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Magnetospheric protection of ``Hot Jupiters'': The key role of magnetodisks in scaling of a planetary magnetospheric obstacle. M. L. Khodachenko 1 , I. I. Alexeev 2 , E. Belenkaya 2 , H. Lammer 1 (1) Space Research Institute, Austrian Academy of Sciences, Graz, Austria,

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Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

Magnetospheric protection

of ``Hot Jupiters'':

The key role of magnetodisks in scaling

of a planetary magnetospheric obstacle

M. L. Khodachenko 1, I. I. Alexeev 2,

E. Belenkaya 2, H. Lammer 1

(1) Space Research Institute, Austrian Academy of Sciences, Graz, Austria,

(2) Institute of Nuclear Physics, Moscow State University, Moscow, Russia,


Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

usual Giants

Hot Jupiters

>0.2 MJ

< 0.3 AU

165 (29%)

Solar system

planets

? Evolution of planets

? Formation of terrestrial

type worlds

  • 33 planets, <10 mEarth

  • 11 planets, < 5 mEarth

  • 465 Exoplanetary systems

  • 556 Exoplanets

  • 57 Multiple Planetary systems

Super-Earths ?


Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

EXOBASE

●Stellar X-ray and EUV induced expansion of the upper atmospheres

Stellar XUV luminosity energy deposition to upper atmospheres


Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

Magnetically protected planet

Early Earth

present Earth

present Venus,

Mars, or Titan

Magnetically non-protected planet

●Soft X-ray and EUV induced expansion of the upper atmospheres

high thermal & non-thermal loss rates

The size of magneto-

sphere is a crucial

parameter

Thermal escape: particle energy > WESC

 Jeans escape–particles from “tails”

 hydrodynamic escape – all particles

Non-thermal escape:

 Ion pick-up

 Sputtering (S.W. protons & ions)

 Photo-chemical energizing & escape

 Electromagnetic ion acceleration


Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

Busse, F. H., Phys. Earth Planet. Int.,12, 350, 1976

Interval of possible values for

planetary magnetic dipole:

Mmax … Mmin

J.-M. Grießmeier, A&A, 2004, 425, 753

J.-M. Grießmeier,Astrobiology, 2005,5

Stevenson, D.J., Rep. Prog. Phys., 46, 555, 1983

Mizutani, H., et al., Adv. Space Res., 12, 265, 1992

Mizutani, H., et al., Adv. Space Res., 12, 265, 1992

Sano, Y., J. Geomag. Geoelectr, 45, 65, 1993

●Magnetic moment estimation from scaling laws  range for possible M

rc - radius of the dynamo region (“core radius”): rc ~ MP0.75 RP-0.96

c - density in the dynamo region

- conductivity in the dynamo region

 - planet angular rotation velocity


Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

●Magnetic moment estimation from scaling laws  range for possible M

 Limitation of Mby tidal locking [Grießmeier, J.-M., et al., Astrobiology, 5(5), 587, 2005]

Tidal locking strongly reduced magnetic moments

HD 209458b : M = (0.005 … 0.10) MJup


Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

●Non-thermal mass loss of a Hot Jupiter with a dipole type magnetosphere

(a problem of protection against of strong atm. erosion)

Khodachenko et al., PSS, 55, 631, 2007; Khodachenko et al., Astrobiology, 7, 167, 2007

CME induced H+ ion pick-up loss at 0.05 AU for ‘Hot Jupiters’  HD209458 b

Mass loss ~1011 g/s even for weak CMEs & Mmax strong magn. protection in reality


Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

J.-M. Grießmeier, A&A, 2004, 425, 753

Relatively large amount of observed Hot Jupiters (29%):

”survival” of close-in giants indicates their efficient protection against of

extreme plasma and radiation conditions

All estimations were based on too simplified model

Magnetospheric protection of exoplanets was studied assuming a simple

planetary dipole dominated magnetosphere

 dipole mag. field B = Bdip ~ M / r3 balances

stellar wind ram pressure

 big M are needed for the efficient protection

(but tidal locking  small M  small Rs)

Specifics of close-in exoplanets  new model

 strong mass lossof a planet should lead to formation of a plasma disk

(similar to Jupiter and Saturn)  Magnetodisk dominated magnitosphere

 more complete planetary magnetosphere model, including the whole

complex of the magnetospheric electric current systems


Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

●Paraboloid Magnetospheirc Model (PMM) for ‘Hot Jupiters’

Semi-analytical model. Key assumption: magnetopause is approximated by

paraboloid of revolution along planet-star (VSW) line

PMM considers mag. field of different currentsystems on the boundaries

and within the boundaries of a planetary magnetopause:

 planetary magnetic dipole;

 current system of magnetotail;

 magnetodisk;

 magnetopause currents;

 magnetic field of stellar wind,

partially penetrated into the

magnetospheric obstacle.

I.Alexeev, 1978, Geomag.&Aeronomia, 18, 447.

I.Alexeev et al., 2003, Space Sci. Rev., 107, 7.

I.Alexeev, E.Belenkaya, 2005, Ann. Geophys., 23, 809.

M.Khodachenko et al., ApJ, 2011 (submitted)


Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

●Paraboloid Magnetospheirc Model (PMM) for ‘Hot Jupiters’

Formation of magnetodisk

 “sling” model:

dipole mag. field can drive plasma

in co-rotation regime only inside

“Alfvenic surface” (r < RA); Centrifugal

inertial escape of plasma for r>RA

 “material-escape driven” models:  Hydrodynamicescape of plasma

(a) Fully ionized plasma outfow – Similarity with

heliospheric current sheet (disk)

(b)Partially ionized material outflow

Background magn.field (dipole),

charge separation electric field,

ambipolar diffusion, azimuth.Hall

current in equator.plane


Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

RA

●Paraboloid Magnetospheirc Model (PMM) for ‘Hot Jupiters’

Formation of magnetodisk – “sling” model (analogy with the Jupiter):

 “Alfvénic surface” radius RA

Co-rotation until = ,

RA:

 is estimated from thermal mass loss

Increase of and  decrease of RA


Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

scaled in Jovian parameters

 Increase of ωp , dMp(th) /dt  increase of RS

●Paraboloid Magnetospheirc Model (PMM) for ‘Hot Jupiters’

Magnetic field structure in PMM with magnetodisk

 r < RA: magnetic field of dipole (~R-3)

 r > RA: conservation of m.flux reconnected across the disc

 m.field of the disk (and current density)~R-2

Determination of sub-stellar magnetopause distance:

pressure balance condition

 Decrease of RA increase of RS


Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

●Paraboloid Magnetospheirc Model (PMM) for ‘Hot Jupiters’

Magnetosphere at 0.045 AU, RS = 8.0 RJ (tidally locked)

Magnetosphere at 0.3 AU, RS = 24.2 RJ (tidally un-locked)


Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

●Paraboloid Magnetospheirc Model (PMM) for ‘Hot Jupiters’

 magnetospheric parameters (estimated and calculated)

(Jupiter)


Magnetospheric protection of hot jupiters the key role of magnetodisks in scaling

Magnetodisks of close-in giant exoplanets (Hot Jupiters) influence

the structure and character of their manetospheres, leading to a new

type of „magnetodisk dominated“ magnetosphere.

Extended up to (40 – 70) % magnetodisk magnetospheres, as compared

the to dipole type ones, may efficiently protect planetary environments,

even close to a host star.