arXiv subjects

Scott W. McIntosh

Publications and source records attributed to Scott W. McIntosh.

At least 19 recordsLinked to original sources

arXiv2024

Deciphering Solar Magnetic Activity: Some (Unpopular) Thoughts On the Coupling of the Sun's "Weather" and "Climate"

The Sun exhibits episodic surges of magnetic activity across a range of temporal and spatial scales, the most prominent of which is the 11-ish year modulation of sunspot production. Beside the ~170 (min to max) decadal variation in sunspot production there is a less-explored quasi-annual variation in the range of 25-50 sunspots/year in magnitude. In addition, there is there is a slower, ~80 year period, 10-50 variation in the sunspot number, that is commonly referred to as the 'Gleissberg Cycle.' Using a suite of contemporary and historical observations we will illustrate these elements of our star's episodic behavior and present a hypothesis that may provide a consistent physical link between the observed 'climatic', 'decadal' and 'seasonal' magnetic variation of our star.

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arXiv2023

Deciphering Pre-solar-storm Features Of September-2017 Storm From Global And Local Dynamics

We investigate whether global toroid patterns and the local magnetic field topology of solar active region AR12673 together can hindcast occurrence of the biggest X-flare of solar cycle (SC)-24. Magnetic toroid patterns (narrow latitude-belts warped in longitude, in which active regions are tightly bound) derived from surface distributions of active regions, prior/during AR12673 emergence, reveal that the portions of the South-toroid containing AR12673 was not tipped-away from its north-toroid counterpart at that longitude, unlike the 2003 Halloween storms scenario. During the minimum-phase there were too few emergences to determine multi-mode longitudinal toroid patterns. A new emergence within AR12673 produced a complex/non-potential structure, which led to rapid build-up of helicity/winding that triggered the biggest X-flare of SC-24, suggesting that this minimum-phase storm can be anticipated several hours before its occurrence. However, global patterns and local dynamics for a peak-phase storm, such as that from AR11263, behaved like 2003 Halloween storms, producing the third biggest X-flare of SC-24. AR11263 was present at the longitude where the North/South toroids tipped-away from each other. While global toroid patterns indicate that pre-storm features can be forecast with a lead-time of a few months, its application on observational data can be complicated by complex interactions with turbulent flows. Complex/non-potential field structure development hours before the storm are necessary for short term prediction. We infer that minimum-phase storms cannot be forecast accurately more than a few hours ahead, while flare-prone active regions in peak-phase may be anticipated much earlier, possibly months ahead from global toroid patterns.

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arXiv2022

Uniting The Sun's Hale Magnetic Cycle and `Extended Solar Cycle' Paradigms

Through meticulous daily observation of the Sun's large-scale magnetic field the Wilcox Solar Observatory (WSO) has catalogued two magnetic (Hale) cycles of solar activity. Those two (~22-year long) Hale cycles have yielded four ($\sim$11-year long) sunspot cycles (numbers 21 through 24). Recent research has highlighted the persistence of the "Extended Solar Cycle" (ESC) and its connection to the fundamental Hale Cycle - albeit through a host of proxies resulting from image analysis of the solar photosphere, chromosphere and corona. This short manuscript presents the correspondence of the ESC, the surface toroidal magnetic field evolution, and the evolution of the Hale Cycle. As Sunspot Cycle 25 begins, interest in observationally mapping the Hale and Extended cycles could not be higher given potential predictive capability that synoptic scale observations can provide.

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arXiv2021

Deciphering Solar Magnetic Activity: 140 Years Of The `Extended Solar Cycle' -- Mapping the Hale Cycle

We investigate the occurrence of the "extended solar cycle" (ESC) as it occurs in a host observational data spanning 140 years. Investigating coronal, chromospheric, photospheric and interior diagnostics we develop a consistent picture of solar activity migration linked to the 22-year Hale (magnetic) cycle using superposed epoch analysis (SEA) using previously identified Hale cycle termination events as the key time for the SEA. Our analysis shows that the ESC and Hale cycle, as highlighted by the terminator-keyed SEA, is strongly recurrent throughout the entire observational record studied, some 140 years. Applying the same SEA method to the sunspot record confirms that Maunder's butterfly pattern is a subset of the underlying Hale cycle, strongly suggesting that the production of sunspots is not the fundamental feature of the Hale cycle, but the ESC is. The ESC (and Hale cycle) pattern highlights the importance of 55\degree\ latitude in the evolution, and possible production, of solar magnetism.

