S&P 500 vs. Geomagnetic Ap Index and Kp Index

S&P 500 vs. Ap Index (May–Nov 2026).  Projected Ap Index Peaks (+4-Day Lag) = Expected S&P 500 Lows:

Oct 14 (Wed), Oct 17 (Sat), Oct 26 (Mon), Nov 4 (Wed), Nov 13 (Fri), Nov 22 (Sun).

The time it takes for a Coronal Mass Ejection (CME) to reach the Earth depends on several factors, such as the speed of the CME, the density of the solar wind, and the position of the Earth relative to the Sun. On average, a CME can take anywhere from 1 to 5 days to reach the Earth: fast CMEs (speeds > 1000 km/s) 1-2 days, average CMEs (speeds ~500-1000 km/s) 2-3 days, and slow CMEs (speeds < 500 km/s) 3-5 days.

Geomagnetic disturbances (elevated Ap index) are hypothesized to subtly impair collective mood and heighten risk aversion. Market participants may misattribute this psychological distress to economic fundamentals, leading elevated Ap to precede S&P 500 lows and trend reversals by a short lag of a few calendar days.

To evaluate this relationship, historical NOAA 45-day Ap forecasts (updated daily) were parsed into a continuous daily series using the most recent available issues. These values were correlated against daily S&P 500 close-to-close and absolute returns across 0 to +5 calendar-day lags from January 1, 2020, to present. Across the full sample, the 45-day forecast displays only modest directional correlation with next-day price movements; its primary statistical signal is a positive link to subsequent absolute returns (volatility), currently peaking around +4 to +5 days.

However, this optimal lag lacks long-term stability—holding near +4 days throughout the summer and early fall before shifting in recent windows—reflecting the limited predictive skill of multi-week geomagnetic forecasts. Comparative analysis shows that NOAA's 27-day Ap outlook provides neither stronger directional lead times nor greater stability than the 45-day series. Because the 27-day projection updates only weekly, its lower publication frequency introduces additional noise, making lead-lag relationships harder to measure than in the daily 45-day series.

The Ap Index (used in NOAA's 45- and 27-day forecasts) is the linear counterpart of the quasi-logarithmic Kp Index (used in NOAA's 3-day forecast). Each 3-hour Kp value converts to an equivalent amplitude via a fixed table (Kp 0→0, 1→3, 2→7, 3→15, 4→27, 5→48, 6→80, 7→140, 8→240, 9→400); the daily Ap is the average of those eight 3-hour values. The two indices therefore track the same geomagnetic activity on different scales.

 

NOAA's latest 3-day forecast above shows a peak Kp of 5 (equivalent Ap ≈ 48) on Tuesday, October 13, between 06:00 and 09:00 UTC (2:00–5:00 a.m. ET). Shifting that interval forward by three calendar days points to Friday, October 16; a four-day shift points to Saturday. This suggests another S&P 500 low may arrive by the end of the trading week.

To evaluate shorter-term dynamics, 180 days of NOAA 3-day Kp forecasts were compiled, converted to 3-hour equivalent Ap, adjusted to Eastern Time (ET), and exhaustively tested across lags of 0 to 120 hours against hourly S&P 500 closes to identify the shift with the strongest negative correlation to price level. The latest weekly charts above display hourly S&P 500 OHLC bars (left scale) overlaid with the 3-hour equivalent Ap series shifted forward by the optimal +45 hours on an inverted right scale. Each panel spans Saturday through the following Sunday to show the complete trading week in context.  

 

This optimal +45-hour lag differs from the +3 to +5 calendar-day lag observed on daily Ap charts because the NOAA 3-day forecast model (updated twice daily at 00:30 and 12:30 UTC; during EDT / UTC−4, this corresponds to 8:30 p.m. ET the previous day and 8:30 a.m. ET the same day) evaluates high-resolution, short-horizon Kp/Ap data against hourly prices over a shorter sample window, where forecast decay and short-term noise shift the best-fit alignment relative to multi-month realized daily Ap metrics.

 

See also:

TPR (August 22, 2026) - S&P 500 vs. Ap Index: +3-Day Lag and Limits of Multi-Week Forecasting.

