THE ACCURACY OF USING THEULYSSESRESULT OF THE SPATIAL INVARIANCE OF THE RADIAL HELIOSPHERIC FIELD TO COMPUTE THE OPEN SOLAR FLUX

2009 ◽  
Vol 701 (2) ◽  
pp. 964-973 ◽  
Author(s):  
M. Lockwood ◽  
M. Owens
Keyword(s):  
Solar Flux ◽  
Spatial Invariance ◽  
Open Solar Flux

THE RISE AND FALL OF OPEN SOLAR FLUX DURING THE CURRENT GRAND SOLAR MAXIMUM

2009 ◽  
Vol 700 (2) ◽  
pp. 937-944 ◽  
Author(s):  
M. Lockwood ◽  
A. P. Rouillard ◽  
I. D. Finch
Keyword(s):  
Solar Maximum ◽  
Solar Flux ◽  
Open Solar Flux

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

2004 ◽  
Vol 22 (4) ◽  
pp. 1395-1405 ◽  
Author(s):  
M. Lockwood ◽  
R. B. Forsyth ◽  
A. Balogh ◽  
D. J. McComas
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Magnetic Fields ◽  
Interplanetary Magnetic Field ◽  
Radial Component ◽  
Solar Flux ◽  
Interplanetary Magnetic Fields ◽  
Sunspot Minimum ◽  
Open Flux ◽  
Open Solar Flux

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 near-Earth 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) model are of the order of 9–15% and for the PFSS method, based on solar magnetograms, are of the order of 13–47%. The model of Solanki et al. is based on the continuity equation of open flux, and uses the sunspot number to quantify the rate of open flux emergence. It predicts that the average open solar flux has been decreasing since 1987, as is observed in the variation of all the estimates of the open flux. This decline combines with the solar cycle variation to produce an open flux during the second (sunspot maximum) perihelion pass of Ulysses which is only slightly larger than that during the first (sunspot minimum) perihelion pass. Key words. Interplanetary physics (interplanetary magnetic fields) – Solar physics, astrophysics and astronomy (magnetic fields)

scholarly journals Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr – Part 4: Near-Earth solar wind speed, IMF, and open solar flux

2014 ◽  
Vol 32 (4) ◽  
pp. 383-399 ◽  
Author(s):  
M. Lockwood ◽  
H. Nevanlinna ◽  
L. Barnard ◽  
M. J. Owens ◽  
R. G. Harrison ◽  
...  
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Geomagnetic Activity ◽  
Solar Wind Speed ◽  
Flow Speed ◽  
Solar Flux ◽  
Solar Wind Flow ◽  
Ap Index ◽  
Aa Index ◽  
Open Solar Flux

Abstract. In the concluding paper of this tetralogy, we here use the different geomagnetic activity indices to reconstruct the near-Earth interplanetary magnetic field (IMF) and solar wind flow speed, as well as the open solar flux (OSF) from 1845 to the present day. The differences in how the various indices vary with near-Earth interplanetary parameters, which are here exploited to separate the effects of the IMF and solar wind speed, are shown to be statistically significant at the 93% level or above. Reconstructions are made using four combinations of different indices, compiled using different data and different algorithms, and the results are almost identical for all parameters. The correction to the aa index required is discussed by comparison with the Ap index from a more extensive network of mid-latitude stations. Data from the Helsinki magnetometer station is used to extend the aa index back to 1845 and the results confirmed by comparison with the nearby St Petersburg observatory. The optimum variations, using all available long-term geomagnetic indices, of the near-Earth IMF and solar wind speed, and of the open solar flux, are presented; all with ±2σ uncertainties computed using the Monte Carlo technique outlined in the earlier papers. The open solar flux variation derived is shown to be very similar indeed to that obtained using the method of Lockwood et al. (1999).

scholarly journals Centennial changes in the solar wind speed and in the open solar flux

2007 ◽  
Vol 112 (A5) ◽  
pp. n/a-n/a ◽  
Author(s):  
A. P. Rouillard ◽  
M. Lockwood ◽  
I. Finch
Keyword(s):  
Solar Wind ◽  
Wind Speed ◽  
Solar Wind Speed ◽  
Solar Flux ◽  
Open Solar Flux
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