Exploring the Connection between Helioseismic Travel Time Anomalies and the Emergence of Large Active Regions during Solar Cycle 24
We investigate deviations in the mean phase travel time of acoustic waves preceding the emergence of 46 large active regions observed by the Helioseismic and Magnetic Imager. In our investigation, we consider two different procedures for obtaining the mean phase travel time, by minimizing the differ...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/acc836 |
| _version_ | 1797702531991732224 |
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| author | John T. Stefan Alexander G. Kosovichev |
| author_facet | John T. Stefan Alexander G. Kosovichev |
| author_sort | John T. Stefan |
| collection | DOAJ |
| description | We investigate deviations in the mean phase travel time of acoustic waves preceding the emergence of 46 large active regions observed by the Helioseismic and Magnetic Imager. In our investigation, we consider two different procedures for obtaining the mean phase travel time, by minimizing the difference between cross-correlations and a reference, as well as the Gabor wavelet fitting procedure. We cross-correlate the time series of mean phase travel time deviations with the surface magnetic field and determine the peak correlation time lag. We also compute the perturbation index—the area integrated mean phase travel time deviations exceeding quiet Sun thresholds—and compare the time of peak perturbation index with the correlation time lag. We find that the lag times derived from the difference minimization procedure precede the flux emergence for 36 of the 46 active regions, and that this lag time has a noticeable correlation with the maximum flux rate. However, only 28 of the active regions have peak perturbation index times in the range of 24–48 hr prior to the flux emergence. Additionally, we examine the relationship between the properties of the emerged active regions and the strength of helioseismic signals prior to their emergence. |
| first_indexed | 2024-03-12T04:52:22Z |
| format | Article |
| id | doaj.art-f28c6811b2494217be849b271a1b14e4 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T04:52:22Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-f28c6811b2494217be849b271a1b14e42023-09-03T09:21:58ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-019481110.3847/1538-4357/acc836Exploring the Connection between Helioseismic Travel Time Anomalies and the Emergence of Large Active Regions during Solar Cycle 24John T. Stefan0https://orcid.org/0000-0002-5519-8291Alexander G. Kosovichev1https://orcid.org/0000-0003-0364-4883Department of Physics, New Jersey Institute of Technology , Newark, NJ 07102, USA ; jts25@njit.eduDepartment of Physics, New Jersey Institute of Technology , Newark, NJ 07102, USA ; jts25@njit.edu; NASA Ames Research Center , Moffett Field, Mountain View, CA 94040, USAWe investigate deviations in the mean phase travel time of acoustic waves preceding the emergence of 46 large active regions observed by the Helioseismic and Magnetic Imager. In our investigation, we consider two different procedures for obtaining the mean phase travel time, by minimizing the difference between cross-correlations and a reference, as well as the Gabor wavelet fitting procedure. We cross-correlate the time series of mean phase travel time deviations with the surface magnetic field and determine the peak correlation time lag. We also compute the perturbation index—the area integrated mean phase travel time deviations exceeding quiet Sun thresholds—and compare the time of peak perturbation index with the correlation time lag. We find that the lag times derived from the difference minimization procedure precede the flux emergence for 36 of the 46 active regions, and that this lag time has a noticeable correlation with the maximum flux rate. However, only 28 of the active regions have peak perturbation index times in the range of 24–48 hr prior to the flux emergence. Additionally, we examine the relationship between the properties of the emerged active regions and the strength of helioseismic signals prior to their emergence.https://doi.org/10.3847/1538-4357/acc836Solar active regionsSolar magnetic flux emergenceHelioseismology |
| spellingShingle | John T. Stefan Alexander G. Kosovichev Exploring the Connection between Helioseismic Travel Time Anomalies and the Emergence of Large Active Regions during Solar Cycle 24 The Astrophysical Journal Solar active regions Solar magnetic flux emergence Helioseismology |
| title | Exploring the Connection between Helioseismic Travel Time Anomalies and the Emergence of Large Active Regions during Solar Cycle 24 |
| title_full | Exploring the Connection between Helioseismic Travel Time Anomalies and the Emergence of Large Active Regions during Solar Cycle 24 |
| title_fullStr | Exploring the Connection between Helioseismic Travel Time Anomalies and the Emergence of Large Active Regions during Solar Cycle 24 |
| title_full_unstemmed | Exploring the Connection between Helioseismic Travel Time Anomalies and the Emergence of Large Active Regions during Solar Cycle 24 |
| title_short | Exploring the Connection between Helioseismic Travel Time Anomalies and the Emergence of Large Active Regions during Solar Cycle 24 |
| title_sort | exploring the connection between helioseismic travel time anomalies and the emergence of large active regions during solar cycle 24 |
| topic | Solar active regions Solar magnetic flux emergence Helioseismology |
| url | https://doi.org/10.3847/1538-4357/acc836 |
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