Hand-considered hypotheses, 5801–5900
Space weather and geomagnetism, written one at a time: magnetospheric dynamics, geomagnetic induction, ionospheric physics, ground-level effects and instrument networks. Each entry states a claim, names a mechanism, and gives a measurement that would separate it from its nearest rival; the logical form chosen for that entry is printed above the text, and no two entries share one, so that repetition of the argument rather than of the subject can be checked by eye. None has been tested. No citation is invoked and no number is presented as measured: every magnitude offered is marked as the estimate it is. Nothing here restates a standard model result or repeats an item from the earlier sets.
Solar wind, magnetosheath and the magnetopause
Misattribution of a measured decay
H5801. Ring-current decay rates measured after a storm's minimum are usually attributed to charge exchange with geocoronal hydrogen, yet a substantial part of the apparent decay is adiabatic: as the magnetosphere deflates, drifting particles move to weaker field and their energy falls. The two processes differ in their dependence on solar-wind dynamic pressure, which sets the inflation, while charge exchange depends on density and species. Recomputing decay during two moderate storms with the same pressure history but different oxygen content of the ring current would separate them, because charge exchange scales with composition and the adiabatic term does not.
Bound from total pressure balance
H5802. The standoff distance of the dayside magnetopause is set by the solar-wind ram pressure plus the magnetosphere's internal pressure, so a boundary that reaches geosynchronous orbit during a storm should require an inflated ring current as well as strong ram pressure; the bound is one of total pressure balance, not of ram pressure alone. Sorting deep boundary crossings by the ring current's simultaneously measured pressure would place them all at high internal pressure, while ram-pressure-matched crossings without it would stop farther out.
Threshold in a geometric angle
H5803. Magnetosheath jets are usually counted as a high-Mach-number phenomenon, yet their occurrence should be governed mainly by the angle between the interplanetary field and the bow-shock normal, since that angle decides whether the shock is quasi-parallel and can transmit coherent structures downstream. Jet counts at fixed solar-wind speed across a range of cone angles would test this. If the angle controls occurrence, the jet rate will collapse at small cone angles without any change in Mach number.
Inversion of a standard inference
H5804. The dayside reconnection rate is commonly inferred from the cross-polar-cap potential, but the potential is also limited by the ionosphere's ability to supply current, so the inference inverts a saturated quantity and understates reconnection when conductance is low. The mechanism is a conductance-dependent ceiling on the potential, not a change at the magnetopause. Comparing the potential with in-situ reconnection signatures during low-conductance winter conditions would show the potential flat while the signatures strengthen.
Identity of two named structures
H5805. Flux transfer events and the vortices shed along the magnetopause's flanks may be one population described twice, with the difference in appearance coming from where the observing spacecraft crosses the structure. Kelvin-Helmholtz vortices rolled up at the flank produce field-aligned flux ropes that a dayside traversal would record as a classic flux transfer event. A spacecraft repeatedly crossing the same flank at two downstream distances would show the ropes growing and pairing if the identity holds, and remaining fixed if it does not.
Screening by a cold reservoir
H5806. Dense cold plasma draped over the dayside magnetopause lowers the local Alfven speed and can throttle reconnection there, so the reconnection rate should fall during intervals when a plasmaspheric drainage plume reaches the dayside. The plume raises the mass density without raising the magnetic field, lowering the inflow speed that reconnection can draw. Pairing magnetopause crossings inside and outside a plume at similar magnetic shear would show the reconnecting flow suppressed in the plume.
Focusing by a flow gradient
H5807. Jets in the magnetosheath are not born as fast flow but as flow that has been focused, and the focusing is stronger where the downstream velocity gradient is largest. The mechanism is continuity, because a transverse gradient compresses streamlines and raises the speed without adding momentum. Mapping jet locations onto the modelled downstream gradient rather than onto the shock's subsolar point would put the jets where the gradient is steep.
Sign discrimination by an interplanetary component
H5808. The hemispheric asymmetry of the ground magnetic response to the same solar-wind driver changes sign with the sign of the interplanetary By, because By tilts the dayside merging geometry and shifts the closed-field footpoints toward one pole. The asymmetry is therefore a geometric consequence of the merging line's tilt, not a difference in conductance between the hemispheres. Stations at conjugate latitudes with matched conductance, sorted by the sign of By, would show the asymmetry reversing while the conductance stays fixed.
Common driver of two periodicities
H5809. Two periodicities reported in the dayside magnetosphere, one at the magnetopause and one in the ionosphere, are usually treated as separate oscillations, but both may be the response to a single periodic driver in the foreshock. The foreshock's ULF waves compress the magnetopause and drive field-line resonance at the same frequency, so the two records are coherent without either causing the other. Coherence between a foreshock monitor and a ground magnetometer at the same frequency, with a phase lag matching the Alfven travel time, would establish the common driver.
