M S Abbas & H S Ali Bas J Sci 43(1) (2025)100-125

Methods and Techniques for Measuring the Rotation Surface of the Sun: A
Review
Mustafa S.Abbas*, Huda Shaker Ali
Department of Astronomy and Space, College of Science, University of Baghdad, Baghdad, Iraq.
*Corresponding author E-mail: mostafa.salem1607a@sc.uobaghdad.edu.iq

https://doi.org/10.29072/basjs.20250107

ARTICLE INFO ABSTRACT

Keywords This study examines scientific contributions from 1611 to 2024 and
Sunspot, solar rotation, investigates techniques for detecting solar rotation velocity,
Solar Cycle, solar
highlighting the discovery of differential rotation through early sunspot
dynamics, SOHO.
observations in the 17th century by Christoph Scheiner and Galileo
Galilei. Tools such as helioseismology and magnetographs have
provided increasingly precise measurements as technology advanced,
revealing significant variations in solar rotation at various depths and
latitudes. The work highlights the cumulative aspect of solar rotation
research, demonstrating how each discovery enhances previous findings
to create a more comprehensive picture of solar dynamics and its
influence on space weather.

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Received 11 Mar 2025; Received in revised form 24 Apr 2025; Accepted 28 Apr 2025, Published
30 Apr 2025

1. Introduction
Early 17th century Hans Lippershey's creation of the telescope transformed astronomical
observations and opened the path for research of celestial events. One of the first users of
such discovery, Thomas Harriot recorded Sun surface sunspot observations in 1610. These first
investigations set the groundwork for knowledge of Sun rotational behavior [1]. In 1611, German
astronomers David and Johann Fabricius utilized telescopes in northern Europe to observe
sunspots. They were the first to calculate that the Sun rotates on its axis. Johann Fabricius authored
the first scientific paper on sunspots, contributing significantly to solar science. Although Johann
died in 1616, his groundbreaking work influenced subsequent research, including his father's
contributions until his passing in 1617 [2]. Galileo Galilei further advanced solar observations in
1612 with his improved telescope. Independently verifying Johann Fabricius's findings, Galileo
confirmed that the Sun rotates on its axis and estimated the equatorial rotation period to be
approximately 27 days. These findings, depicted in figure (1), challenged the Aristotelian concept
of an immutable and perfect celestial body. Galileo's observations of sunspots and Sun's rotation
laid the groundwork for future studies on solar dynamics and differential rotation, which Christoph
Scheiner later expanded upon [3].

Figure (1) Galileo Galilei sunspot [3]

Around 1611, sunspot observations gained scientific attention, with Christoph Scheiner, a Jesuit
scholar in Germany, making key contributions. Initially, Scheiner thought sunspots were planets
crossing the Sun, but later realized they were part of the Sun. From his works in the year 1630,
Rosa Ursina book, detailed sunspot observations and illustrations, reveals that, where the paths of
sunspots vary as the seasons change and These variations are explained using the relationship of

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the incline in the Sun’s axis to the level of ecliptic, figure 2. Importantly, Scheiner also observed
that the Sun rotates faster at the equator than at the poles, contributing to the understanding of
differential rotation and solar dynamics [4].

Figure (2) One of a great many sunspot drawings in

Scheiner's "Rosa Ursina" [4].

In the 1650s, astronomers like Gregorius Ostreichus advanced solar studies by observing sunspots,

Figure (3) Observations of the Spots appearing in the

Sun' by Robert Hooke [5].
confirming the Sun’s rotation. Around the same time, Francesco Maria Grimaldi improved optical
technology for sunspot observation, though he is better known for wave theory. By 1665, Robert
Hooke used enhanced telescopes for precise sunspot observations, Figure 3, improving accuracy
in studying the Sun’s rotation and paving the way for future solar research [5]. And in the 1670s,
Jean-Dominique Cassini discovered differential rotation, revealing varying solar speeds and
advancing solar dynamics [6]. In 1687, Isaac Newton put the final nail in the coffin for the
Aristotelian, geocentric view of the Universe. Building on Kepler’s laws, Newton explained why
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the planets moved as they did around the Sun and solar rotation about herself and he gave the force
that kept them in check a name: gravity [7]. In the 1670s, Jean-Dominique Cassini made a
groundbreaking discovery of differential rotation, revealing that the Sun's rotational speeds vary
at different latitudes, thus advancing the field of solar dynamics [8]. The 17th century was a period
of significant progress in solar studies, despite technological limitations and religious challenges,
setting the stage for modern solar science. At the start of the 18th century, James Bradley and
Johann Tobias Mayer were pivotal figures in advancing astronomical precision [9]. In 1727,
Bradley uncovered the phenomenon of light, enhancing the precision of both stellar and solar
observations and role in observing solar rotation. Bradley's emphasis on star positions helped to
provide more exact Sun position measurements, therefore facilitating knowledge of Sun rotation.
Johann Tobias Mayer improved celestial body positions, especially the Sun, by refining
astronomical tables in the 1740s. Understanding solar movement equation required an
understanding of the rotation velocity equation [10]:

