Transcript LISN MODEL 2011.11

LISN Model/Data Inversion to Determine the
Drivers of the Low-Latitude Ionosphere
(Comparisons with JRO ISR Drift Measurements)
Vince Eccles (Modeling)
Space Environment Corporation, Providence, Utah
Erhan Kudeki (JRO ISR)
University of Illinois
Cesar Valladares (LISN)
Boston College
Assimilation of Ionospheric Data for
the Low-Latitude Ionosphere
• Ionospheric model-data assimilation methods typically modify
electron density specifications to best match TEC observations.
– 3D ionospheric density specification.
• Ensemble physics-based ionospheric model-data assimilation
modifies the vertical plasma drift and meridional F region neutral
wind to produced an ensemble of ionospheric specifications for
model-data inversion to reproduce TEC observations.
– 3D ionospheric density specification.
– Vertical plasma drift and meridional F region wind.
• Ensemble physics-based ionosphere & electric field model modifies
a 3D neutral wind description to produce an ensemble of
ionospheric specifications for model-data inversion to reproduce
observations.
–
–
–
–
3D ionospheric density specification.
Vertical and horizontal plasma drifts
3D neutral wind.
Penetration electric fields
Physics-based Model-Data Inversion
for the LISN Region
• The LISN Model-Data inversion uses a self-consistent
physics-based ionosphere & electric field model and a full
neutral wind description to produce an ensemble of
results for model-data inversion.
– LLIONS: Low-Latitude Ionospheric Sector Model
– SEF: Simple Electric Field Model
– Tidal description of Neutral Winds
• E region tides
– Solar diurnal, semi-diurnal
(phase, magnitude)
– Lunar semi-diurnal (phase, magnitude)
• F region winds
– My own secret recipe for zonal winds. (HWM07 sort of)
– Meridional F region winds are tidal extensions of the E region
with ad hoc additions as assimilation requires.
Physics-based Models: LLIONS
• Single magnetic meridian model based on the low-latitude
portion of the Ionospheric Forecast Model (IFM).
• Solves for H+, O+, NO+, O2+ , and e- densities based on
solar spectrum, neutral density, neutral winds, & vertical
plasma drift.
Physics-based Models: SEF
• Single magnetic meridian electric field model based on a
global electric field model using field-line-integrated physics.
• Solves for zonal and vertical electric fields (ExB plasma
drifts) based on conductivities and neutral winds in the
magnetic meridian sector (it approx. reproduces the global
model results)
LLIONS-SEF Model
• Scherliess & Fejer
vertical drift model and
zonal drifts from Fejer.
• LLIONS-SEF with
HWM 2007
• LLIONS-SEF with best
tides and F region winds
Methodology
F Region Winds
cross-equator and
zonal winds
E Region Tides
phase and magnitudes
of Hough modes
Penetration E Field
Boundary Condition
Monte Carlo generator of drivers around climatology
Drivers
Drivers
Drivers
Drivers
Drivers
LISN Sensors
Magnetometer
Dynasonde
GPS-TEC
Optimizer
LISN Conditions
Optimal
Representation
Drivers
LLIONS
HEED
Repre sentations
Repre sentations
Repre sentations
Repre sentations
Repre sentations
Public Access to Physics-Based
Processing of LISN Data
• Results to be placed at LISN
data center.
• Near real-time processing by
end of project.
LISN Model-Data Study
Fall 2009 Period
• Model/data study with LISN instruments
– Magnetometers (electric fields)
– VIPIR (F peak height & density)
• September-October used for the determination
of neutral wind drivers
– Electric fields & ionosphere distribution being
self-consistent with the neutral wind fields
VIPER and Magnetometer Data
Observed in Peruvian Sector
(Lunar Tides?)
Solar & Lunar Driven Tides on
Vertical Plasma Drift
Neutral Winds Definition for Fall 2009
1. Used magnetometer and VIPIR observations to optimally
determine tides.
2. Thermal-driven tide definition from October data.
-
Solar diurnal tide: (1,-2) Hough mode
3. Gravitational-driven tides definition from Fall data.
– Solar semi-diurnal tide: (2,2) Hough mode
– Lunar Semi-diurnal tide: (2,2) Hough mode
Model Results
VIPIR
Scherliess & Fejer
Simple Electric Field
Does the single definition work for the whole LISN Region?