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arXiv2021

Solar Wind Helium Abundance Heralds Solar Cycle Onset

We study the solar wind helium-to-hydrogen abundance's ($A_\mathrm{He}$) relationship to solar cycle onset. Using OMNI/Lo data, we show that $A_\mathrm{He}$ increases prior to sunspot number (SSN) minima. We also identify a rapid depletion and recovery in $A_\mathrm{He}$ that occurs directly prior to cycle onset. This $A_\mathrm{He}$ Shutoff happens at approximately the same time across solar wind speeds ($v_\mathrm{sw}$), implying that it is formed by a mechanism distinct from the one that drives $A_\mathrm{He}$'s solar cycle scale variation and $v_\mathrm{sw}$-dependent phase offset with respect to SSN. The time between successive $A_\mathrm{He}$ shutoffs is typically on the order of the corresponding solar cycle length. Using Brightpoint (BP) measurements to provide context, we infer that this shutoff is likely related to the overlap of adjacent solar cycles and the equatorial flux cancelation of the older, extended solar cycle during Solar Minima.

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arXiv2020

Overlapping Magnetic Activity Cycles and the Sunspot Number: Forecasting Sunspot Cycle 25 Amplitude

The Sun exhibits a well-observed modulation in the number of spots on its disk over a period of about 11 years. From the dawn of modern observational astronomy sunspots have presented a challenge to understanding -- their quasi-periodic variation in number, first noted 175 years ago, stimulates community-wide interest to this day. A large number of techniques are able to explain the temporal landmarks, (geometric) shape, and amplitude of sunspot "cycles," however forecasting these features accurately in advance remains elusive. Recent observationally-motivated studies have illustrated a relationship between the Sun's 22-year (Hale) magnetic cycle and the production of the sunspot cycle landmarks and patterns, but not the amplitude of the sunspot cycle. Using (discrete) Hilbert transforms on more than 270 years of (monthly) sunspot numbers we robustly identify the so-called "termination" events that mark the end of the previous 11-yr sunspot cycle, the enhancement/acceleration of the present cycle, and the end of 22-yr magnetic activity cycles. Using these we extract a relationship between the temporal spacing of terminators and the magnitude of sunspot cycles. Given this relationship and our prediction of a terminator event in 2020, we deduce that Sunspot Cycle 25 could have a magnitude that rivals the top few since records began. This outcome would be in stark contrast to the community consensus estimate of sunspot cycle 25 magnitude.

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arXiv2020

Prediction of the in situ coronal mass ejection rate for solar cycle 25: Implications for Parker Solar Probe in situ observations

The Parker Solar Probe (PSP) and Solar Orbiter missions are designed to make groundbreaking observations of the Sun and interplanetary space within this decade. We show that a particularly interesting in situ observation of an interplanetary coronal mass ejection (ICME) by PSP may arise during close solar flybys ($< 0.1$~AU). During these times, the same magnetic flux rope inside an ICME could be observed in situ by PSP twice, by impacting its frontal part as well as its leg. Investigating the odds of this situation, we forecast the ICME rate in solar cycle 25 based on 2 models for the sunspot number (SSN): (1) the forecast of an expert panel in 2019 (maximum SSN = 115), and (2) a prediction by McIntosh et al. (2020, maximum SSN = 232). We link the SSN to the observed ICME rates in solar cycles 23 and 24 with the Richardson and Cane list and our own ICME catalog, and calculate that between 1 and 7 ICMEs will be observed by PSP at heliocentric distances $< 0.1$ AU until 2025, including 1$σ$ uncertainties. We then model the potential flux rope signatures of such a double-crossing event with the semi-empirical 3DCORE flux rope model, showing a telltale elevation of the radial magnetic field component $B_R$, and a sign reversal in the component $B_N$ normal to the solar equator compared to field rotation in the first encounter. This holds considerable promise to determine the structure of CMEs close to their origin in the solar corona.

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arXiv2020

Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST)

The Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities which will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the Daniel K. Inouye Solar Telescope hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute.

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arXiv2020

Global maps of the magnetic field in the solar corona

Understanding many physical processes in the solar atmosphere requires determination of the magnetic field in each atmospheric layer. However, direct measurements of the magnetic field in the Sun's corona are difficult to obtain. Using observations with the Coronal Multi-channel Polarimeter, we have determined the spatial distribution of the plasma density in the corona, and the phase speed of the prevailing transverse magnetohydrodynamic waves within the plasma. We combine these measurements to map the plane-of-sky component of the global coronal magnetic field. The derived field strengths in the corona from 1.05 to 1.35 solar radii are mostly 1-4 Gauss. These results demonstrate the capability of imaging spectroscopy in coronal magnetic field diagnostics.