Jeffrey A. Hansen  (February 2, 2026) - Physics-Based Forecasts of Investment Sentiment.

Jeffrey A. Hansen (October 2, 2026) - Physics-Based Forecasts: US Equities.

TPR - Sun and Markets.

Physics-Based Forecasts of Investment Sentiment | Jeffrey A. Hansen

Hansen's February 2026 paper Physics-Based Forecasts of Investment Sentiment proposes that shifts in investor optimism and pessimism correlate with heliocentric planetary orbital geometry, sunspot activity, and Schumann resonance stability, rather than solely with economic news. The clock of investor sentiment is a roughly 90° Sun–vertex angle (86°–94°) between the Mercury–Saturn center, weighted by tidal force (T ∝ m/r³), and the Jupiter–Neptune center, with weights fitted in December 2000 to Hansen's Market Resilience Index (MRI). Clusters of these configurations define Anxiety-Free Periods (AFPs)—multi-month stretches of investor optimism—that typically fade when the final 90° column expires (plotted orange in charts below).

 

Geometry of the Inner Orbital Center (Mercury, Venus, Earth, Mars, Jupiter, Saturn) and the Outer Orbital Center (Jupiter, Saturn, Uranus, Neptune; Jupiter and Saturn sit in both centers): two mass-weighted planetary-group centers with the Sun at the vertex. When the angle is near 90° (Hansen uses 86°–94°), an AFP column is active, plotted as orange bars/columns in the US Stock Market Price Level chart below.

Physics Times the Turn; Economics Sizes the Move

Across thirteen AFPs from 1933–2024, the average cumulative gain is about 28%, followed by a 13% post-peak decline—near the 98th and 95th percentiles of duration-matched history. Physics is proposed to time the turn; economics to size it. 

 

Thirteen AFPs, named by the year of the price peak (1933-2024, exact dates in the chart above): geometry window = first 90° event through last 90° event; prior/post lows and returns are his market annotations (visually dated orange on the DJIA chart below). Average prior low is about 2½ months before the first event. The fourteenth cluster is the 2026 AFP (not in the 1933–2024 sample). Appendix U dates its 90° Fridays as Apr 24–May 22, 2026; Aug 07–Sep 18, 2026; and Nov 20–Dec 04, 2026. There is no completed peak/post-low for that episode yet.

US Stock Market Price Level (Log) vs. AFPs, 1920–2024.

A century of prices with orange AFP columns; column height represents intensity.

Each column is one 90° configuration event. A cluster of those bars is one Anxiety-Free Period.

2026 has three columns (late April–May, August–September, November–December).

 

Pre-peak ("boom") and post-peak ("bust") cumulative returns for the thirteen Anxiety-Free Periods since 1933, with empirical percentile ranks based on duration-matched periods in the full weekly Dow Jones Industrial Average history. The ranks measure the share of same-duration historical periods with less extreme returns. High percentiles show that gains consistently fall in the extreme tail, while declines do so in most cases. 

From Orbital Angles to Schumann Standing Waves to Human Physiological Entrainment

Market impact is attributed not to the angle itself, but to a four-step causal chain ending in Schumann-type modes, the Earth's ionospheric waveguide ringing at approximately 8, 14, and 21 Hz. A 90° configuration is hypothesized to laminarize solar emissions, stabilize ionospheric height, and lock global standing-wave frequencies near 14–21 Hz; this coherence is then linked to analytical optimism, with overlap in the 13–30 Hz EEG band.

Hypothesized causal mechanism for Anxiety-Free Periods. The diagram proposes a causal chain from solar-system geometry through solar emissions, ionospheric stability, global electromagnetic standing waves, and human physiological entrainment. It is repeated at the start of each section, highlighting the relevant step; here, Element 1 is highlighted.

Established Space-Weather Physics and Speculative Solar-Geometry Links

Stabilized solar output and ionospheric height extend accepted space-weather physics; the solar-geometry and cognition links remain speculative. Intensity scales with outer-group clustering, measured by Sun-to-outer-center distance, which is offered as the reason 1937 and 1987 were violent while 2006 was mild. Intensity is already represented by the column heights in the US Stock Market Price Level chart above.

