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The measurement of solar differential rotation that used sunspot as tracer
Source publication
The differential rotation is the result of the interaction between rotation and convection and causes dynamo circulation that affects the cycle of solar activity. Tracer method using features in the photosphere such as sunspot is a simple method to measure the differential rotation. In this study, 98 individual sunspots on January 8-22, 2013 and Au...
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Citations
... There are much fewer studies on the movement of individual sunspots. In the article (Permata and Herdiwijaya , 2019), 98 individual sunspots were used to study rotation in 2013. The average rotational rate ω(θ) = 14.376+0.6sin 2 θ deg/day was found. ...
The differential rotation of individual sunspots and pores is analyzed according to Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI) observations processing in the period 01.05.2010 – 31.05.2024. To accurately track sunspots, we processed 5 images for each day. To determine the polarity of the magnetic field, we superimposed the contours of sunspots on observations of magnetic fields at the same time. This made it possible to track the movement of more than 175 thousand individual sunspots and pores. It is found that the rotation rate of individual sunspots and pores differs significantly from the differential rotation of sunspot groups. In particular, solar pores with no penumbra and a characteristic area of S ≈ 10 μhm rotate ≈ 1.7% slower than regular sunspots with penumbra. Perhaps this is due to a change in the rotation rate with depth in the convective zone, namely in the leptocline (0.95R⊙). Sunspots and pores of the leading polarity have rotation rate of ≈ 2.3% faster than trailing polarity spots. This difference is probably due to the movement of the spots when the arches of the magnetic field rise.
... Sunspots around the solar equator have a sidereal rotation period (with respect to the fixed stars) of about 24.47 days, which gives an average synodic rotation period (as seen from Earth) of near 26.25 days, whereas for sunspots at heliographic latitude H = ±45 • , the synodic period is roughly 28.9 days (Ruždjak et al., 2017;Permata and Herdiwijaya, 2019). The rotation periods of the solar corona are harder to measure accurately but also show differential rotation, but to a lesser degree than the photosphere (Mancuso et al., 2020;Morgan, 2011). ...
We generate reconstructions of signed open solar flux (OSF) for the past 154 years using observations of geomagnetic activity. Previous reconstructions have been limited to annual resolution, but this is here increased by a factor of more than 13 by using averages over Carrington rotation (CR) intervals. We use two indices of geomagnetic activity, the homogeneous aa index, aaH, and the IDV(1d) index; a combination of the two is fitted to OSF estimates from near-Earth interplanetary satellite data. For 1995 – 2022, these are corrected for excess flux (i.e. orthogardenhose flux and switchbacks) using strahl electrons. For 1970 – 2022, we also use the absolute values of the radial component of the near-Earth interplanetary magnetic field \({\langle }|{\langle }B_{r}{\rangle }_{\tau }|{\rangle }_{CR}\), where the excess flux is allowed for by adopting the optimum averaging interval \({\tau }\) of 20 h. However, in the interval 1970 – 1995, data gaps in the interplanetary data are a serious problem. The errors that these missing data cause in CR averages of OSF are evaluated by synthetically masking data for CRs that have a full complement, using the same number and time series of data gaps as for the CR in question. Given the potential for missing data to generate large errors, we use the near-continuous 1995 – 2022 data to derive the best-fit combination of the geomagnetic data and employ the 1970 – 1995 data for testing in which we can readily allow for the errors caused by data gaps. Errors caused by inaccuracies in the geomagnetic data are shown to be considerably smaller than the uncertainties due to the polynomial fitting. It is shown that the new reconstructions are consistent with the previous annual estimates and that there is considerable variability in the OSF values from one CR to the next; in particular, in high-activity solar cycles, there can be individual CRs in which the OSF exceeds that for adjacent CRs by a factor as large as two.
