scholarly journals Equatorward propagating auroral arcs driven by ULF wave activity: Multipoint ground- and space-based observations in the dusk sector auroral oval

2017 ◽  
Vol 122 (5) ◽  
pp. 5591-5605 ◽  
Author(s):  
L. J. Baddeley ◽  
D. A. Lorentzen ◽  
N. Partamies ◽  
M. Denig ◽  
V. A. Pilipenko ◽  
...  
Keyword(s):  
Auroral Oval ◽  
Wave Activity ◽  
Ulf Wave ◽  
Auroral Arcs ◽  
Dusk Sector

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 Ion shell distributions as free energy source for plasma waves on auroral field lines mapping to plasma sheet boundary layer

2004 ◽  
Vol 22 (6) ◽  
pp. 2115-2133 ◽  
Author(s):  
A. Olsson ◽  
P. Janhunen ◽  
W. K. Peterson
Keyword(s):  
Boundary Layer ◽  
Free Energy ◽  
Plasma Sheet ◽  
Wave Activity ◽  
Plasma Sheet Boundary Layer ◽  
In Situ Data ◽  
Bernstein Waves ◽  
Field Lines ◽  
Auroral Arcs ◽  
Polar Satellite

Abstract. Ion shell distributions are hollow spherical shells in velocity space that can be formed by many processes and occur in several regions of geospace. They are interesting because they have free energy that can, in principle, be transmitted to ions and electrons. Recently, a technique has been developed to estimate the original free energy available in shell distributions from in-situ data, where some of the energy has already been lost (or consumed). We report a systematic survey of three years of data from the Polar satellite. We present an estimate of the free energy available from ion shell distributions on auroral field lines sampled by the Polar satellite below 6 RE geocentric radius. At these altitudes the type of ion shells that we are especially interested in is most common on auroral field lines close to the polar cap (i.e. field lines mapping to the plasma sheet boundary layer, PSBL). Our analysis shows that ion shell distributions that have lost some of their free energy are commonly found not only in the PSBL, but also on auroral field lines mapping to the boundary plasma sheet (BPS), especially in the evening sector auroral field lines. We suggest that the PSBL ion shell distributions are formed during the so-called Velocity Dispersed Ion Signatures (VDIS) events. Furthermore, we find that the partly consumed shells often occur in association with enhanced wave activity and middle-energy electron anisotropies. The maximum downward ion energy flux associated with a shell distribution is often 10mWm-2 and sometimes exceeds 40mWm-2 when mapped to the ionosphere and thus may be enough to power many auroral processes. Earlier simulation studies have shown that ion shell distributions can excite ion Bernstein waves which, in turn, energise electrons in the parallel direction. It is possible that ion shell distributions are the link between the X-line and the auroral wave activity and electron acceleration in the energy transfer chain for stable auroral arcs.

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

&lt;p&gt;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 (&lt;strong&gt;ULF&lt;/strong&gt;) 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.&lt;/p&gt;&lt;p&gt;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 &amp; 2 and Pioneer 10 &amp; 11). We found several-hundred wave events consisting of wave packets parallel or transverse to the mean magnetic field, interpreted as fast-mode or Alfv&amp;#233;nic MHD wave activity, respectively. Parallel and transverse events were often coincident in space and time, which may be evidence of global Alfv&amp;#233;nic 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 &amp;#8220;magic frequencies&amp;#8221; often reported in existing literature.&lt;/p&gt;&lt;p&gt;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.&lt;/p&gt;

scholarly journals Correspondence between the latitudinal ULF wave power distribution and auroral oval in conjugate ionospheres

2018 ◽  
Author(s):  
V.A. Martines-Bedenko ◽  
V.A. Pilipenko ◽  
M.D. Hartinger ◽  
M.J. Engebretson ◽  
D.A. Lorentzen ◽  
...  
Keyword(s):  
Power Distribution ◽  
Auroral Oval ◽  
Wave Power ◽  
Ulf Wave

scholarly journals Ground-based and satellite observations of high-latitude auroral activity in the dusk sector of the auroral oval

2001 ◽  
Vol 19 (10/12) ◽  
pp. 1683-1696 ◽  
Author(s):  
K. Kauristie ◽  
T. I. Pulkkinen ◽  
O. Amm ◽  
A. Viljanen ◽  
M. Syrjäsuo ◽  
...  
Keyword(s):  
Solar Wind ◽  
High Latitude ◽  
Auroral Oval ◽  
Outer Edge ◽  
Satellite Observations ◽  
Mhd Waves ◽  
Clear Correlation ◽  
Close Relationship ◽  
Magnetic Pulsations ◽  
Dusk Sector

Abstract. On 7 December 2000, during 13:30–15:30 UT the MIRACLE all-sky camera at Ny Ålesund observed auroras at high-latitudes (MLAT ~ 76) simultaneously when the Cluster spacecraft were skimming the magnetopause in the same MLT sector (at ~ 16:00–18:00 MLT). The location of the auroras (near the ionospheric convection reversal boundary) and the clear correlation between their dynamics and IMF variations suggests their close relationship with R1 currents. Consequently, we can assume that the Cluster spacecraft were making observations in the magnetospheric region associated with the auroras, although exact magnetic conjugacy between the ground-based and satellite observations did not exist. The solar wind variations appeared to control both the behaviour of the auroras and the magnetopause dynamics. Auroral structures were observed at Ny Ålesund especially during periods of negative IMF BZ. In addition, the Cluster spacecraft experienced periodic (T ~ 4 - 6 min) encounters between magnetospheric and magnetosheath plasmas. These undulations of the boundary can be interpreted as a consequence of tailward propagating magnetopause surface waves. Simultaneous dusk sector ground-based observations show weak, but discernible magnetic pulsations (Pc 5) and occasionally periodic variations (T ~ 2 - 3 min) in the high-latitude auroras. In the dusk sector, Pc 5 activity was stronger and had characteristics that were consistent with a field line resonance type of activity. When IMF BZ stayed positive for a longer period, the auroras were dimmer and the spacecraft stayed at the outer edge of the magnetopause where they observed electromagnetic pulsations with T ~ 1 min. We find these observations interesting especially from the viewpoint of previously presented studies relating poleward-moving high-latitude auroras with pulsation activity and MHD waves propagating at the magnetospheric boundary layers.Key words. Ionosphere (ionosphere-magnetosphere interaction) – Magnetospheric physics (auroral phenomena; solar wind – magnetosphere interactions)

scholarly journals The ionospheric response during an interval of Pc5 ULF wave activity

2000 ◽  
Vol 18 (2) ◽  
pp. 0257-0261
Author(s):  
M. Lester ◽  
J. A. Davies ◽  
T. K. Yeoman
Keyword(s):  
Wave Activity ◽  
Ionospheric Response ◽  
Ulf Wave

scholarly journals Features of Nightside ULF Wave Activity in the Ionosphere

2019 ◽  
Vol 124 (11) ◽  
pp. 9203-9213 ◽  
Author(s):  
X.Y. Ouyang ◽  
J. Bortnik ◽  
J. Ren ◽  
J.J. Berthelier
Keyword(s):  
Wave Activity ◽  
Ulf Wave

scholarly journals The 8 June 2000 ULF wave activity: A case study

2012 ◽  
Vol 117 (A2) ◽  
pp. n/a-n/a ◽  
Author(s):  
M. Piersanti ◽  
U. Villante ◽  
C. Waters ◽  
I. Coco
Keyword(s):  
Wave Activity ◽  
Ulf Wave
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