Amplitude ceiling in a coupling
H5810. The ground amplitude of a sudden impulse is not proportional to the solar-wind dynamic-pressure jump alone, because the impulse couples to the ground through the ionospheric current system and that coupling saturates. The saturation arises when the pressure jump drives a conductance increase faster than the current can follow, so the ground amplitude per unit pressure jump should fall as the jump grows, and the fall should set in at a smaller jump where the background conductance is already high. Matched jumps recorded on one meridian at noon and at midnight would show the ratio bending at two different jump sizes, which a linear coupling could not produce.
Mismatch of timescales
H5811. Radiation-belt electron flux dropout at the start of a storm is often attributed to magnetopause shadowing, but the dropout's duration is set by how long the outer boundary stays compressed, which is usually shorter than the observed depletion. A slower loss process must therefore continue after the boundary retreats. Comparing the recovery of the outer boundary with the recovery of electron flux at the same drift shell would show the flux lagging the boundary if an additional loss is at work.
Geometry mimicking an asymmetry
H5812. The dawn-dusk asymmetry of magnetosheath density is generally read as a dynamical effect, yet part of it is geometric: the aberration of the solar wind by Earth's orbital motion displaces the flow pattern relative to the Sun-Earth line. Correcting for aberration removes a known, calculable part of the asymmetry. Recomputing the asymmetry in aberrated coordinates would show the residual shrinking to the size expected from the magnetopause's own flaring.
Partial cancellation of two sources
H5813. Field-aligned currents driven at the magnetopause and those driven in the magnetosheath flow in opposite senses over part of their path, so their ground signatures cancel where the two overlap and a weak deflection can mark strong coupling rather than weak. The cancellation is a property of the current geometry, not of the coupling efficiency. Satellite current measurements paired with ground magnetograms on the same meridian would show the ground minimum coinciding with a maximum of the total current.
Selection bias in a crossing census
H5814. Reports that the magnetopause is usually found near a particular standoff distance inherit the orbits of the spacecraft that found it, because crossings are recorded where spacecraft linger. A census weighted by dwell time rather than by count would shift the reported mean outward. Recomputing the distribution with each crossing weighted by the time spent in that radial bin is a test that needs no new data.
Rectification of an oscillating input
H5815. Oscillating solar-wind pressure should produce a net dawn-to-dusk current in the ionosphere even when its average is zero, because the ionosphere's conductance rises faster under compression than it falls under rarefaction; the rectification is a nonlinearity of the conductance, not a net momentum input. A long interval of periodic pressure oscillation with zero mean, compared with a steady interval of the same mean pressure, would show a persistent offset of the cross-polar-cap current only in the oscillating case.
Control by dipole tilt geometry
H5816. The seasonal difference in dayside reconnection is usually assigned to the dipole tilt changing the shear across the magnetopause, but tilt also changes the area of the dayside boundary exposed to a given interplanetary field direction. Separating the two requires a geometry in which shear is fixed while the exposed area changes. Binning reconnection signatures by tilt at fixed shear angle, using conjunctions between a dayside spacecraft and a ground radar, would isolate the area term.
Magnetotail and substorms
Order of events between two candidates
H5817. Near-Earth neutral-line reconnection and current disruption are still placed on either side of substorm onset, and the argument turns on timing that is usually quoted to the resolution of the instruments rather than to the physics. If reconnection begins tailward of the disruption site, the mid-tail flow burst must precede the disruption's magnetic signature by the Alfven travel time between them. Comparing onset times at two radially separated spacecraft with a common timing reference would place the earlier event without ambiguity.
Conservation of entropy in a compression
H5818. Flux pile-up in the near-Earth tail cannot raise the pressure of a closed flux tube without raising its entropy, so pile-up events that show pressure rising at constant entropy must be compressions of an open or newly closed tube rather than accumulation of closed flux. The distinction is measurable because entropy is a function of pressure and flux-tube volume, both of which are observed. Events sorted by whether their entropy rises would divide into two populations with different subsequent behaviour.
Spatial fingerprint of a closure path
H5819. The substorm current wedge closes through the ionosphere along the conductance gradient rather than along a fixed meridian, so the wedge's azimuthal position should track the evening-sector conductance boundary through the season. A fixed-meridian model would predict no seasonal motion. Mapping wedge positions from a meridian chain across equinox and solstice would show the displacement if conductance controls closure.
Resonance condition met intermittently
H5820. Pi2 pulsations are usually treated as a cavity resonance excited at onset, but the cavity's frequency depends on the plasmasphere's size, so the same broadband onset impulse should ring at different periods as the plasmasphere erodes through a storm. A fixed period across a storm would argue against a cavity mode. Tracking Pi2 period against an independently measured plasmapause location through one storm separates the two.
