Space Weather in the Equatorial Ionosphere

1
Space Weather in the Equatorial Ionosphere

• Robert Stening
• School of Physics, University of New South Wales

Acknowledge help from Dr J Du, IPS Radio and
Space Services
2
(No Transcript)
3
Variability Source
Atmospheric Tidal Winds Driving Ionospheric Dynamo
Equatorial Electrojet
Magnetic Variations DH
Electric Field E
Vertical Ion Drifts
Plasma Bubbles
Ion Density Gradients
Equatorial Anomaly
Scintillation
Communication Problems
GPS Problems
4
(No Transcript)
5
(No Transcript)
6
 
 
3m radar signal/noise (original Wes Swartz-
Cornell)
7
Vert. Drift velocities, Heights of max.
backscattered power, Spread F layers.
Equinox, solar maximum
From Fejer et al, 1999
8
Scintillation Occurrence at Indonesian Station
(crest).
1988
Monitor results
Model
1999
From Cervera et al Radio Sci 2001
9
WAAS (Wide Area Augmentation System)
10
(No Transcript)
11
What conditions are necessary for bubble
formation?

• Most often occurs at equinox and solar maximum.
• Often inhibited by magnetic disturbance
• More likely if both end of field line pass into
  darkness at the same time
• Lasts longer into night if electric field
  reversal is weak

12
Low solar flux
Peru. Radar echo occurrence
Medium solar flux
Hysell Burcham Clemson University
High solar flux
High Kp
Low Kp
13
Scintillation maximises when sunset at same
time at each end of field line.
From Tsunoda (1985)
14
Modelled spread F growth rates (Du et al)
15
What measurable parameters might help forecast
bubble formation?

• Vertical drifts are the main factor but not
  always measured
• Ground-based magnetic fields as a proxy?
• Need model and measure drift DH relationship
• C/NOFS satellite

16
Modelling problems

• Is equatorial electrojet controlled locally or is
  it part of the worldwide current system?

17
Modelling problems

• Is equatorial electrojet controlled locally or is
  it part of the worldwide current system?
• Or a bit of both?

18
Modelling problems

• Is equatorial electrojet controlled locally or is
  it part of the worldwide current system?
• Or a bit of both?
• ?Are the day-to-day changes due to tidal changes
  or local wind changes?

19
Modelling problems

• Is equatorial electrojet controlled locally or is
  it part of the worldwide current system?
• Or a bit of both?
• ?Are the day-to-day changes due to tidal changes
  or local wind changes?
• Why does latitude profile not model correctly?

20
Trivandrum DH
120
70
21
DH
Vertical Drift Vel.
Comparison of Drift velocities with DH for 11
days (10-13 LT) from Anderson et al
22
Vertical field
Points observed Curve -simulation
Northward field
86 nT added to X simulation
23
DH
DZ
African chain latitude profiles
24
Data
Worldwidecomponent
Model
Total electrojet current
Fambitakoye et al (1976) African data
25
Communication/Navigation Outage Forecasting
System Launch 2003
26
DZ
Points data Curves -simulation
DY
DX added 86 nT
27
(No Transcript)