wsa model and forecasts

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1 WSA Model and Forecasts WSA Model and Forecasts Nick Arge Nick Arge Space Vehicles Directorate Air Force Research Laboratory

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WSA Model and Forecasts. Nick Arge Space Vehicles Directorate Air Force Research Laboratory. WSA Coronal & Solar Wind Model. Schatten Current Sheet Model. PFSS Model. Solar Wind Model (e.g., 1D Kinematic model, ENLIL, HAF) (5-30 Rs to 1AU). 5-30 Rs. 2.5 Rs. Source Surface. - PowerPoint PPT Presentation

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Page 1: WSA Model and Forecasts

1

WSA Model and ForecastsWSA Model and Forecasts

Nick ArgeNick ArgeSpace Vehicles Directorate

Air Force Research Laboratory

Page 2: WSA Model and Forecasts

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Source Surface

PFSS Model

Schatten Current Sheet Model

5-30 Rs

2.5 Rs

Plot courtesy Sarah McGregor (BU/CISM)

Solar Wind Model

(e.g., 1D Kinematic

model, ENLIL, HAF)

(5-30Rs to 1AU)

WSA Coronal & Solar Wind ModelWSA Coronal & Solar Wind Model

Page 3: WSA Model and Forecasts

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PFSSPFSS++SCS MODEL (R = 5.0 SCS MODEL (R = 5.0 RR)) Predicted Solar Wind Speed at 5.0 Predicted Solar Wind Speed at 5.0 RR

(New Empirical Relationship )(New Empirical Relationship )

5.3

5.7θ1

3/1

3

6.18.51

5.1265θ,

b

ef

fVs

bskm s-1

Where:

fs = Magnetic field expansion factor.

θb = Minimum angular distance that an open field footpoint lies from nearest coronal hole boundary (i.e., Angular depth inside a coronal hole)

WSA Model Coronal OutputWSA Model Coronal OutputC

oron

al H

oles

Cor

onal

Fie

ld (

5.0R

)

Page 4: WSA Model and Forecasts

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IMF directed radially toward from Sun.

IMF directed radially away from Sun.

Solar Wind Speed and IMF Polarity in the Ecliptic Solar Wind Speed and IMF Polarity in the Ecliptic Driven by Daily Updated Photospheric Field MapsDriven by Daily Updated Photospheric Field Maps

Page 5: WSA Model and Forecasts

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Solar Wind Speed Predictions & ObservationsSolar Wind Speed Predictions & Observations IMF Polarity Predictions & ObservationsIMF Polarity Predictions & Observations

Predictions & Observations:Near Solar MaximumPredictions & Observations:Near Solar Maximum

Page 6: WSA Model and Forecasts

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Solar Wind Speed Predictions & ObservationsSolar Wind Speed Predictions & Observations

Predictions & ObservationsPredictions & Observations

Solar Wind Speed Predictions & ObservationsSolar Wind Speed Predictions & Observations

Page 7: WSA Model and Forecasts

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Validated 8 years of WSA predictions Event-based approach: high speed enhancements (HSE):

Captures more than 72% of the observed HSE events Most of the false HSEs are small Missed HSEs: are small events or transients Timing of HSEs shows no offset. Slight underestimation of magnitude

of fastest events – probably due to transients

Observed

HSE No HSE

Model

HSE 166 36

No HSE 64 -

Contingency Tables

Missed

False

Observed

Model

Boston University Boston University ValidationValidation of WSA Event-Based of WSA Event-Based Approach: (High Speed Events)Approach: (High Speed Events)

( Owens et al., JGR 2005)( Owens et al., JGR 2005)

Page 8: WSA Model and Forecasts

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Corrections that often need to be applied to photospheric field maps (depending on the observatory):

• Line-of-sight fields need to be converted to radial orientation (including effects due to the Solar b angle).

• Observational evidence suggests this is generally true except in strong active regions!

• Monopole moment needs to be removed.

• Polar fields need to be corrected and filled (when necessary).

• Can use historical data for retrospective studies.

• Field corrected (when necessary) for magnetic field saturation effects.

• Flux transport processes (differential rotation, meridional flow, diffusion, etc.)

