1. Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures
Christina Chu
University of Alaska Fairbanks Geophysical Institute
GEM Student Tutorial 12 June 2012
Logo: gi
Picture: M. Jason Ahrns
Picture courtesy J. Ahrns

2. What Kinds of Phenomena?
Hot Flow Anomalies
Foreshock Bubbles, Cavities, Cavitons, Compressional Boundaries
Density Holes
Magnetopause Reconnection
Plasma Entry to Mantle
Flux Transfer Events
Topics in this powerpoint will be discussed in the GEM focus group “Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures”
Why should we care?
Disruptions can be carried through bow shock causing changes in magnetosheath which can lead to surface waves in the magnetopause
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

3. Hot Flow Anomalies (HFAs)
Occur at the bow shock
Characterized by
Flow deflection
Temperature increase
Schwartz et al. [1985]
Hot diamagnetic cavity=active current sheet=HFA
HFA Simulation from N. Omidi
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

4. Hot Flow Anomaly Formation Theory
Discontinuity in solar wind hits bow shock
Coupling between incoming solar wind beam and reflected ion beam = heating
HFA expands causing the signatures seen
Ni B vx Ti vy vz
and
Image:
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

5. Identifying HFAs Young/proto HFA Mature HFA Bx, By, Bz B n vx, vy, vz
Zhang et al. [2010]
Young/proto HFA
Mature HFA
Bx, By, Bz B n
vx, vy, vz
Ion E
e- E
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

6. Extraterresterial HFAs
Earth (intrinsic magnetic field)
Venus (no intrinsic magnetic field)
Mars (weak to no intrinsic magnetic field)
Saturn (intrinsic magnetic field)
Heliopause
Images:
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

7. Venus HFA Slavin et al. [2009], Messenger
Collinson et al. [2012], Venus Express
Centered on IMF discontinuity
Inward convective motional electric fields
Decreased core magnetic field
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

8. Mars HFA Øieroset et al. [2001], Mars Global Surveyor
Mars has no magnetopause – this eliminates HFA generation at planetary magnetopauses.
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

9. Saturn HFA Masters et al. [2009], Cassini 17 HFAs identified
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

10. HFA Simulated at Termination Shock
Giacalone and Burgess [2010]
2D hybrid simulation of heliospheric current sheet and termination shock
θCN = inclination of current sheet to shock normal
HFA formation θCN < 60°
Color indicates the final value of the total plasma density at the end of the simulation.
Blue corresponds to densities equal to the starting density whereas red indicates plasma density that is four times the starting density.
The direction of the magnetic field is indicated by the “+” (out of the page) and “-” (into the page)
Original density = blue
4 x original density = red
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

11. Ionospheric Observations of HFAs
Deformation of the magnetopause generates field-aligned currents (FACs) into the auroral ionosphere
FAC signatures are measured on the ground as magnetic impulse events (MIEs) or traveling convection vortices (TCVs) [Glassmeier et al., 1989; Sitar et al., 1998]
Sometimes, brightening of dayside aurora is observed coincident with HFA/TCV signatures
Wong, C.Y.J. and Fillingim, M.O. [2011]
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

12. HFAs: Some Open Questions
How are electrons being heated?
How do HFA structures evolve with time?
How do HFAs form?
Are they related to the quasi-parallel or to the quasi- perpendicular shock?
How do HFAs impact the magnetosphere and ionosphere?
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

13. Foreshock Region Property of collisionless plasma shocks
Contains particles and waves associated with shock
foreshock
Bow shock
magnetosphere
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

14. Foreshock Region E ExB Ecliptic plane
Le and Russell [1994] E
ExB
Ecliptic plane
Christina Chu University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

15. Foreshock Cavities Foreshock Caviton
Bulk flow nearly identical to the solar wind.
Decrease in magnetic field and density
Temperature and pressure inside are slightly greater than that in the solar wind.
Foreshock Caviton
Like foreshock cavity but is immersed in sea of ULF waves
Blanco-Cano et al. [2011]
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

16. Foreshock Compressional Boundaries
Simulations showing the foreshock compressional boundary at different Alfven mach numbers.
Formation: expansion of foreshock with strong wave particle interactions.
Associated with density and magnetic field decrease below solar wind levels.
Omidi et al. [2009]
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

17. Foreshock Bubbles
Omidi et al. [2010]
Turner et al. [2011]
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

18. Density Holes
Regions of space where the density suddenly falls by ten times but the temperature of the remaining gas leaps from 1e5 ºC to 1e7 ºC.
Are different from hot flow anomalies
Density holes are shorter in duration than HFAs
Christina Chu University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

19. Magnetopause Reconnection
Large-scale properties of reconnection at the magnetopause
The physics of magnetic reconnection at the dayside magnetopause
Quasi-steady versus time dependent reconnection at the dayside magnetopause
Plasma transport including particle entry and energization through reconnection and diffusive processes at the dayside magnetospheric boundary
Impacts of the bow shock/magnetosheath and the cusp/ionosphere systems on dayside magnetopause reconnection
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

20. Magnetopause Reconnection
NIMF
SIMF
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

21. Flux Transfer Events
ISEE 1 and 2 saw signatures that looked like multiple magnetopause crossings
It was determined that those signatures were magnetic ropes on the magnetosphere boundary
Plasma within magnetosheath FTE's flows at or above the surrounding magnetosheath flow velocity
Mixture of magnetospheric and magnetosheath plasma.
ALSO good FTE explaination
Christina Chu University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

22. Flux Transfer Events Slide from zhang themis fte pdf,
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

23. Questions? Again, why should we care?
Solar wind disruptions (ie in density, magnetic field, etc.) can be carried through bow shock causing changes in magnetosheath which can lead to surface waves in the magnetopause
Questions?
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

24. Extra Slides Christina Chu University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

25. Identifying HFAs Christina Chu
Zhang et al. [2010]
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

26. Flux Ropes in HFAs Flux Ropes
Helical field structures with core fields
Often have current sheets at edges (to separate it from the surrounding plasma)
Guide field is often present – creates twisted flux rope, with twist field wrapped around an axis of guide field
Mulligan, Russell, Luhmann [2000]
Interplanetary Magnetic Clouds: Statistical patterns and radial variations; mulligan, russell, luhmann
Russell and Elphic
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures

27. Plasma Entry to Mantle Mantle
de-energized magnetosheath plasma densities: few times cm-3
temperatures: ~100 eV
tailward flow velocities: km/s
Velocity Filter Effect
Low-energy ions (blue) take longer to mirror from the ionosphere than higher energy ions (red),
Low-energy ions are convected further across field lines,
As one moves towards the magnetosphere, have decreasing energy and density (with deeper penetration into the mantle).
Christina Chu
University of Alaska Fairbanks
GEM 2012 Student Tutorial – Transient Phenomena at the Magnetopause and Bow Shock and Their Ground Signatures