 

Ap Index, F10.7, and Sunspots as Fellow Travelers

The same geometry used to time AFPs is associated with tighter co-movement among Ap Index, F10.7, sunspots, and Oulu neutron-monitor counts when the outer planets cluster. Geomagnetic and radio-flux series are treated as companions of standing-wave stability rather than as separate daily trading signals.

 Correlations of Solar Energy Metrics by High Intensity and Low Intensity Weeks.

Ap, F10.7, sunspots, and Oulu neutrons co-move more tightly when the outer group is clustered.

The Frozen Eight-Driver Orbital Model

An eight-driver orbital model—six frozen orbital-geometry factors covering planet-group angles, distances, and clusters, plus the predicted AFP and M-Spike series—was calibrated through late 2000 and then frozen. Using NASA coordinates alone, it forecasts the 14-week RSI from December 2000 through April 2024. Here, 14-week RSI means Wilder's Relative Strength Index calculated on weekly bars with a 14-week lookback: Hansen's proxy for multi-month price momentum and investor sentiment, rather than the more common 14-day RSI. The M-Spike is a short-term orbital-geometry factor—not an RSI or an AFP—computed from planet-group positions and read on DJIA/S&P prices as a multi-week M pattern: lift, mid-dip, rebound, and fade. About 88% of predicted turns match actual turns within ±1 week, versus a chance baseline near 0.25% (p < 0.001).

Predicted and Actual 14-week RSI for the US Stock Market, December 1, 2000–April 1, 2024.

Frozen-model path versus realized RSI and log price; the 88% out-of-sample test begins here.

 

When Price Rises but Sentiment Does Not

When actual RSI runs below the geometry path, as in 2007–08, Hansen interprets the divergence as economically driven pessimism despite rising prices. Pre- and post-event weekly returns around 26 individual 90° events differ less than 0.01% (p < 0.0001).

 

 Predicted and Actual 14-week RSI, Periods A and B. Arrow A marks the 2007–08

actual-RSI divergence below geometry; B marks an AFP in which both rise together.

 

The Limited Schumann-Resonance Test

Usable standing-wave data exist only from June 2015 through December 2021. However, it is not a published Schumann-resonance product. Hansen built the series himself from British Geological Survey magnetometer records at Eskdalemuir, Scotland. Within that window, the predicted 2017 AFP series is associated with frequency stability in modes 2–3 (p < 0.001), although R² is only about 0.05—the most direct test of standing-wave market impact, but also the thinnest.

 

US stock-market price and indicators for the 2017 Anxiety-Free Period and M-Spike episodes, June 05, 2015–December 31, 2021. The chart overlays market price, episode indicators, and ellipses A–D marking notable relationships between price patterns and episodic signals. It also shows modes 2 and 3 electromagnetic standing-wave stability, measured on weekends from 8 a.m. to 4 p.m. local time and lagged approximately two weeks. 

Sunspots as the Longer Proxy

Solar activity is more stable during 21 of 26 90° events and more often declines by day +21 after an event ends. Shorter geometry-defined M-Spikes (53 cases, 1940–2023) show weaker weekly-return significance (p ≈ 0.19).

 

Mega Cycle and Phase 1 Valuations

The same inner–outer angle maps onto a four-phase Mega Sentiment Cycle. Phase 1, from 0° to the AFP at 90°, has accounted for about 32% of weeks since 1942 but 53% of returns, with higher S&P 500 P/E ratios but no corresponding growth differential.

 

Mega Sentiment Cycle (2004–2027), showing its four phases, the timing of Anxiety-Free Periods, and the changing Inner Center–Sun–Outer Center angle. Stock Index Price refers to the DJIA, S&P 500, or related ETFs. 

How Panic Is Supposed to Spread

A Geoffrey Moore-style adoption model divides the market into Pioneers (~15%), Early Majority (~35%), Late Majority (~35%), and Laggards (~15%). Micro geometry is said to move the Pioneers, while the Mega cycle moves the slower half. During Phase 1, roughly half the market remains optimistic, so valuation alone is judged unlikely to force a crash larger than 30%.