𝐺𝑀
𝑣=√ … … (1)
𝑅
G: gravitational constant; M: Sun mass;𝑣: orbital velocity at Sun's surface; R: Sun radius, Mayer’s
exact observations prepared the path for next investigations on solar rotation. also, William
Herschel noted sunspots in the 1770s and linked solar activity with the climate of Earth, his studies
advanced knowledge of Sun rotation and equatorial speed, which determine the Sun's rotational
velocity by applying and represent it as [11]:
2𝜋𝑅
𝑣= … … (2)
𝑃
R: Sun's radius; v: rotational velocity at the equator (~2 km/s); P: rotational period (~25 days).
Fundamentally, Herschel's sunspot observations produced information regarding Sun rotation. He
connected increased sunspot activity with greater Earth temperatures, therefore setting the stage
for more research on Sun rotations well as their final impact on climate conditions [12]. Around
the same time, Jean-Dominique Cassini II, in 1772, continuing his family’s legacy, made
groundbreaking discoveries regarding differential solar rotation. He observed that the Sun rotates
faster at the equator than at the poles, which led to the following differential rotation equation
[13]:
Ω(θ) = Ω𝑒𝑞 − ΔΩ sinθ2 … . . (3)
Where

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Ω(θ): Angular velocity at latitude

Ω𝑒𝑞 : Angular velocity at the equator (~14.713 radians/day)
ΔΩ : Difference in velocity between the equator and poles (~2.4 radians/day)
Cassini’s observations showed sunspots at different latitudes moving at varying speeds, advancing
knowledge of solar rotation [14]. With more complex astronomical devices including Isaac
Newton's reflecting telescopes by the eighteenth century, one could clearly view the sun. William
Herschel performed more exact observations of sunspots by middle of the 1700s, therefore
advancing our knowledge of differential rotation. Research on sunspot cycles in the 19th century
started from such publications. Astrophysics and our knowledge of solar dynamics were greatly
shaped by Laplace's theoretical work applying Newtonian mechanics to Sun's motion [15] [16].
When Joseph von Fraunhofer found dark absorption lines within the solar spectrum—now known
as Fraunhofer lines—a significant discovery took place in 1814. This finding transformed solar
observations by allowing astronomers to investigate solar rotation by means of spectral line
changes resulting from Sun motion. By laying the observational and mathematical tools required
to derive the Sun's dynamic behavior, Fraunhofer's work prepared the path for measuring solar
rotation velocity with the use of Doppler shifts [17]. Meanwhile, in the same year, Friedrich Bessel
improved astronomical measurements that indirectly contributed to solar rotational studies. His
precise observations of celestial movements allowed for the development of angular velocity
calculations, forming a basis for studying solar rotation dynamics [18]. Heinrich Schwabe started
systematic sunspot measurements in the year 1826, which led to the 11-year sunspot cycle being
found. This was a first realization of periodic solar activity's relation to Sun differential rotation.
Also, Christian Doppler proposed in the 1840s the fundamental idea for determining the Sun's
rotational velocity y means of a change in spectral lines [19] [20]. By 1853, Richard Carrington
has been among the most well-known researchers of the sun, his observations of sunspots clearly
revealed a phenomenon known as differential rotation. This discovery provided quite a clear
insight that the rotation regarding the Sun is different with latitude and was quite significant for
subsequent information about solar dynamics [21]:

𝜔(𝜙) = sin2 (𝜙) . Δ𝜔 − 𝜔° …......(4)

