Habitability and the Evolution of Life Under Our Magnetic Shield

Abstract Examination of the temporal variability properties of several strong optical recombination lines in a large sample of Galactic Wolf–Rayet (WR) stars reveals possible trends, especially in the more homogeneous WC than the diverse WN subtypes, of increasing wind variability with cooler subtypes. This could imply that a serious contender for the driver of the variations is stochastic, magnetic subsurface convection associated with the 170 kK partial-ionization zone of iron, which should occupy a deeper and larger zone of greater mass in cooler WR subtypes. This empirical evidence suggests that the heretofore proposed ubiquitous driver of wind variability, radiative instabilities, may not be the only mechanism playing a role in the stochastic multiple small-scaled structures seen in the winds of hot luminous stars. In addition to small-scale stochastic behaviour, subsurface convection guided by a global magnetic field with localized emerging loops may also be at the origin of the large-scale corotating interaction regions as seen frequently in O stars and occasionally in the winds of their descendant WR stars.

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A multi-wavelength analysis of the WASP-12 planetary system

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311020126 ◽

2010 ◽

Vol 6 (S276) ◽

pp. 163-166 ◽

Cited By ~ 1

Author(s):

Luca Fossati ◽

Carole A. Haswell ◽

Cynthia S. Froning

Keyword(s):

Magnetic Field ◽

Atmospheric Pollution ◽

Planetary System ◽

Light Curves ◽

Absorption Lines ◽

Transiting Planets ◽

Multi Wavelength ◽

Global Magnetic Field ◽

Solar Type ◽

Solar Type Star

AbstractWASP-12 is a 2 Gyr old solar type star, hosting WASP-12b, one of the most irradiated transiting planets currently known. We observed WASP-12 in the UV with the Cosmic Origins Spectrograph (COS) on HST. The light curves we obtained in the three covered UV wavelength ranges, all of which contain many photospheric absorption lines, imply effective radii of 2.69±0.24 RJ, 2.18±0.18 RJ, and 2.66±0.22 RJ, suggesting that the planet is surrounded by an absorbing cloud which overfills the Roche lobe. We clearly detected enhanced transit depths at the wavelengths of the MgII h&k resonance lines. Spectropolarimetric analysis of the host star was also performed. We found no global magnetic field, but there were hints of atmospheric pollution, which might be connected to the very unusual activity of the host star.

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42. Solar cosmic radiation and the interstellar magnetic field

Symposium - International Astronomical Union ◽

10.1017/s0074180900237984 ◽

1958 ◽

Vol 6 ◽

pp. 404-419 ◽

Cited By ~ 1

Author(s):

A. Ehmert

Keyword(s):

Magnetic Field ◽

Solar Radiation ◽

Cosmic Radiation ◽

The Sun ◽

High Latitudes ◽

Narrow Angle ◽

The Earth ◽

Order Of Magnitude ◽

The Impact ◽

Impact Zones

The increase of cosmic radiation on 23 February 1956 by solar radiation exhibited in the first minutes a high peak at European stations that were lying in direct impact zones for particles coming from a narrow angle near the sun, whilst other stations received no radiation for a further time of 10 minutes and more. An hour later all stations in intermediate and high latitudes recorded solar radiation in a distribution as would be expected if this radiation fell into the geomagnetic field in a fairly isotropic distribution. The intensity of the solar component decreased at this time at all stations according to the same hyperbolic law (~t–2).It is shown, that this decreasing law, as well as the increase of the impact zones on the earth, can be understood as the consequence of an interstellar magnetic field in which the particles were running and bent after their ejection from the sun.Considering the bending in the earth's magnetic field, one can estimate the direction of this field from the times of the very beginning of the increase in Japan and at high latitudes. The lines of magnetic force come to the earth from a point with astronomical co-ordinates near 12·00, 30° N. This implies that within the low accuracy they have the direction of the galactic spiral arm in which we live. The field strength comes out to be about 0·7 × 10–6gauss. There is a close agreement with the field, that Fermi and Chandrasekhar have derived from Hiltner's measurements of the polarization of starlight and the strength of which they had estimated to the same order of magnitude.

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