Chapter 1: Summary

The magnetic fields and dynamics of solar polars play a crucial role in the 10.7-year Schwabe cycle, the 22-year magnetic cycle, the approximately 81-year Gleissberg cycle, and the roughly 200-year grand cycle. The meridional circulation, torsional oscillations, and the convective zone top wedges located in the sub-photospheric region are considered the "codons" for predicting the next (even a batch of) solar cycle(s). The open magnetic field lines in the polar regions provide the initial mass and energy for the fast solar wind, thus playing a vital role in controlling solar activity and driving space weather.

Despite decades of long efforts by scientists, there are still significant gaps in our understanding of it. The Ulysses satellite, jointly developed and launched in 1990 by NASA and ESA, operated until 2007 but lacked remote-sensing instruments. In 2020, ESA launched the Solar Orbiter with a target inclination of 34 degrees to observe the solar polar regions from the side, yet it remains ineffective for observing the polar regions directly. So far, there have been no imaging observations of the solar polar regions from a vantage point outside the ecliptic plane, leading to an insufficient understanding of the behavior and evolution of the solar polar magnetic fields. This observational gap leaves three fundamental questions unanswered:

1） How does the solar dynamo operate and drive the solar magnetic cycles?

2） What is the driving source of the fast solar wind?

3） How do space weather processes originate globally from the Sun and propagate throughout the solar system?

In recent years, with the rapid development of China's solar exploration missions, the CHASE satellite was launched in 2021 into a solar-synchronous orbit, blazing a trail; ASO-S followed with even clearer remote-sensing instruments. The remote-sensing instruments on these two satellites, particularly the Lyman-α Solar Telescope on ASO-S, which pioneered observations of the solar transition region in this band. In 2021, the soft X-ray extreme ultraviolet imager on FY-3E became China's first space-based solar telescope; in 2022, the solar transition region imager on the new technology experimental satellite also began relevant observations. Combined with observations from satellites such as SDO, SOHO, STEREO, Solar Orbiter, Hinode, and PSP, hundreds of important papers have been published in major journals.

The Solar Polar Observatory (SPO) mission aims to address these three unresolved scientific questions by conducting high-latitude imaging observations of the solar polar regions. To achieve its scientific objectives, the SPO will carry at least six remote-sensing instruments and four in-situ instruments. If the Advanced Helioseismology Imager (AHI) under discussion is successfully designed and approved, SPO will be a super SOHO+Ulysses detector, achieving highly definition helioseismic observations from the solar core to comprehensive, multi-dimensional remote-sensing imaging of the inner heliosphere. The six remote-sensing instruments, including the HMI (Helioseismic and Magnetic Imager), EUT (EUV telescope, comprising a multi-band EUV imager and a full-disk integrated spectrometer), VISCOR (Visible Light Coronagraph), VLACOR (Very Large-angle Coronagraph), XIT (X-ray Imaging Telescope), and RWA (Radio Wave Analyzer), will measure the vector magnetic field and Doppler velocity field in the photosphere and observe the Sun in EUV, X-ray, and radio bands, imaging the corona and heliosphere out to hundreds of solar radii. The four in-situ instruments, namely the Solar Wind Ion Mass Spectrometer (SWIMS), Solar Wind Ion Retarding Potential Analyzer (SWIRPA), Solar Energetic Particle Analyzer (SEPA), and Magnetometer (MAG), will measure the physical parameters of the solar wind plasma, high-energy particles, and interplanetary magnetic field, enabling in-situ detection of the magnetic field and low-and high-energy particles in the solar wind.

The SPO mission can:

1） Provide key vector magnetic and Doppler velocity measurements for the polar regions at latitudes above 80° (≈82° - 85°), deepening our understanding of the origin of the solar magnetic cycle;

2） Offer unprecedentedly clear direct imaging observations of the solar polar regions and in-situ measurements of charged particles and magnetic fields in these regions, revealing the mass and energy sources driving the fast solar wind;

3） Provide observational constraints to enhance our modeling and forecasting of the 3D-MHD mesoscale structures of the solar wind and the propagation of space weather events. Also, facilitate the training and generation of more coupled values in solar wind magnetosphere-ionosphere systems.

This's just a summary section. Tomorrow, I will tell about the historical achievements in polar solar magnetic field observations, as well as the background, current status, and prospects of China's SPO mission. Stay tuned!