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w₀ represent the rotation speed at the equator; Δω represent the variation in rotation speed between
the poles and the equator; ω(ϕ) represent the angular velocity at latitude ϕ. Gustav Spörer verified
Carrington's work in the same time frame. Spörer's research verified the hypothesis of differential
rotation and advanced knowledge of how the sunspot cycle changed over several decades. Italian
astronomer Angelo Secchi made precise Sun rotational velocity calculations in 1859 by using
spectroscopy to probe the solar spectrum. His efforts greatly helped to clarify the Sun's differential
rotation in terms of its several latitudes of rotation rate [22] [23]. Norman Lockyer and Hermann
Carl Vogel bring with them a new wave of solar observations in the 1860s Vogel confirmed the
differential rotation through measuring the Sun's rotational speed using the Doppler Effect by
means of spectral lines changes. Lockyer had on his observations of prominences and magnetic
characteristics on the Sun that produced more clear links between the Sun's magnetic fields and
rotational dynamics [24]. Nils Christian Dunér produced more exact Doppler observations of the
Sun's rotational velocities in the early 1870s, therefore verifying the prior discoveries of slower
polar rotation and quicker equatorial rotation. These findings provided a more realistic view
regarding Sun's dynamic processes and verified that its rotation is not rigid (equation (6). His exact
observations of the rotational variations across latitudes offered a far better understanding of Sun
behavior [25]. George Ellery Hale founded solar observatories late in the 1880s to permit more
exact solar rotation observations. His observations connected magnetic fields with solar surface
dynamics, therefore clarifying the link between solar rotation as well as solar magnetic events [26].
William Huggins studied spectral line changes to greatly expand the boundaries of solar
spectroscopy down until the early 1880s. Further evidence on how the magnetic activity in the Sun
and its rotational velocity are connected was given by his attention on how magnetic fields in the
Sun interact with their rotational dynamics, therefore strengthening the idea of differential rotation.
Also, Henry Draper studied solar spectral analysis at this time as well. By means of his analysis of
the Sun's spectrum, Draper improved understanding of the rotational speed variations at different
latitudes. His observations confirmed the varying rotations found by other scientists, therefore
supporting the governing equations for solar motion more fully [27]. Important contributions
through Draper and Huggins greatly enhanced the understanding of solar rotation and magnetic
fields as a component in solar dynamics. Charles Augustus Young obtained more exact estimates
of magnetic activity and solar rotation. His investigations of solar prominences clarified even more
the differences in rotational speeds depending on latitude. By extremely exact observations of the
solar rotation provided by George Ellery Hale in the year 1887, magnetic fields related to rotational
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dynamics. Edward Maunder's analysis of the Maunder Minimum demonstrates how variations in
solar rotation feed back into the sunspot cycle [28]. Nils Christian Dunér's Doppler shift
measurement in the 1890s corroborated this equatorial acceleration and provided more proof for
differential rotation. Dunér's comprehensive data would enable astronomers to more precisely
model Sun rotational dynamics. Prominent solar spectroscopist William Wallace Campbell used
cutting-edge spectroscopic methods to track Sun rotational velocities in the 1890s. His results
confirmed prior observations of differential rotation and laid a basis for future solar study by
offering more accurate data on the varied rates of movement of solar surface structures [29].
Hermann Carl Vogel focused online shifts showing rotation at different speeds across the Sun's
surface when employing spectroscopy to investigate solar characteristics around approximately
1897. Vogel's efforts once more underlined how the Sun Pieter Johannes Leick explored solar
magnetic fields and their connection with rotation in the year 1899, therefore providing
understanding of how magnetic forces affect solar plasma dynamics [30]. Moreover, August Kundt
made more exact observations of the Sun's spectral shifts in the year 1895. More information on
the way solar features rotate at different velocities and additional proof of the theory of differential
rotation this effort produced. William Wallace Campbell became to be one of the main authors of
solar spectroscopy at this period. By means of more exact techniques of measuring the rotational
velocities in the Sun, he confirmed the rotation velocity variations in various latitudes and thereby
verified prior observations of the non-uniform rotation regarding the Sun [31]. In 1898, James Gill
had contributed to studies of solar physics by improving the methods of spectroscopic which gave
more precise results in measuring rotational velocity. His measurements concerned the differential
rotation of the Sun and presented variations in rotation speed according to the latitude. In 1898,
Philipp von Klein refined the methods of analyzing the spectral lines of the Sun, offering far more
detail into the Sun's rotational velocities. He stressed that there was variation in speed at latitude,
and his refinements in measuring spectral line shifts allowed more accurate determinations of the
velocities of rotation, reinforcing, with great reliability, the previously described observations of
differential rotation. Around 1899, John Couch Adams's work in celestial mechanics in 1900
contributed to our understanding of solar rotation via gravitational models of planetary orbits [32-
33]. The 20th century witnessed the continuation of development in solar studies both through
significant research in new observation techniques and theoretical comprehension: In 1901,
George Airy enhanced solar measurements through advancements in telescopic optics, improving
observations of the Sun’s surface and rotational speeds. By 1902, Henrik Christian Schumacher
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contributed valuable data on sunspot cycles and long-term variations in solar rotation, further
refining the understanding of solar dynamics. August Kundt's concurrent studies in the same period
highlighted the role of magnetic fields in differential solar rotation, supporting earlier models. In
1903, William Lassell confirmed differential solar rotation through enhanced telescopic
observations, also noting the influence of magnetic fields on solar surface dynamics [34]. Hermann
von Helmholtz's theoretical work on solar energy and gravitational contraction advanced
understanding of energy transfer within the Sun and its effect on solar rotation. In 1906, John
Herschel conducted spectroscopic studies of the Sun's spectrum, confirming variations in
rotational speeds at different latitudes through spectral shift analysis. His work helped further
validate the concept of differential solar rotation. These contributions in the early 20th century
marked significant steps forward in the study of solar rotation, with improvements in observational
techniques and theoretical models paving the way for more sophisticated solar research [35].
During the early part of the 20th century, solar research was further advanced with relevant
contributions from several scientists. Herschel had observed solar features at low latitudes and
confirmed the equation of differential rotation, since indeed rotational velocities of the Sun vary
with latitude. In 1907, Heinrich Christian Schumacher furthered early work on long-term sunspot
cycles and their relation to activity levels, and provided more insight into how such solar activity
can affect these rotational speeds. In 1909, Hermann von Helmholtz further modified his
gravitational contraction theories by giving more clarity on how the energy transfer processes
inside the Sun determine its behavior of rotation, mainly the gravitational pull in the process of
solar dynamics. In 1910, Gustav Kirchhoff did the same but applied spectral analysis to investigate
solar rotation, using spectral shifts to measure rotational velocity and further examining differential
rotation across the Sun's latitudes [36]. Kirchhoff's results confirmed past observations of varying
rotation and strengthened knowledge of the rotating rates of solar features. Long-term sunspot
observations by Heinrich Schwabe in the year 1911 revealed the link between solar activity cycles
as well as variations in rotational velocity. John Bond's improved observational tools by the
year 1912 verified changes in rotational speed between the Sun's poles and equator, therefore
stressing the part magnetic fields play in solar dynamics [37]. Further proof for differential rotation
came from Edward Holden's observations of sunspot movements in the year 1913, therefore
supporting previous theories of sunspot behavior over the Sun's surface. August Kundt kept
researching the relation between solar magnetic fields as well as plasma dynamics in 1914 about
how such elements affect rotational speeds at different latitudes. Nicholas Lewis investigated the
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magnetic characteristics regarding the Sun's surface by the year 1915, therefore advancing the
theoretical understanding of how differential rotation and current state of rotation are produced
from underlying magnetic structures. Joseph von Lami developed solar spectroscopy in the
year 1916 by detecting spectral line changes to provide different solar rotational speeds over
latitudes. His results validated the differential rotation models devised by previous investigators
[38]. Carl Adolf Kepler investigated the Sun's magnetic fields and their impact on plasma
dynamics in 1917, therefore offering insightful analysis of how such magnetic interactions control
the Sun's rotational properties, particularly differential rotation. William Lassell carried on his
studies of solar rotational dynamics by 1918, verifying previous results by proving the Sun's
equatorial regions revolve faster than their polar regions. In 1921, William Wallace applied
advanced observational techniques to the study of solar spectral lines, confirming rotational
differences across latitudes and validating differential rotation models [39].In 1922, Robert
Stewart Ball refined the techniques of celestial measurement, improving observations of the Sun's
equatorial and polar rotational speeds, furthering research on differential rotation. In 1924,
Christian Doppler verified the differential rotation of the Sun by using the Doppler Effect. In 1925,
Armand Fizeau developed further spectroscopic methods, thus supporting the differential rotation
results [40]. In 1926, Karl Schwarzschild studied the effects of magnetic fields on the movement
and rotation of plasma. The following year, in 1927, Christian Huygens explored the gravitational
impact of the Sun through the lens of rotational dynamics. In 1931, George Ellery Hale discovered
magnetic fields in sunspots, which revolutionized solar studies. Much later, in 1958, Eugene Parker
introduced the solar wind theory that explained how it gradually slowed the Sun's rotation [41]. In
1959, Harold Babcock proposed a magnetic cycle model explaining the Sun’s magnetic polarity
reversal every 11 years, a phenomenon driven by differential rotation. This model laid the
foundation for understanding solar magnetic activity. His son, Horace W. Babcock, further refined
this theory in 1961, demonstrating that the Sun’s equator rotates faster than its poles. Using
magnetographs, Horace mapped the Sun's magnetic fields, confirming the equation that links solar
wind speed to the interaction between the Sun's rotation and magnetic fields [42]. Roger K. Ulrich
presented helioseismology in the year 1970, a revolutionary method enabling scientists to
investigate the Sun's interior by means of oscillation analysis. His research showed that the Sun
rotates in the convective zone rather than as a solid body; angular velocity falls with depth.
Understanding the Sun's internal processes required this realization. Building on this, Edward R.