... Sunspots around the solar equator have a sidereal rotation period (with respect to the fixed stars) of about 24.47 days which gives an average synodic rotation period (as seen from Earth) of near 26.25 days, whereas for sunspots at heliographic latitude Λ H = ±45 • this period is roughly 28.9 days (Ruždjak et al., 2017;Permata and Herdiwijaya, 2019). The rotation periods of the solar corona are harder to measure accurately but also show differential rotation, but to a lesser degree than the photosphere (Mancuso et al., 2020;Morgan, 2011). ...
We generate reconstructions of signed Open Solar Flux (OSF) for the past 154 years using observations of geomagnetic activity. Previous reconstructions have been limited to annual resolution but this is here increased by a factor of more than 13 by using averages over Carrington Rotation (CR) intervals. We use two indices of geomagnetic activity: the homogeneous aa index, aa H , and the IDV (1d) composite index and a combination of the two is fitted to OSF estimates from near-Earth interplanetary satellite data. For 1995-2022 these are corrected for excess flux (i.e., orthogardenhose flux and switchbacks) using strahl electrons. For 1970-2022 we also use the absolute values of the radial component of the near-Earth interplanetary magnetic field ⟨|⟨B r ⟩ τ |⟩ CR , where the excess flux is allowed for by using the optimum averaging interval τ of 20 hrs. However, in the interval 1970-1995 data gaps in the interplanetary data are a serious problem. The errors that these missing data cause in CR averages of OSF are evaluated by synthetically masking data for CRs that have a full complement of data, using the same number and time series of data gaps as for the CR in question. Given these errors can be large, we use the near-continuous 1995-2022 data to derive the best-fit combination of the geomagnetic data and employ the 1970-1995 data for testing that can allow for the errors caused by data gaps. Errors caused by inaccuracies in the geomagnetic data are shown to be considerably smaller than the uncertainties due to the polynomial fitting. It is shown that the new reconstructions are consistent with the previous annual estimates and that there is considerable variability in the OSF values from one CR to the next: in particular, in high-activity solar cycles there can be individual CRs in which the OSF exceeds that for adjacent CRs by a factor as large as two.
... Sunspots around the solar equator have a synodic rotation period (as seen from Earth) of near 26.25 days, whereas for sunspots at heliographic latitude Λ H = ±45 • this period is roughly 28.9-days (Ruždjak et al., 2017;Permata and Herdiwijaya, 2019). Solar corona rotation rates are harder to measure accurately but also show differential rotation, but to a lesser extent than the photosphere (Mancuso et al., 2020;Morgan, 2011). ...
We generate reconstructions of signed Open Solar Flux (OSF) for the past 154 years using observations of geomagnetic activity. Previous reconstructions have been limited to annual resolution but this is here increased by a factor of more than 13 by using averages over Carrington Rotation (CR) intervals. We use two indices of geomagnetic activity: the homogeneous aa geomagnetic index, aa H , and the IDV(1d) composite index and a combination of the two is fitted to OSF estimates from near-Earth interplanetary satellite data. For 1995-2022 these are corrected for excess flux (i.e., orthogardenhose flux and switchbacks) using strahl electrons. For 1970-2022 we also use the absolute values of the radial component of the near-Earth interplanetary magnetic field ⟨|⟨ B r ⟩ τ |⟩ CR , where the excess flux is allowed for by using the optimum averaging interval τ of 20 hrs. However, in the interval 1970-1995 data gaps in the interplanetary data are a serious problem. The errors that these missing data cause in CR averages of OSF are evaluated by synthetically masking data for CRs that have a full complement of data, using the same number and time series of data gaps as for the CR in question. Given these errors can be large, we use the near-continuous 1995-2022 data to derive the best-fit combination of the geomagnetic data and employ the 1970-1995 data for testing that can allow for the errors caused by data gaps. Errors caused by inaccuracies in the geomagnetic data are shown to be considerably smaller than the uncertainties due to the polynomial fitting. It is shown that the new reconstructions are consistent with the previous annual estimates and that there is considerable variability in the OSF values from one CR to the next: in particular, in high-activity solar cycles there can be individual CRs in which the OSF exceeds that for adjacent CRs by a factor as large as two.
