1. Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena
Christina Chu
University of Alaska Fairbanks Geophysical Institute
GEM Student Tutorial 16 June 2013
Logo: gi
Picture: M. Jason Ahrns
Theoretical &experimental studies so far suggest 4 main classes of transient magnetopause/boundary layer processes
flux transfer events(FTEs)[ Russel and Elphic,1978, 1979; Cowley et al., 1991],
impulsive plasma penetration events(PTEs)[ Lemaire and Roth, 1978],
Solar wind pressure variations [Sibeck, 1990],
Kelvin-Helmholz instabilities [Wei et al., 1990].
Picture courtesy J. Ahrns

2. What Kinds of Phenomena?
Hot Flow Anomalies
Foreshock Bubbles
Density Holes
Magnetopause Reconnection
Kelvin Helmholtz
Flux Transfer Events
Topics in this powerpoint will be discussed in the GEM focus group “Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena”
Picture:
Why should we care?
Disruptions can be carried through bow shock
causes changes in magnetosheath
can lead to waves in the magnetopause
will affect ionosphere & thermosphere
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

3. Hot Flow Anomalies (HFAs)
Occur at the bow shock
Characterized by
Flow deflection
Temperature increase B
Schwartz et al. [1985] n v
Hot diamagnetic cavity=active current sheet=HFA
Let’s start with a specific phenomena, then examine its dayside MIT effects. The effects for most phenomena are very similar. Te
HFA Simulation from N. Omidi Ti
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

4. Hot Flow Anomaly Formation Theory
Solar wind discontinuity hits bow shock; convection E focuses ions into discontinuity
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:
Motional electric field points inward on the HFA on at least 1 side.
Beam-beam instabilities thermalized the two cold particle distributions, resulting in a single heated population within a cavity bounded by density and magnetic field strength enhancements.
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

5. 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 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

6. Foreshock Region Property of collisionless plasma shocks
Contains particles and waves associated with shock
ion foreshock
foreshock
e- foreshock
Bow shock
Now let’s talk about the foreshock.
For Earth, we’ve discussed IMF and bow shock. Particles travel earthward along field lines, are reflected back [sunwards] up along field lines. => forms foreshock.
E- foreshock is further upstream than ion foreshock bc e- are lighter mass (can travel further). High energy can go further upstream.
Note that foreshock boundary doesn’t line up with IMF, see next slide for explanation.
What causes waves in the foreshock?
foreshock is magnetically connected with the shock and populated with backstreaming particles.
The foreshock is a very dynamic region, where the interaction of backstreaming ions with the incoming solar wind generates ultralow frequency (ULF) waves (see the special issue of the Journal of Geophysical Research , 86 , 1981). The waves are generally nonlinear and
result in particle heating and acceleration. In the quasiparallel geometry, upstream ULF waves are convected to the shock and are responsible for the shock cyclic reformation.
The origin of the waves has been explained in terms of
kinetic instabilities [Gary , 1991; Blanco-Cano and Schwartz ,
1997] generated by foreshock ion distributions. Because the
waves propagate upstream in the plasma frame with a speed
much smaller than the upstream flow, they are convected
toward the shock by the solar wind and suffer a change in
their sense of polarization.
Blanco-cano paper: Foreshock waves: When thetavB = 0 , the dayside magnetosheath plasma is
hotter than when thetavB = 45 . Further, due to reconnection
and IMF draping, large structures with heated and compressed
plasma form downstream. In addition, flux transfer
events (FTE) are detected [Omidi et al. , 2004]. Although it
is beyond the scope of this work to discuss magnetospheric
features, it is important to mention that the asymmetry
observed on the magnetosphere tail arises because the radial
IMF produces two null points on the magnetopause, one on
the dayside and one on the nightside.
magnetosphere
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

7. Foreshock Phenomena Foreshock Cavities Foreshock Cavitions
Foreshock Compressional Boundaries
Foreshock Bubbles
Christina Chu University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