Necessary but not sufficient condition
H5821. A southward interplanetary field is necessary for a substorm but not sufficient, and the missing condition is a minimum in the tail's flux content rather than a threshold in the field's magnitude. The field opens the door and the flux content decides whether the tail can release. Selecting intervals with identical southward field but different preceding flux loading would show onsets only in the well-loaded set.
Threshold crossed cumulatively
H5822. Substorm onset should depend on the time integral of the dayside reconnection rate since the last onset rather than on the instantaneous rate, because the tail stores flux and releases it only when the stored amount crosses a threshold. Instantaneous-rate models predict onsets during bursts of driving and miss them during steady driving. Sorting onsets by the accumulated flux since the previous onset would give a narrower distribution than sorting by the instantaneous rate.
Hysteresis in a loading cycle
H5823. The relation between tail stretching and interplanetary driving should be hysteretic, because the tail remains stretched after the driving stops and the same driving level then corresponds to two different configurations on the way in and on the way out. The mechanism is the finite lifetime of the closed flux against reconnection. Plotting stretching against driving for a full loading-unloading cycle would show a loop whose width measures that lifetime.
Period set by a mass reservoir
H5824. Sawtooth events have a period often attributed to a reconnection clock, but a period set by the draining of a mass reservoir fits the same observations. Each event ejects a plasmoid whose mass must be replenished by the solar wind before the next, so the period should scale with the mass loading rate rather than with the field strength. Comparing periods during intervals of matched field strength but different solar-wind density would separate the two.
Transport signature of an injection
H5825. Dipolarization fronts carry energetic electrons into the inner magnetosphere, and the energy spectrum of the injected population should steepen with distance from the front because the faster electrons outrun the slower ones. The steepening is a propagation effect, not an acceleration signature. Two spacecraft separated along the front's propagation path would record spectra whose difference fixes the propagation speed independently.
Mapping error read as a missing population
H5826. Bursty bulk flows are mapped to ionospheric flow channels by field-line tracing, and a mismatch between the number of flows and the number of channels is usually attributed to missing flux tubes rather than to mapping error. The mapping error grows with uncertainty in the tail's field model, which is largest where the field is weakest. Comparing channel counts using two independent field models for the same interval would show whether the mismatch is model-dependent.
Energy conversion bounded by geometry
H5827. Flow braking in the near-Earth tail converts kinetic energy into field-aligned currents, and the conversion efficiency should be bounded by the ratio of the braking region's transverse size to the flow's inertial length; that bound is a property of the plasma, not of the driver. Measuring current density and braking length across several events would place the efficiency below the bound in every case and near it in the strongest flows.
Budget that should close
H5828. The mass carried away in plasmoids should account for the mass lost from the closed tail during the same interval, and the budget is rarely checked because plasmoid mass is poorly measured. A systematic excess of plasmoid mass over the closed-tail loss would point to a source inside the tail rather than at its boundary. Comparing the two over a series of substorms with reliable plasmoid crossings would make the budget diagnostic.
Modulation of an efficiency
H5829. The latitude of substorm onset varies with the solar cycle, and the variation is usually assigned to a change in the solar-wind driver; part of it should come instead from the cycle's effect on the ionospheric conductance that the onset current must close through. The conductance changes by a larger factor than the driver over a cycle. Recomputing onset latitudes from a conductance-corrected current wedge over two consecutive cycles would reduce the apparent trend.
Rate inferred from a state change
H5830. The nightside reconnection rate is inferred from the rate at which the polar cap shrinks, but the cap's area responds to both reconnection and transport of flux across the cap boundary, so a shrinking cap can occur during steady reconnection. The inference assumes a closed budget that the transport term violates. Comparing cap contraction rates with the cross-cap potential over intervals of strong flow would show the discrepancy growing with the transport.
The ring current and the storm-time inner magnetosphere
Misattribution to the sky of a ground effect
H5831. Part of every storm-time depression recorded at a ground observatory is induced in the Earth rather than produced in the ring current, and the induced part differs between observatories because crustal conductivity differs; corrections that assume a globally uniform induction are why the same storm gives different depths at coastal and inland stations. Differencing a coastal and an inland observatory after removing the ring-current geometry would isolate the induced term.
Two components with different decay
H5832. The recovery of the storm-time field is usually fitted with a single decay time, yet the partial ring current decays faster than the symmetric one because it depends on continued injection from the tail. A two-component decay should show the early recovery controlled by the partial component and the late recovery by the symmetric one. Fitting local-time-resolved fields from a longitudinal chain would expose the two rates.
