scholarly journals Poleward-moving recurrent auroral arcs associated with impulse-excited standing hydromagnetic waves

2019 ◽  
Vol 3 (4) ◽  
pp. 305-313 ◽  
Author(s):  
HuaYu Zhao ◽  
◽  
Xu-Zhi Zhou ◽  
Ying Liu ◽  
Qiu-Gang Zong ◽  
...  
Keyword(s):  
Auroral Arcs ◽  
Hydromagnetic Waves

Some Characteristics of Irregular Micropulsations Pi2 at High Latitude Stations

1971 ◽  
Vol 49 (18) ◽  
pp. 2338-2349 ◽  
Author(s):  
Jagdish C. Gupta ◽  
Robert J. Stening
Keyword(s):  
High Latitude ◽  
Maximum Amplitude ◽  
Lower Latitude ◽  
Different Types ◽  
Baker Lake ◽  
Hydromagnetic Waves ◽  
Relationship Of ◽  
The Relationship ◽  
Maximum Occurrence

Pi2 micropulsations were studied for the period July 12 to August 16, 1968, from four observatories at different latitudes in Canada. Maximum occurrence was near midnight with a preference for 5–6 h UT at all longitudes studied. The relationship of Pi2 occurrence to magnetic bays and to Kp is examined. The correlation of Pi amplitudes and periods with Kp and other parameters reveals a different pattern for lower latitude stations (Ottawa and Meanook) compared with Baker Lake (73.9 °N). These results are interpreted as evidence for two different types of Pi in the different latitude regions, the lower latitude Pi being associated with hydromagnetic waves on the plasmapause. In studies of simultaneous Pi events at the four stations, the maximum amplitude occurred most frequently at Meanook. Polarization of such events was found to be different at different stations and so previously reported patterns of Pi polarization could not be confirmed.

scholarly journals Spectral observations of FUV auroral arcs and comparison with inverted-V precipitating electrons

2010 ◽  
Vol 115 (A9) ◽  
pp. n/a-n/a ◽  
Author(s):  
C. N. Lee ◽  
K. W. Min ◽  
J.-J. Lee ◽  
G. K. Parks ◽  
M. O. Fillingim ◽  
...  
Keyword(s):  
Auroral Arcs

Preferential acceleration of heavy ions from thermal velocities

1968 ◽  
Vol 46 (10) ◽  
pp. S638-S641 ◽  
Author(s):  
D. B. Melrose
Keyword(s):  
Frequency Spectrum ◽  
High Frequency ◽  
Heavy Ions ◽  
Crab Nebula ◽  
Low Frequency ◽  
High Frequency Waves ◽  
Hydromagnetic Waves ◽  
The Crab Nebula ◽  
Low Frequency Waves

The acceleration of ions from thermal velocities is analyzed to determine conditions under which heavy ions can be preferentially accelerated. Two accelerating mechanisms involving high-and low-frequency hydromagnetic waves respectively are considered. Preferential acceleration of heavy ions occurs for high-frequency waves if the frequency spectrum falls off faster than (frequency)−1. For the low-frequency waves heavy ions are less effectively accelerated than lighter ions. However, very heavy ions can be preferentially accelerated, the abundances of the very heavy ions being enhanced by a factor Ai over the thermal abundances. Acceleration of ions in the envelope of the Crab nebula is considered as an example.

Tidal excitation of hydromagnetic waves and their damping in the Earth

1994 ◽  
Vol 274 ◽  
pp. 219-241 ◽  
Author(s):  
R. R. Kerswell
Keyword(s):  
Growth Rate ◽  
Growth Rates ◽  
Outer Core ◽  
Decay Rates ◽  
Wave Disturbance ◽  
Instability Mechanism ◽  
The Earth ◽  
Elliptical Instability ◽  
Hydromagnetic Waves

We examine the possibility that the Earth's outer core, as a tidally distorted fluid-filled rotating spheroid, may be the seat of an elliptical instability. The instability mechanism is described within the framework of a simple Earth-like model. The preferred forms of wave disturbance are explored and a likely growth rate supremum deduced. Estimates are made of the Ohmic and viscous decay rates of such hydromagnetic waves in the outer core. Rather than a conclusive disparity of scales, we find that typical elliptical growth rates, Ohmic decay rates and viscous decay rates all have the same order for plausible core fields and core-to-mantle conductivities. This study is all the more timely considering the recent realization that the Earth's precession may also drive similar instabilities at comparable strengths in the outer core.

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