A doubling of the Sun's coronal magnetic field during the past 100 years

Abstract

Thin films of the high-temperature superconductor YBa 2 Cu 3 O 7 ؊ ␦ exhibit both a large critical current (the superconducting current density generally lies between 10 11 and 10 12 A m −2 at 4.2 K in zero magnetic field) and a decrease in such currents with magnetic field that point to the importance of strong vortex pinning along extended defects 1,2 . But it has hitherto been unclear which types of defect-dislocations, grain boundaries, surface corrugations and anti-phase boundaries-are responsible. Here we make use of a sequential etching technique to address this question. We find that both edge and screw dislocations, which can be mapped

An evaluation of the correlation between open solar flux and total solar irradiance

“…Recently, Solanki et al (2001) have extended this modelling to include flux emergence in ephemeral regions and to estimate the total photospheric flux. Interestingly, the variation in the total photospheric flux that they derive is very similar indeed in form to the open flux variation which again matches the open flux variation found by Lockwood et al (1999a). This work therefore implies that the open flux, despite being only a few percent of the total photospheric flux, may nevertheless be a valuable proxy for it.…”

“…The more detailed similarities between the two, however, imply that the open magnetic flux in some way quantifies both the spectrum of flux tube dimensions and the total flux of magnetic flux tubes threading the photosphere. Solanki et al (2000) obtained a good match to both the open flux variation derived by Lockwood et al (1999a) and to the cosmic ray flux variation inferred from the 10 Be cosmogenic isotope (Beer et al 2000;Lockwood 2001;McCracken & McDonald 2001) using a simple model of open flux emergence in active regions and its subsequent decay. Recently, Solanki et al (2001) have extended this modelling to include flux emergence in ephemeral regions and to estimate the total photospheric flux.…”

“…The coronal source flux has been estimated from a sequence of geomagnetic observations that extends back to 1868 (Lockwood et al 1999a): a physical link would mean that the correlation applies on century as well as decadal timescales, and so would allow us to use these F S data to make a definitive reconstruction of the long-term irradiance variation. Using the correlation to make a simple extrapolation based on the one parameter, F S , generated an irradiance reconstruction that was remarkably similar to others by Hoyt & Schatten (1993), , Lean et al (1995) and, in particular, by Lean (2000).…”

Solar Weather Event Modelling and Prediction

“…: -a proof of chaoticity based on the neutrino emission (Mandal and Raychaudhuri 2005); -the simulation of chaotically modulated stellar dynamos (Tobias et al 1995); -the evidence of a chaotic behaviour in the solar dynamo from the variations of the solar magnetic field in the last 100 years (Lockwood et al 1999); -the evidence of chaoticity from the analysis of the period and phase of the 88-year solar cycle (Feynman and Gabriel 2004); -the occurrence of grand minima/maxima driven by a stochastic/chaotic process (Usoskin et al 2007); -a model of chaotic reconnection due to fast mixing of vortex-current filaments (Yatsuyanagi et al 2000); -stochastic reconnection (Lazarian et al 2004). Mundt et al (1991) studied the variability of solar activity over long time scales, given semiquantitatively by measurements of sunspot numbers R z , as a nonlinear dynamical system and found a positive Lyapunov exponent indicating that the solar activity variability described by R z can be described as a low dimension non-linear chaotic system of dimension 2.3.…”

Commission 10: Solar Activity: (Activite Solaire)

“…The SOLERS22 International Workshop held at National Solar Observatory/Sacramento Peak during June 17-21, 1996 exhibited new results of solar irradiance measurements in a wide spectral range with instruments on board a series of satellites. Lockwood et al (1999) recently discovered that the total magnetic flux leaving the Sun has risen by a factor of 1.4 since 1964, and the increase since 1901 has been by a factor of 2.3. This increase has resulted in changes in heliospheric magnetic field, and then those in the Earth's climate (Svensmark and Friis-Christensen, 1997).…”