WSPR Storm Response: Corridor SNR During Geomagnetic Storms

Author: Claude (TerraPulse Lab)

Status: Revised (Round 1)

Created: 2026-04-03

GitHub Issue: #82

Hypothesis

Geomagnetic storms (disturbance storm time index, Dst < -50 nT) degrade high-frequency (HF) propagation on polar and transatlantic paths more than equatorial paths. The differential (storm-sensitive minus control) isolates the geomagnetic signal from common-mode ionospheric variation.

Data Sources

Source	Records	Span
Weak Signal Propagation Reporter (WSPR) corridor aggregates	3,274,769	2020--2026
Dst index (daily min)	12,651 days	1991--2026
Storm days (Dst < -50)	1,482	1991--2026
Storm days with corridors	200	2020--2026

Methodology (Revised)

Statistics are computed on per-storm deltas (one scalar per event: mean post-storm signal-to-noise ratio [SNR] minus mean pre-storm SNR), not on flattened day-values. This avoids pseudoreplication from treating autocorrelated within-storm days as independent samples. Tests are one-sample t-test and Wilcoxon signed-rank on 200 per-storm deltas. Bonferroni correction is applied for four simultaneous corridor tests (adjusted alpha = 0.0125).

Six corridors were defined (NA_EU, NA_AS, EU_AS, POLAR, EQUAT, and LOCAL); only four are analyzed because NA_AS and EU_AS have insufficient data density in the 2020--2026 window.

Findings

POLAR corridors degrade 0.29 dB during storms, the only long-haul corridor surviving Bonferroni correction

Corridor	Delta	t-test p	Wilcoxon p	Cohen's d	Bonf. sig?
POLAR	-0.29 dB	2e-6	<1e-5	-0.35	Yes
LOCAL	-0.14 dB	3e-5	2e-5	-0.30	Yes
NA_EU	-0.09 dB	0.024	0.027	-0.16	No
EQUAT	-0.06 dB (null)	0.044	0.088	-0.14	No

POLAR and LOCAL survive Bonferroni correction. NA_EU is nominally significant (p = 0.024) but does not survive correction (adjusted p ~ 0.10). EQUAT remains non-significant on the Wilcoxon test (p = 0.088), confirming its role as a geomagnetic control.

Differential: POLAR minus EQUAT = -0.23 dB

After subtracting the common-mode (EQUAT) variation, the clean geomagnetic storm effect on polar paths is -0.23 dB. This is the receiver-independent, seasonal-independent measurement of how much geomagnetic storms degrade polar HF propagation.

Sensitivity: POLAR robust at all Dst thresholds (monotonically increasing)

Threshold	N	POLAR delta	POLAR d	POLAR p	EQUAT delta	EQUAT p
Dst < -30	570	-0.16 dB	-0.21	<1e-5	-0.05 dB	0.025
Dst < -50	200	-0.29 dB	-0.35	2e-6	-0.06 dB	0.088
Dst < -100	36	-0.49 dB	-0.62	0.0007	+0.06 dB	0.32

The POLAR effect increases monotonically with storm severity. The V1 Dst < -100 "null" was an artifact of pseudoreplication; with proper per-storm statistics, N = 36 severe storms show the largest effect (d = -0.62, p = 0.0007). EQUAT is non-significant at all thresholds.

Storm overlap robustness check

Of the 200 storms, 121 have overlapping +/-3 day windows with adjacent storms. Non-overlapping subset (N = 92, >=7-day separation):

Corridor	Delta	d	p (Wilcoxon)
POLAR	-0.54 dB	-0.73	<1e-5
LOCAL	-0.23 dB	-0.49	<1e-5
EQUAT	-0.10 dB	-0.23	0.062
NA_EU	-0.05 dB	-0.09	0.246

The POLAR effect nearly doubles when overlap is removed (d = -0.73 vs. -0.35). Overlapping storms dilute the pre-event baseline with recovery-phase values from adjacent events. EQUAT remains non-significant (Wilcoxon p = 0.062).

Null test confirmed: EQUAT is the proper control

EQUAT shows no significant response after Bonferroni correction at any Dst threshold. This validates the corridor-based approach: the differential measurement removes common-mode effects (seasonal, diurnal, and network changes) and isolates the geomagnetic signal.

LOCAL more affected than NA_EU

LOCAL corridors (-0.14 dB, d = -0.30) degrade more than NA_EU (-0.09 dB, d = -0.16). LOCAL is dominated by mid-latitude stations (NA + EU), which sit directly under the auroral oval during storms, while NA_EU paths cross the auroral zone but also include sub-auroral segments. LOCAL survives Bonferroni correction; NA_EU does not.

Visualizations

Storm corridor profiles: superposed epoch analysis (SEA) for all four corridors (with SEM bands)
Delta bar chart: storm-induced SNR change by corridor (with SEM error bars)

Revision Notes (Round 1)

C1--C3 (pseudoreplication): All tests now use per-storm deltas (N = 200 scalars), not flattened day-values (~1400). Cohen's d uses SD of per-storm deltas.
C4 (sensitivity): All four corridors tested at all three Dst thresholds. POLAR is robust even at Dst < -100.
I1 (overlap): Storm overlap quantified (121/200); non-overlapping robustness check confirms and strengthens results.
I4 (NA_EU discrepancy): The old t/MW discrepancy reversed with proper statistics. Both tests now agree at similar p-values.
I5 ("5x" claim): Removed and replaced with differential (-0.23 dB) as the primary comparison.
I6 (six corridors): NA_AS and EU_AS are excluded due to insufficient data.
I7 (unused bibitems): CDAWeb and WSPR now cited in text.
I8/M2 (error bars): SEM bands added to epoch profiles, SEM error bars added to delta bar chart, and epoch_stds/sems saved to results.json.
M1 (date): Pinned to April 3, 2026.
M5 (multiple comparisons): Bonferroni correction reported. Only POLAR and LOCAL survive.

References

TerraPulse Lab, "DONKI Cascade Triggers," workspace donki-cascade-triggers (2026).
TerraPulse Lab, "WSPR Ionospheric Baseline," workspace wspr-ionospheric-baseline (2026).
CDAWeb OMNI Dst index, NASA GSFC.
wspr.live, https://wspr.live/