 

The 2026 Live Overlap

Phase 1 of Hansen's Mega Sentiment Cycle—the long inner–outer angle from 0° up to the next AFP at 90°—runs from autumn 2022 until the first 90° column of 2026, projected for late April–May, with peak geometry-driven euphoria in late May, a second lift by early August, and a third close in early December. A moderate M-Spike overlaps the first column, making April–June the unstable hinge.

 

The chart (December 06, 2024 to January 01, 2027) shows the US stock-market price level (log) through July 18, 2025—the analysis date—along with the drivers of the three 90° configuration events comprising the 2026 Anxiety-Free Period and the M-Spike as of June 2025. Forward map showing the three 2026 AFP columns, overlapping M-Spike, May peak, and June hinge. US Stocks refers to the DJIA, S&P 500, or related ETFs. 

2026 AFP Map and the Boom-Then-Fade Hypothesis 

Hansen's sketch is: enter several weeks before an AFP, hold through the cluster high, exit on the Micro Market Resilience Index; he prefers equal-weight S&P 500 or the DJIA as cleaner sentiment gauges. That is a multi-month calendar, not a daily trigger and not proof that high valuations cannot break.

 

2026 is one such labeled window: three separate 90° columns, not a continuous anxiety-free bid into year-end. The first and strongest was late April–May (peak late May). An overlapping M-Spike made April–June the hinge—historically a dip zone, not a melt-up. A weaker second lift was dated August–September. The third column, late November–early December, ends the cluster; Hansen's average script is a boom during the bars and about −13% after the peak. 2006 barely rose, so an AFP is not a guarantee of higher prices. November–December is the close of the episode, not "anxiety-free until Christmas."

 

Use that map to watch whether price, Ap, sunspots, and standing-wave stability follow the boom-then-fade pattern. For next-week risk keep short-horizon Ap/Kp and real-time L1 solar wind—those still have skill. The Schumann link rests on one AFP and $R^2 \approx 0.05$; 2026 is the live joint test of cavity-mode coherence, solar-metric co-movement, and that price script. Do not size as if the mechanism were already proven. Hansen's paper is research, not investment advice.

 

Reference:

Jeffrey A. Hansen (February 2, 2026) - Physics-Based Forecasts of Investment Sentiment: 

Evidence from Past Boom-and-Bust Periods and the Anticipated Dynamics of 2026. 

Jeffrey A. Hansen is founder of CPM Investing LLC and an asset-allocation researcher who began in geophysics and natural-resource exploration, later evaluating quantitative investment managers at Russell Investments, advising investment firms on technology adoption and product development, managing global multi-asset funds at Nikko AM America, and since 2015 specializing in asset-allocation research and ETF model portfolios for individual investors. 

Hansen's latest August 7, 2026 forecast.

S&P 500 vs. Hansen's "Micro Driver" (data input and formula undisclosed), digitized from the weekly chart in his August 7 forecast above and plotted against the daily S&P 500 for clarity. The "Micro Driver" path shows rising prices into Sep 4 (Fri), a trough around Oct 2 (Fri), followed by a higher peak around Oct 16 (Fri), a trough on Nov 27 (Fri), and a weaker bounce into Dec 25 (Fri).

Hansen Anxiety-Free Periods 1933-2051

The model uses two planetary centers of gravity: the Inner Orbital Center, a weighted mix of Mercury, Venus, Earth, Jupiter, and Saturn, and the Outer Orbital Center, a weighted mix of Jupiter, Saturn, Uranus, and Neptune, with a line from the Sun to each center. Hansen's AFP clock is simply how close the opening angle is to a right angle. He counts a "column" when it falls between 86° and 94°. Because the inner planets move quickly, the angle wobbles in and out of the band, so an AFP is usually a handful of orange bars or columns spread over a few months, not one solid year. To calculate Hansen's Anxiety-Free Periods through 2051, his published weights and NASA/JPL planetary positions were used.

Hansen AFPs, 1933–2051: Orange columns mark weeks of Anxiety-Free Periods, when the Sun–vertex angle between the inner (Mercury–Saturn) and outer (Jupiter–Neptune) planet-group centers (black curve in the lower panel) falls within the 86°–94° band; column height quantifies the number of weeks within the band. The upper panel overlays AFPs with a black line showing detrended DJIA weekly closing values. Looks pretty random. Hardly something worth betting the farm on.

