Predictions of local ground geomagnetic field fluctuations during the 7-10 November 2004 events studied with solar wind driven models

The 7-10 November 2004 period contains two events for which the local ground magnetic field was severely disturbed and simultaneously, the solar wind displayed several shocks and negative <i>B<sub>z</sub></i> periods. Using empirical models the 10-min RMS and at Brorfelde (BFE, 11.67° E, 55.63° N), Denmark, are predicted. The models are recurrent neural networks with 10-min solar wind plasma and magnetic field data as inputs. The predictions show a good agreement during 7 November, up until around noon on 8 November, after which the predictions become significantly poorer. The correlations between observed and predicted log RMS is 0.77 during 7-8 November but drops to 0.38 during 9-10 November. For RMS the correlations for the two periods are 0.71 and 0.41, respectively. Studying the solar wind data for other L1-spacecraft (WIND and SOHO) it seems that the ACE data have a better agreement to the near-Earth solar wind during the first two days as compared to the last two days. Thus, the accuracy of the predictions depends on the location of the spacecraft and the solar wind flow direction. Another finding, for the events studied here, is that the and models showed a very different dependence on <i>B<sub>z</sub></i>. The model is almost independent of the solar wind magnetic field <i>B<sub>z</sub></i>, except at times when <i>B<sub>z</sub></i> is exceptionally large or when the overall activity is low. On the contrary, the model shows a strong dependence on <i>B<sub>z</sub></i> at all times

Solar mean magnetic field variability: A wavelet approach to Wilcox Solar Observatory and SOHO/Michelson Doppler Imager observations

Solar mean magnetic field (SMMF) measurements from the Wilcox Solar Observatory and with the SOHO/MDI instrument are described and analyzed. Even though two completely different methods of observation are used, the two data sets obtained show a strong similarity. Using continuous wavelet transforms, SMMF variability is found at a number of temporal scales. Detected SMMF signals with a 1–2 year period are considered to be linked to variations in the internal rotation of the Sun. Intermediate SMMF oscillations with a period of 80–200 days are probably connected to the evolution of large active regions. We also find evidence for 90 min variations with coronal mass ejections as a suggested origin

Transverse-Momentum and Pseudorapidity Distributions of Charged Hadrons in pp Collisions at √s=7 TeV

Charged-hadron transverse-momentum and pseudorapidity distributions in proton-proton collisions at √s=7 TeV are measured with the inner tracking system of the CMS detector at the LHC. The charged-hadron yield is obtained by counting the number of reconstructed hits, hit pairs, and fully reconstructed charged-particle tracks. The combination of the three methods gives a charged-particle multiplicity per unit of pseudorapidity dNch=dη ⃒|η|\u3c0.5= 5.78 ± 0.01(stat) ± 0.23(syst) for non-single-diffractive events, higher than predicted by commonly used models. The relative increase in charged-particle multiplicity from √s=0.9 to 7 TeV is [±66.1 ± 1.0(stat) ± 4.2(syst)]%. The mean transverse momentum is measured to be 0.545 ± 0.005(stat) ± 0.015(syst) GeV/c. The results are compared with similar measurements at lower energies

Transverse-Momentum and Pseudorapidity Distributions of Charged Hadrons in pp Collisions at √s=7 TeV

Charged-hadron transverse-momentum and pseudorapidity distributions in proton-proton collisions at √s=7 TeV are measured with the inner tracking system of the CMS detector at the LHC. The charged-hadron yield is obtained by counting the number of reconstructed hits, hit pairs, and fully reconstructed charged-particle tracks. The combination of the three methods gives a charged-particle multiplicity per unit of pseudorapidity dNch=dη ⃒|η|\u3c0.5= 5.78 ± 0.01(stat) ± 0.23(syst) for non-single-diffractive events, higher than predicted by commonly used models. The relative increase in charged-particle multiplicity from √s=0.9 to 7 TeV is [±66.1 ± 1.0(stat) ± 4.2(syst)]%. The mean transverse momentum is measured to be 0.545 ± 0.005(stat) ± 0.015(syst) GeV/c. The results are compared with similar measurements at lower energies

Probing BFKL Dynamics in the Dijet Cross Section at Large Rapidity Intervals in ppbar Collisions at sqrt{s}=1800 and 630 GeV

Inclusive dijet production at large pseudorapidity intervals (delta_eta) between the two jets has been suggested as a regime for observing BFKL dynamics. We have measured the dijet cross section for large delta_eta in ppbar collisions at sqrt{s}=1800 and 630 GeV using the DO detector. The partonic cross section increases strongly with the size of delta_eta. The observed growth is even stronger than expected on the basis of BFKL resummation in the leading logarithmic approximation. The growth of the partonic cross section can be accommodated with an effective BFKL intercept of a_{BFKL}(20GeV)=1.65+/-0.07.Comment: Published in Physical Review Letter