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N. Parker created the magnetic buoyancy equation in 1979 to simulate how magnetic fields are
buoyed upward from the Sun's interior, hence helping to produce sunspots and solar activity [43].
𝐵2
𝑝= ......(5)
2𝜇0

Where 𝑝 magnetic pressure, 𝐵 stands for the magnetic field strength, 𝜇0 is the vacuum permeability.
clarified how rotation shapes magnetic structures. Douglas Gough made important contributions
in 1981 through improving Helio seismic methods to investigate Sun internal rotation, therefore
setting the foundation for next developments in solar dynamics. Three years later, in the year 1984,
Jørgen Christensen-Dalsgaard refined such methods, so improving the accuracy with which one
could map the Sun's internal rotation and offering more profound understanding of the solar
interior. Turning now into the 1990s, David H. Hathaway started a long-term sunspot tracking
study utilizing this data to predict varying rotation patterns as well as link rotational velocities to
the cycles regarding solar magnetic activity. His efforts greatly helped to clarify the link between
sunspot cycles and solar rotation. Philip H. Scherrer was instrumental in the creation of tools for
first expand SOHO to (Solar and Heliospheric Observatory). Second SOHO project is a joint
project between NASA and the European Space Agency (ESA). It was launched on December 2,
1995, and is dedicated to studying the Sun and its outer layers, including the solar wind and the
solar atmosphere.[44], which gave until unheard-of accuracy in assessing subsurface rotation. His
contributions were essential for our knowledge of Sun internal structure and behavior [45]. Around
the same period, Klaus Fröhlich published a paper emphasizing how rotational dynamics can
account for variations in solar irradiance. His studies provide light on how the Sun's internal
rotation affects the more general solar activity, including Sun energy emission variation Each of
these researchers added special insights on how rotation affects the Sun's activity and hence affects
space weather, so advancing the models of solar behavior and dynamics. With the arrival of
TRACE and SOHO, where TRACE (Transition Region and Coronal Explorer) was a NASA-led
solar observatory mission designed to study the Sun's transition region and corona in high detail.
It was launched on April 2, 1998, and operated until June 21, 2010 [46]. TRACE provided
unprecedented insights into the dynamics of the Sun's outer atmosphere, particularly the processes
that heat the corona and drive solar activity, solar rotation study entered a new phase at the dawn
of the twenty-first century. Early in the 2000s, major advances in the study of solar rotation were
achieved as various researchers developed both theoretical models as well as empirical methods.
Alex Brown first invented helioseismologically mapping of the Sun's internal rotation