Hansen Anxiety-Free Periods (2026–2051).

 

There are 16 clusters from 1935 to 2051. After the current 2026 AFP, the next full cluster is November 2032–July 2033. Then comes a long empty stretch: the angle falls toward 0° (the two centers lined up) and does not re-enter the band until a weak July 2050 graze and a full 90° column in January 2051. Gaps with no AFPs are 2027–31 and 2034–49. 

 

2026 Real-World Test: Watch Timing Window. Respect Uncertainty. Never Bet the Farm.

The orange AFP columns are a real, rebuildable orbital clock. However, they are not a price clock. The Dow's detrended path already has its own slow waves—wars, inflation, bubbles, QE. An AFP arrives roughly every 7–13 years, so some columns will naturally land near highs, selloffs, or dead middles. That happens with or without the 90° angle doing anything. 

Hansen's stronger claim is window timing. But his sample is only thirteen episodes: +28% on average, followed by −13%, with durations matched to extreme percentiles. Misses matter: 2006 barely moved; 1937 and 1987 were ugly. The proposed chain—stable Sun → ionosphere → Schumann → mood—rests on a tiny Schumann window and an R² ≈ 0.05. The "Micro Driver" projection line in the August 7 forecast looks impressively strong, its inputs and formula are understandably undisclosed, and it could be a weekly spectrum-cycle composite projection, unrelated to the AFP columns. The M-Spike formula is also unpublished, though it can be deduced as an exactly repeating, non-astronomical 55-week/385-day mystery cycle, with p ≈ 0.19.

 

So 2026 is a fascinating real-world test of Physics-Based Forecasts of Investment Sentiment—but still not proof that the theory works or doesn’t. Orbital geometry can be projected indefinitely into the future. And trader and investor sentiment? Maybe not. If 2026 fails to deliver the usual boom-then-fade, that failure is evidence against the theory. If it rhymes, fine—but it is still one more cluster, not a law. Watch the timing windows. Respect the uncertainty. Never bet the farm on orbital geometry—nor anything else.

 

See also:

TPR (2026) - S&P 500 vs. Ap Index: +3-Day Lag and Limits of Multi-Week Forecasting.

Nassim Nicholas Taleb (2001) - Fooled by Randomness: The Hidden Role of Chance in Life and in the Markets.

Mark Douglas (2000) - The Probabilistic Mindset of Successful Traders.

S&P 500 vs. Jupiter–Saturn Cycle: A Clock, Not a Crystal Ball

Derived mainly from M.A. Vukcevic's insights and solar-activity formula linking heliocentric Jupiter–Saturn sidereal orbits to model the sunspot cycle, the concept below uses a proprietary higher harmonics formula to project S&P 500 market swings.

S&P 500 vs. Jupiter–Saturn Cycle | H2 2026.

Over 90% of tradeable, high-amplitude waves develop in the 7 to 12-day window. 

  

Jupiter's sidereal period is ≈11.86 years, Saturn's ≈29.46 years, their synodic period ≈19.86 years, and the Jupiter–Saturn spring-tide period ≈9.93 years. These tidal frequencies bracket the ~11-year Schwabe sunspot cycle, while the Vukcevic and Scafetta formulas treat Jupiter–Saturn orbital geometry as a pacemaker of the solar dynamo. With no consistent polarity or directional bias for the S&P 500, the blue Jupiter–Saturn curve inflects within a 1-to-11.9-day window (median 7.0 days, mean 6.3), and swings ≥7 days are bisected (blue squares) to optimize short-term correlation.

 

S&P 500 vs. Jupiter–Saturn Cycle | H1 2026.

 

The Jupiter–Saturn curve is not a crystal ball and it will not say whether to buy or sell. It is a clock. Two slow planetary rhythms were folded into a single wavy line, then sped up so that what once took years now takes days. That line rises, falls, and bottoms out again and again.

S&P 500 vs. Jupiter–Saturn Cycle | H2 2025.

 

S&P 500 vs. Jupiter–Saturn Cycle | H1 2025.