8. Foreshock Cavities [ Billingham et al. 2008] Formation:
Pressure of suprathermal ions within bundles of field lines connected to the bow shock causes bundles to expand outward
Compresses nearby plasmas and magnetic fields in regions of space not connected to the bow shock
Observe: Decrease in magnetic field and density. Can be flanked by regions of enhanced density and magnetic field strength.
Bulk flow nearly identical to the solar wind.
Temperature and pressure inside are only slightly greater than that in the solar wind
Hot, diffuse ions may be found inside cavities, but not outside
Events do not lie centered on IMF tangential discontinuities intersecting the bow shock
In observations for ~1-3 minutes
“foreshock crater” in Thomas and Brecht [1988] paper.
Filled with suprathermal ion population
ion populations never become nearly isotropic, ion
temperatures never reach the values previously reported
for HFAs, and pressures within the cavities are only slightly
greater than those outside.
292 foreshock
cavities in IMP-8 observations during a 7-month period
during Apparently, foreshock cavities are far more
common than HFAs.
It has been suggested that foreshock cavity suprathermal
particles may have been accelerated from the bow shock in
accordance with the Fermi model, mirroring from scattering
centres which are approaching one another. The efficiency
of the process depends only on the approach speed of the
scattering centres, so long as the bow shock is supercritical
and ion reflection at the shock significant. If the downstream
scattering centres are relatively static near the shock,
and the upstream scatterers are solar wind inhomogeneities,
the acceleration will be more efficient in higher speed solar
wind (see e.g. Scholer, 1985). The Mach number dependence
would be seen only in the form of a threshold above which
the shock is supercritical.
[Sibeck et al. 2002]
Schawrtz et al 2006
suprathermal: In plasmas, ions with characteristic velocities much larger than the characteristic local thermal (Maxwellian) velocity are known as fast ions, or, equivalently, superthermal or suprathermal ions. Fast ions can be created by beam injection, radiofrequency wave heating, fusion reactions, scattering from energetic photons (X rays or gamma rays), laser-plasma interactions, and other methods. The free energy in fast ion populations can drive plasma instabilities. In plasmas whose temperature is below the peak fusion reactivity, fast ions are more likely to produce fusion reactions, and one then distinguishes between thermonuclear reactions and beam-target reactions.
[ Billingham et al. 2008]
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

9. Foreshock Cavitons
Observations: always immersed in sea of compressive ULF waves
Decrease in magnetic field and density flanked by regions of enhanced density and magnetic field strength
Hot, diffuse ions may be found inside and outside cavitons (≤100keV)
≤1 minute in spacecraft observations
Simulations suggest they are produced by interaction of two wave modes:
parallel propagating sinusoidal plasma waves
oblique propagating linearly polarized fast magnetosonic waves
Irregular shapes, ~1-2RE
suprathermal ion fluxes
observed by Cluster also show that cavitons are immersed in
diffuse ion regions
do not
find any differences between the suprathermal ion pressure
inside the cavitons and at its surroundings. This is in contrast
to the results obtained for foreshock cavities, where the
suprathermal ion pressure is clearly enhanced inside the
cavity.
Blanco-Cano et al. [2009]
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

10. Foreshock Compressional Boundaries (FCB)
Simulations showing the foreshock compressional boundary at different Alfven mach numbers.
[Rojas-Castillo et al., 2013]
Omidi et al. [2009]
Formation: expansion of foreshock with strong wave particle interactions.
Density and magnetic field decrease below solar wind levels
Type of boundary:
Sometimes is transition region between the pristine solar wind plasma and foreshock plasma
At other times, it separates a region with large-amplitude waves from regions with high-frequency small-amplitude waves
Simulation results:
FCBs increase with increasing Mach number and exhibit a steepened, shock-like structure at large Mach numbers
FCB is not in general coincident with the ion beam or ULF boundaries
Global hybrid code model results
a bundle of IMF lines connected to the bow shock resulted in the formation of a convecting foreshock bounded by FCBs.
Variations of the IMF with time resulted in the back-and-forth motion of the FCB over the spacecraft, generating time series signatures consistent with foreshock cavities (Sibeck et al. [2008] suggested that the back-and-forth motion of the FCB over a spacecraft in response to varying IMF orientations would generate signatures in time series data similar to those observed during foreshock cavities)
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

11. Foreshock Bubbles (FB)
Formation: Rotational discontinuity in solar wind interacts with back- streaming ions in foreshock, causes deflections of back-streaming ions.
Omidi et al. [2010]
Observations:
Core: Depreressed density and magnetic field strength, deflected flow, increased temperatures
Can have compressions on upstream side
Turner et al. [2011]
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

12. 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.
Average spacecraft observation time: 20sec, have been reported for ~4sec duration.
Event lifetime unknown
Size: ~1 gyroradius
[Wilber et al., 2008]
Are different from hot flow anomalies
Density holes are shorter in duration than HFAs
Show more velocity variations than foreshock cavitons. (also can occur in pristine sw where cavitons cannot)
Christina Chu University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

