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

44 Marco.Rademacher@inf.fu-berlin.de

Thank you!

kmur@kft.umcs.lublin.pl