Geoscience Reference
In-Depth Information
Table 3.1.
Typical characteristics of various
Pc
-pulsations observed in the magne-
tosphere. See: http://www.oulu.fi/ spaceweb/textbook/ulf.html
Compressional Poloidal
Compressional Toroidal
Toroidal
Pc
3
,
4
Pc
5
Pc
5
Pc
3
,
4
Pc
5
τ
(s)
20-30
≥
100
300-600
20-40
300-600
Polarization
b
ν
b
ν
,b
b
ϕ
b
ϕ
Amplitude
≤
5nT
∼
10 nT
δB/B
0
∼
5-10 nT
0.2-0.5
LT
6-16
11-24
Day
6;18
L-shell
1.8-10
6-8
16-21; 3-6
6.6-9
equatorial
7-8;
>
10
node
tail, 10-22
[83]
m
2-5
50-100
20 [115]
([52], [96])
Ground/
Simultan.
Space
Resonance
2nd FLR-
Cavity
harmonics
Open
resonator
Source
Upstream
Drift-mirror Mirror
Upstream Kelv.-Helm.
waves
instab.
instab. [52]
waves
instab. [70]
3. Poloidal
Pc
4 are related to injections of energetic plasma and subsequent
low activity or convection electric field; occurring at the second harmonic
field line resonance frequency.
4. Compressional
Pc
5 are related to of high beta plasma (ion injections).
5. Toroidal
Pc
5 are the fundamental mode field line resonances; source in the
flanks.
6. Incoherent noise increases with magnetic activity.
Excluded from the table are noise oscillations with a broadband spectrum.
According to [1], they are visible on both the morning and evening sides
of the magnetosphere in the
L
9 interval and make up a considerable
part - about 25% of all the observed pulsations. A general tendency has
been revealed: a rise in the level of noise waves correlated with an increase in
magnetic activity.
≈
5
−
References
1. Anderson, B. J., An overview of spacecraft observations of 10 s to 600 s period
magnetic pulsations in the Earth's magnetosphere. In
Solar Wind Sources of
Magnetospheric Ultra-Low-Frequency Waves
, eds. M. J. Engebretson, K. Taka-
hashi, and M. Scholer, AGU Geophysical Monogr. Ser.,
81
, 25-43, American
Geophysical Union, Washington, DC, 1994.
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