Composition control of a timescale
H5833. The recovery rate of the ring current depends less on the solar-wind driver than on the oxygen fraction of the ring current, because oxygen charge-exchanges with geocoronal hydrogen faster than hydrogen does at ring-current energies. A storm with high oxygen content should therefore recover faster at matched pressure. Comparing recovery times for storms with composition measured by a passing spacecraft would order them by oxygen fraction.
Transport limit on a refilling time
H5834. Plasmaspheric refilling is limited by the flux of ionospheric ions along the field line rather than by diffusion in the outer plasmasphere, so the refilling time should scale with field-line length rather than with L-shell alone. The two scalings coincide for a dipole and diverge during a storm when the field is distorted. Refilling observed at two longitudes after the same storm would show the distortion if flux, rather than diffusion, sets the rate.
Threshold in a cold density
H5835. EMIC waves should be unable to grow when the cold plasma density falls below a threshold set by the hot proton anisotropy, because the growth rate falls faster than the anisotropy can compensate. The threshold predicts that dropout events stop appearing late in the recovery, when the plasmasphere has refilled. Sorting EMIC observations by an independently inferred cold density would show a sharp onset at the same value.
Resonance with the wrong harmonic
H5836. Magnetosonic waves are usually invoked to accelerate electrons at the second harmonic of the proton gyrofrequency, but the same waves can resonate with electrons at a higher harmonic where the wave power is weaker and the resonance broader. The broader resonance matters more when the electron distribution is smooth. Comparing the pitch-angle diffusion inferred from wave power at two harmonics would show the higher harmonic dominating at the energies where the distribution lacks structure.
Competition of two timescales
H5837. Shielding of a penetration electric field takes the time needed for the region-2 current to build, so its duration should track the Alfven transit time from the equatorial plane to the ionosphere rather than the duration of the solar-wind driver. Two events with the same driver duration but different plasma density should shield on different timescales. Comparing penetration events with the ambient density inferred from a magnetometer chain's ULF response would test the competition.
Coupling to a secondary population
H5838. Cold ion outflow should accompany a subauroral polarization stream, with a flux that scales with the stream's electric field, because the same field that drives the stream also lifts the ions. The outflow is a consequence, not an independent phenomenon to be explained separately. Measuring the outflow above a stream with a radar and the stream's field with a magnetometer chain would test the scaling.
Reservoir hidden between two measurements
H5839. The warm plasma cloak, which sits between the plasmasphere and the ring current, can supply most of the mass the ring current needs during a storm, and its neglect biases composition budgets. The cloak is invisible to cold-plasma imagers and too cold for energetic-particle instruments, so it falls between the two. A storm-time mass budget assembled from both instrument types would show the deficit that the cloak fills.
Energy accounting for an accelerated population
H5840. Ion conics from the auroral zone carry more energy than the field-aligned potential drop can supply if the drop is inferred from the electron spectrum, because the inferred drop misses the part of the potential below the spacecraft. The energy discrepancy is a measurement-geometry effect. Comparing conic energies at two spacecraft altitudes over the same flux tube would show the discrepancy shrinking with altitude.
Efficiency of injection into a trap
H5841. Only a fraction of the plasma injected by each substorm is trapped in the ring current, and that fraction should fall as the injection's energy rises, because higher-energy plasma drifts on shells that intersect the magnetopause sooner. The efficiency is a geometric loss, not a saturation of the source. Comparing the ring-current increase with the injected flux for injections of different energies would show the fraction decreasing.
Consistency between two independent measurements
H5842. The ring current's pressure inferred from the ground magnetic field and that inferred from energetic neutral atoms must agree if both are correctly calibrated, and any disagreement should scale with the assumed current geometry rather than with the pressure itself. Ground-based estimates assume a symmetric current, while the neutral-atom measurement does not. Comparing the two through the recovery phase, when asymmetry is small, isolates the geometry error.
Radiation belts and wave-particle interaction
Threshold in a distribution's shape
H5843. Chorus growth requires an electron anisotropy above a threshold that depends on the ratio of plasma frequency to gyrofrequency, so the same anisotropy should produce chorus at one altitude and not another. The altitude dependence comes from the density gradient along the field line. Comparing chorus observations at two spacecraft separated in altitude along the same field line, during the same event, would test the threshold.
Two names for one loss process
H5844. Hiss-driven loss and the formation of the slot region are usually described as separate phenomena, but the slot is where the hiss loss timescale is shorter than the radial diffusion timescale. The identity means that any change in the slot's depth must be accompanied by a change in local hiss power, not only in the source population. Comparing slot depth with measured hiss power over a season would test the identity.
