULF waves generated by substorm injection: a case study

2010 ◽  
Vol 28 (8) ◽  
pp. 1499-1509 ◽  
Author(s):  
T. K. Yeoman ◽  
D. Yu. Klimushkin ◽  
P. N. Mager
Keyword(s):  
Phase Variation ◽  
Wave Activity ◽  
Wave Number ◽  
Ulf Wave ◽  
Azimuthal Wave ◽  
Azimuthal Wave Number ◽  
Source Particle ◽  
Phase Propagation ◽  
Field Lines

Abstract. A case study of SuperDARN observations of Pc5 Alfvén ULF wave activity generated in the immediate aftermath of a modest-intensity substorm expansion phase onset is presented. Observations from the Hankasalmi radar reveal that the wave had a period of 580 s and was characterized by an intermediate azimuthal wave number (m=13), with an eastwards phase propagation. It had a significant poloidal component and a rapid equatorward phase propagation (~62° per degree of latitude). The total equatorward phase variation over the wave signatures visible in the radar field-of-view exceeded the 180° associated with field line resonances. The wave activity is interpreted as being stimulated by recently-injected energetic particles. Specifically the wave is thought to arise from an eastward drifting cloud of energetic electrons in a similar fashion to recent theoretical suggestions (Mager and Klimushkin, 2008; Zolotukhina et al., 2008; Mager et al., 2009). The azimuthal wave number m is determined by the wave eigenfrequency and the drift velocity of the source particle population. To create such an intermediate-m wave, the injected particles must have rather high energies for a given L-shell, in comparison to previous observations of wave events with equatorward polarization. The wave period is somewhat longer than previous observations of equatorward-propagating events. This may well be a consequence of the wave occurring very shortly after the substorm expansion, on stretched near-midnight field lines characterised by longer eigenfrequencies than those involved in previous observations.

scholarly journals Global estimates of plasmaspheric losses during moderate disturbance intervals

2010 ◽  
Vol 28 (1) ◽  
pp. 27-36 ◽  
Author(s):  
M. Spasojevic ◽  
B. R. Sandel
Keyword(s):  
Solar Wind ◽  
Electric Field ◽  
Boundary Layers ◽  
Total Mass ◽  
Density Ratio ◽  
Individual Case ◽  
Number Density ◽  
Inner Magnetosphere ◽  
Moderate Disturbance ◽  
Global Estimates

Abstract. For a set of five moderate disturbance events, we calculate the total number of He+ ions removed the plasmasphere using calibrated global EUV images. In each of the events, between ~0.6 and 2.2×1030 He+ ions are removed from a region of the inner magnetosphere from L=1.5 to 5.5. This loss constitutes between 20% and 42% of the initial He+ distribution. The lost percentage is correlated with the number of hours of strongly positive solar wind electric field (Ey>2.5 mV/m). Also, the total amount of material removed from the plasmasphere is estimated by using several values of the He+ to H+ number density ratio. The total mass lost is found to be in the range of 20 to 80 metric tons although for each individual case the estimate can vary by over 50% depending on assumed density ratio. We also attempt to distinguish between losses to the ionosphere and losses to the dayside boundary layers by estimating losses interior and exterior to the newly formed plasmapause boundary. For the events studied, losses inside the new plasmapause constitute between 24% to 54% of the total number of He+ ions lost.

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

2018 ◽  
Vol 123 (2) ◽  
pp. 1086-1099 ◽  
Author(s):  
A. W. Degeling ◽  
I. J. Rae ◽  
C. E. J. Watt ◽  
Q. Q. Shi ◽  
R. Rankin ◽  
...  
Keyword(s):  
Plasma Density ◽  
Inner Magnetosphere ◽  
Ulf Wave
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