Solar Wind Model Driver:Solar Wind Model Driver:Photospheric Field Synoptic MapsPhotospheric Field Synoptic Maps

Page 9: WSA Model and Forecasts

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Modeling Results With & Without Polar Field Modeling Results With & Without Polar Field Corrections AppliedCorrections Applied

Polar Fields Not Corrected Polar Fields Corrected

Der

ived

Cor

onal

Hol

es

Der

ived

Cor

onal

Hol

es

Solar Wind Speed Predictions (WSA Model) and Observations

Poles NOT Corrected

Poles Corrected

Page 10: WSA Model and Forecasts

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Monopole Moments in Synoptic MapsMonopole Moments in Synoptic Maps

Split bi-polar Region

Corresponding Negative polarity missing

Page 11: WSA Model and Forecasts

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Time Evolution of Photospheric & Time Evolution of Photospheric & Coronal FeaturesCoronal Features

Page 12: WSA Model and Forecasts

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Observed & Predicted IMF Polarity

Observed & Predicted Solar Wind Speed

Solar Wind Sources Near & Far From Active RegionsSolar Wind Sources Near & Far From Active RegionsWSA Model Predictions & Observations: CR2027WSA Model Predictions & Observations: CR2027

+ / — = Outward/(Inward) Footpoint Field Polarity

Cor

onal

Hol

esC

oron

al F

ield

(5.

0R)

Ph

otos

ph

eric

Fie

ld &

Cor

onal

Hol

e B

oun

dar

ies

NSO/SOLIS

Page 13: WSA Model and Forecasts

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Observed & Predicted IMF Polarity

Observed & Predicted Solar Wind Speed

Solar Wind Sources Near & Far From Active RegionsSolar Wind Sources Near & Far From Active RegionsWSA Model Predictions & Observations: CR2028WSA Model Predictions & Observations: CR2028

+ / — = Outward/(Inward) Footpoint Field Polarity

NSO/SOLIS

Cor

onal

Hol

esC

oron

al F

ield

(5.

0R)

Ph

otos

ph

eric

Fie

ld &

Cor

onal

Hol

e B

oun

dar

ies

Page 14: WSA Model and Forecasts

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Observed & Predicted IMF Polarity

Observed & Predicted Solar Wind Speed

+ / — = Outward/(Inward) Footpoint Field Polarity

NSO/SOLIS

Cor

onal

Hol

esC

oron

al F

ield

(5.

0R)

Ph

otos

ph

eric

Fie

ld &

Cor

onal

Hol

e B

oun

dar

ies

Solar Wind Sources Near & Far From Active RegionsSolar Wind Sources Near & Far From Active RegionsWSA Model Predictions & Observations: CR2029WSA Model Predictions & Observations: CR2029

Page 15: WSA Model and Forecasts

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1) The WSA model predicts ambient solar wind speed and IMF polarity 1-7 days in advance at L1.

Model validated using 8 years (~1 solar cycle) of predictions & the results are VERY encouraging.

2) Careful handing of the input photospheric magnetic field data is essential for improving the predictive success of the model. In particular,

• Monopole moments.• Polar fields.• Radial field Assumption.• Flux transport processes.

3) The ability of the WSA model to successfully predict solar wind speed appears to be a function of the proximity of its source regions to strong active regions. That is

If the source region is close to (far from) a strong active region, then the model’s speed predictions are generally poor (good).

Possible reasons why the model performs less well when the solar wind source lies near an active region.

- Fields near active regions are not potential, as the WSA model assumes. (MHD and/or Force Free coronal model could help here).

- The model assumes that the photospheric field is radial everywhere.

Observational evidence suggests this is generally true except in strong active regions! (Direct measurement of radial fields needed in active regions).

- A different empirical solar wind speed relationship is required near active regions.

SummarySummary

Page 16: WSA Model and Forecasts

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WSA Coronal - ENLIL MHD Solar Wind WSA Coronal - ENLIL MHD Solar Wind Model Coupling Model Coupling (A (A Joint AFRL-CISM Effort)Joint AFRL-CISM Effort)

Output of WSA MODEL Output of WSA MODEL (R = 21.5 (R = 21.5 RR))

Coronal Field Strength

Solar Wind Speed

ENLIL 3D MHD Solar Wind ModelENLIL 3D MHD Solar Wind Model

Output of ENLIL MODEL at 1AUOutput of ENLIL MODEL at 1AU

Page 17: WSA Model and Forecasts

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Schatten Current Sheet Model (SCS): 2.5 – 21.5 R