Discriminating by pitch angle rather than energy
H5845. EMIC-driven loss and magnetopause shadowing both deplete the outer belt and are usually separated by energy; pitch angle does it better, because shadowing removes particles on large drift shells regardless of pitch angle while EMIC loss removes particles near the loss cone first. The pitch-angle distribution therefore carries the signature. Comparing distributions before and after two dropout events with different solar-wind drivers would sort them.
Non-uniqueness of an inversion
H5846. The radial diffusion coefficient extracted from phase space density gradients is not unique, because a gradient can be produced by local acceleration as well as by diffusion; the inversion assumes a source-free region that the data rarely provide. Imposing two different source assumptions on the same phase space density profile would produce two diffusion coefficients differing by more than the profile's uncertainty.
Upper bound on a coupling coefficient
H5847. ULF wave power can drive radial diffusion no faster than the rate at which the waves' azimuthal mode number matches the drift resonance, so the diffusion coefficient is bounded by the wave power at the resonant mode number rather than by the total power. Total power overestimates the coefficient whenever the spectrum is broad. Computing the coefficient from narrow-band power at the resonant mode number would bring it below the bound in every case.
Phase-space signature of a nonlinear process
H5848. Nonlinear chorus interaction can trap electrons in phase and produce a flat region in the pitch-angle distribution where linear diffusion would produce a gradient. The flat region's width grows with wave amplitude, so it is a signature of nonlinearity rather than of the source. Comparing distributions during weak and strong chorus intervals would show the flat region appearing only in the strong ones.
Spatial pattern from a boundary condition
H5849. Butterfly pitch-angle distributions are usually explained by a localized source at high pitch angle, but a similar pattern arises from a loss cone that is narrower at the equator than at the mirror point, which is a boundary condition rather than a source. The two produce different distributions at energies above the source's peak. Comparing the distribution's shape at two energies would separate them.
Budget of precipitation against a reservoir
H5850. Microburst precipitation removes electrons from the outer belt at a rate that should be detectable as a decrease of the trapped population when the bursts are summed over a drift orbit. The budget is rarely tested because the bursts are measured at one point. A spacecraft in a drifting orbit that crosses a fixed microburst region repeatedly would show the trapped flux decreasing after each crossing.
Loss channel opened by an unrelated phenomenon
H5851. Lightning-generated whistlers can precipitate slot-region electrons, so the slot's lower edge should show a diurnal variation following global lightning activity. The coupling is through the whistler's ducting along the field line, which is strongest at night. Comparing slot-edge fluxes at fixed magnetic local time but different lightning seasons would show the variation.
Seed limitation rather than wave limitation
H5852. The outer belt's peak flux should be limited more strongly by the number of seed electrons supplied by substorm injections than by the chorus wave power that accelerates them, because acceleration cannot amplify a population that is not there. The seed number varies by a larger factor between events than the wave power does. Comparing peak flux with injection counts and with chorus power across several storms would order the two controls.
Order between a source and a loss
H5853. Hiss intensification is often reported after substorm onset, and the ordering is used to argue that substorm electrons generate the hiss. A similar ordering arises if the hiss is generated by the same convection enhancement that injects the electrons, with the hiss arriving later only because its growth takes time. Comparing hiss onset with the convection onset rather than with the electron onset would test the attribution.
Ceiling on a refilling rate
H5854. The slot region refills no faster than radial diffusion supplies electrons across it, and diffusion is slowest where the phase space density gradient is smallest, so refilling should proceed in steps rather than smoothly. The steps correspond to the gradient passing through the region where wave-particle interactions are weakest. A time series of slot fluxes at one energy would show the steps if diffusion, rather than local acceleration, controls refilling.
Frame error in a threshold
H5855. The cutoff latitude of solar protons is usually computed in a dipole field, but the real field's day-night asymmetry displaces the cutoff by a few degrees at low altitude, and the displacement changes with the field's own variability. The error is in the frame, not in the protons. Comparing cutoff latitudes measured by a polar-orbiting spacecraft with those computed in a dynamic field model for the same day would show the displacement tracking the model.
Ground-level signature of a rigidity threshold
H5856. The latitude profile of a cosmic-ray decrease should peak at the station whose cutoff rigidity matches the spectral break that the storm's compressed field introduces, and the break moves equatorward as the field is compressed, so the peak station should change during a single event. The mechanism is rigidity-dependent access, with the break set by the shift of the cutoff rather than by the spectrum's overall steepness. A chain of neutron monitors spanning cutoffs, read at two stages of the same decrease, would show the peak migrating if the break controls the profile.
Ionospheric electrodynamics and structure
Identity of a conductivity enhancement
H5857. The equatorial electrojet's strength is usually attributed to the Cowling conductivity, but a similar enhancement follows from the geometry of the horizontal field alone, and separating the two requires an independent measurement of the Pedersen conductivity. The two mechanisms predict different altitude profiles of the current. Comparing current profiles from a rocket sounding with those inferred from a magnetometer chain would separate them.
