Tidal Structures in the Equatorial Ionosphere
C. Y. Huang1, S. H. Delay2, E. K. Sutton1, and P. A. Roddy1,
1Air Force Research Laboratory2Boston College
MURI Workshop28 October 2010
Outline
• Broad Plasma Decreases (BPDs) in C/NOFS PLP – description
• Detrending C/NOFS PLP plasma densities - procedure
• Statistical analysis of detrended plasma densities for June 2008
• GRACE neutral density residuals for June 2008
2
Communication/Navigation Outage Forecast System
• Launched May 2008 into low-inclination orbit
• Goal is forecasting of scintillation
• 5 experiments – Planar Langmuir Probe– Vector Electric Field Investigation– Ion Velocity Monitor / Neutral Wind Monitor– RF Beacon– GPS
4
Simultaneous Broad Plasma Decreases C/NOFS and DMSP22 – 23 UT, 19 June 2008
C/NOFS BPD:Altitude 400 – 450 km, width 5 hrs LT
DMSP BPD:Altitude 840 km, width 30 latitude
[Huang et al., 2009, GRL]
Detrend C/NOFS Plasma Densities
• Variations in plasma density obscured by changing orbital altitude
• Detrend PLP densities using IRI (ver. 2007.3) as follows:
Ndet = N(PLP) * (IRI(500)/IRI(C/NOFS))
N(PLP) is the density measured by PLP along the orbit;
IRI (500) is the model value at 500 km, at the equator, at C/NOFS longitude, UT, DOY etc.;
IRI (C/NOFS) is the model value at C/NOFS location, UT, DOY etc.
• Use 1-minute averages of PLP densities• Result - densities all mapped to 500 km altitude, equator• Plots show density as function of geographic longitude
5
6
C/NOFS Orbit 953, 19 June 2008
7
Initial and Detrended C/NOFS DensitiesOrbit 953, 19 June 2008
Dayside Detrended Plasma Densities June 2008
8
5 104
1 105
1.5 105
2 105
8-10LT
Ave
. Det
. Den
s
0
5 104
1 105
1.5 105
6-8LT
Ave
Det
. Den
s
5 104
1 105
1.5 105
2 105
2.5 105
0 60 120 180 240 300 360
10-12LT
Ave
Det
. Den
s
Geog. Long
1 105
1.5 105
2 105
2.5 105
3 105
12-14LT
Ave
Det
Den
s
1 105
2 105
3 105
4 105
14-16LT
Ave
Det
. Den
s
0
1 105
2 105
3 105
0 60 120 180 240 300 360
16-18LTA
ve D
et. D
ens
Geog. Long
IRI PLP
Nightside Detrended Plasma DensitiesJune 2008
9
0
1 105
2 105
3 105
18-20LT
Ave
Det
. Den
s
0
1 105
2 105
3 105
20-22LT
Ave
Det
. Den
s
0
5 104
1 105
0 60 120 180 240 300 360
22-24LT
Ave
Det
. Den
s
Geog. Long
0
2 104
4 104
0-2LT
Ave
Det
Den
s0
1 104
2 104
2-4LT
Ave
. Det
. Den
s
0
2 104
4 104
6 104
0 60 120 180 240 300 360
4-6LT
Ave
Det
. Den
s
Geog. Long
IRI
PLP
Ionospheric Tidal Structures
• PLP data analyzed from May 2008 to December 2009
• Climatology of tidal structures similar to planetary wave climatology (strongest in June – August, weakest around December –January)
• Other C/NOFS experiments show similar wave-4 structures (electric fields, ion drifts, n/n)
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-30
-15
0
15
30
0 60 120 180 240 300 360Neu
tral
Den
sity
Res
idu
als
Geographic Longitude
June 2008 Plasma and Neutral Densities 20-22 LT Sector
0
5 104
1 105
Ni(
PL
P)
12
-20
-10
0
10
20
0 60 120 180 240 300 360Neu
tral
Den
sity
Res
idu
als
Geographic Longitude
5 104
1 105
1.5 105
2 105
2.5 105
N(P
LP
)
June 2008 Plasma and Neutral Densities 10-12 LT Sector
Summary
• Detrended PLP densities show tidal structures, most obvious on dayside
• Deep minimum persists on nightside around 330 (SAA)
• Climatology of plasma tides agrees with planetary wave source
• GRACE averaged neutral densities also show tidal structures
• Ion/neutral tides do not coincide!
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