3 research outputs found
Effect of Polarimetric Noise on the Estimation of Twist and Magnetic Energy of Force-Free Fields
The force-free parameter , also known as helicity parameter or twist
parameter, bears the same sign as the magnetic helicity under some restrictive
conditions. The single global value of for a whole active region gives
the degree of twist per unit axial length. We investigate the effect of
polarimetric noise on the calculation of global value and magnetic
energy of an analytical bipole. The analytical bipole has been generated using
the force-free field approximation with a known value of constant and
magnetic energy. The magnetic parameters obtained from the analytical bipole
are used to generate Stokes profiles from the Unno-Rachkovsky solutions for
polarized radiative transfer equations. Then we add random noise of the order
of 10 of the continuum intensity (I) in these profiles to simulate
the real profiles obtained by modern spectropolarimeters like Hinode (SOT/SP),
SVM (USO), ASP, DLSP, POLIS, SOLIS etc. These noisy profiles are then inverted
using a Milne-Eddington inversion code to retrieve the magnetic parameters.
Hundred realizations of this process of adding random noise and polarimetric
inversion is repeated to study the distribution of error in global and
magnetic energy values. The results show that : (1). the sign of is
not influenced by polarimetric noise and very accurate values of global twist
can be calculated, and (2). accurate estimation of magnetic energy with
uncertainty as low as 0.5% is possible under the force-free condition.Comment: 33 pages, 6 figures, 1 table; Accepted for publication in the Ap
Calibration and Monitoring of the Pierre Auger Observatory
Contributions to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009International audienceReports on the atmospheric monitoring, calibration, and other operating systems of the Pierre Auger Observatory. Contributions to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009
The Cosmic Ray Energy Spectrum and Related Measurements with the Pierre Auger Observatory
Submissions to the 31st International Cosmic Ray ConferenceInternational audienceStudies of the cosmic ray energy spectrum at the highest energies with the Pierre Auger Observatory