solar wind interaction with the comet halley and venus k. murawski university of m. curie...
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Solar wind interaction with the comet Halley and
Venus
K. MurawskiUniversity of M. Curie Skłodowska
Outline
• Overview of solar wind interaction with magnetic and non-magnetic bodies
• Numerical simulations of the solar wind interaction with Venus
• Numerical simulations of the solar wind interaction with the comet Halley
• Summary
A global view of the Heliosphere
Solar system - Icy Matter ...
Jan Oort’s Cometary Cloud
Outskirts of the Solar system - Comets
Properties of the solar wind
1 AU
ne
≈ 5 cm-3
T ≈ 105 K |B
IMF| ≈ 5 nT
vsw
≈ 400 km/s v
A≈ 30 - 50 km/s
cS
≈ 60 km/s
highly conducting plasmahighly conducting plasma
electrons, protons + alpha-particleselectrons, protons + alpha-particles
radial expansionradial expansion
magnetic field “frozen” in the plasmamagnetic field “frozen” in the plasma
SW = super-sonic + super-alfvénicSW = super-sonic + super-alfvénic
InterplanetaryMagnetic
FieldPlanetary Obstacle
Radial PlasmaOutflow
SolarRotation
TYPES OF INTERACTION TYPES OF INTERACTION WITH THE SOLAR WINDWITH THE SOLAR WIND
INTERNALINTERNALMAGNETIC MAGNETIC
FIELDFIELDATMOSPHEREATMOSPHERE
VENUSVENUS
MARSMARS
EARTHEARTH
EARTH'S EARTH'S MOONMOON
MERCURMERCURYY
COMETSCOMETS
SATURNSATURN
JUPITERJUPITER
URANUSURANUS
NEPTUNNEPTUN
GANIMEDE
Simplest case:Simplest case:Earth's MOONEarth's MOON
NONO magnetic field magnetic fieldNONO atmosphere atmosphere
MOON – typeMOON – type no magnetic fieldno magnetic field
negligibly thin atmospherenegligibly thin atmosphere
insulating materialinsulating material
submerged in a flowing plasmasubmerged in a flowing plasma
absorptionabsorption of particles of particles
no bow shockno bow shock upstream upstream
plasma – absorption plasma – absorption wakewake
magnetic field magnetic field parallelparallel to the upstream flow → to the upstream flow → no effectno effect
magnetic field magnetic field perpendicularperpendicular to the flow to the flow → → minimal effectminimal effect
Illustration of the interplanetary plasma flow and magnetic-field perturbation by the nonconducting moon. The wake created by solar-wind absorption closes more quickly when the magnetic field is not aligned with the undisturbed flow.
SW interactions with SW interactions with magnetizedmagnetized bodiesbodies
and an and an atmosphereatmosphere
Obstacle = magnetosphereObstacle = magnetosphere
EARTH – type (Jupiter, Saturn)
Plasma structures of the Earth's magnetosphere
bow shock magnetosheath
magnetopause
cusp
lobes
neutral sheettrapping region
plasma sheet
ionosphere
plasmasphere
solar wind
strong magnetic fieldstrong magnetic field
substantial atmospheresubstantial atmosphere
SW interactions with SW interactions with magnetizedmagnetized bodiesbodies
but without an atmospherebut without an atmosphere
Obstacle = magnetosphereObstacle = magnetosphere
MERCURY - typeMERCURY - type strong magnetic fieldstrong magnetic field
no gravitationally bound atmosphereno gravitationally bound atmosphere
Plasma structures of the Mercury's magnetosphere
magnetosheath
lobes
magnetopausebo
w shoc
k
cusp
solar wind
SimilaritiesSimilarities and and differencesdifferences with Earthwith Earth
MagnetosphereMagnetosphere Absence of an atmosphere Absence of an atmosphere
and ionosphereand ionosphere Solar wind conditionsSolar wind conditions Mercury has a larger Mercury has a larger
fractional volume of its fractional volume of its magnetospheremagnetosphere no stable trapping regionsno stable trapping regions closed magnetic flux tubesclosed magnetic flux tubes
Solar wind – primary source Solar wind – primary source of magnetospheric plasmaof magnetospheric plasma
Plasma sheet – higher Plasma sheet – higher densitiesdensities 0.382 AU
Mercury
COMETSCOMETS
NONO internal internal magnetic fieldmagnetic fieldbut atmospherebut atmosphere
Obstacle = exosphereObstacle = exosphere
What is Solar Wind?COMETS
Comet Structure
• Nucleus: main solid core of the comet.
