Origin of the Continuous Component of the Variation in the Solar and Stellar Activity Spectra

AbstractStellar activity has a particularly strong influence on planets at small orbital distances, such as close-in exoplanets. For such planets, we present two extreme cases of stellar variability, namely stellar coronal mass ejections and stellar wind, which both result in the planetary environment being variable on a timescale of billions of years. For both cases, direct interaction of the streaming plasma with the planetary atmosphere would entail servere consequences. In certain cases, however, the planetary atmosphere can be effectively shielded by a strong planetary magnetic field. The efficiency of this shielding is determined by the planetary magnetic dipole moment, which is difficult to constrain by either models or observations. We present different factors which influence the strength of the planetary magnetic dipole moment. Implications are discussed, including nonthermal atmospheric loss, atmospheric biomarkers, and planetary habitability.

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ROSAT observations of V471 Tauri, showing that stellar activity is determined by rotation, not age

Monthly Notices of the Royal Astronomical Society ◽

10.1046/j.1365-8711.1998.01607.x ◽

1998 ◽

Vol 297 (4) ◽

pp. 1145-1150 ◽

Cited By ~ 16

Author(s):

P. J. Wheatley

Keyword(s):

Stellar Activity

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Stellar activity, differential rotation, and exoplanets

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311015067 ◽

2010 ◽

Vol 6 (S273) ◽

pp. 89-95 ◽

Cited By ~ 1

Author(s):

A. F. Lanza

Keyword(s):

Time Series ◽

Differential Rotation ◽

Solar Irradiance ◽

Giant Planet ◽

Total Solar Irradiance ◽

Short Term ◽

Stellar Activity ◽

Transiting Planets ◽

Spot Model ◽

Spot Activity

AbstractThe photospheric spot activity of some of the stars with transiting planets discovered by the CoRoT space experiment is reviewed. Their out-of-transit light modulations are fitted by a spot model previously tested with the total solar irradiance variations. This approach allows us to study the longitude distribution of the spotted area and its variations versus time during the five months of a typical CoRoT time series. The migration of the spots in longitude provides a lower limit for the surface differential rotation, while the variation of the total spotted area can be used to search for short-term cycles akin the solar Rieger cycles. The possible impact of a close-in giant planet on stellar activity is also discussed.

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The stellar activity-rotation relationship revisited: Dependence of saturated and non-saturated X-ray emission regimes on stellar mass for late-type dwarfs

Astronomy and Astrophysics ◽

10.1051/0004-6361:20021560 ◽

2002 ◽

Vol 397 (1) ◽

pp. 147-157 ◽

Cited By ~ 479

Author(s):

N. Pizzolato ◽

A. Maggio ◽

G. Micela ◽

S. Sciortino ◽

P. Ventura

Keyword(s):

Stellar Mass ◽

Late Type ◽

Stellar Activity ◽

X Ray

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A four-dimensional random motion at finite speed

Journal of Applied Probability ◽

10.1239/jap/1165505211 ◽

2006 ◽

Vol 43 (4) ◽

pp. 1107-1118 ◽

Cited By ~ 10

Author(s):

Alexander D. Kolesnik

Keyword(s):

Brownian Motion ◽

Poisson Process ◽

Transition Density ◽

Random Motion ◽

Characteristic Functions ◽

Conditional Distributions ◽

Continuous Component ◽

Absolutely Continuous ◽

Finite Speed ◽

Uniform Law

We consider the random motion of a particle that moves with constant finite speed in the space ℝ4 and, at Poisson-distributed times, changes its direction with uniform law on the unit four-sphere. For the particle's position, X(t) = (X1(t), X2(t), X3(t), X4(t)), t > 0, we obtain the explicit forms of the conditional characteristic functions and conditional distributions when the number of changes of directions is fixed. From this we derive the explicit probability law, f(x, t), x ∈ ℝ4, t ≥ 0, of X(t). We also show that, under the Kac condition on the speed of the motion and the intensity of the switching Poisson process, the density, p(x,t), of the absolutely continuous component of f(x,t) tends to the transition density of the four-dimensional Brownian motion with zero drift and infinitesimal variance σ2 = ½.

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