Reversal as a separate current
H5858. The counter-electrojet is usually treated as a reversal of the same current system, but it may be a separate current at a different altitude that dominates once the electrojet weakens. The two hypotheses predict different magnetic signatures at stations off the magnetic equator. A latitudinal chain would show whether the reversal appears first at the equator or at the flanks.
Geometry of a current focus
H5859. The focus of the Sq current system moves with season and solar activity, and part of the motion is a geometric projection of a fixed current onto a tilted magnetic field rather than a motion of the current itself; the projection changes with the field's declination. Computing the focus in magnetic coordinates rather than geographic ones would remove the apparent motion if geometry owns it.
Sign rule for a penetration field
H5860. The polarity of the prompt penetration electric field at the equator is set by the sign of the interplanetary field's dawn-dusk component and by the latitude of the reconnection site, so the same By can produce either polarity depending on the season. The rule is geometric, not statistical. Sorting penetration events by season at fixed By would show the polarity reversing.
Delayed response of a second system
H5861. The disturbance dynamo's effect on the equatorial electrojet is delayed by the time the thermospheric wind takes to travel from the auroral zone, so the delay should scale with distance and wind speed rather than with the storm's main phase. The delay is a transport time. Comparing the delay at two longitudinal sectors would show it scaling with the auroral-to-equator distance.
Overestimate from a second motion
H5862. Subauroral polarization streams are inferred from the drift of the ionosphere, but the drift also contains a contribution from the neutral wind's dynamo, so the inferred field overestimates the stream when the wind is strong. The wind contribution is largest near dusk, where the streams are also strongest. Comparing streams with and without an independent wind measurement would show the overestimate concentrated at dusk.
Closure path imposed by a boundary
H5863. The auroral electrojet closes partly through the polar cap and partly through mid-latitudes, and the division changes with the conductance of the subauroral region rather than with the electrojet's own strength. The closure path is set by the path of least resistance, which moves with the boundary. Comparing the mid-latitude magnetic signature of two equally strong electrojets under different subauroral conductance would show the division.
Ceiling from a current supply
H5864. The polar cap potential cannot exceed the value at which the region-1 current's closure through the ionosphere reaches the Pedersen conductance's limit, so the potential should saturate at a value that changes with season. The saturation is a property of the ionosphere, not of the solar wind. Comparing the saturation value in summer and winter at matched driving would show the seasonal ceiling.
Degeneracy between two currents
H5865. Region-1 and region-2 currents produce similar ground signatures at some latitudes, so a single-meridian magnetometer cannot separate them without an assumption about the boundary between them. The degeneracy is broken by the sign of the gradient across that boundary. A two-meridian chain would show the gradient reversing where the boundary passes between the stations.
Structure set by a gradient
H5866. A field-aligned current sheet's width is set by the transverse gradient of the ionospheric conductance rather than by the current's magnitude, so a narrow sheet can carry a small current. The width scales inversely with the gradient. Comparing sheet widths from a radar's conductance map with those from a magnetometer inversion would test the scaling.
Coupling from a neutral wave
H5867. Travelling atmospheric disturbances drive ionospheric currents through the dynamo effect, and the current should lead the wave's density perturbation by a quarter period because the current responds to the wave's velocity rather than its density. The phase relation is a signature of the dynamo mechanism. Comparing current and density perturbations at the same location would show the quarter-period lead.
Profile inferred from an integration
H5868. The magnetic crochet's amplitude is used to infer a flare's ionising flux, but the ground field integrates the conductivity enhancement over altitude, so the same flux produces different amplitudes depending on the pre-flare profile. The profile, not the flux, controls the amplitude at low solar elevation. Comparing crochets at two solar zenith angles for the same flare class would show the profile's effect.
Natural experiment on a known driver
H5869. A solar eclipse removes a known fraction of the ionising flux over a known path, so any current system that does not respond in proportion to the removed flux must be controlled by something else. The eclipse is a controlled perturbation, not a curiosity. Comparing the electrojet's response to eclipses of different magnitudes at the same local time would test the proportionality.
Threshold for an instability
H5870. Equatorial spread F requires a seed perturbation whose amplitude exceeds a threshold set by the background density gradient, so the same gradient can be stable on one night and unstable on the next according to the seed. The seed comes from gravity waves and from the evening terminator's gradient. Comparing nights with matched gradients but different gravity-wave activity would test the threshold.
Convergence that concentrates a layer
H5871. Sporadic E forms where the wind shear converges ions, and the layer's density is set by the convergence rate rather than by local ion production, so a layer can form where production is low. The convergence is a property of the wind field's vertical structure. Comparing layer densities with the shear measured by a radar would test the control.
