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

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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

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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

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6

C/NOFS Orbit 953, 19 June 2008

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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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