• Tail: gas and dust particles released by the comet.
• Coma: gases and dust released by the comet when energy from the sun heats the comet and causes the solid materials to turn into a gas.
Comet Tails• Comets develop tails
only when the get close enough to the Sun.
• Comet tails always point away from the Sun—This is how scientists first realized the existence of solar wind.
Comet – type Comet – type no internal magnetic fieldno internal magnetic field
substantial atmospheresubstantial atmosphere
Solar WindContact SurfaceNucleus
Cometo-pause
Bow Shock
Ionosphere
Numerical model - MHD
Numerical results
Numerical results
Numerical results
Numerical results
Numerical results
Numerical results
SW interactions with SW interactions with unmagnetizedunmagnetized bodies bodies
with a substantial with a substantial atmosphereatmosphere
Obstacle = ionosphereObstacle = ionosphere
Venus
VENUS – typeVENUS – type
weak magnetic field or non at allweak magnetic field or non at all
substantial atmospheresubstantial atmosphere
Illustration of the steps that lead to the formation of an ionospheric planetary obstacle in a flowing plasma like the solar wind. Ionization by solar radiation, for example, is followed by diversion of the external plasma flow only if that flow is magnetized.
Planetary Atmosphere
(neutral atoms and molecules)
Ionosphere (photoions)
Solar radiation
Solar Wind Wake
Bow Shock
Interplanetary Magnetic Field Magnetosheath
induced Magnetotail
Ionosphere
Magnetic Barrier
Structure of the Ionosphere
Brace and Kliore, 1991
Location of the obstacle Location of the obstacle boundaryboundary
ionospheric ionospheric pressure pressure
nnii k T k Tii
Bow Shock
Magnetic Field Lines
Magnetic Barrier
Ionosphere
Streamlines of Solar Wind Plasma Flow
Ionopause
external pressureexternal pressurennswswkTkTswsw + + ρvρv22 + + BB22 / 2μ / 2μ
00
thermal pressure
solar wind dynamic pressure
magnetic pressure of the interplanetary magnetic
field
Induced magnetotailInduced magnetotail
Bow Shock
Magnetotail
Z_vso
X_vsoY_vso
Pick – up and escape Pick – up and escape processesprocesses
Illustration of planetary pickup – ion trajectories of Venus. The cycloid sizes are approximately scaled for O+ (oxygen is the main constituent of the Venus upper atmosphere).
Photoion
Escape
Energetic neutral atoms
(ENAs)Escape
Ionospheric magnetic fieldIonospheric magnetic field
Examples of observed altitude profiles for the ionospheric electron densities (points) and magnetic fields (solid line) at Venus. The ionopause is located where the magnetosheath field decreases and the plasma density increases.
Orbit 186 Orbit 177 Orbit 176
Iono-pause
Iono-pause
Iono-pause
Ne(cm-3)
2001601208010060201006020 80400 0 40 80100
500
400
300
200
Alt
itu
de
(km
)
102 105104103 106 102 105104103 106102 105104103 106
Number Density (cm-3)
Alt
itud
e (K
m)
Solar wind
Numerical model - Draping magnetic field lines
Physical model – 2 component MHD
Parameters of the physical model
Pressure distribution
bow shockionosphere
magnetic barrier
IMF
Interaction region
Pressure profiles in the subsolar region
X
Plasma profiles
X
Magnetic field lines and nightside ionosphere
IMF
Solar wind
X
Z
Y
XZ plane
XY plane
Concluding remarksConcluding remarks Flowing plasma interactions with various types of Flowing plasma interactions with various types of
magnetized magnetized planets orplanets or
unmagnetizedunmagnetized / weakly magnetized bodies / weakly magnetized bodies
Each plasma interaction has Each plasma interaction has distinctive featuresdistinctive features
EarthEarth: : magnetic field and atmospheremagnetic field and atmosphere
MercuryMercury: : magnetic field but NO atmospheremagnetic field but NO atmosphere
Moon like bodiesMoon like bodies: : neither a magnetic field nor an atmosphereneither a magnetic field nor an atmosphere
VenusVenus and and MarsMars: : no internal magnetic field but a substantial no internal magnetic field but a substantial atmosphereatmosphere
CometsComets: : atmospheres with insignificant bodiesatmospheres with insignificant bodies