S&P 500 vs. NOAA Kp/Ap Forecasts | October 26–30, 2026

NOAA's latest 3-Day Kp Forecast (issued October 27, 2026, at 8:30 AM ET; updated twice daily and shifted +55 hours in the chart below) currently projects a dip on Wednesday, 8:00–11:00 PM ET.

 

NOAA's latest 45-Day Ap Forecast (issued October 26, 2026, at 8:00 PM ET; updated daily and shifted +4 CD in the chart above) projects a high for Thursday, October 29, and a low for Wednesday, November 4.

 

KMAS 3- and 7-Day Solar Wind Forecast based on ACE Observations: Solar wind speed at Earth near 400 km/s, up from 360 km/s on October 26. Transit time from the Sun was about 4 days 8 hours, or 4.1–4.8 days across the recent 360–420 km/s range.

Solar wind near 400 km/s is ordinary, not a high-speed stream, and speed alone does not raise Kp or Ap. Geomagnetic activity increases when the interplanetary magnetic field turns south and the solar wind is fast or dense. Neither condition exists now. Latest Kp at 15:00 UTC on October 27 is 1 (Ap about 4). Over the prior 24 hours, Kp ranged from 0.7 to 2.7 (Ap about 3–12): quiet to unsettled, with no storm. 

Assumptions and methodology:

TPR (2026) - S&P 500 vs. Geomagnetic Ap Index and Kp Index.  

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

 

 Week of Oct 19-23, S&P 500 futures vs. NOAA 3-day Kp (Last issued Oct 23, 2026, 8:30 AM ET).

 

See also:
TPR (October 26, 2026) - S&P 500 November Seasonality in Midterm Election Years.

S&P 500 vs. NOAA Kp/Ap Forecasts | October 19–23, 2026

NOAA's latest 3-Day Kp Forecast, updated twice daily, projects a high Monday–Tuesday, low and reversal Wednesday, and recovery into early Friday.

 

 NOAA's latest 45-Day Ap Forecast, updates daily, however, projects a low for Saturday, October 24.

 

Assumptions and methodology:

TPR (2026) - S&P 500 vs. Geomagnetic Ap Index and Kp Index.  

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

 

 Result: Week of Oct 19-23, 2026 hourly S&P 500 futures vs. NOAA 3-day Kp, last issued Oct 23, 2026, 8:30 AM ET.

 

Seasonal Cycle for October 2026.

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 about 15 hours to 6 days to reach the Earth: fast CMEs (speeds > 1000 km/s) 15 hours–2 days, average CMEs (speeds ~500–1000 km/s) 2–4 days, and slow CMEs (speeds < 500 km/s) 4–6 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 (2026) - S&P 500 vs. Ap Index: +3-Day Lag and Limits of Multi-Week Forecasting.

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

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

TPR - Sun and Markets.

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.

"Does the Son of the Dust Know Anything More Beautiful?" | Einar Ben

Following the intense Northern Lights displays triggered by a G4 geomagnetic storm on January 19, 2026, forecasts now predict a Kp index of 4 for January 21. These auroras are currently visible across Iceland, Greenland, and the northern parts of Scandinavia, Russia, Canada and Alaska.

 

 Iceland, January 20, 2026.

 

» Does the son of the dust know anything more beautiful
than the palace of gods in electronic flames?
By the universe bosom everything is fire
and decoration of slithering northern lights.
From the seventh heaven to the ocean’s horizon... «

 
Norðurljós ("Northern Lights") by Einar Ben (1864–1940).

  

NOAA SWPC daily maximum expected global geomagnetic conditions (Kp) for the coming 27 days.

 

See also:

Financial Markets and Solar Activity.

Helioeconomics.

SPX vs Sunspots | 36 - 48 Hour Forecast

Current Solar Data from NOAA (HERE + HERE)

The number  of sunspots in existence at any one time is continually subject to change as some disappear and new ones emerge. As the sun
rotates on its own axis, these sunspots are visible at 27-day intervals, the approximate period required for the sun to make one complete
rotation. The 27-day sunspot cycle causes variations in the ionization density of the layers on a day-to-day basis.

S&P 500 vs 10.7 cm Radio Flux | April - May 2016

The NOAA-forecasts on 10.7 cm flux are updated daily.

Yesterday Sunspots Increased = Today Market Should Decline

However, the daily sunspot number reached a 2 year high (154) while the SoLunar Map signals an upturn in the stock market (see also HERE)

Highest Daily Sunspot Number since April 2014

Source: NOAA

SPX vs Sunspots

Sunspots shifted +49 days

The Ap index measures geomagnetic activity and the 10.7 cm Flux is considered a sunspot-proxy.
Source: NOAA

SPX vs Sunspots

 

Sunspots shifted +49 days

Sunspot Cycle 24: "None of us alive have ever seen such a weak cycle"

Conventional wisdom holds that solar activity swings back and forth like a simple pendulum.  At one end of the cycle, there is a quiet time with few sunspots and flares. At the other end, Solar Maximum brings high sunspot numbers and solar storms. It’s a regular rhythm that repeats every 11 years. 