13. Magnetic Field Decrease Density Decrease Flow Deflection
Temperature Increase
Solar Wind
HFA
Yes
Tangential discontinuity
Foreshock Cavity No
Pristine solar wind
Foreshock Caviton
ULF Waves
Foreshock Compressional Boundary
Expansion of foreshock with strong wave particle interactions
Foreshock Bubble
Rotational Discontinuity
Density Hole ?
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

14. Magnetic Reconnection
Dayside reconnection may be source of waves
Dayside magnetospheric boundary effects
plasma transport
particle entry and energization
diffusive processes
Dayside reconnection may be source of waves (ex near cusp region)
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

15. Magnetopause Reconnection
NIMF
SIMF
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

16. Magnetopause Reconnection
NIMF
SIMF
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

17. Magnetopause Reconnection
Total power in the magnetic field fluctuations Hz
These group of points are due to cavity movement for NIMF vs. SIMF (reconnection gives rise to MHD and ion cyclotron waves). Some points may be due to a gradient in the magnetic field strength when traveling from a cavity to surrounding regions and vice versa.
Cusp location may shift
Regions with high magnetic field fluctuations may shift
[Chu et al. 2010]
Christina Chu University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

18. Dayside Effects of Magnetopause Reconnection
Reconnection jets in magnetosheath
Precipitating protons into the atmosphere
Dayside proton auroral spots
Southward IMF: auroral oval near local noon is bright over a wide range of local times
Northward IMF: localized electron and ion spots of emission occurs poleward of the auroral oval
Sub-Alfvénic flows and a plasma depletion layer in the high latitude magnetosheath next to the MP (gas dynamic models predict super- Alfvénic flows)
The solar wind itself is a stream of hydrogen atoms, separated into their constituent protons and electrons. When electrons find routes into our atmosphere, they collide with and excite the atoms in the air. When these atoms release their energy, it is emitted as light, creating the glowing "curtains" we see as the aurora borealis in the far north and the aurora australis in the far south. Dayside proton auroral spots are caused by protons "stealing" electrons from the atoms in our atmosphere.
A bright proton spot poleward of the oval
appears at 14 MLT and 81 latitude.
Northward IMF: localized electron [Milan et al. , 2000] and ion [Frey et al. , 2002] spot of emission occurs poleward of the auroral oval
Reconnection changes TEC counts (TEC is measure of line of sight density)
[Phan et al., 2003]
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

19. Flux Transfer Events
From
Plasma within magnetosheath FTE's flows at or above the surrounding magnetosheath flow velocity
Mixture of magnetospheric and magnetosheath plasma.
Slide from zhang themis fte pdf,
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

20. Dayside Effects of Flux Transfer Events
Northward moving auroral structure with east-west motion that depends on IMF By [Karlson et al., 1996]
Magnetosheath ion injection
Plasma convection in ionosphere
Ion upflow from ionosphere in wake of FTE [Lockwood et al., 1988]
Bursts structured and rapid flow in high latitude dayside ionosphere [Todd et al., 1986]
FTEs have been observed at Mercury
Night
Auroral signature
Depends on IMF By
Positive By: moves into prenoon sector
Negative By: moves into postnoon sector
Moves to polar cap as FTE penetrates to lower L shells.
Todd keyword eiscat
Christina Chu University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

21. Kelvin-Helmholtz Kelvin-Helmholtz waves (KHW)and vortices
typically observed at magnetosphere flanks
Has also been reported at dayside near-cusp magnetopause [Hwang et al, 2012]
northward (IMF) conditions, which minimizes the magnetic tension forces
that stabilize the KHI at the subsolar side of the magnetopause
and LLBL. [Hasegawa et al., 2009; Fairfield et al., 2000,2007]
explanations for this preference have been
suggested, including: competition with a tearing mode that suppresses KHI development for large magnetic shear under
southward IMF [Chen et al. , 1993, 1997; Farrugia et al. ,
2003]; the formation of a slow rarefaction region with a
magnetic pressure maximum just inside the magnetopause
under southward IMF [Miura , 1995]; the formation of a thin
KH-unstable plasma sheet layer between the northern and
southern lobes during southward IMF that stabilizes the KHI
due to the intense lobe magnetic field [Hashimoto and
Fujimoto , 2005]; and, the formation of a dense LLBL resulting
from high-latitude reconnection that lowers the threshold
of the KHI during northward IMF [Hasegawa et al. , 2009].
The first in-situ observation of Kelvin-Helmholtz waves at high latitude magnetopause during strongly dawnward interplanetary magnetic field conditions ;
The dayside near-cusp magnetopause is
rarely unstable to the KHI mainly because to the intense geomagnetic
field (compared to that in the LLBL). Even though
the magnetic fields in the two velocity-shear, sub-boundary
layers are either parallel or antiparallel, if the wave vector
points significantly away from the direction perpendicular to
the two magnetic fields, large magnitudes of those magnetic
fields easily increase the right-hand term of equation (1),
resulting in the suppression of the generation of KHI
Inner boundary layer have abundant high energy particles, low density, high temperature.consistent with KHW at flank?
Vortices are generated in the Boundary layer of flanks giving rise to currents going into (out of) the ionosphere in the prenoon(postnoon) sector. Postnoon: votricity associated w/ accel e- and aurora between 1400 and 1600
[Hasegawa et al. 2001]
Christina Chu University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