Edited June 30Jun 30 by 千年极寒

Chapter 2: The History of Research on Solar Polar Magnetic Field

Most solar polar observations are from the ecliptic plane.

Since the early 20th century, the interplanetary solar wind has been confirmed. From 1943 to 1958, Parker, Alfvén et al. formulated the 3D-MHD magnetohydrodynamics equations, which underpin solar wind physics numerical forecasting. These equations consist of several key partial differential equations:

Where ρ is the plasma density, "v" is the plasma velocity, t is time, "p" is the magnetic fluid pressure, B is the magnitude of magnetic induction intensity, μ₀ is the vacuum magnetic permeability, "g" is the gravitational acceleration, "e" is the specific internal energy, and Q is other energy sources or energy dissipation terms.

Equation one expresses conservation of mass in the plasma. It shows the relationship between the rate of change of plasma density over time and the divergence of the plasma. The density variation at any point in the plasma is due to the convergence or divergence of the plasma, indicating that mass cannot be created or destroyed but can only be transferred with the plasma motion.

Equation two reflects conservation and change of plasma momentum. The left side represents the rate of change of plasma velocity over time and the acceleration caused by spatial variations in velocity. The right side includes forces such as gas pressure gradient force, electromagnetic force related to the magnetic field, and gravity. It shows that the change in plasma momentum depends on the resultant force and reflects the alteration of the plasma's state of motion under the influence of various forces.

Equation three describes conservation and transformation of plasma energy. The left side involves the rate of change of total plasma energy (sum of internal, kinetic, and magnetic energy) over time and the total energy flux. The right side includes energy changes caused by gravitational work and other energy sources or dissipation terms. It demonstrates the mutual transformation of internal energy, kinetic energy, and magnetic energy during plasma motion, as well as the transport and dissipation of energy in space.

Equation four is the normalization equation, a fundamental theory for the NLFFF method. It ensures that the magnetic field is source-free, indicating that magnetic field lines are closed curves with no magnetic monopoles. This aligns with Maxwell's equations and ensures the mathematical description of the magnetic field in magnetohydrodynamics is realistic and physically interpretable.

Due to the tilt of the Sun's rotation axis relative to the ecliptic plane normal, about 7.25 degrees, the solar polar regions can be observed from the ecliptic plane during specific periods. Although the viewing angle exceeds 82 degrees, during the equinoxes in March and September, the Sun's south and north poles can be observed from Earth.

In the fall of 1961, Babcock, Parker et al. reported an average magnetic field strength of about 1G in the solar polar regions. In the 1970s, Deng et al. used a full-disk magnetograph at the Huairou Solar Observatory of the Chinese Academy of Sciences to observe the polarization of the 532.4nm Fe I line. They modeled the high-latitude vector magnetic field and found that during the minimum between SC22 and SC23, the net magnetic flux in the south polar region was approximately 2.5×10²² Mx, comparable to the interplanetary magnetic field (IMF) strength measured at 1.0AU. Their numerical inversion model also revealed significant depth variations in the magnetic field strength distribution in the quiet solar photosphere. The bottom magnetic field was mainly weak, less than 50mT, with an average peak of 25mT and a tail extending to 150mT. A small peak existed at 100-110mT, indicating that these strengths dominated in the thousand-gauss fields of the network flux tubes. With height variation, the magnetic field distribution changed significantly due to magnetic field weakening and flux tube expansion.

Since the launch of the Hinode satellite by JAXA/NASA in 2006, its Solar Optical Telescope (SOT) equipped with a Stokes spectro-polarimeter (SP) has enabled higher spatiotemporal and spectral resolution observations of the polar magnetic field. Tsuneta et al., 2021 used Milne-Eddington inversion code to obtain vector maps of the polar magnetic field. They found vertical magnetic flux tubes in the polar regions (70°–90° latitude) with isolated unipolar patches of about 1000G. Horizontal magnetic fields were also widespread. During the solar minimum, the ratio of positive to negative magnetic flux in the polar regions was approximately 1/2, indicating that only about 1/3 of the magnetic flux remained open. Jin et al.'s further research identified over 300 small-scale bipolar magnetic emergences (BMEs) in the polar regions. These BMEs had randomly distributed magnetic axes that did not follow the common Hale's law or Joy's law in active regions. Using polar observation data from Hinode/SOT-SP (2012–2021), Yang et al. (2020) studied the long-term variation of polar magnetic fields (see Figure 1).