Modeling Lunar Tides
Conclusions for Fall 2009 Study
• Single diurnal solar tide with single definition for Solar and
Lunar semi-diurnal tides provide a reasonable neutral wind
driver definition to drive the low-latitude
ionosphere/electric field model for the September through
November 2009.
– Solar diurnal (1,-2) tide with 130 m/s magnitude with static
phase.
– Semi-diurnal (2,2) for both solar and lunar with identical
magnitude (65 m/s) with a static phase definition for each.
• Departures are assumed to be high-latitude inputs and/or
tropospheric weather inputs into the neutral winds.
LISN Model-Data Inversion
• Goal is to identify the drivers of ionosphereelectric fields in the LISN region.
– Neutral wind specification is determined using an
ensemble of model runs, then use data and simdata to determine the optimal tidal definition.
– The data-model inverstion is performed over two
time scale epochs of 2 months and 1 day to obtain
the periodic wind structure and the aperiod wind
structure, respectively
2 Time Scales - Assimilation
• Two time scales
• 2 months data used to determine current epoch drivers
– Solar & Lunar gravitationally-driven semi-diurnal tides.
– Solar thermal diurnal tide.
– Adjustments to meridional F region wind (from Hough mode)
• 1 day data used to examine departures from long time
scale driver definition
– Penetration electric fields
– Aperiodic winds (tropospheric weather & storm dynamo winds)
• Benefit of this approach identifies specific
sources for the neutral wind structure. Rather
than just the 3D neutral wind structure.
Test Winter/Spring 2009
• Jicamarca Radar ISR observations available to
test assimilation results (January 2009).
• GPS-TEC and magnetometer data used for
Peruvian sector for winter/spring 2009.
• Same solar & lunar tidal structure?
LISN TEC
for Peruvian Sector
Jan 1-15, 2009
Jicamarca Radar Data Required
• The assimilation of TEC was unsuccessful.
– “Best” match required zero wind velocities.
– The observed very low TEC values could not be
matched.
• The LLIONS results do not match ionosphere
observations during very low solar conditions
– Needed to stepping back from assimilation to examine
ionization model of LLIONS
– Used the Jicamarca vertical drifts to reduce unknowns.
LLIONS Model
Reexamination
Jicamarca Radar Observatory
2009 Jan 9-13
These data are reduced to provide
Vertical drifts and zonal drifts for
LLIONS.
Required LLIONS Correction
• The LLIONS ionization determination requires
a secondary photo electron component. This
component was too large for the very low solar
conditions of 2009.
• This was adjusted to produce the observed
TEC values given the vertical plasma drifts
observed by Jicamarca radar.
JRO drifts & Best Tide Definition
• Smaller (than Fall
value) gravitational tide
magnitude (30 m/s).
• Smaller thermal tide
magnitude (80 m/s)
• Same phases as
previous study of Fall
2009
Comparison to Magnetometer Obs
A small amplitude 4rd tidal mode reveals itself during the lunar phase
where the solar and lunar gravitational tides cancel each other (5th-8th).
When the lunar and solar gravitational tides constructively superimpose,
then the 4th tidal mode is not apparent (10th-16th).
LLIONS Adjustments for
Very Low Solar Conditions
• The neutral wind tides that best matched the Jicamarca
Observations were used in LLISN-SEF with the new
photo electron parameterization.
• GPS-VTEC predictions are now approximately correct.
• Meridional F region wind adjustment is the remaining
important adjustment for the assimilation.
Current Situation of
LISN Model/Data Inversion
• The LLIONS model better matches the
observe TEC for very low conditions.
– The lunar tidal component is smaller than
determined in the Fall 2009 study. Correction?
– F region North-South wind modification will be
obtained for long scale assimilation.
– Finally, perform aperiod 1-day assimilation.
Summary
• The LISN model-data assimilation is performed
to determine regular and aperiodic drivers of the
low-latitude ionosphere.
• Doing this at two difference time-scales creates
additional insight into the component drivers of
the neutral wind.
• There is a possibility that a single tidal description
of thermal (F10.7 dependence) and gravitational
tides may capture most of the quiet time
variations of ionospheric weather.