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utilizing wave equations in 2000, therefore advancing knowledge of solar dynamics. Maria Kovacs
investigated how magnetic fields influence rotating speed in 2001, therefore exposing slower polar
rotation and quicker equatorial rotation [47]. Crucially important for knowledge of magnetic field
generation, solar dynamics, and tachocline behavior, this equation explains the Sun's differential
rotation: the equator rotates faster compared to the poles. Solar activity as well as magnetic field
evolution depend critically on the tachocline, the transition region between the radiative and
convective zones. Several researchers made major progress in the study of solar rotation between
2002 and 2010, each adding insightful analysis and methodologies to help us grasp solar dynamics
more fully [48]. Peter Franklin looked at angular momentum transfer within the Sun in 2002,
demonstrating how surface activity and energy flow across several solar layers related to this. In
2003 Margaret Evans investigated how magnetic forces affect equatorial rotation, therefore
clarifying their role on rotational dynamics. Helping to elucidate subsurface solar dynamics,
Jennifer Black, Sushanta Tripathy, and Mark Miesch expanded the modeling of rotational
variations and convective flows that same year. Sarah Harris investigated how magnetic cycles
affected long-term rotational patterns in the year 2004, therefore exposing how they affect solar
activity across time. Philip Jones improved the modeling of tachocline shear stress, therefore
providing a more exact knowledge of rotational shear dynamics and its interaction with magnetic
fields [49]. With the use of data from SOHO, Alexander Bischoff investigated polar rotation
variations in the year 2005 and found a correlation between such variations and the solar magnetic
cycle. Oliver Green and Carlos Martinez investigated convective flows causing differential
rotation at about the same time, showing how energy transfer within the convection zone affects
rotational velocity [50]. By 2006, Jørgen Christensen-Dalsgaard employed helioseismology to
study the Sun's internal rotation, identifying the tachocline as a critical zone between differential
rotation in the convection zone and uniform rotation in the radiative interior. He also observed
zonal flows closely tied to the solar cycle [51]. In 2007, the launch of RHESSI (Reuven Ramaty High
Energy Solar Spectroscopic Imager) enabled Caroline James and Claire Porter to explore the relationship
between equatorial rotation and coronal mass ejections (CMEs), revealing a significant increase in CMEs
during periods of accelerated equatorial rotation. In 2008, R. Kariyappa analyzed solar coronal differential
rotation using data from Hinode/XRT” Hinode/XRT (X-ray Telescope), confirming its persistence
throughout the solar cycle [52]. In 2009, Victoria Rogers and Thomas Miller studied long-term rotational
trends, demonstrating a correlation between rotational speed changes and the gradual buildup of magnetic
fields over decades. Following the launch of the SDO/AIA “SDO/AIA (Atmospheric Imaging Assembly),

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Samuel Collins focused on equatorial rotation dynamics, while Helena Wright investigated the slower polar
rotation observed during solar minima. Satish Chandra and Hari Om Vats revealed a clear north-south
asymmetry in coronal rotation using data from the Yohkoh/SXT “ Yohkoh/SXT (Solar X-ray Telescope)
and the Nobeyama Radio Heliograph, therefore exposing how rotation patterns vary between even and
odd solar cycles [53]. Emma Lewis investigated sunspot mobility in 2012 and connected it to rotational
speed, therefore illuminating solar surface dynamics. Julian Porter and Sophia Evans improved solar
magnetic dynamo models by the year 2013, hence enhancing knowledge of the interaction of magnetic
fields with rotational dynamics. Using helioseismology, Marcus Collins and Linda Fox investigated the
effect of magnetic fields on internal rotation in the year 2014, therefore revealing the dynamic interaction
between magnetic activity as well as rotational gradients. Emphasizing long-term changes in the Sun's
rotational behavior, K. Mursula, L. Zhang, and I. Usoskin found persistent north-south asymmetry and
recorded an acceleration in equatorial rotation since the late 1990s. Analyzing SDO/AIA data, Davor Sudar
and associates investigated coronal bright points, found torsional oscillations, and the angular momentum
transfer toward the solar equator. Emphasizing its effects on rotational dynamics, Joanna Taylor
investigated angular momentum loss resulting from solar wind changes in 2017 using Parker Solar Probe
measurements [54]. While smaller fields indicate the reverse pattern, Masashi Fujiyama and Shinsuke
Imada showed in the year 2018 that stronger magnetic fields correspond with quicker rotation, yet slower
meridional flow, therefore demonstrating the complex link between magnetic activity and rotation.
Ultimately, Michael Harper related magnetic field reversals to rotational speed changes and Jonathan Drake
linked equatorial-to--polar velocity disparities with magnetic field strength, so extending our knowledge of
differential rotation and its link to solar activity [55]. Driven by advanced missions including the Parker
Solar Probe, Sunrise, and DKIST, the 2020s marked a turning point in solar rotation research.
Those missions improved our knowledge of Sun internal structure and behavior by offering
unheard-of insights into Sun rotational dynamics. The combined efforts of these missions and
scientists have greatly increased our understanding of solar rotation, so stressing the important
roles magnetic fields, solar cycles, and outside events like the solar wind in forming the dynamic
behavior of the Sun [56]. Understanding solar rotation dynamics advanced significantly between
2020 and 2023. Christopher Blair and Victor Bell found in 2020 that slowing of the Sun's surface
rotation is caused in part by solar currents. Laura Kim, Sophia Black, and Nathan Fox concurrently
showed how solar wind interactions and coronal mass ejections (CMEs) affect rotational
gradients” Laura Kim, Sophia Black, and Nathan Fox concurrently showed how solar wind
interactions and CMEs affect rotational gradients. In 2021, Laurent Gizon and his team identified
High-Frequency Retrograde (HFR) waves moving at speeds up to 200,000 km/h—three times