22. Kelvin-Helmholtz Waves at High Latitude
Observed for north IMF
Properties depend on IMF orientation
Wavelengths are relatively smaller than those of KHW detected at the flank of the magnetopause near the dawn-dusk terminator
Observed global fluctuations of magnetopause
May play important role in particle and momentum transfer from the solar wind to the magnetosphere
[Hwang et al, 2012]
transiently enhanced
solar wind dynamic pressure implies that the
variations of the solar wind dynamic pressure have acted as a
seed fluctuation for the generation of the KHW
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

23. Dayside Response Bow shock ripples Magnetopause motion
Magnetopause deformation
Ionospheric disturbances related to FACs (TCVs, MIEs)
Compressional waves (equatorial regions)
Alfven waves (polar regions)
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

24. Bow Shock Ripples
Ripples in the contour of the bow shock can lead to high speed jets downstream (magentosheath). [Hietala et al. 2009]
Consider the streamlines of plasma flow across a curved high MA shock.
A shock primarily decelerates the component of the upstream velocity V1 parallel to the shock normal
A shock crossing leads to efficient compression and deceleration in regions where the angle α between V1 and the normal, n, is small.
Wherever α is large, the shock mainly deflects the flow while the plasma speed stays close to the upstream value.
The plasma is still compressed so that the higher density together with the high speed leads to a jet of very high dynamic pressure.
HFAs and FBs can deform the bow shock
Christina Chu University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

25. Ionospheric Observations of HFAs
HFAs deform the magnetopause and low-latitude boundary layer.
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)
Sometimes, brightening of dayside aurora is observed coincident with HFA/TCV signatures
Wong, C.Y.J. and Fillingim, M.O. [2011]
[Glassmeier et al., 1989; Sitar et al., 1998]
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

26. HFAs and Traveling Convection Vortices (TCVs)
TCV – electrodynamic coupling between dayside low latitude boundary layer (inner edge) and ionosphere.
Solar wind dynamic pressure changes produce small-scale ionospheric current systems
Observable in ground magnetometer data.
Ultraviolet imagers may detect intense TCVs
Downward flowing e- induce intense upward field-aligned currents. Ultraviolet imagers are sensitive to emissions produced by e- impact on N2.
Magnetometer data
Each row is data from a different station.
HFA interval highlighted in green.
UV emissions due to transient current system
UV intensification grows in strength and propagates westward.
[Sitar et al., 1998]
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

27. Thermosphere Response
Thermosphere density variation amplitude correlated to F10.7
F10.7 correlated to sunspot number
Sunspots are associated with faster solar wind
Fast solar wind speeds associated with higher occurrence of phenomena (ie HFAs, FBs)
May be thermosphere density response to phenomena in this presentation
1979 neutral density data black is data, red is best fit curve.
Christina Chu University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

28. Questions? Again, why should we care?
Solar wind disruptions (ie in density, magnetic field, etc.) can be carried through bow shock
causes changes in magnetosheath
can lead to waves in the magnetopause
causes phenomena in ionosphere & thermosphere
Questions?
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

29. Extra Slides Christina Chu University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

30. Identifying HFAs Proto HFA Mature HFA Bx, By, Bz B n vx, vy, vz
Young HFA
Mature HFA
Bx, By, Bz B n
vx, vy, vz
Ion Energy
Zhang et al. [2010]
e- Energy
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

31. Identifying HFAs Christina Chu
Zhang et al. [2010]
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

32. 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 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

33. 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 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

34. Saturn HFA Masters et al. [2009], Cassini 17 HFAs identified
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

35. 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 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