Boundary maintained against diffusion
H5872. The mid-latitude trough's equatorward edge is maintained against diffusion by the electric field's drift, so the edge's sharpness should scale with the field's magnitude rather than with the density's gradient. The edge is a balance, not a source. Comparing edge widths at two field strengths would show the sharper edge at the stronger field.
Transport that outruns chemistry
H5873. Polar cap patches are transported across the cap faster than their plasma can recombine, so their density at the exit should be set by the transit time rather than by the source density. The transit time depends on the cross-cap potential. Comparing patch densities at the cap's entrance and exit would show the loss scaling with the potential.
Quantity inferred from an assumed geometry
H5874. Ionospheric conductance inferred from a satellite magnetometer assumes a current-sheet geometry that the satellite cannot verify, so the conductance carries the geometry's error; the error is largest where the sheet is tilted relative to the orbit. Comparing conductances from two satellites crossing the same sheet at different angles would expose the geometry dependence.
Hidden driver of a known current
H5875. The E-region dynamo's current is usually computed from the neutral wind inferred from the F-region, but the E-region wind can differ in direction because the two regions are coupled by the field line only weakly at night. The difference is largest after sunset, when the F-region wind decouples. Comparing currents with E-region winds measured by a radar would show the discrepancy growing after sunset.
Induction, ground effects and technology
Amplification by a conducting boundary
H5876. The coastal enhancement of geomagnetically induced currents should depend on the shelf's width relative to the induction skin depth, so a narrow shelf concentrates the electric field more than an open coast, and the largest currents should occur where the two are comparable. An estimate of the relevant scale is tens of kilometres. Comparing currents at two coastal substations with different shelf widths during the same event would order the enhancements by width.
Corrosion budget with a hidden term
H5877. Pipeline corrosion potentials include a telluric term that is usually attributed to the coating, but the term's spectrum follows the magnetospheric source rather than the coating's impedance. The telluric current enters through the earthing, not the coating. Comparing potential logs at two pipeline sections with different earthing would show the telluric term changing while the coating is unchanged.
Signature that identifies its cause
H5878. Transformer half-cycle saturation produces even harmonics, while other current effects produce odd ones, so the harmonic pattern identifies the mechanism rather than merely the magnitude. The even harmonics come from the asymmetric flux excursion. Monitoring harmonics at two transformers with different core designs during the same event would show the even-harmonic ratio tracking the core's saturation point.
Non-uniqueness of a conductivity inversion
H5879. The geoelectric field that drives induced currents is inferred from magnetometer data by assuming a conductivity profile, and different profiles that fit the magnetograms equally well give electric fields differing by a factor of about two, an estimate. The non-uniqueness is inherent to the one-dimensional assumption. Comparing fields from two profiles that both fit the same observatory would bound the uncertainty.
Three-dimensional effect read as temporal
H5880. The coast effect makes the horizontal magnetic field rotate and grow near a conductivity contrast, and the rotation can be mistaken for a change in the source current's orientation; the effect is static in space and appears as a temporal rotation only when the source moves. Comparing the field's polarisation at a coastal and an inland station during a quiet interval would show the rotation without a moving source.
Source geometry from a ground gradient
H5881. The auroral electrojet's height and width are degenerate in a single-station inversion, but a two-station gradient breaks the degeneracy because height and width affect the gradient differently. The ratio of the gradient to the field is the discriminator. Comparing ratios at two station separations would place the current's height without additional assumptions.
Distortion that mimics a source change
H5882. Magnetotelluric distortion by shallow conductivity anomalies rotates the electric field, and the rotation is often interpreted as a change in the source's polarisation. The distortion is fixed in space, so it should not vary with the source's azimuth if the anomaly is shallow. Comparing distortion angles across events with different source polarisations would show the angle fixed.
Local anomaly in a global field
H5883. A crustal conductivity anomaly can amplify induced currents at a site by a factor of several, an estimate, while leaving the magnetometer's field nearly unchanged, so current hotspots need not coincide with magnetic anomalies. The anomaly affects the electric field, which the magnetometer does not measure. Comparing induced currents at two sites with similar magnetic fields but different crustal structure would test the amplification.
Gradient rather than a field
H5884. Current in a long conductor is driven by the electric field integrated along its path, and that field depends on the spatial structure of the magnetic disturbance as well as on its local amplitude. A site can therefore carry a large current under a small local field if the field changes steeply across the region. Comparing the current with the field measured at the site and at a neighbouring site would show the spatial structure controlling it.
Coupling into an engineered network
H5885. Track circuits in railway signalling respond to telluric currents at frequencies below the signalling band, so geomagnetic disturbances should appear as false occupancies whose rate scales with the electric field's rate of change rather than with its magnitude. The coupling is inductive through the rails. Comparing false-occupancy logs with the electric field's derivative would test the scaling.
