A “digital tide gauge” for the ionosphere — using WSPR spots as signals of opportunity.
Traveling Ionospheric Disturbances (TIDs) are wave-like disturbances in ionospheric electron density and layer height. On HF paths they can present as slow, repeating changes in focusing/defocusing and effective reflection geometry — your signal “breathes” even when the transmitter is stable.
NEW: Periodogram (Lomb–Scargle)
The bottom panel is a Lomb–Scargle periodogram of the residual. This is designed for unevenly sampled data (WSPR spots are “bursty”).
Peaks in the 10–120 minute range are exactly the kind of “heartbeat” you expect from MSTIDs
and related gravity-wave driven structure — when the residual really is wave-like, rather than just sunrise/sunset drift.
How to read the periodogram without fooling yourself
A “real” feature tends to (a) recur in time, (b) appear across multiple links within a corridor, and (c) shift gently with conditions.
One lonely spike on one lonely path is usually just that path being temperamental — which, to be fair, is HF’s entire personality.
Jump to a corridor, then expand it:
High-density trans-Atlantic corridor. Best starter for spotting coherent residual oscillations (candidate MSTIDs) and for comparing multiple UK RX sites.
Lower-spot-count than NA East. Useful for long-haul geometry changes and ‘patchy openings’. Longer window helps.
Often bursty and open/close dominated. When open, residual oscillations can be very clear; flutter tends to expose disturbed paths quickly.
Typically low spot counts. When it appears, watch for ‘shredded’ residuals and higher flutter if the path grazes disturbed regions. Longer window improves the odds.
Low counts in your sample windows, but worth keeping: north–south-ish geometry is good for separating ‘real’ wave-like behaviour from pure sunrise/sunset drift.
Your VK3QN→UK RX results are promising. Long path / short path mixtures can show up as regime shifts; TIDs are better seen in the residual as smoother periodic motion.
Good for ‘flutter’ demonstrations: when the path is disturbed, residuals go jagged and the flutter index rises. Often sparse—long window recommended.
Short-hop regional propagation. Often the ‘everything lands here’ band when DX is difficult.
Generally steadier than 20 m; useful control band for disturbance comparisons.
Sometimes short-hop, sometimes overshoots. Good comparator against long-haul corridors.
More opening/closing dominated. When open, residual structure can be very clear.