Potential Field Source Surface Model (PFSS): 1.0 – 2.5 R

Coupled Model: PFSS+SCSCoupled Model: PFSS+SCS

Schatten, 1971; Wang and Sheeley 1995

2.5 R

21.5 R

Solar Wind Model

(e.g., 1D Kinematic

model, ENLIL, HAF)

Page 18: WSA Model and Forecasts

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LOS B Field Remapped to Heliographic Coordinates

Model InputModel Input Magnetic Field Measurements at the PhotosphereMagnetic Field Measurements at the Photosphere

Courtesy Mount Wilson Solar Observatory

LOS Disk Image: Magnetograms

LOS B Field Remapped to Heliographic Coordinates & Converted to Radial

Page 19: WSA Model and Forecasts

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• Validated 8 years of WSA predictions • Mean Squared Error (MSE)

• 3 day old magnetograms give optimal prediction• No systematic time lag• Skill scores low on average (<10%)

Boston University Validation of WSA Boston University Validation of WSA ( Owens et al., JGR 2005)( Owens et al., JGR 2005)

MSE(A) < MSE(B)(Same for correlation coefficients)

Hypothetical Example

Courtesy Matt Owens (BU/CISM)

Page 20: WSA Model and Forecasts

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Validating Coronal Models Using Coronal HolesValidating Coronal Models Using Coronal Holes

Solar Minimum Solar Maximum Short After Solar Maximum

MAS/SAIC

de Toma, Arge, and Riley (2005)

Page 21: WSA Model and Forecasts

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Photospheric Field Synoptic Map TypesPhotospheric Field Synoptic Map Types

Page 22: WSA Model and Forecasts

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Solar Wind Speed Predictions & ObservationsSolar Wind Speed Predictions & Observations IMF Polarity Predictions & ObservationsIMF Polarity Predictions & Observations

Predictions & Observations:Near Solar MinimumPredictions & Observations:Near Solar Minimum

Page 23: WSA Model and Forecasts

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A Technique For Filling Missing Polar RegionsA Technique For Filling Missing Polar Regions

Boundary Values used to Fill Poles

•Pole

Equator

• Pole

Weighted mean of boundary values used to fill the poles. The weighting is function of inverse distance raised to some power.

Page 24: WSA Model and Forecasts

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Daily-Updated Synoptic Map With Poles FilledDaily-Updated Synoptic Map With Poles Filled

Pole filled using a “noisy” boundary.*

Pole filled using a “trimmed” boundary.*

*Note, the synoptic maps shown here are NOT from CR1921 or 1922 but illustrate well why filling the poles needs to be done very carefully!

Page 25: WSA Model and Forecasts

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Synoptic Map TypesSynoptic Map Types

  

DAILY UPDATED MAP

Longitude

Latitude

+90º

360º250º 250º

FULL CARRINGTON MAP

-90º

Cut fromPrevious

Map

0º347º

DAILY UPDATED MAP

New Magnetogram

Weighting Functions ~13º

Latitude

-90ºLongitude

+90º

347º 360º

Latitude

0º Longitude

+90º

360º-90º

347º

DAILY UPDATED FRAME MAP

Merged Field Data

Unmerged Field Data From Latest

Magnetogram

347º

Zhao Frame Method

(a)

(b)

(c)

Page 26: WSA Model and Forecasts

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Solar Wind Speed Predictions & Observations

IMF Polarity Predictions & Observations

Solar Wind Speed Predictions & Observations

IMF Polarity Predictions & ObservationsICME ICME

Solar Wind Predictions Using Photospheric Field Maps Solar Wind Predictions Using Photospheric Field Maps With Different Grid ResolutionsWith Different Grid Resolutions

5 Degree 2.5 Degree

Arge et al. 2005Arge et al. 2004

Page 27: WSA Model and Forecasts

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Observed & Predicted IMF Polarity

Observed & Predicted Solar Wind Speed

NSO/SOLIS

WSA Model Predictions & Observations: CR2018WSA Model Predictions & Observations: CR2018

+ / — = Outward/(Inward) Footpoint Field Polarity

Cor

onal

Hol

esC

oron

al F

ield

(5.

0R)

Ph

otos

ph

eric

Fie

ld &

Cor

onal

Hol

e B

oun

dar

ies