Troughs hold the edge — ignoring the rest saves energy. Troughs are the only feature showing positive 
statistical skill (+3 points over random chance). Peaks and midpoints offer zero edge over a coin flip.

After matching it to years of S&P 500 prices, only one part of the clock is worth attention: the low points, the troughs. The test is blunt. Each blue mark is given three calendar days to sit near a real 2% swing in the daily highs and lows; the same test is then run on random dates, so the extra percentage is the only thing that counts as skill. Troughs clear that bar. Peaks do not. Midpoints, whether a swing is cut in half by time or by height, do not either.

 Troughs mark volatility, not directional certainty. Blue troughs lean slightly toward S&P swing lows (+3 points),
but cannot guarantee direction. Attempting to trade blue crests yields negative skill vs. baseline expectation.

 

Target multi-day windows over intraday precision. Maximum predictive edge (+3.3 to +3.4 points) centers on 2%–3%
swings over a 2 to 3-day window. Expecting immediate same-day triggers introduces unnecessary market noise.

 

Those extra three points are modest, and they still do not pick a side. The color of the line — up or down — does not mean the market will follow. A trough lining up with an S&P low beats chance by about three points; a trough lining up with an S&P high does not. A peak is no better at calling a high than a low. In other words, a trough can sit under a rally or a selloff. It is a date when a real swing is a little more likely to finish, not a forecast of direction.

 

S&P 500 vs. Jupiter–Saturn Cycle | H2 2024.

 

S&P 500 vs. Jupiter–Saturn Cycle | H1 2024.

 

Used that way, the method is simple. The next trough is read from the calendar, including Saturdays and Sundays; the formula does not pause for the weekend. 

 

Filter out the daily ripples to trade the 7–12 day cycle. Short cycles under 6 days represent market interference
with negligible height. Over 90% of meaningful amplitude occurs within the 7–12 day wave structure.

A short window opens around that date: two days before through three days after, which is the same band in which most of those 63% of hits actually land. If the trough falls on a weekend, the window runs from the Thursday before through the Wednesday after. Inside that window nothing is done until the S&P itself speaks. 

 

S&P 500 vs. Jupiter–Saturn Cycle | H2 2023.

 

S&P 500 vs. Jupiter–Saturn Cycle | H1 2023.

 

The wait is for price to carve a high and then drop at least two percent from that high, using the day’s actual high and low, not the close — that may be treated as a short, with risk defined just above the high. Or the wait is for price to carve a low and then rise at least two percent from that low — that may be treated as a long, with risk defined just under the low. Only the first such reversal is taken. If the window closes and neither has happened, there was no trade. The little wrinkles on the blue line are skipped as well: if the fall into a trough was tiny, it is interference, not a beat, and it can be ignored.

S&P 500 vs. Jupiter–Saturn Cycle | H2 2022.

 

S&P 500 vs. Jupiter–Saturn Cycle | H1 2022.

The position is left when it has paid twice what was risked, or when price completes a two-percent swing the other way, or when the next serious trough arrives. Then the wait begins again. A signal will not appear every week, and that is the point. A good year of this habit is a handful of attempts, not a lifestyle. Three extra points versus picking dates at random is not a license to force a trade; costs, hesitation, and the occasional late swing that lands a week off the mark can wipe the edge out.

S&P 500 vs. Jupiter–Saturn Cycle | H2 2021.

S&P 500 vs. Jupiter–Saturn Cycle | H1 2021.

 

S&P 500 vs. Jupiter–Saturn Cycle | H2 2020.

S&P 500 vs. Jupiter–Saturn Cycle | H1 2020.

What is being practiced is attention, not prediction. The market still has to print the turn in the window, in its own highs and lows, or there is no trade. Used that way, the curve earns a place on the desk: a reminder to look up for a few days, then to look away until the next low. 

 

Jupiter–Saturn Cycle | H1 2027. 

 

See also:

Previous S&P 500 vs. Jupiter–Saturn Cycle examples [HERE].  

TPR (August 22, 2026) - S&P 500 vs. Ap Index: +3-Day Lag and Limits of Multi-Week Forecasting.