Figure 1. The radial magnetic flux distribution in the polar caps

(Click here to access the original resolution image)

Polar view of the radial magnetic flux distribution in the polar caps observed by Hinode. (a) Radial magnetic field in the north polar cap measured in 2012, 2015, 2019, and 2021. (b) Similar to (a) but for the south pole. The plus signs mark the poles, and the solid curves indicate the latitude separated by 5°. Figure from Yang et al.

They found that the polar magnetic reversal lagged behind low-latitude regions, indicating polar magnetic flux transport. Additionally, Yang et al. discovered that except during the polarity reversal phase of the solar cycle, the radial magnetic flux density in high-latitude regions was weaker than in low-latitude regions. To explore the subsurface meridional flow behind these observations, Yang et al. employed a surface flux transport model to simulate the global radial magnetic field. The mathematical treatment was as follows:

Where Bᵣ is the radial magnetic field; T is time; R is the radius of the sun; θ is the latitude angle; "uθ" is the latitudinal component of the meridional flow, expressed as:

Where θₘᵢₙ and θₘₐₓ are the latitudes of the polar boundary (usually taken as ≥60 °), and C is the velocity constant; D is the diffusion coefficient of ultrafine grains; S is the source term of magnetic flux, which is taken as 0 in the simulation in the text.
What's more, Xu et al. (2021) studied the migration of Polar Crown Filaments (PCFs) towards the poles over the past 100 years, covering solar cycles 16–24. The data were mainly from full-disk Hα images of the Kodaikanal Solar Observatory (India), Kanzelhoehe Solar Observatory, and Big Bear Solar Observatory. PCFs were visually identified and their polarward drift measured by linear regression. They found significant north-south asymmetry in PCF migration, with northern PCFs usually reaching higher latitudes first. Also, no strong correlation was found between PCF migration speed and the maximum sunspot number. However, in the SH, PCF speed correlated with the long-term trend of the differential-rotation latitude gradient B ( r=0.51 ) and its first derivative ( r=0.90 ). There was also no strong link between PCF speed and the maximum sunspot number ( r=0.43 in the north and r=0.34 in the SH ).

Yang et al.'s research revealed a maximum polar meridional flow of 11 m/s between 0° and 70°N and a maximum equatorward meridional flow of 3 m/s between 70° and 90° latitude. In addition to photospheric magnetic field observations, observations of the upper solar atmosphere in polar regions are also crucial. Coronal holes are regions where open magnetic field lines extend into interplanetary space. They appear as dark areas in extreme ultraviolet (EUV) and X-ray bands and are the primary source regions of the fast solar wind. Observations over the past two decades have revealed many small-scale quasi-current systems in coronal holes, including spicules in the chromosphere, network jets in the transition region, and EUV propagating intensity disturbances (called jets). These features may be driven by small-scale magnetic reconnection in the solar atmosphere, operating on scales of a few hundred kilometers and triggered by rapid changes in the photospheric magnetic field on timescales of less than 5 minutes. Hinode observations of X-ray jets showed two distinct velocities, about 200 and 800 km/s. The large number of X-ray jets and the evident high-speed outflows suggest a possible contribution to the fast solar wind. In addition to jets observed in plume regions, Tian et al. reported repetitive jets in non-plume regions at temperatures of about 10⁵–10⁶ K using IRIS, SDO, Hinode, and PROBA-2 observations. The exact contribution of these small-scale jet features to the solar wind remains a topic of ongoing debate in heliophysics. Chromospheric spicules, which are ubiquitous, are also considered potential mass contributors to the solar wind. De Pontieu et al. (2007) and McIntosh et al. (2011) reported that Alfvén waves carried by spicules have sufficient energy flux to accelerate the solar wind. De Pontieu et al. noted that the energy flux of Alfvén waves carried by spicules in the chromosphere is about 10⁵ erg/cm²/s, comparable to the energy flux required for the solar wind. This provides sufficient energy for solar wind acceleration. In the lower corona, as height increases, the amplitude of Alfvén waves decays due to atmospheric damping during propagation, causing their energy to gradually dissipate. McIntosh et al. further confirmed this conclusion through ground-based observations at the Big Bear Observatory. However, their exact contribution remains an unresolved issue. The Solar Ultraviolet Measurement of Emitted Radiation (SUMER) instrument on the SOHO mission provides high-resolution spectroscopic observations of the Sun at different positions. Hassler et al. (1999) used the Ne VIII 77 nm emission line to study mid-latitude quiet solar regions and polar regions. They showed that the strongest upflow plasma in mid-latitude regions occurs at the edges of convective cells, while in polar regions, the plasma is predominantly blueshifted. SUMER also regularly conducts polar spectroscopic measurements. Hinode mission observations indicate that the nascent fast solar wind in polar coronal holes originates in the transition region and propagates along open magnetic field lines. Harry et al. (2020) revealed enhanced non-thermal velocities, i.e., line broadening in coronal Fe XII emission lines, based on six years of study of polar regions. SUMER observations of various ions suggest that these ions are heated by ion cyclotron waves, which are generated through mode conversion of Alfvén waves.
The third part of the article will be published tomorrow, stay turned！

