summer thresher final presentation
TRANSCRIPT
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Categoriza*on of Cusp Structures in the Magnetosphere
Summer Thresher, Walla Walla University Mentors: Karlheinz Tra9ner and Bill Peterson
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What is the Magnetopause?
Magnetopause: the boundary between the solar wind and the geomagneBc field. • Equilibrium surface between two regimes. The inside dominated by the Earth’s magneBc field, the outside by solar wind plasma and magneBc field pressure.
Regions Magnetosphere • Plasma Sheet • RadiaBon Belts • LLBL: Low LaBtude
Boundary Layer • Cusp – Focus of
magnetopause magneBc field lines
• Bow shock • Solar Wind and IMF
Earth
(IMF)
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• The interplanetary magneBc field (IMF) merges with the geomagneBc field lines at the magnetopause.
• This allows solar wind plasma into the Earth’s magnetosphere, streaming into the cusps.
• ReconnecBon on the Dayside opens the magneBc field lines
• ReconnecBon on the nightside closes the field lines, injecBng the ions and electrons into the ionosphere, creaBng the aurora.
MagneBc ReconnecBon
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The Aurora • IMF opens field lines • Convected into the magneBc tail
• Nightside reconnecBon line (closes the field line)
• Field line retracts, plasma flows into the ionosphere
• Aurora created
• Coordinated campaign THEMIS satellites and All Sky Cameras
• Direct result of reconnecBon • Dynamics of aurora indicate how dynamic reconnecBon is
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ReconnecBon LocaBon
Southward IMF: Dayside -‐ equatorial IMF moves with the Solar Wind
• ReconnecBon has been observed in two primary regions. • LocaBon is determined by the direcBon of the IMF
S N
Northward IMF: Poleward of the Cusp. IMF moves against Solar Wind
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The angle of the IMF in a coordinate system aligned to the dipole field of the Earth.
Importance: • Parameter that organizes the informaBon best, will be used for
later tasks
IMF Clock Angle
z (N = 0°)
y `
θ
IMF
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Task I Objec*ves: • Use data from POLAR satellite, from March 1996 to December 1998.
• Categorize and organize cusp crossing data for specific cusp signatures and structures
• Combine cusp structures with solar wind data from the WIND spacecrac
• Locate any trends in the data and explain different features of reconnecBon
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Task I
Type 1: Smooth Single
Type 2: MulBple
Criteria for Type 1: Single Smooth • Smooth structure, no jagged peaks • No more than one dispersion per plot
Criteria for Type 2: MulBple • Contains the same smooth
dispersion as Type 1 • MulBple dispersions per plot • Dispersions separated by disBnct
spaBal gap
Types 1 & 2: • Caused by Southward IMF • ReconnecBon occurs on the Dayside • Fast ions arrive first, slow ions later
Task I
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Task I Type 4: • Caused by Northward IMF • ReconnecBon occurs poleward of the
cusps • Ions of all energies allowed, all are
slowed to approximately same velocity
Criteria for Type 4: Box • Flat top • Straight sides
Type 4: Box
Criteria for Type 3: Structured • “None of the above” • Does not meet criteria for Types 1, 2
or 4. • Can include pulsaBng reconnecBon
lines, or characterisBcs of the others
Type 3: Structured
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Task I Errors and Difficul*es • CategorizaBon subject to
interpretaBon.
• Vast quanBty of plots and
informaBon.
Results • “Smooth Single”
dispersions consistently posses clock angles between 220° and 270°
• Same dispersions also tend to occur around the Spring equinox (March 20th) of each year. WHY?!
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Task II Objec*ves: • Use a selected list of MP Shear Angle Plots from WIND
satellite (3/1996 – 12/1998) • Clock angles between 55° and 95°, 265° and 305°: transiBon
from S to N field • Remove plots with |Bx/B|> 0.7 • Find the transiBon region when the Southward dispersion
becomes the Northward box
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Task II Plot Details: • Northward shear angle plots • IMF draped over the geomagneBc field,
so you can see the angle between the field lines
• Clock angles between 55° and 95°, 265° and 305°
• Know South Dispersion, North Box • Test Bpping point as IMF moves from
South to North In the locaBon model, Bx/B values greater than 0.7 become messy. Remove them by separaBng plots into two separate categories:
• Events |Bx/B| ≤ 0.7 • Large IMF |Bx/B| > 0.7
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Task II Result: Many of the plots with Northern IMF angles possessed characterisBcs of dayside reconnecBon (S) not poleward (N). No clear range where the transiBon occurs from Smooth to Box.
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Task III Objec*ves: • Use POLAR color spectrograms (Task I plots) divided into 10
minute segments • Locate plots with any high flux “overlap” – indicates mulBple
reconnecBon lines • Combine plots with solar wind data to determine any trends
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Task III “Overlap Criteria” • Red areas (high flux) horizontally overlap other areas of red
• “Cords” of flux form disBnct lines – do not cross each other
• Different entry points of plasma along the MP
Results and Future Work: • Approximately 9.8% of the 10-‐mintue plots contain overlap, or
24.5% of the total events – lower than expected. • Calculate entry points and see how they line up
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Task IV Objec*ves: • Use data sets from Double Star satellites, which crossed the
MP at a reconnecBon lines • Using IDL program, created by my mentor, generate plots for
ACE and WIND satellites. • Compare predicBon models with the actual observed
locaBons of reconnecBon.
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Input data from both files, “33” and “110” as shown below.
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MP Shear Solar Wind
Bow Shock MP Plasma Beta
Plots Generated
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Generate and record values. Alfven Mach Number: • Based on Alfven velocity –a
characterisBc velocity in the plasma
• If the solar wind streaming around the MP becomes super-‐alfvenic reconnecBon locaBon becomes unstable.
• MA # > 1
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Examples: Good Plots Observed: 87.8°
ACE: 92.9°
Observed: 63.7° WIND: 78.2°
Observed: 154.1° ACE: 165.0°
Observed: 165.9° ACE: 165.8°
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Examples: Anomalies
Observed: 151.4° ACE: 127.9°
Observed: 153.5° WIND: 132.8° Observed: 176.1°
ACE: 112.5°
Observed: 50.3° ACE: 80.0°
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Task IV Errors and Difficul*es: • Forgexng to “print” plots • Not changing satellite posiBon acer every plot
Results: • Most plots agreed with the model’s predicBon • Anomalies in the plots had the same angles as the smooth
plots in Task I (220° to 270°). (We don’t get it…)
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Future Work
Last Week: • Fix some errors that sBll exist in Task IV • Tackle a new task laid out by my mentor
Distant Future Work: • Look more closely at all the data to determine trends • ConBnue to test and fix the predicBon model
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Acknowledgements • NSF and the CU-‐Boulder REU Program • Erin Wood and Marty Snow • Mentors: Karlheinz Tra9ner and Bill Peterson • LASP Community
References: Tra9ner, K. J., S. M. Petrinec, S. A. Fuselier, N. Omidi, and D. G., Sibeck (2012), Evidence of mul.ple reconnec.on lines at the magnetopause from cusp observa.ons, J. Geophys. Res., 117, A01213, doi:10.1029/2011JA017080.
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QuesBons?