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arXiv2020

Time-Latitude Distribution of Prominences for 10 Solar Cycles: A study using Kodaikanal, Meudon and Kanzelhohe Data

Solar prominences are structures of importance because of their role in polar field reversal. We study the long-term variation of the time latitude distribution of solar prominences in this article. To accomplish this, we primarily used the digitised disc-blocked Ca II K spectroheliograms as recorded from Kodaikanal Solar Observatory for the period of 1906 -- 2002. For improving the data statistics we included full disc H_alpha images from Meudon and Kanzelhohe Observatory which are available after 1980. We developed an automated technique to identify the latitudinal locations of prominences in daily images from all three datasets. Derived time-latitude distribution clearly depicted pole-ward migration of prominence structures for 10 cycles (15-24). Unlike previous studies, we separated the rate of pole-ward migration during on-set and near pole, using piece-wise linear fits. In most cases, we found acceleration in pole-ward migration with the change occurring near +/- 70 degree latitudes. The derived migration rates for such large number of solar cycles can provide important inputs towards understanding polar field build-up process.

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arXiv2020

The drivers of active region outflows into the slow solar wind

Plasma outflows from the edges of active regions have been suggested as a possible source of the slow solar wind. Spectroscopic measurements show that these outflows have an enhanced elemental composition, which is a distinct signature of the slow wind. Current spectroscopic observations, however, do not have sufficient spatial resolution to distinguish what structures are being measured or to determine the driver of the outflows. The High-resolution Coronal Imager (Hi-C) flew on a sounding rocket in May, 2018, and observed areas of active region outflow at the highest spatial resolution ever achieved (250 km). Here we use the Hi-C data to disentangle the outflow composition signatures observed with the Hinode satellite during the flight. We show that there are two components to the outflow emission: a substantial contribution from expanded plasma that appears to have been expelled from closed loops in the active region core, and a second contribution from dynamic activity in active region plage, with a composition signature that reflects solar photospheric abundances. The two competing drivers of the outflows may explain the variable composition of the slow solar wind.

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arXiv2020

Termination of Solar Cycles and Correlated Tropospheric Variability

The Sun provides the energy required to sustain life on Earth and drive our planet's atmospheric circulation. However, establishing a solid physical connection between solar and tropospheric variability has posed a considerable challenge across the spectrum of Earth-system science. The canon of solar variability, the solar fiducial clock, lies almost exclusively with the 400 years of human telescopic observations that demonstrates the waxing and waning number of sunspots, over an 11(ish) year period. Recent research has demonstrated the critical importance of the underlying 22-year magnetic polarity cycle in establishing the shorter sunspot cycle. Integral to the manifestation of the latter is the spatio-temporal overlapping and migration of oppositely polarized magnetic bands. The points when these bands emerge at high solar latitudes and cancel at the equator are separated by almost 20 years. Here we demonstrate the impact of these "termination" points on the Sun's radiative output and particulate shielding of our atmosphere through the dramatically rapid reconfiguration of solar magnetism. These events reset the Sun's fiducial clock and present a new portal to explore the Sun-Earth connection. Using direct observation and proxies of solar activity going back six decades we can, with high statistical significance, demonstrate an apparent correlation between the solar cycle terminations and the largest swings of Earth's oceanic indices---a previously overlooked correspondence. Forecasting the Sun's global behavior places the next solar termination in early 2020; should a major oceanic swing follow, our challenge becomes: when does correlation become causation and how does the process work?

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arXiv2020

Timing Terminators: Forecasting Sunspot Cycle 25 Onset

Recent research has demonstrated the existence of a new type of solar event, the "terminator." Unlike the Sun's signature events, flares and Coronal Mass Ejections, the terminator most likely originates in the solar interior, at or near the tachocline. The terminator signals the end of a magnetic activity cycle at the Sun's equator and the start of a sunspot cycle at mid latitudes. Observations indicate that the time difference between these events is very short, less than a solar rotation, in the context of the sunspot cycle. As the (definitive) start and end point of solar activity cycles the precise timing of terminators should permit new investigations into the meteorology of our star's atmosphere. In this letter we use a standard method in signal processing, the Hilbert transform, to identify a mathematically robust signature of terminators in sunspot records and in radiative proxies. Using a linear extrapolation of the Hilbert phase of the sunspot number and F10.7 solar radio flux time series we can achieve higher fidelity historical terminator timing than previous estimates have permitted. Further, this method presents a unique opportunity to project, from analysis of sunspot data, when the next terminator will occur, May 2020 ($+4$, $-1.5$ months), and trigger the growth of sunspot cycle 25.

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arXiv2019

What the sudden death of solar cycles can tell us about the nature of the solar interior

We observe the abrupt end of solar activity cycles at the Sun's equator by combining almost 140 years of observations from ground and space. These "terminator" events appear to be very closely related to the onset of magnetic activity belonging to the next sunspot cycle at mid-latitudes and the polar-reversal process at high-latitudes. Using multi-scale tracers of solar activity we examine the timing of these events in relation to the excitation of new activity and find that the time taken for the solar plasma to communicate this transition is of the order of one solar rotation, but could be shorter. Utilizing uniquely comprehensive solar observations from the Solar Terrestrial Relations Observatory (STEREO), and Solar Dynamics Observatory (SDO) we see that this transitional event is strongly longitudinal in nature. Combined, these characteristics imply that magnetic information is communicated through the solar interior rapidly. A range of possibilities exist to explain such behavior: the presence of magnetic reconnection in the deep interior, internal gravity waves on the solar tachocline, or that the magnetic fields present in the Sun's convection zone could be very large, with a poloidal field strengths reaching 50k - considerably larger than conventional explorations of solar and stellar dynamos estimate. Regardless of mechanism responsible, the rapid timescales demonstrated by the Sun's global magnetic field reconfiguration present strong constraints on first-principles numerical simulations of the solar interior and, by extension, other stars.