Edited June 30Jun 30 by 千年极寒

Chapter 3: The Groundbreaking Significance of the Ulysses and Solar Orbiter Mission in In Situ Detection of the Solar Polar Magnetic Field

Due to observational limitations within the ecliptic plane, the aforementioned findings were obtained indirectly. However, in situ observations outside the ecliptic plane, particularly in polar regions, have been rare. In this context, the Ulysses spacecraft, launched in 1990, and the ongoing Solar Orbiter mission have played a pioneering role in solar polar observation. The latter is gradually moving out of the ecliptic plane. Ulysses utilized Jupiter’s gravitational assist to achieve a high-inclination orbit of approximately 80° relative to the ecliptic plane. This enabled the Ulysses mission to fly over the solar poles multiple times during its mission period, completing three polar orbits covering different phases of solar cycles 22 and 23 (each orbital period was about 6 years). Although Ulysses did not carry remote sensing imaging instruments, its in situ instrument package provided crucial measurements of charged particles across various energy spectra and magnetic field properties at a distance of about 1.34 AU from the Sun. These data offered unprecedented insights into the structure and dynamics of the heliosphere from high solar latitudes.

As shown in Figure 2, Ulysses’ first orbit covered the solar minimum period, revealing that the solar wind speed in the polar regions was higher than in the equatorial regions.

Figure.2. (a)–(c) Polar plots of the solar wind speed, colored by the Interplanetary Magnetic Field (IMF) polarity for Ulysses’ three polar orbits. (d) Contemporaneous values for the smoothed sunspot number (black) and heliospheric current sheet till (red). Figure from McComas et al.

Its second perihelion passage detected a more complex global solar wind structure across all solar latitudes. The fast solar wind emanating from polar coronal holes was measured at a speed of about 750 km/s. As the Sun rotates differentially, the fast wind streams extending from the equatorial regions of polar coronal holes interact with the slow wind streams from the equatorial flow bands. Due to solar rotation, co-rotating interaction regions (CIRs) are formed. Ulysses’ orbit allowed for wide-angle observations of CIRs, a significant advantage of polar orbits, greatly enhancing our understanding of the three-dimensional magnetic topology of the heliosphere. These conclusions are explicitly and thoroughly elaborated in the book "Understanding Space Weather and the Physics Behind It" by the renowned American solar physicist Delores Knipp (first published in 2020).

P.S.

I strongly recommend members who want to further their academic studies in space weather to read this book, which is very helpful for you and can greatly enhance your theoretical foundation.

The polar solar wind emanates from the open magnetic field lines of the poles, carrying frozen magnetic flux tubes and tracers of their coronal regions of origin.

P.S. The Principle of Flux Freezing in Magnetohydrodynamics (MHD):

In an ideal MHD environment, the principle of flux freezing can be represented by the following equation:

Induction of the equation:

It shows that the rate of change of magnetic induction B with time is related to the curl of the cross product of velocity field v and magnetic field B.In ideal magnetohydrodynamics (MHD), Ohm’s law is E+v×B=0, where E is the electric field strength. This equation reflects the relationship between the electric field, magnetic field, and velocity field under ideal conductivity. From this, the rate of change of magnetic flux can be derived. Considering a contour C moving with the plasma, which spans a surface S, according to Faraday’s law of electromagnetic induction, after simplification, we get:

Combined with the induction equation, it follows that dΦ/dt = 0, i.e., the magnetic flux Φ remains constant over time, thus illustrating the principle of flux freezing.

Magnetic flux freezing imposes constraints on plasma motion, restricting plasma movement in the direction perpendicular to the magnetic field lines. This constraint is significant in the solar atmosphere and interplanetary space, such as in the propagation of the solar wind and interplanetary coronal mass ejections (ICMEs), where magnetic topology plays a guiding and constraining role in plasma flow.