Reality, however, is more complicated. Astronomers have been counting sunspots for centuries, and they have seen that the solar cycle is not perfectly regular. For one thing, the back-and-forth swing in sunspot counts can take anywhere from 10 to 13 years to complete; also, the amplitude of the cycle varies. Some solar maxima are very weak, others very strong (HERE). 

But "none of us alive have ever seen such a weak cycle [as the sunspot cycle 24]", said Dr. Leif Svalgaard of Stanford University and other prominent solar scientists at the 2013 Fall Meeting of American Geophysical Union (AGU), held on December 11, 2013 in San Francisco. This solar max is weak, and the overall current cycle conjures up comparisons to the famously feeble Solar Cycle 14 in the early 1900s (see also HERE & HERE).

John Hampson recently expected the "solar cycle 24′s flat top to end by mid-2014", and one of two possibities playing out: "One, equities peak out within the next 6 months, commodities don’t come again, and we thereafter enter the typical post-solar-peak recession (deflationary). Or, two, equities are peaking now and commodities are breaking upwards out of their large consoliation triangles since 2011 to produce a typical late-cyclical final rally and help tip the weak economy into that recession." (see also HERE).

Credits: John Hampson

Credits: Jan Alvestad

 

Credits: Jan Alvestad

Solar Tides & Financial Markets | Al Larson

Astrophysics & Chaos [Mar 30, 1999]

"The Solar Energy System does affect markets. The Sun gives off radiation which varies by about 2 percent. These variations are caused by tidal forces that the revolving planets exert on the gases in the Sun.

These tides cause vortexes in the Sun’s surface leading to solar flares, coronal holes, and magnetic storms. The energy changes from these are carried to Earth on an ionized stream of particles called the Solar Wind.

When the Solar Wind reaches Earth it is deflected around the Earth by the Earth’s magnetic field. 

This creates a magnetosphere around the Earth. At the poles ionized particles can penetrate the Earth’s atmosphere. Changes in the solar radiation cause changes in the voltage in the ionosphere.

This in turn causes changes in the electrical currents flowing through people standing on the Earth. These emotional swings account for about 40 percent of price motion."

 

Al Larson a.k.a. Hanns Hannula [extracted from his "Cash in on Chaos Newsletter" @ www.moneytide.com - more HERE & HERE]

 

Hans Hannula (1991): A Lunar Chaos Theory; p. 14

SPX vs Solar Activity

Last 30 Days Daily Solar Data

Solar flares and CMEs are intense flashes of extreme radiation emanating from the Sun.  

The ejected material is a plasma consisting primarily of electrons and protons, but may contain small quantities of heavier elements such as helium, oxygen, and even iron. 

Most solar flares and coronal mass ejections originate in magnetically active regions around visible sunspot groupings. 

Near solar maxima the Sun produces about three CMEs every day, whereas near solar minima there is about one CME every five days (see also HERE).

3-day Solar-Geophysical Forecast

Solar flares are classified according to the peak flux as Class A, -B, -C, -M or -X Flares (ranged from small to large). Daily Solar Data, a 3-day Report of Solar and Geophysical Activity, as well as a 45 Day F10.7cm Flux Forecast are provided free of charge by the U.S. Dept. of Commerce, NOAA, Space Weather Prediction Center.

For the purpose of market timing only Class M and -X flares are relevant. However, not every flare ejected by the Sun is directed towards the Earth. But if it is, the solar storm takes 2 days +/- to trigger a geomagnetic storm. In 2003, the Federal Reserve Bank of Atlanta did a study on the effects of solar storms on stock market traders: "Unusually high levels of geomagnetic activity have a negative, statistically and economically significant effect on the following week’s stock returns for all US stock market indices."   

www.helios.izmiran.rssi.ru

Therefore, some 2 days +/- after an earth-directed Class M or Class X flare a drop in the stock markets should be expected.

So what about the latest Class M flares on September 8th and 9th? They will miss to hit the Earth (see also HERE). Instead various 10.7cm Flux Forecasts suggest the stock markets will keep wedging up into around the New Moon (Sep 15) or even the Equinox (Sep 22). Please note: Solar-, lunar- and other astro-indicators frequently fail around Equinoxes (inversion periods are: March 21 - April 7, , June 7 - July 7, September 9 - October 11, December 8 - January 6).