J/A+A/635/A79       Pitch-angle distributions of solar wind   (Carcaboso+, 2020)

Characterisation of suprathermal electron pitch-angle distributions: Bidirectional and isotropic periods in solar wind. Carcaboso F., Gomez-Herrero R., Espinosa Lara F., Hidalgo M.A., Cernuda I., Rodriguez-Pacheco J. <Astron. Astrophys. 635, A79 (2020)> =2020A&A...635A..79C 2020A&A...635A..79C (SIMBAD/NED BibCode)
ADC_Keywords: Sun ; Solar system Keywords: Sun: heliosphere - coronal mass ejections (CMEs) - solar wind - methods: data analysis - methods: statistical - methods: analytical Abstract: Suprathermal electron pitch-angle distributions (PADs) contain substantial information about the magnetic topology of the solar wind. Their characterisation and quantification allow us to automatically identify periods showing certain characteristics. This work presents a robust automatic method for the identification and statistical study of two different types of PADs: bidirectional suprathermal electrons (BDE, often associated with closed magnetic structures) and isotropic (likely corresponding to solar-detached magnetic field lines or highly scattered electrons). Spherical harmonics were fitted to the observed suprathermal PADs of the 119-193eV energy channel of STEREO/SWEA from March 2007 to July 2014, and they were characterised using signal processing analysis in order to identify periods of isotropic and bidirectional PADs. The characterisation has been validated by comparing the results obtained here with those of previous studies. Interplanetary coronal mass ejections (ICMEs) present longer BDE periods inside the magnetic obstacles. A significant amount of BDE remain after the end of the ICME. Isotropic PADs are found in the sheath of the ICMEs, and at the post-ICME region likely due to the erosion of the magnetic field lines. Both isotropy and BDE are solar-cycle dependent. The isotropy observed by STEREO shows a nearly annual periodicity, which requires further investigation. There is also a correspondence between the number of ICMEs observed and the percentage of time showing BDE. A method to characterise PADs has been presented and applied to the automatic identification of two relevant distributions that are commonly observed in the solar wind, such as BDE and isotropy. Four catalogues (STEREO-A and STEREO-B for isotropic and BDE periods of at least 10min) based on this identification are provided for future applications. Description: Pitch-angle distributions observed by STEREO-A during 1st March 2007 and 31st July 2014. A moving window of approximately 20 minutes calculates the time percentage of fulfilling the condition A2>0, gamma>15% and SNR24>5.76dB. If the condition is fulfilled for at least 10 minutes of that moving window, the period is a candidate for the list. When two or more candidates have a separation of less than 2 hours, they are considered as the same event. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file bidirsta.dat 150 1227 Bidirectional periods in solar wind observed by STEREO-A (2007-03-03, 2014-07-16) bidirstb.dat 150 1333 Bidirectional periods in solar wind observed by STEREO-B (2007-03-01, 2014-07-29) isosta.dat 150 2125 Isotropic periods in solar wind observed by STEREO-A (2007-03-01, 2014-07-31) isostb.dat 150 2367 Isotropic periods in solar wind observed by STEREO-B (2007-03-01, 2014-07-29) -------------------------------------------------------------------------------- Byte-by-byte Description of file: *.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 19 A19 "datime" Obs.begin Beginning date (UTC) 21- 39 A19 "datime" Obs.end End date (UTC) 41- 47 F7.2 min Dur Time duration 49- 70 A22 --- Cat Catalogued (1) 72- 76 F5.2 nT B ? Magnetic field 78- 81 F4.2 nT e_B ? Magnetic field error 83- 87 F5.2 -- Beta ? Plasma beta 89- 93 F5.2 -- e_Beta ? Plasma beta error 95-100 F6.2 % Ripple ? Anisotropy index gamm 102-105 F4.2 % e_Ripple ? Anisotropy index gamma error 107-112 F6.2 --- SNR24 ? SNR24 index, in dB unit 114-117 F4.2 --- e_SNR24 ? SNR24 index error, in dB unit 119-127 E9.4 K Tp ? Proton temperature 129-137 E9.4 K e_Tp ? Proton temperature error 139-145 F7.2 km/s Vsw ? Solar wind speed 147-150 F4.2 km/s e_Vsw ? Solar wind speed error -------------------------------------------------------------------------------- Note (1): Cataloged flags as follows: FF = Fast-Forward shock FR = Fast-Reverse shock ICME = Interplanetary Coronal Mass Ejection Post-ICME = Rear part of ICME (defined as 1.2 times its duration) SIR = Stream Interaction Region No = No catalogued -------------------------------------------------------------------------------- Acknowledgements: Fernando Carcaboso, fernando.carcaboso(at)edu.uah.es History: 10-Mar-2020: on-lien version 03-Sep-2020: LABELS CORRECTED !!!! (from author)
(End) Patricia Vannier [CDS] 03-Feb-2020
The document above follows the rules of the Standard Description for Astronomical Catalogues; from this documentation it is possible to generate f77 program to load files into arrays or line by line