The Magnetic Field of Massive Rotating Bodies*

Blackett, P. M. S.

doi:10.1038/159658a0

Cited by 253 publications

(91 citation statements)

References 21 publications

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“…The ram pressure of the solar wind depends on the star-planet distance d, while the size of the planet's magnetosphere is related to its magnetic moment. Blackett (1947) demonstrated that planetary-scale, dynamo-driven magnetic fields are scalable, with a functional dependence on body mass, radius, and angular frequency; and the presence of planetary-scale magnetic fields around the gas giants shows that his analysis does not depend on the actual composition of the conducting fluid in the planet's interior. Blackett's law relates a planet's magnetic moment (its surface field times its radius cubed, BR 3 ) to its rotation rate and mass by…”

Section: The Radiometric Bode's Lawmentioning

confidence: 99%

The Radiometric Bode’s Law and Extrasolar Planets

Lazio

Farrell

Dietrick³

et al. 2004

ApJ

124

177

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We predict the radio flux densities of the extrasolar planets in the current census, making use of an empirical relation-the radiometric Bode's law-determined from the five ''magnetic'' planets in the solar system (the Earth and the four gas giants). Radio emission from these planets results from solar wind-powered electron currents depositing energy in the magnetic polar regions. We find that most of the known extrasolar planets should emit in the frequency range 10-1000 MHz and, under favorable circumstances, have typical flux densities as large as 1 mJy. We also describe an initial, systematic effort to search for radio emission in low radio frequency images acquired with the Very Large Array (VLA). The limits set by the VLA images (%300 mJy) are consistent with, but do not provide strong constraints on, the predictions of the model. Future radio telescopes, such as the Low Frequency Array and the Square Kilometer Array, should be able to detect the known extrasolar planets or place austere limits on their radio emission. Planets with masses much lower than those in the current census will probably radiate below 10 MHz and will require a space-based array.

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Section: The Radiometric Bode's Lawmentioning

confidence: 99%

The Radiometric Bode’s Law and Extrasolar Planets

Lazio

Farrell

Dietrick³

et al. 2004

ApJ

124

177

View full text Add to dashboard Cite

show abstract

“…In the dynamo region the mass density is ρ c and the conductivity is σ. At least two further scaling laws exist, but they are of no relevance in this context: the first scaling ("Blackett's law") originally proposed by Blackett (1947) was based on a hypothesis that was later disproved experimentally. As a result, the theory was withdrawn (Blackett 1952).…”

Section: Effect Of Tidal Locking On Planetary Magnetic Momentsmentioning

confidence: 99%

The effect of tidal locking on the magnetospheric and atmospheric evolution of “Hot Jupiters”

Grießmeier

Stadelmann

Penz

et al. 2004

A&A

200

230

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Abstract. We study the interaction between the planetary magnetosphere and atmosphere of the close-in extrasolar planets HD 209458b and OGLE-TR-56b with the stellar wind during the evolution of their host stars. Recent astrophysical observations of solar-like stars indicate that the radiation and particle environments of young stars are orders of magnitudes larger than for stars with ages comparable to the sun (∼4.6 Gyr). We model the interaction for the present and for early evolutionary stages, showing that it is possible that "Hot Jupiters" have an ionosphere-stellar wind interaction like Venus. Our study suggests that the internal magnetic field of exoplanets orbiting close to their host stars may be very weak due to tidal locking. The magnetic moments can be less than one tenth of the value presently observed for the rapidly rotating planet Jupiter. We find that the stronger stellar wind of younger solar-type stars compresses the magnetosphere to a standoff distance at which the ionized part of the upper atmosphere, hydrodynamically expanded by the XUV-flux, builds an obstacle. Because of a much larger stellar wind particle flux during the first ∼0.5 Gyr after the host stars arrived on the Zero-Age-Main-Sequence, "Hot Jupiters" may have not been protected by their intrinsic magnetic fields, even if one neglects the effect of tidal locking. In such a case, the unshielded upper atmosphere will be affected by different ionization and non-thermal ion loss processes. This contributes to the estimated neutral hydrogen loss rates of about ≥10 10 g/s of the observed expanded exosphere of HD 209458b (Vidal-Madjar et al. 2003) and will be an ionized part of the estimated upper energy-limited neutral hydrogen loss rates of about 10 12 g/s (Lammer et al. 2003a).

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“…The observations and experiments supporting the S-B conjecture include the early work of Blackett [18] and Wilson [27]. Observational evidence for the S-B conjecture was compiled by Sirag [28], who compared the predictions of Eq.…”

Section: Nmgecmentioning

confidence: 99%

“…The Schuster-Blackett (S-B) conjecture [17,18] suggests a gravitational origin of the magnetic fields in rotating neutral bodies, i.e., a non-minimal gravitational-electromagnetic coupling (NMGEC). An early attempt to make a theory that encompasses the S-B conjecture was made by Pauli [19].…”

Section: Jhep00(2009)000mentioning

confidence: 99%

Origin of 10¹⁵–10¹⁶G magnetic fields in the central engine of gamma ray bursts

Opher¹

2010

J. Cosmol. Astropart. Phys.

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Various authors have suggested that the gamma-ray burst (GRB) central engine is a rapidly rotating, strongly magnetized, (∼ 10 15 − 10 16 G) compact object. The strong magnetic field can accelerate and collimate the relativistic flow and the rotation of the compact object can be the energy source of the GRB. The major problem in this scenario is the difficulty of finding an astrophysical mechanism for obtaining such intense fields. Whereas, in principle, a neutron star could maintain such strong fields, it is difficult to justify a scenario for their creation. If the compact object is a black hole, the problem is more difficult since, according to general relativity it has "no hair" (i.e., no magnetic field). Schuster, Blackett, Pauli, and others have suggested that a rotating neutral body can create a magnetic field by non-minimal gravitational-electromagnetic coupling (NMGEC).The Schuster-Blackett form of NMGEC was obtained from the Mikhail and Wanas's tetrad theory of gravitation (MW). We call the general theory NMGEC-MW. We investigate here the possible origin of the intense magnetic fields ∼ 10 15 −10 16 G in GRBs by NMGEC-MW.Whereas these fields are difficult to explain astrophysically, we find that they are easily explained by NMGEC-MW. It not only explains the origin of the ∼ 10 15 − 10 16 G fields when the compact object is a neutron star, but also when it is a black hole.

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The Magnetic Field of Massive Rotating Bodies*

Cited by 253 publications

References 21 publications

The Radiometric Bode’s Law and Extrasolar Planets

The Radiometric Bode’s Law and Extrasolar Planets

The effect of tidal locking on the magnetospheric and atmospheric evolution of “Hot Jupiters”

Origin of 10¹⁵–10¹⁶G magnetic fields in the central engine of gamma ray bursts

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The Magnetic Field of Massive Rotating Bodies*

Cited by 253 publications

References 21 publications

The Radiometric Bode’s Law and Extrasolar Planets

The Radiometric Bode’s Law and Extrasolar Planets

The effect of tidal locking on the magnetospheric and atmospheric evolution of “Hot Jupiters”

Origin of 1015–1016G magnetic fields in the central engine of gamma ray bursts

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Origin of 10¹⁵–10¹⁶G magnetic fields in the central engine of gamma ray bursts