Correlation of ICME Magnetic Fields at Radially Aligned Spacecraft     

S. W. Good  R. J. Forsyth  J. P. Eastwood  C. Möstl 《Solar physics》2018,293(3):52

The magnetic field structures of two interplanetary coronal mass ejections (ICMEs), each observed by a pair of spacecraft close to radial alignment, have been analysed. The ICMEs were observed in situ by MESSENGER and STEREO-B in November 2010 and November 2011, while the spacecraft were separated by more than 0.6 AU in heliocentric distance, less than 4° in heliographic longitude, and less than 7° in heliographic latitude. Both ICMEs took approximately two days to travel between the spacecraft. The ICME magnetic field profiles observed at MESSENGER have been mapped to the heliocentric distance of STEREO-B and compared directly to the profiles observed by STEREO-B. Figures that result from this mapping allow for easy qualitative assessment of similarity in the profiles. Macroscale features in the profiles that varied on timescales of one hour, and which corresponded to the underlying flux rope structure of the ICMEs, were well correlated in the solar east–west and north–south directed components, with Pearson’s correlation coefficients of approximately 0.85 and 0.95, respectively; microscale features with timescales of one minute were uncorrelated. Overall correlation values in the profiles of one ICME were increased when an apparent change in the flux rope axis direction between the observing spacecraft was taken into account. The high degree of similarity seen in the magnetic field profiles may be interpreted in two ways. If the spacecraft sampled the same region of each ICME (i.e. if the spacecraft angular separations are neglected), the similarity indicates that there was little evolution in the underlying structure of the sampled region during propagation. Alternatively, if the spacecraft observed different, nearby regions within the ICMEs, it indicates that there was spatial homogeneity across those different regions. The field structure similarity observed in these ICMEs points to the value of placing in situ space weather monitors well upstream of the Earth.  相似文献   

Rotational period of WD 1953–011– a magnetic white dwarf with a star-spot     

C. S. Brinkworth  T. R. Marsh  L. Morales-Rueda  P. F. L. Maxted  M. R. Burleigh  S. A. Good 《Monthly notices of the Royal Astronomical Society》2005,357(1):333-337

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Comparison of the effective temperatures, gravities and helium abundances of DAO white dwarfs from Balmer and Lyman line studies     

S. A. Good  M. A. Barstow  J. B. Holberg  D. K. Sing  M. R. Burleigh  P. D. Dobbie 《Monthly notices of the Royal Astronomical Society》2004,355(3):1031-1040

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Dual-Temperature Acceleration Radiation     

Good  M. R. R.  Mitra  A.  Zarikas  V. 《Astronomy Reports》2021,65(10):942-946

Astronomy Reports - We solve for a system that emits acceleration radiation at two different temperatures. The equilibrium states occur asymptotically in Planck distributions and transition...  相似文献   

FUSE observations of PG1342+444: new insights into the nature of the hottest DA white dwarfs     

M. A.Barstow  S. A.Good  J. B.Holberg  M. R.Burleigh  N. P.Bannister  I.Hubeny  R.Napiwotzki 《Monthly notices of the Royal Astronomical Society》2002,330(2):425-434

We present Far Ultraviolet Spectroscopic Explorer ( FUSE ) observations of the very hot  (T_eff≈60 000 K)  DA white dwarf PG1342+444, describing our data reduction and analysis techniques. The spectrum reveals a number of photospheric absorption lines from high ionization species along with numerous interstellar features. The photospheric detections include the 1031.9- and 1037.0-Å O  vi lines which are seen for the first time in a hot DA atmosphere and are usually associated with the much hotter PG1159 stars and so-called O  vi  central stars of planetary nebulae. Estimates of the stellar effective temperature made independently using both the Balmer and Lyman series lines are in disagreement  (T_eff≈67 000  and ≈54 000 K respectively), when taking into account just the statistical uncertainties in the analyses. However, the presence of weak absorption from the C  iii multiplet near 1176 Å, which is predicted to be much stronger if the star were as cool as the Lyman measurement suggests, leads us to favour the higher temperature. PG1342+444 appears to have enhanced C, Fe and Ni abundances in its atmosphere compared with all the other G191−B2B-like DA white dwarfs, which might affect the temperature structure of the atmosphere if not homogeneously distributed, as assumed in this study.  相似文献   

Comparisons of VHF radar,optical, and temperature fluctuation measurements ofC n 2 ,r 0 andθ 0     

Eaton  F. D.  Peterson  W. A.  Hines  J. R.  Peterman  K. R.  Good  R. E.  Beland  R. R.  Brown  J. H. 《Theoretical and Applied Climatology》1988,39(1):17-29

Theoretical and Applied Climatology - Comparisons are made of profiles of the refractive index structure parameter (C 2 ) and two derived quantities, transverse coherence length (r 0) and...  相似文献   

Abrupt CO2 experiments as tools for predicting and understanding CMIP5 representative concentration pathway projections     

Peter Good  Jonathan M. Gregory  Jason A. Lowe  Timothy Andrews 《Climate Dynamics》2013,40(3-4):1041-1053

A fast simple climate modelling approach is developed for predicting and helping to understand general circulation model (GCM) simulations. We show that the simple model reproduces the GCM results accurately, for global mean surface air temperature change and global-mean heat uptake projections from 9 GCMs in the fifth coupled model inter-comparison project (CMIP5). This implies that understanding gained from idealised CO₂ step experiments is applicable to policy-relevant scenario projections. Our approach is conceptually simple. It works by using the climate response to a CO₂ step change taken directly from a GCM experiment. With radiative forcing from non-CO₂ constituents obtained by adapting the Forster and Taylor method, we use our method to estimate results for CMIP5 representative concentration pathway (RCP) experiments for cases not run by the GCMs. We estimate differences between pairs of RCPs rather than RCP anomalies relative to the pre-industrial state. This gives better results because it makes greater use of available GCM projections. The GCMs exhibit differences in radiative forcing, which we incorporate in the simple model. We analyse the thus-completed ensemble of RCP projections. The ensemble mean changes between 1986–2005 and 2080–2099 for global temperature (heat uptake) are, for RCP8.5: 3.8 K (2.3 × 10²⁴ J); for RCP6.0: 2.3 K (1.6 × 10²⁴ J); for RCP4.5: 2.0 K (1.6 × 10²⁴ J); for RCP2.6: 1.1 K (1.3 × 10²⁴ J). The relative spread (standard deviation/ensemble mean) for these scenarios is around 0.2 and 0.15 for temperature and heat uptake respectively. We quantify the relative effect of mitigation action, through reduced emissions, via the time-dependent ratios (change in RCPx)/(change in RCP8.5), using changes with respect to pre-industrial conditions. We find that the effects of mitigation on global-mean temperature change and heat uptake are very similar across these different GCMs.  相似文献