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arXiv2019

Signature of Extended Solar Cycles as Detected from Ca II K Synoptic Maps of Kodaikanal and Mount Wilson Observatory

In the recent years there has been a resurgence of the study of Extended Solar Cycles (ESCs) through observational proxies mainly in Extreme Ultraviolet. But most of them are limited only to space-based era covering only about two solar cycles. Long-term historical data-sets are worth in examining the consistency of ESCs. Kodaikanal Solar Observatory (KSO) and Mount Wilson Observatory (MWO) are the two major sources of long-term Ca II K digitised spectroheliograms covering the temporal spans 1907-2007 and 1915-1985 respectively. In this study, we detected supergranule boundaries, commonly known as networks, using the Carrington maps from both KSO and MWO datasets. Subsequently we excluded the plage areas to consider only quiet sun (QS) and detected small scale bright features through intensity thresholding over the QS network. Latitudinal density of those features, which we named as `Network Bright Elements' (NBEs), could clearly depict the existence of overlapping cycles with equator-ward branches starting at latitude $\approx 55^{\circ}$ and taking about $15\pm1$ years to reach the equator. We performed superposed epoch analysis to depict the similarity of those extended cycles. Knowledge of such equator-ward band interaction, for several cycles, may provide critical constraints on solar dynamo models.

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arXiv2018

Roadmap for Reliable Ensemble Forecasting of the Sun-Earth System

The authors of this report met on 28-30 March 2018 at the New Jersey Institute of Technology, Newark, New Jersey, for a 3-day workshop that brought together a group of data providers, expert modelers, and computer and data scientists, in the solar discipline. Their objective was to identify challenges in the path towards building an effective framework to achieve transformative advances in the understanding and forecasting of the Sun-Earth system from the upper convection zone of the Sun to the Earth's magnetosphere. The workshop aimed to develop a research roadmap that targets the scientific challenge of coupling observations and modeling with emerging data-science research to extract knowledge from the large volumes of data (observed and simulated) while stimulating computer science with new research applications. The desire among the attendees was to promote future trans-disciplinary collaborations and identify areas of convergence across disciplines. The workshop combined a set of plenary sessions featuring invited introductory talks and workshop progress reports, interleaved with a set of breakout sessions focused on specific topics of interest. Each breakout group generated short documents, listing the challenges identified during their discussions in addition to possible ways of attacking them collectively. These documents were combined into this report-wherein a list of prioritized activities have been collated, shared and endorsed.

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arXiv2018

Solar Physics from Unconventional Viewpoints

We explore new opportunities for solar physics that could be realized by future missions providing sustained observations from vantage points away from the Sun-Earth line. These include observations from the far side of the Sun, at high latitudes including over the solar poles, or from near-quadrature angles relative to the Earth (e.g., the Sun-Earth L4 and L5 Lagrangian points). Such observations fill known holes in our scientific understanding of the three-dimensional, time-evolving Sun and heliosphere, and have the potential to open new frontiers through discoveries enabled by novel viewpoints.

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arXiv2018

On the Magnetic and Energy Characteristics of Recurrent Homologous Jets from An Emerging Flux

In this paper, we present the detailed analysis of recurrent homologous jets originating from an emerging negative magnetic flux at the edge of an Active Region. The observed jets show multi-thermal features. Their evolution shows high consistence with the characteristic parameters of the emerging flux, suggesting that with more free magnetic energy, the eruptions tend to be more violent, frequent and blowout-like. The average temperature, average electron number density and axial speed are found to be similar for different jets, indicating that they should have been formed by plasmas from similar origins. Statistical analysis of the jets and their footpoint region conditions reveals a strong positive relationship between the footpoint-region total 131 Å intensity enhancement and jets' length/width. Stronger linearly positive relationships also exist between the total intensity enhancement/thermal energy of the footpoint regions and jets' mass/kinetic/thermal energy, with higher cross-correlation coefficients. All the above results, together, confirm the direct relationship between the magnetic reconnection and the jets, and validate the important role of magnetic reconnection in transporting large amount of free magnetic energy into jets. It is also suggested that there should be more free energy released during the magnetic reconnection of blowout than of standard jet events.

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