Long‐term variations in the magnetic fields of the Sun and the heliosphere: Their origin, effects, and implications

Lockwood, Mike

doi:10.1029/2000ja000115

Cited by 93 publications

(98 citation statements)

References 62 publications

(53 reference statements)

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“…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.…”

Section: Discussionmentioning

confidence: 72%

“…The 10 Be isotope is produced in the atmosphere as a spallation product when cosmic rays impact upon oxygen and nitrogen in the atmosphere. The precipitation into the ice sheets means that the abundances found there are convolved with a climate influence that could be a factor in the long-term variation (Beer 2000;Lockwood 2001). The 14 C isotope is, on the other hand, absorbed into tree rings directly in the gaseous state.…”

Section: Discussionmentioning

confidence: 99%

“…In these other cases, a long-term drift was superposed on an 11-year variation associated with the sunspot number, R. In order to quantify this long-term drift, Hoyt and Schatten used solar cycle length L, whereas Lean et al, Lean and Solanki and Fligge used the 11-year smoothed sunspot number, R 11 . Lockwood (2001) has pointed out that there is a strong correlation between the century-scale variations of F S , L and R 11 and thus it is not surprising that these reconstructions are similar in form. However, it M. Lockwood: An evaluation of the correlation between open solar flux and total solar irradiance 679 is surprising that the reconstructions also give similar amplitudes of the long-term drift: for example, Lean et al and Lean quantify this drift by comparison of non-cyclic stars with the Maunder-minimum Sun.…”

Section: Introductionmentioning

confidence: 99%

“…Given that cosmic ray fluxes are also strongly anticorrelated with the heliospheric field that shields the inner heliosphere (Cane et al 1999;Lockwood 2001), this also points to an underlying physical connection between irradiance and the open solar flux.…”

Section: Introductionmentioning

confidence: 99%

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

Lockwood

2002

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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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Section: Discussionmentioning

confidence: 72%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Lockwood

2002

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“…The flux threading r=2.5 R s is called the "coronal source flux" or the (unsigned) "open solar flux", F s . It is the total flux leaving the solar corona and entering the heliosphere by threading the hypothetical "coronal source surface", where the field is purely radial and which is usually taken to be approximately spherical and at r≈2.5 R s (Wang and Sheeley, 1995;Lockwood et al, 1999;Lockwood, 2001). If the averaging timescale is large enough for F o /F s to be considered negligible, the coronal source flux estimate can be obtained from:…”

Section: Introductionmentioning

confidence: 99%

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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Solar Outputs, Their Variations and Their Effects on Earth

Lockwood

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Long‐term variations in the magnetic fields of the Sun and the heliosphere: Their origin, effects, and implications

Cited by 93 publications

References 62 publications

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

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

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

Solar Outputs, Their Variations and Their Effects on Earth

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