Using Polar Faculae to Determine the Sun’s High-latitude Rotation Rate. I. Techniques and Initial Measurements
This paper describes a new way of determining the high-latitude solar rotation rate statistically from simultaneous observations of many polar faculae. In this experiment, I extracted frames from a movie made previously from flat-fielded images obtained in the 6767 Å continuum during 1997–1998 Febru...
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IOP Publishing
2024-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad85d0 |
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| author | Neil R. Sheeley Jr. |
| author_facet | Neil R. Sheeley Jr. |
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| description | This paper describes a new way of determining the high-latitude solar rotation rate statistically from simultaneous observations of many polar faculae. In this experiment, I extracted frames from a movie made previously from flat-fielded images obtained in the 6767 Å continuum during 1997–1998 February and used those frames to construct spacetime maps from high-latitude slices of the favorably oriented south polar cap. These maps show an array of slanted tracks whose average slope indicates the east–west speed of faculae at that latitude, λ _s . When the slopes are measured and plotted as a function of latitude, they show relatively little scatter ∼ 0.01–02 km s ^−1 from a straight line whose zero-speed extension passes through the Sun’s south pole. This means that the speed, v ( λ _s ), and the latitudinal radius, ${{R}}_{\odot }\cos {\lambda }_{s}$ , approach 0 at the same rate, so that their ratio gives a nearly constant synodic rotation rate ∼8.°6 day ^−1 surrounding the Sun’s south pole. A few measurements of the unfavorably oriented north polar cap are consistent with these measurements near the south pole. |
| format | Article |
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| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2024-01-01 |
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| spelling | doaj-art-b75dc6c9ddb744ec98da268b35d84df92024-11-14T06:57:57ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-0197617310.3847/1538-4357/ad85d0Using Polar Faculae to Determine the Sun’s High-latitude Rotation Rate. I. Techniques and Initial MeasurementsNeil R. Sheeley Jr.0https://orcid.org/0000-0002-6612-3498Visiting Research Scientist, Lunar and Planetary Laboratory, University of Arizona , Tucson, AZ 85721, USAThis paper describes a new way of determining the high-latitude solar rotation rate statistically from simultaneous observations of many polar faculae. In this experiment, I extracted frames from a movie made previously from flat-fielded images obtained in the 6767 Å continuum during 1997–1998 February and used those frames to construct spacetime maps from high-latitude slices of the favorably oriented south polar cap. These maps show an array of slanted tracks whose average slope indicates the east–west speed of faculae at that latitude, λ _s . When the slopes are measured and plotted as a function of latitude, they show relatively little scatter ∼ 0.01–02 km s ^−1 from a straight line whose zero-speed extension passes through the Sun’s south pole. This means that the speed, v ( λ _s ), and the latitudinal radius, ${{R}}_{\odot }\cos {\lambda }_{s}$ , approach 0 at the same rate, so that their ratio gives a nearly constant synodic rotation rate ∼8.°6 day ^−1 surrounding the Sun’s south pole. A few measurements of the unfavorably oriented north polar cap are consistent with these measurements near the south pole.https://doi.org/10.3847/1538-4357/ad85d0Solar faculaeSolar rotationSolar cycleSolar magnetic fields |
| spellingShingle | Neil R. Sheeley Jr. Using Polar Faculae to Determine the Sun’s High-latitude Rotation Rate. I. Techniques and Initial Measurements The Astrophysical Journal Solar faculae Solar rotation Solar cycle Solar magnetic fields |
| title | Using Polar Faculae to Determine the Sun’s High-latitude Rotation Rate. I. Techniques and Initial Measurements |
| title_full | Using Polar Faculae to Determine the Sun’s High-latitude Rotation Rate. I. Techniques and Initial Measurements |
| title_fullStr | Using Polar Faculae to Determine the Sun’s High-latitude Rotation Rate. I. Techniques and Initial Measurements |
| title_full_unstemmed | Using Polar Faculae to Determine the Sun’s High-latitude Rotation Rate. I. Techniques and Initial Measurements |
| title_short | Using Polar Faculae to Determine the Sun’s High-latitude Rotation Rate. I. Techniques and Initial Measurements |
| title_sort | using polar faculae to determine the sun s high latitude rotation rate i techniques and initial measurements |
| topic | Solar faculae Solar rotation Solar cycle Solar magnetic fields |
| url | https://doi.org/10.3847/1538-4357/ad85d0 |
| work_keys_str_mv | AT neilrsheeleyjr usingpolarfaculaetodeterminethesunshighlatituderotationrateitechniquesandinitialmeasurements |