36. 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 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

37. 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 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

38. Foreshock Region -vxB=E ExB drift E Ecliptic plane
Le and Russell [1994]
-vxB=E E
ExB drift
Ecliptic plane
vxB sets up convection electric field.
ExB drift is reason why foreshock doesn’t extend all the way to the sun. Is also the reason why the sunward foreshock boundary is not aligned with IMF.
Christina Chu University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

39. Foreshock Cavities – some are encounters with ion foreshock boundary
Transient rotations in the IMF orientation can cause the edge of the foreshock to pass over a spacecraft and then return to its original position.
Spacecraft goes from pristine solar wind, into the foreshock, then back to solar wind.
Sibeck et al 2008
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

40. Foreshock Cavity Effects on Dayside
Pressure variations generated within the foreshock are transmitted downstream across the bow shock into the magnetosheath.
Changing pressures can drive magnetopause motion and trigger magnetopause reconnection, field aligned currents, TCVs.
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

41. Foreshock Caviton Effects on Dayside
Cavitons are carried by the solar wind through the bow shock where their properties may change leading to large density pulses in the magnetosheath that can cause surface waves in the magnetopause.
Global hybrid simulations [Lin and Wang 2005] have shown that cavitons can evolve into structures elongated along field lines
pressure pulses associated with foreshock cavitons cause strong surface perturbations on the magnetopause.
Blanco-Cano et al. [2011]
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

42. FCB Effects on Dayside
FCBs are convected by the solar wind and eventually crosses the bow shock
May cause bow shock ripples, magnetopause deformation, field aligned currents, TCVs.
[Rojas-Castillo et al., 2013]
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

43. Foreshock Bubble Effects on Dayside
Similar to HFAs, FBs should result in globally observable effects
Bow shock ripples
Magnetopause motion
Compressional waves
Ionospheric disturbances related to FACs.
Turner et al. [2011]
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

44. Magnetopause Reconnection Rates
Quasi-steady versus time dependent reconnection at the dayside magnetopause
Impacts of the bow shock/magnetosheath and the cusp/ionosphere systems on dayside magnetopause reconnection
Plasmaspheric plume touching the MP slows reconnection.
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

45. 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.
FTEs are found to travel along the magnetopause surface
ALSO good FTE explaination
Christina Chu University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

46. Shocklets
nonlinear evolution of oblique low-frequency electromagnetic (kinetic magnetosonic) waves, which have been observed upstream of planetary bow shocks and at comet Giacobini-Zinner.
Waves are elliptically polarized and have a sinusoidal form when their amplitude is small, but they become steepened and linearly polarized as they grow in amplitude
High-frequency whistler wave packet is commonly seen at the steepened edge of the shocklet
Steepening of kinetic magnetosonic waves into shocklets: Simulations and consequences for planetary shocks and comets
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

47. Short large-amplitude magnetic structures (SLAMS)
Foreshock phenomena
believed to steepen out of the background ULF wavefield due to the interaction with diffuse ions
left hand polarized in the plasma frame
elliptically polarized and compressive
characterized by brief (5– 20 s) monolithic spikes in magnetic field magnitude, with compression ratio (dB /B0 ) between 2 and 5 times the background field
2-3 RE
Have been seen at Venus
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

48. Solar Wind Pressure Pulses
Dynamic pressure variations of the solar wind drive large amplitude magnetopause motions, giving rise to a partial compression or relaxation of the magnetosphere
Perturbation in the Chapman-Ferraro current closes by field-aligned currents giving a twin-vortex system in the auroral ionosphere. As solar wind discontinuity sweeps over the dayside Magnetosphere morning and evening parts affected. The ionospheric signatures produced should appear as auroral events in both the Postnoon and prenoon sectors.
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

49. Impulsive Plasma Penetration Events
Plasma irregularities in solar wind with excess momentum density may under certain circumstances penetrate into magnetosphere.
If LLBL is penetrated, the ionospheric signatures would be on closed field lines. Motion of ionospheric footprints should be equatorward. Neg By favors prenoon, pos By favors postnoon.
PTEs move equatorward as they move to lower L shells.
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena

50. Plasma Entry to Mantle Mantle
de-energized magnetosheath plasma densities: 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, will observe decreasing energy and density (with deeper penetration into the mantle).
Christina Chu
University of Alaska Fairbanks
GEM 2013 Student Tutorial – Dayside MIT Response to Solar Wind, Bow Shock, Magnetopause Phenomena