Magnetic flux freezing implies a close coupling between magnetic field lines and plasma motion. Plasma motion does not cause magnetic field lines to slip or break but instead moves together with them. This interrelationship can be understood as plasma motion driving magnetic field line motion, while magnetic field lines also constrain plasma motion. However, it should be noted that in the actual interplanetary plasma environment, complex current sheet structures and mesoscale turbulent environments may exist. Due to finite resistivity or other non-ideal effects, the flux-freezing condition may be violated, allowing magnetic reconnection to occur.

The preservation of magnetic field topology: Owing to the conservation of magnetic flux, the topological structure of the magnetic field remains unchanged during plasma motion. For instance, if a region’s magnetic field initially has a specific configuration of magnetic field lines, such as circular, Archimedes spiral shape, Double twisted line shape, Cassini oval line, etc., the topological structure of that region’s magnetic field will be maintained during plasma flow. The connectivity and relative positions of the magnetic field lines will not alter.

The composition of heavy ions and charge states in the solar wind is determined in the chromospheric transition region and the corona. This composition serves as an excellent criterion for identifying the origin of the solar wind, even within highly compressed and heated plasmas. One of the most famous discoveries during the Ulysses mission was that high-energy particles accelerated by interplanetary shocks driven by co-rotating interaction regions (CIRs) are modulated by the solar wind flow up to very high latitudes (>80°). In recent years, the academic community has proposed two mechanisms to explain this unexpected behavior. The more traditional mechanism (the model by Kota and Jokipii) posits that the random motion of photospheric magnetic field footpoints "weaves" the interplanetary magnetic field. Magnetic reconnection and enhanced turbulence above the solar poles contribute to this process. Coupled with a small amount of particle scattering between magnetic field lines, this mechanism can account for the unexpected observations from Ulysses. Magnetic reconnection plays a vital role in the three-dimensional magnetic topology dynamics of CIRs. It can alter large-scale current sheet structures, providing conditions for particle acceleration and transport. Enhanced turbulence above the solar poles also offers an energy source for particle scattering and acceleration. These turbulent structures enable particles to scatter between magnetic field lines, broadening their distribution in high-latitude regions. Furthermore, the interaction between magnetic flux ropes and plasma turbulence can create complex mesoscale magnetic structures, such as magnetic islands and magnetic holes, which further influence particle trajectories and energy variations.

Another novel mechanism involves the systematic latitudinal transport of magnetic field lines (Fisk model). The differential rotation of the photosphere, the superradial expansion of high-speed solar wind from coronal holes, and the rigid rotation of coronal holes collectively lead to significant latitudinal diffusion of the heliospheric magnetic field. Fisk et al. conducted an in-depth discussion on the commonalities and differences between these two mechanisms. Zurbuchen et al.’s research indicates that the temporal variations of the high-latitude magnetic field observed by Ulysses are consistent with Fisk’s theory, with the theoretically predicted 20-day periodicity also detected.

Furthermore, A study (Ashok et al., 2024) analyzed the multi species high-energy particle intensity enhancement event at 1 AU. The event was identified as a CIR structure consisting of a flow interface (SI), forward reverse shock pairs, and an embedded heliosphere current sheet (HCS). Its characteristic is that high-energy (>1MeV) ions exhibit significant flux enhancement at the reverse wave (RW)/shock wave of the CIR structure, with electrons immediately accelerated after passing through the SI and HCS regions, and the flux of low-energy electrons rapidly reaching its peak. At RW, only high-energy electrons (~520keV) exhibit significant local flux enhancement. The CIR structure is subsequently driven by a rapid forward vertical shock wave from a coronal mass ejection (CME), resulting in a significant increase in the flux of low-energy protons and high-energy electrons. For particles accelerated by CIR, the increase in turbulent power at SI and RW may be an important factor in the observed flux enhancement for different species. The presence of ion scale waves near RW suggests that resonance wave particle interactions may be effective energy transmitters between high-energy protons and ion scale waves.