Sunspots Predict US Yield Curve Peak by Mid-2027 | Tom McClellan

The yield curve—measured here using the 10-Year US Treasury Note minus the 1-Year US Treasury Bill—has been steepening since reaching maximum inversion in June 2023, signaling healthier economic growth. Yield curve steepening occurs when long-term rates rise relative to short-term rates, driven by increases at the long end, cuts at the short end, or a mix of both.

► 3-Year Solar Lag: Solar activity cycles peak and bottom roughly 3 years before matching inflections appear in the 10y-1y US Treasury spread.
► Historical Baseline: The maximum yield curve inversion point recorded in June 2023 occurred exactly 3 years after the solar minimum in 2020.
► 2027 Steepening Peak: With Solar Cycle 25 having reached its maximum around July/August 2024, the 3-year lag model projects the current steepening phase to reach its climax around mid-2027.
► Post-2027 Outlook: Beyond the mid-2027 peak, the cyclical relationship points toward a renewed flattening phase as long-term and short-term yields begin converging back toward inversion.

Historically, changes in monthly sunspot activity lead the 10y-1y yield spread by roughly three years. While geopolitical shocks like the 1973–74 Arab Oil Embargo, the 2008 Global Financial Crisis, and the COVID-19 pandemic temporarily disrupt this correlation, the historical pattern consistently re-establishes itself once the crisis passes. For instance, the June 2023 yield curve inversion bottomed precisely three years after the 2020 sunspot minimum. Following the July 2024 peak in sunspot activity, this three-year lag projects a climax in yield curve steepening around July 2027. Beyond mid-2027, the pattern suggests the yield curve will begin flattening as short-term and long-term rates converge.

Reference:
Tom McClellan (August 27, 2026) - Sunspots and the Yield Curve.

See also: 

Vladimir Belkin (2026) - Federal Funds Rates and Solar Activity: Projection through 2031.

TPR (August 26, 2026) - US Treasury Secretary Bessent: "Sanctions Could Disrupt Global Finance!" 

S&P 500 vs. Ap Index: +3-Day Lag and Limits of Multi-Week Forecasting

The chart below illustrates the hypothesis that geomagnetic activity, measured by the planetary Ap index, precedes trend reversals, as geomagnetic disturbances subtly impair collective mood and increase risk aversion. This idea draws on research examining correlations between space weather and financial markets, including evidence of both direct and inverse relationships between Ap—and related Kp and F10.7—readings and subsequent market performance.

S&P 500 vs. Ap Index (Apr-Oct 2026). Projected Ap peaks: Sep 4 (Fri),  Sep 17–20 (Thu-Sun), Oct 1 (Thu). 

Wait 24–35 or so days and the AP–price correlation will look almost perfect again.

 

Chart Construction and Data Sources

The chart overlays the daily S&P 500 with the Ap index shifted forward by three calendar days—the short lag that currently offers the best balance between the classic weekly effect reported in the literature and practical S&P 500 trading-day alignment. The series is then extended using the NOAA 45-day Ap forecast. Historical daily Ap data are sourced from GFZ Potsdam, while the dashed forward segment represents the latest NOAA SWPC 45-day Ap forecast, issued on August 22, 2026. 

 

Limits of the NOAA 45-Day Forecast for Forward Correlation

However impressive the historical correlation may appear, its reliability as a guide to future relationships is inherently limited. NOAA's 45-day Ap forecast is a relatively low-resolution space-weather projection, it is adjusted on a daily basis, and its predictive skill declines rapidly beyond the first week. Moreover, the forecast activity levels shown in the chart are modest (Ap 8–15) and remain well below classic geomagnetic storm thresholds: Ap 8–15 corresponds roughly to Kp 2–3 (quiet to unsettled conditions), while Ap 48 corresponds to Kp 5, the threshold for a NOAA G1 geomagnetic storm. 

  

Latitude-Dependent Solar Rotation and Active-Region Return Times

Sunspots and active regions do not return to the Earth-facing side of the Sun on a fixed schedule. Because the Sun rotates differentially—faster at the equator (~25 days sidereal, or ~27 days synodic as seen from Earth) and progressively slower at higher latitudes (reaching ~30–35 days near the poles)—the time required for a given region to reappear depends on its heliographic latitude. The standard Carrington frame uses a compromise rotation period of 27.2753 days (synodic), which roughly corresponds to the typical 10–20° latitudes of sunspots. Regions at higher latitudes therefore take longer to rotate back into view, while those near the equator return sooner. 