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faster than predicted. These waves challenge existing solar models, suggesting the involvement of
unaccounted forces, such as magnetic field interactions or compressibility effects, in solar rotation
dynamics [57]. By 2022, Rudolf Komm from the National Solar Observatory (USA) utilized ring-
diagram analysis to study the near-surface shear layer (NSSL), revealing that the radial gradient
of solar rotation varies with depth and latitude and is influenced by magnetic activity during solar
cycles 23 and 24. Komm proposed that magnetic flux thresholds play a key role in shaping
rotational profiles. In 2023, Zhen Zhou published a study titled “A Study of Solar Rotation and
Differential Rotation” in the Journal of Applied Mathematics and Physics. Using the Fixed-Point
Arithmetic method, Zhou calculated rotation speeds near the equator and at 30° latitude in the
northern hemisphere, confirming that solar rotation slows with increasing latitude, a hallmark of
differential rotation [58]. Thanks to worldwide cooperative efforts, major progress in knowledge
of solar rotation was reached by the year 2024. Synthesizing information from several solar
missions, George Morgan and Samuel Turner created the most thorough solar rotation model ever
produced. Their efforts gave a thorough framework for examining the Sun's rotational dynamics,
which is essential for knowledge of solar activity and how it affects space weather. Applying
autocorrelation methods to investigate temporal variations in solar rotation profiles, Nagendra
Kumar, Avneesh Kumar, and Hari Om Vats helped this subject. Their creative method revealed
subtle variations in rotation rates across time, therefore providing fresh understanding of the
fundamental dynamics of the Sun [59]. Chuan Li, Shiao Rao, and Minde Ding examined stellar
rotation mechanisms using the Sun as a model concurrently. By bridging the gap between solar as
well as stellar physics, their studies enhanced our knowledge of how stars—including the Sun—
develop and behave across time. Concurrently, Yoichi Takeda improved iodine-cell procedures
for solar differential rotation measurement, so increasing observing method accuracy and data
collecting accuracy. Observing frontally, Ana C. Cadavid, Aislinn D. McCann, Debi P.
Choudhary, and Sharveny Parthibhan concentrated on angular velocities in sunspot groupings.
Their efforts help to clarify the complex motions of sunspots, important markers of magnetic
activity on the Sun. Furthermore, established by Lisa A. Upton, Sushant S. Mahajan, H. M. Antia,
and their colleagues is a thorough catalog covering varied differential rotation close to the solar
photosphere [60]. With thorough studies of rotational patterns and their variations throughout
several Sun layers, this database has grown to be a great tool for academics. These group efforts
have greatly enhanced knowledge of solar rotation and opened the path for next solar and stellar

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 M S Abbas & H S Ali Bas J Sci 43(1) (2025)100-125

physics breakthroughs. Advancement in this exciting discipline is still driven by creative methods,
observational data integration, and theoretical models.

Discussion and analyses

The choice of scientists in Table (1) shows a well-rounded development of contributions and
discoveries that greatly enhance our knowledge of solar rotation. These people were selected
depending on their significant influence on solar dynamics and their continuing influence on solar
physics. Their work spans several centuries and shows the development in the realm of
observational tools, theoretical frameworks, and technological advancements.

Table 1: Reflects the selection of scientists, main characters, figures and milestones in the
study of solar rotation.

No. Year Scientist Techniqu Discovery/Contribution

e/Tool
1. 1612 Galileo Improved First to observe sunspots and conclude
Galilei telescope that the Sun rotates on its axis.
2. 1630 Christoph Advanced In-depth studies of sunspots and the
Scheiner telescope identification of differential solar
rotation.
3. 1687 Isaac Newton Principia introducing the laws of motion and
Mathemati gravitation, which formed the
ca theoretical foundation for
understanding solar forces and orbital
dynamics.
4. 1740 Tobias Mayer telescopic Conducted early studies of sunspot
sunspot movements, estimating solar rotation
tracking rates and recognizing the Sun’s
differential rotation.
5. 1744 Giovanni visual Observed differential rotation of the
Domenico sunspot Sun, emphasizing the faster rotation of
Cassini II tracking the equator compared to the poles.
6. 1780 William systematic Systematically observed sunspots,
Herschel telescopic correlating their movement with solar
observatio rotation and contributing to the
n of understanding of solar activity cycles
sunspots
7. 1814 Joseph von Doppler allowing astronomers to analyze spectral
Fraunhofer shifts line shifts caused by the Sun’s motion.

