The 17 GHz active region number

We report the statistics of the number of active regions (NAR) observed at 17 GHz with the Nobeyama Radioheliograph between 1992, near the maximum of cycle 22, and 2013, which also includes the maximum of cycle 24, and we compare with other activity indexes. We find that NAR minima are shorter than...

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Guardado en:
Detalles Bibliográficos
Publicado: 2014
Materias:
Sun: activity
Sun: magnetic fields
Sun: radio radiation
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v790_n2_p_Selhorst
http://hdl.handle.net/20.500.12110/paper_0004637X_v790_n2_p_Selhorst
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_0004637X_v790_n2_p_Selhorst
record_format dspace
spelling paper:paper_0004637X_v790_n2_p_Selhorst2023-06-08T14:29:12Z The 17 GHz active region number Sun: activity Sun: magnetic fields Sun: radio radiation We report the statistics of the number of active regions (NAR) observed at 17 GHz with the Nobeyama Radioheliograph between 1992, near the maximum of cycle 22, and 2013, which also includes the maximum of cycle 24, and we compare with other activity indexes. We find that NAR minima are shorter than those of the sunspot number (SSN) and radio flux at 10.7 cm (F10.7). This shorter NAR minima could reflect the presence of active regions generated by faint magnetic fields or spotless regions, which were a considerable fraction of the counted active regions. The ratio between the solar radio indexes F10.7/NAR shows a similar reduction during the two minima analyzed, which contrasts with the increase of the ratio of both radio indexes in relation to the SSN during the minimum of cycle 23-24. These results indicate that the radio indexes are more sensitive to weaker magnetic fields than those necessary to form sunspots, of the order of 1500 G. The analysis of the monthly averages of the active region brightness temperatures shows that its long-term variation mimics the solar cycle; however, due to the gyro-resonance emission, a great number of intense spikes are observed in the maximum temperature study. The decrease in the number of these spikes is also evident during the current cycle 24, a consequence of the sunspot magnetic field weakening in the last few years. © 2014. The American Astronomical Society. All rights reserved.. 2014 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v790_n2_p_Selhorst http://hdl.handle.net/20.500.12110/paper_0004637X_v790_n2_p_Selhorst
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Sun: activity
Sun: magnetic fields
Sun: radio radiation
spellingShingle Sun: activity
Sun: magnetic fields
Sun: radio radiation
The 17 GHz active region number
topic_facet Sun: activity
Sun: magnetic fields
Sun: radio radiation
description We report the statistics of the number of active regions (NAR) observed at 17 GHz with the Nobeyama Radioheliograph between 1992, near the maximum of cycle 22, and 2013, which also includes the maximum of cycle 24, and we compare with other activity indexes. We find that NAR minima are shorter than those of the sunspot number (SSN) and radio flux at 10.7 cm (F10.7). This shorter NAR minima could reflect the presence of active regions generated by faint magnetic fields or spotless regions, which were a considerable fraction of the counted active regions. The ratio between the solar radio indexes F10.7/NAR shows a similar reduction during the two minima analyzed, which contrasts with the increase of the ratio of both radio indexes in relation to the SSN during the minimum of cycle 23-24. These results indicate that the radio indexes are more sensitive to weaker magnetic fields than those necessary to form sunspots, of the order of 1500 G. The analysis of the monthly averages of the active region brightness temperatures shows that its long-term variation mimics the solar cycle; however, due to the gyro-resonance emission, a great number of intense spikes are observed in the maximum temperature study. The decrease in the number of these spikes is also evident during the current cycle 24, a consequence of the sunspot magnetic field weakening in the last few years. © 2014. The American Astronomical Society. All rights reserved..
title The 17 GHz active region number
title_short The 17 GHz active region number
title_full The 17 GHz active region number
title_fullStr The 17 GHz active region number
title_full_unstemmed The 17 GHz active region number
title_sort 17 ghz active region number
publishDate 2014
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v790_n2_p_Selhorst
http://hdl.handle.net/20.500.12110/paper_0004637X_v790_n2_p_Selhorst
_version_ 1768546186745085952

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