AbstractBy analyzing the vector magnetograms of Huairou Solar Observing Station (HSOS) taken at the line center (0.0Å) and the line wing (−0.12Å) of FeI λ5324.19Å, we make an estimate of the measured errors in transversal azimuths (δφ) caused by Faraday rotation. Since many factors, such as the magnetic saturation and scattered light, can affect the measurement accuracy of the longitudinal magnetic field in the umbrae of sunspots, we limit our study in the region ∣Bz∣<800G. The main mean azimuth rotations are about 4°, 6°, 7° and 9°, while ∣Bz∣ are in the ranges of 400–500G, 500–600G, 600–700G and 700–800G, respectively. Moreover, we find there is also an azimuth rotation of about 8° at the wavelength offset −0.12Å of the line compared against a previous numerical simulation.We calculate the average electric currents (Jz) of 393 magnetograms in the region 500G<∣Bz∣<800G. After the average correction to azimuths with the above estimations, the mean value of current in active regions 〈Jz〉 shows an obvious return-to-zero tendency: changing from the original 0.234×10−2Am−2 to 0.5×10−4Am−2. We also present the mean electric current in the region 20G<∣Bz∣<500G, which is −0.6×10−4Am−2, and nearly the same magnitude as the above corrected value (0.5×10−4Am−2). Both are around zero. In addition, we calculate Jz in the region ∣Bz∣>500G (no the upper limit). At 0.5×10−5Am−2, the 〈Jz〉 presents little difference with the value in the region 500G<∣Bz∣<800G, which shows those pixels of ∣Bz∣>800G are few in most of the magnetograms and give little contribution to Jz. The correction is promising and Faraday rotations in the region 500G<∣Bz∣<800G are main interference effect on the determination of Jz in the vector magnetograms at HSOS.
Probing the method of correcting Faraday rotation in vector magnetograms
Advances in Space Research ; 42 , 5 ; 888-894
2007-06-26
7 pages
Article (Journal)
Electronic Resource
English
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