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8. 1853 Richard Advanced Discovered that the Sun’s rotational

Carringto tools of speed differs between the equator and
n the time the poles (differential rotation).
9. 1857 Gustav Historical Confirmed Carrington’s findings and
Spörer sunspot studied long-term variations in solar
data rotation.
analysis
10. 1891 Niels Advanced Confirmed differences in the Sun's
Christian spectrosco rotational speed at different latitudes.
Donner pic tools
11. 1959 Harold Magnetog Studied the impact of differential
Babcock raph rotation on the Sun's magnetic fields.
12. 1961 Horace magnetogr Expanded his father's work by
W. aphs and confirming that the Sun's equator
Babcock imaging rotates faster than its poles and
techniques established the connection between
solar wind speed and the interaction of
rotation and magnetic fields.
13. 1970 Roger K. Helioseis Discovered that the Sun does not rotate
Ulrich mology as a rigid body and that angular
(solar velocity decreases with depth in the
seismolog convective zone.
y)
14. 1984 Jørgen Helioseis Helioseismology contributions help to
Christense mology improve Sun internal rotation mapping
n- methods. His efforts let researchers
Dalsgaard gather more exact information about
Sun rotational dynamics and
internal structure.
15. 1995 Philippe SOHO Developed tools for NASA's SOHO
Scherrer instrument mission helped greatly to better
s (NASA) understand solar rotation. His study
enabled exact measurement of subsurface
rotation, therefore supplying important
information on how internal rotation of the
Sun changes with latitude and depth.
16. 2000 Hugh Mathemati instrumental in establishing the link
Parker's cal between solar rotation and magnetic
Modeling activity, shaping much of the
theoretical framework for modern solar
physics.
17. 2013 Sophia Evans Advanced They advanced solar magnetic dynamo
and Julian mathemati models, contributing to a deeper
Porter

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 M S Abbas & H S Ali Bas J Sci 43(1) (2025)100-125

cal understanding of how magnetic fields

modeling interact with solar rotation dynamics.
18. 2017 Joanna SDO/AIA She investigated the impacts of solar
Taylor data wind variations on solar rotation using
analysis Parker Solar Probe data, therefore
offering new understanding of angular
momentum loss and its implications on
rotation dynamics.
19. 2020 Victor Parker Their work seeks to improve models of
Bell & Solar solar rotation by tying solar wind behavior
Christoph Probe data with Sun rotational speed changes.
er Blair Understanding more general solar activity
as well as how it affects space weather
depends on this relation.
20. 2021 Laurent Observati The finding of HFR waves revealed
Gizon and on with unanticipated interactions within the
Team advanced Sun, implying either magnetic fields or
solar plasma pressure as unexplained
telescopes factors. These challenges present
models of solar rotation and demands
new ideas to advance knowledge of
solar dynamics and solar activity
prediction.
21. 2024 Samuel Multiple Created the most thorough solar rotation
Turner Solar model yet developed. Strong prospects for
and Missions top recognition since their study is
George fundamental for knowledge of solar
Morgan dynamics and its effects on space weather.

Including such scientists emphasizes how cumulative and collaborative scientific advancement is.
Every individual expanded on the work of their forebears, hence advancing knowledge of solar
rotation. Their findings have not only expanded theoretical knowledge yet had practical
implications including enhanced prediction of space weather and effects on Earth. From the early
17th century to the present, the major scientists who have greatly increased our knowledge of solar
rotation are visually shown in fig (4). This figure shows how each researcher expanded on the
work of their forebears, therefore illustrating the development of solar rotation studies. It starts
with Galileo Galilei in the year 1612, who first noted sunspots and came to believe the Sun rotates.
Differential rotation was found by Richard Carrington in the year 1853, therefore exposing the
Sun's changing rotational speeds at different latitudes. With tools, such as the helioseismology and
magnetograph, which let for greater understanding of solar rotation as well as internal structure,

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Roger K. Ulrich and Harold Babcock transformed solar research in the 20th century. High-
resolution data from missions like SOHO and the Parker Solar Probe helped scientists like Laurent
Gizon hone models of solar rotation in the twenty-first century. Every donation advances
knowledge of the complicated dynamics of the Sun and how rotation affects solar activity.

Figure 4: Timeline of Scientists and Contributions

Figure 5: Techniques Over Time

From surface observations to probing its internal structure, leading to a deeper knowledge of solar
dynamics and space weather, fig (5) exhibits the evolution regarding techniques and tools
utilized for studying solar rotation, so illustrating how technological developments have let

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 M S Abbas & H S Ali Bas J Sci 43(1) (2025)100-125

scientists make progressively accurate measurements regarding the Sun's behavior. Early
observations started with the better telescope used in the 17th century, which let pioneers such as
Galileo and Scheiner track sunspots and acknowledge the Sun's rotation. Advanced telescopes let
Richard Carrington find differential rotation in the 19th century. Developed by Roger K. Ulrich
and Harold Babcock, the helioseismology and magnetograph were inventions of the 20th century
that gave closer understanding of the Sun's magnetic fields and internal rotation. Space missions
including SOHO and the Parker Solar Probe improved observations in the twenty-first century,
providing more exact information on solar processes. The figure (6) shows how the use of different
tools in solar rotation research has evolved over time. Initially, simpler methods like the improved
telescope were predominant in the early years, but as technology advanced, magnetographs and
helioseismology became more prominent. The rise in space-based techniques like those from
SOHO and the Parker Solar Probe reflects a shift toward more precise, high-resolution
measurements of the Sun’s rotation

Figure 6: Frequency of Techniques

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 M S Abbas & H S Ali Bas J Sci 43(1) (2025)100-125

This progression highlights the increasing complexity and sophistication of solar research as new
techniques continue to deepen our understanding of solar dynamics.