The Solar Orbiter mission, launched by the European Space Agency in 2020, aims to perform a close flyby of the Sun every 150 days, venturing inside Mercury’s orbit. The mission will employ a series of Venus Gravity Assists (VGA) to gradually incline the spacecraft’s orbit out of the ecliptic plane, reaching a maximum solar latitude of 34°. Equipped with six remote sensing instruments, including the Extreme Ultraviolet Imager (EUI), Spectral Imaging of the Coronal Environment (SPICE), Polarimetric and Helioseismic Imager (PHI), Spectrometer/Telescope for Imaging X-rays (STIX), Coronagraph Metis, and Solar Orbiter Heliospheric Imager (SoloHI), as well as four in situ instruments, namely the Solar Wind Analyzer (SWA), Radio and Plasma Waves (RPW) instrument, Magnetometer (MAG), and Energetic Particle Detector (EPD), Solar Orbiter is well-prepared for its observations. Although the currently acquired data are still limited to low-latitude regions very close to the ecliptic plane, Solar Orbiter has already demonstrated its capability to provide valuable insights into the solar polar regions. The EUI has pushed the boundaries of spatial resolution in extreme ultraviolet imaging and discovered small-scale transient brightenings dubbed "campfires." Its High-resolution Imager (HRI) allows scientists to observe the fine structures of the solar atmosphere at a recent perihelion of 0.29 AU, capturing details as small as 200 km (comparable in size to Manhattan Island). By combining the far-side magnetic maps obtained from PHI with those from SDO/HMI, Loeschl et al. introduced in a 2024 article the first multi-perspective integrated view of the solar magnetic field based on SO/PHI and SDO/HMI data. During Solar Orbiter’s perihelion passage in February 2021, the research team utilized data from the Polarimetric and Helioseismic Imager (SO/PHI) on board Solar Orbiter and the Helioseismic and Magnetic Imager (SDO/HMI) in Earth orbit to construct a synthetic view of the line-of-sight magnetic field for Carrington Rotation CR2240.

Figure.3. Synoptic map covering CR 2240 based on SO/PHI observations. The coloured sectors show the SO/PHI (red) and SDO/HMI (yellow) contributions at different longitudes. The dates (DD.MM) in the corners of the marked SO/PHI and SDO/HMI contributions indicate the start (right) and end (left) dates of each sector.

To integrate data from the two instruments, the researchers adjusted the SDO/HMI synthesis process to accommodate SO/PHI data, particularly addressing the issue of significant gaps in SO/PHI observation intervals and avoiding severe blurring in overlapping regions of the two datasets. Ultimately, the first multi-perspective integrated view using SDO/HMI and SO/PHI data was successfully created with an observation period of only 16 days. Compared to the standard SDO/HMI synthetic view, the multi-perspective integrated view captures numerous magnetic field evolutions that occur between the dates when the two instruments observe the same solar longitude, changes that would be missed by the standard synthetic view. This study provides a new method for more promptly mapping the entire solar surface magnetic field, offering a more accurate reflection of the Sun’s rapid magnetic field changes and providing more precise initial field data for applications such as solar wind speed prediction.

Furthermore, coordinated in situ measurements by Solar Orbiter and Parker Solar Probe (PSP) indicate that the damping of Alfvén waves and mechanical work are sufficient to drive the heating and acceleration of the fast solar wind in the inner heliosphere. As Solar Orbiter gradually increases its solar latitude to 34°, it is expected to deliver increasingly valuable data to complement high-latitude solar observations.

In the next section, I will introduce the current challenges in in situ observation of the solar polar magnetic field, the proposal process of the Chinese Academy of Sciences’ SPO, and the current engineering progress and future mission outlook.

Stay turned!

Edited June 30Jun 30 by 千年极寒

1 hour ago, 千年极寒 said:

P.S.

I strongly recommend members who want to further their academic studies in space weather to read this book, which is very helpful for you and can greatly enhance your theoretical foundation.

Not to be rude, but personally I would like you to participate in the discussions. That’s why we need a forum. Your knowledge would help to solve the questions that arise in the process of analyzing an event. If there was a lot of free time, I would re-read all the scientific literature. So far I have to learn new things as new events arise. It’s easier to remember, at least for me.

Removed post

Edited June 30Jun 30 by hamateur 1953
Not pertinent

5 hours ago, Samrau said:

Not to be rude, but personally I would like you to participate in the discussions. That’s why we need a forum.

Yeah, I really hope so, but I haven't always had a lot of time so far. There're still some important things to do this summer vacation. Once I have completely freed up my resources, I will answer more of everyone's questions in about half a month. I hope my answer will be helpful to everyone. Thank you for reminding me:)

Edited July 1Jul 1 by 千年极寒