 

Solar Activity Snapshot: Comparing Sunspot distribution on the Earth-facing and far sides of the Sun (August 22, 2026). 

From above the Sun's north pole, its rotation is counterclockwise, carrying sunspots from left to right.

 

Reading the Raben Earthside and Farside Maps 

The Raben maps above illustrate this directly: The Earthside view shows currently visible active regions, identified by NOAA numbers and activity-color coding, while the Farside view highlights returning regions with meridian lines estimating the number of days until they may reappear, assuming a uniform rotation rate. In reality, those return times can stretch or compress with latitude. A high-latitude complex visible on the farside today, for example, may take several additional days to rotate back into Earth view compared with a low-latitude region. 

 

How Returning Regions Drive F10.7 and Ap

These returning regions influence both the 10.7 cm radio flux (F10.7) and geomagnetic activity (Ap and Kp). F10.7 serves as a direct proxy for solar EUV/UV output associated with active regions and plages; when a large active complex rotates onto the Earth-facing disk, F10.7 typically rises. Ap, by contrast, responds more indirectly: high-speed solar-wind streams from coronal holes, as well as coronal mass ejections launched from Earth-directed active regions, can disturb the magnetosphere and elevate the planetary Ap index. 

 

Construction of the 27-Day and 45-Day NOAA Forecasts

Consequently, the 27-day forecast for F10.7 and the geomagnetic Ap and Kp indices and the 45-day Ap/F10.7 forecast issued and updated daily by NOAA SWPC, are both built around the expected recurrence of these features through solar rotation. The 27-day forecast is essentially a recurrence forecast, assuming that active regions and coronal holes will reappear roughly one Carrington rotation later. The 45-day forecast extends this approach farther into the future, blending recurrence-based estimates with a longer-term background trend.

The time a Coronal Mass Ejection (CME) takes to reach Earth depends mainly on its density and solar-wind conditions:. fast CMEs (>1,000 km/s) arrive in 1–2 days, average CMEs (500–1,000 km/s) in 2–3 days, and slow CMEs (<500 km/s) in 3–5 days.

The Moon's orbit through Earth's magnetosphere, and the corresponding reduction in solar wind ion flux as it enters the magnetotail cavity near full Moon (0°), provides one example of how the solar wind–magnetosphere configuration can influence geomagnetic conditions. More broadly, the semiannual variation of geomagnetic activity is linked to the interaction between the solar wind and Earth's tilted magnetic field, which typically causes increased geomagnetic disturbances around the equinoxes and lower activity around the solstices.

Why Multi-Week Ap Forecasts Remain a Coarse Guide

That is precisely why attempts to forward correlate 27-day and 45-day Ap forecasts with the S&P 500 are inherently limited. The Sun's differential rotation, the uncertain evolution of active regions—including their growth, decay, or disappearance while on the farside—the variable geoeffectiveness of individual regions, and the chaotic nature of solar-wind–magnetosphere coupling all erode day-to-day predictability.  

 

KMAS 3- and 7-day solar wind forecast based on ACE observations.

GFZ high resolution 3-day forecast of ap30, ap60 and ap indices.

 

Hence, multi-week Ap and F10.7 forecasts should be interpreted primarily as defining a broad solar-activity envelope rather than as precise day-by-day projections capable of supporting a tight forward correlation with daily S&P 500 returns. By contrast, short-horizon tools—such as the NOAA 3-day forecast, the LSTM-based 72 hour Ap predictor, and real-time L1 solar-wind data—retain greater predictive value for near-term market conditions.

  

See also:

Jeffrey A. Hansen (2026) - Physics-Based Forecasts of Investment Sentiment. 

Vladimir Belkin (2024) - Strong Inverse Correlation between Ap Index and Gold Price.  

Lifang Peng et al. (2019) - Ap Index of Geomagnetic Activity and S&P 500 Returns. 

Anna Krivelyova & Cesare Robotti (2003) - Playing the Field: Geomagnetic Storms and the Stock Market.