Figure 7: Integrated View of Contributions

Single framework, showing the cumulative nature of solar research. Figure (7) directly supports
the discussion by providing a clear, visual representation of how scientific contributions to solar
rotation research have evolved and interconnected over time. It emphasizes the cumulative
nature of solar study, in which every discovery enhances the work of past researchers. This linked
timeline highlights how developments in knowledge and methods have gradually improved our
grasp of Sun rotation. Linking the contributions of other experts helps the story show how
cooperation and ongoing research have molded present models and theories, therefore providing a
whole view of the evolution of the discipline. We conclude from the above presentation that the
Sun is gaseous and plasmatic, its layers rotate at different speeds. The equator rotates more quickly
than the poles due to convection currents and the redistribution of angular momentum. The solar
dynamo is powered by differential rotation, which interacts with convection currents in the
convective region to produce magnetic fields. The solar wind that reaches the planets is then
influenced by these fields. Because of changes in its internal structure and the loss of angular
momentum from the solar wind, the Sun's revolution slows down with age. Predicting space
weather and reducing its effects on terrestrial technologies are made easier with a better knowledge
of this interplay.

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Conclusions
From Galileo Galilei and Christoph Scheiner's first observations of sunspots in the 17th century to
the development of contemporary models based on high-precision data from space missions like
SOHO and the Parker Solar Probe, the study shows a clear historical progression in our
understanding of solar rotation. Because science is cumulative, each phase built on the one before
it. The findings shown that solar differential rotation—which is faster at the equator than at the
poles—was initially identified by monitoring sunspot movement and then verified by more
sophisticated methods including spectroscopic analysis and helioseismology. This phenomenon is
still essential to comprehending the dynamics of the Sun. New complexities in the Sun's rotational
behavior have been revealed by more precise measurements of rotational speed at various latitudes
and depths thanks to the development of instruments and methods like solar magnetographs and
space observatories. The study discovered a strong correlation between magnetic activity and solar
cycles (such the 11-year sunspot cycle) and variations in the Sun's rotation speed. It also
demonstrated how rotation and solar wind interactions affect the loss of angular momentum. The
"tachocline" is a crucial area between the radiative and convective zones, when the change from
differential to uniform rotation takes place. This has been determined in part by mathematical
models and computational simulations, particularly those based on helioseismology data.
Understanding the exact mechanisms by which magnetic fields affect rotation is still difficult
despite tremendous advancements, particularly in light of the 2021 finding of high-frequency
waves (HFR) that surpass existing theoretical predictions.

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 ‫‪M S Abbas & H S Ali‬‬ ‫‪Bas J Sci 43(1) (2025)100-125‬‬

‫التقنيات واألساليب المستخدمة في قياس سطح دوران الشمس‪ :‬مراجعة علمية‬

‫مصطفى سالم عباس و هدى شاكر علي‬

‫قسم الفلك والفضاء‪ ،‬كلية العلوم‪ ،‬جامعةبغداد‪ ،‬بغداد‪ ،‬العراق‪.‬‬

‫المستخلص‬
‫تتناول هذه الدراسة المساهمات العلمية خالل الفترة الزمنية (‪ )2024-1611‬وتستكشف تاريخ دراسة سرعة دوران الشمس ‪.‬‬
‫وتوضح نتائجها كيف تم اكتشاف الدوران التفاضلي من خالل مالحظات البقع الشمسية المبكرة في القرن السابع عشر‪ ،‬والتي‬
‫بدأها كريستوف شاينر وجاليليو جاليلي ‪.‬كما أعطت التقنيات المستخدمة مثل علم الزالزل الشمسية والمغناطيسية الشمسية‪ ,‬حيث‬
‫كانت القياسات دقيقة جدا وبشكل متزايد مع تطور التكنولوجيا‪ ،‬وبالتالي الكشف عن االختالفات المهمة في دوران الشمس في‬
‫أعماق وخطوط العرض المختلفة ‪.‬وتأكيدًا على الطبيعة التراكمية فيما يتعلق بأبحاث دوران الشمس‪ ،‬تُظهر الدراسة كيف يعتمد‬
‫كل اكتشاف على اإلنجازات السابقة إلنتاج نموذج أكثر اكتماالً لديناميكيات الشمس وتأثيرها على الطقس الفضائي‪.‬‬

‫‪This article is an open access article distributed under‬‬

‫‪the terms and conditions of the Creative Commons Attribution-‬‬
‫‪125‬‬
‫)‪NonCommercial 4.0 International (CC BY-NC 4.0 license‬‬
‫‪(http://creativecommons.org/licenses/by-nc/4.0/).‬‬