Our changing Sun

Lockwood, Mike; Stamper, R.; Wild, M.; Balogh, A.; Jones, G. H.

doi:10.1093/astrog/40.4.4.10

Cited by 22 publications

(36 citation statements)

References 27 publications

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“…Subsequently, this result has been confirmed during the pole-to-pole "fast" latitude scan during the first perihelion pass and during the second ascent of Ulysses to the southern polar region (Lockwood et al (1999b) and Smith et al (2001), respectively). Recently, the second perihelion pass has underlined the generality of the result .…”

Section: Introductionmentioning

confidence: 60%

Open solar flux estimates from near-Earth measurements of the interplanetary magnetic field: comparison of the first two perihelion passes of the Ulysses spacecraft

et al. 2004

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Abstract.Results from all phases of the orbits of the Ulysses spacecraft have shown that the magnitude of the radial component of the heliospheric field is approximately independent of heliographic latitude. This result allows the use of nearEarth observations to compute the total open flux of the Sun. For example, using satellite observations of the interplanetary magnetic field, the average open solar flux was shown to have risen by 29% between 1963 and 1987 and using the aa geomagnetic index it was found to have doubled during the 20th century. It is therefore important to assess fully the accuracy of the result and to check that it applies to all phases of the solar cycle. The first perihelion pass of the Ulysses spacecraft was close to sunspot minimum, and recent data from the second perihelion pass show that the result also holds at solar maximum. The high level of correlation between the open flux derived from the various methods strongly supports the Ulysses discovery that the radial field component is independent of latitude. We show here that the errors introduced into open solar flux estimates by assuming that the heliospheric field's radial component is independent of latitude are similar for the two passes and are of order 25% for daily values, falling to 5% for averaging timescales of 27 days or greater. We compare here the results of four methods for estimating the open solar flux with results from the first and second perehelion passes by Ulysses. We find that the errors are lowest (1-5% for averages over the entire perehelion passes lasting near 320 days), for near-Earth methods, based on either interplanetary magnetic field observations or the aa geomagnetic activity index. The corresponding errors for the Solanki et al. (2000)

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Section: Introductionmentioning

confidence: 60%

Open solar flux estimates from near-Earth measurements of the interplanetary magnetic field: comparison of the first two perihelion passes of the Ulysses spacecraft

et al. 2004

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“…Lockwood et al (1999b) have shown that this was also true for the pole-to-pole fast-latitude perihelion pass. The result has been explained by and in terms of the pressure transverse to the flow in the expanding solar wind at r s between about 2.5 and 10R s (1R s is a mean solar radius) where the plasma beta is very low.…”

Section: Estimating the Coronal Source Fluxmentioning

confidence: 67%

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

Lockwood

2002

A&A

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Abstract. The correlation between the coronal source flux FS and the total solar irradiance ITS is re-evaluated in the light of an additional 5 years' data from the rising phase of solar cycle 23 and also by using cosmic ray fluxes detected at Earth. Tests on monthly averages show that the correlation with FS deduced from the interplanetary magnetic field (correlation coefficient, r = 0.62) is highly significant (99.999%), but that there is insufficient data for the higher correlation with annual means (r = 0.80) to be considered significant. Anti-correlations between ITS and cosmic ray fluxes are found in monthly data for all stations and geomagnetic rigidity cut-offs (r ranging from −0.63 to −0.74) and these have significance levels between 85% and 98%. In all cases, the fit is poorest for the earliest data (i.e., prior to 1982). Excluding these data improves the anticorrelation with cosmic rays to r = −0.93 for one-year running means. Both the interplanetary magnetic field data and the cosmic ray fluxes indicate that the total solar irradiance lags behind the open solar flux with a delay that is estimated to have an optimum value of 2.8 months (and is within the uncertainty range 0.8-8.0 months at the 90% level).

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“…The most direct method for computing open solar flux has been made possible by the discovery by the Ulysses spacecraft that the radial component of the heliospheric field is independent of heliographic latitude Lockwood et al, 1999b). This discovery has been explained in terms of the low plasma β of the expanding solar wind at around 1.5 R S <r<10 R S , where slightly non-radial flow allows the magnetic flux to redistribute itself, to give latitude-independent tangential magnetic pressure and thus a uniform radial field component (Suess and Smith, 1996).…”

Section: The Open Solar Magnetic Flux Estimatesmentioning

confidence: 99%

Oscillations in the open solar magnetic flux with a period of 1.68 years: imprint on galactic cosmic rays and implications for heliospheric shielding

Rouillard

Lockwood

2004

Ann. Geophys.

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Abstract. An understanding of how the heliosphere modulates galactic cosmic ray (GCR) fluxes and spectra is important, not only for studies of their origin, acceleration and propagation in our galaxy, but also for predicting their effects (on technology and on the Earth's environment and organisms) and for interpreting abundances of cosmogenic isotopes in meteorites and terrestrial reservoirs. In contrast to the early interplanetary measurements, there is growing evidence for a dominant role in GCR shielding of the total open magnetic flux, which emerges from the solar atmosphere and enters the heliosphere. In this paper, we relate a strong 1.68-year oscillation in GCR fluxes to a corresponding oscillation in the open solar magnetic flux and infer cosmic-ray propagation paths confirming the predictions of theories in which drift is important in modulating the cosmic ray flux.

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Our changing Sun

Cited by 22 publications

References 27 publications

Open solar flux estimates from near-Earth measurements of the interplanetary magnetic field: comparison of the first two perihelion passes of the Ulysses spacecraft

Open solar flux estimates from near-Earth measurements of the interplanetary magnetic field: comparison of the first two perihelion passes of the Ulysses spacecraft

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

Oscillations in the open solar magnetic flux with a period of 1.68 years: imprint on galactic cosmic rays and implications for heliospheric shielding

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