Voltage that integrates a field
H5886. Submarine cable voltages integrate the electric field over thousands of kilometres, so they measure the field's large-scale average rather than its local value, and a cable can show a signal when coastal magnetometers show none; the integration is a spatial filter. Comparing cable voltages with an average of coastal magnetometers along the route would test the filter.
System property that hides a driver
H5887. The reactive power absorbed by a transformer during a geomagnetic disturbance depends on the grid's loading as well as on the induced current, so the same current produces different voltage depression at different load levels. The dependence is a property of the network, not of the storm. Comparing voltage depression at two load levels during the same event would separate the two.
Baseline that absorbs a signal
H5888. Observatory baselines are set by absolute measurements taken at intervals of months, so a slow secular change in the field can be absorbed into the baseline and removed from the record. The absorption is a high-pass filter with a cutoff set by the absolute measurement schedule. Comparing the secular variation from two observatories with different absolute schedules would show the filter's effect.
Seasonal change in the ground
H5889. Seasonal changes in the ground's conductivity, from soil moisture and from frost, change the induced field at a site by a measurable fraction, an estimate, so a seasonal cycle in induced currents need not imply a seasonal cycle in the magnetosphere. The ground's conductivity is the hidden variable. Comparing current seasonality at sites with different soil types would test the ground's role.
Resolution set by array geometry
H5890. A magnetotelluric array can resolve a conductivity anomaly only if its station spacing is smaller than the anomaly's depth, so a deep anomaly can be invisible to a dense but small array. The resolution limit is geometric. Comparing inversions of the same data with two station subsets would show the anomaly appearing only in the subset with the larger aperture.
Instruments, observatories and networks
Instrument response mistaken for signal
H5891. Fluxgate magnetometers drift with temperature at a rate that can exceed the geophysical signal over a season, an estimate, and the drift is usually removed by a linear correction that assumes a constant coefficient; the coefficient itself varies with the electronics' temperature. Comparing two sensors at the same site with different thermal environments would show the residual drift.
Reference frame that rotates
H5892. A magnetometer's orientation error of a fraction of a degree produces an apparent rotation of the horizontal field that a reader would otherwise attribute to a change in the source's polarisation. The error is fixed in the instrument frame, so it should not vary with the source. Comparing polarisation angles at two nearby stations with independently surveyed orientations would expose the error.
Disagreement explained by bandwidth
H5893. Proton-precession and fluxgate magnetometers at the same observatory disagree during storms because the proton instrument samples more slowly, so it aliases the rapid variations that the fluxgate resolves. The disagreement is a bandwidth effect, not a calibration error. Comparing the two records after low-pass filtering to the proton instrument's bandwidth would remove the disagreement.
Aliasing of a fast process
H5894. Pi1 pulsations at periods of a few seconds are aliased by one-second sampling into apparent longer-period oscillations, so a reported Pi1 period can be an artefact of the sampling interval. The aliased period is the difference between the true period and the sampling period. Comparing the same interval recorded at two sampling rates would show the apparent period changing with the rate.
Ceiling imposed by the sensor
H5895. A fluxgate's dynamic range limits the storm-time field it can record, and clipping appears first in the component aligned with the ring current's field, so a clipped record looks like a saturation of the physical current rather than of the instrument. The clipping is asymmetric between components. Comparing the same storm at a station with a wider-range instrument would show the clipped peak flattening.
Ground coupling as a hidden input
H5896. A magnetometer's record contains a secondary field from the telluric currents that the same ionospheric source drives in the ground beneath it, and the secondary field differs between sites with different soil conductivity. The term is small, of order a nanotesla during a strong event, an estimate, but systematic. Comparing two sensors a few hundred metres apart on different soil, both referenced to the same absolute standard, would show the difference.
Coherence limited by timing
H5897. Array coherence between distant magnetometers is limited by timing errors in the acquisition systems, so a coherence that falls with distance can reflect the clocks rather than the physics. The timing error appears as a phase ramp across the array. Comparing coherence computed with and without a common clock reference would test the limit.
Gaps that select the events
H5898. Data gaps in an observatory record are more likely during storms, when power and communications fail, so the surviving events are biased toward weak storms. The bias is a selection effect, not a physical absence of strong events. Comparing the storm distribution in a record with gaps against one from a site with backup power would show the bias.
Slow signal a baseline cannot see
H5899. A secular change of a few nanoteslas per year, an estimate, is smaller than the baseline's uncertainty between absolute measurements, so the change can be distributed arbitrarily between the baseline and the record; the ambiguity is a property of the differencing, not of the field. Comparing records from two observatories with independent absolute schedules would bound the ambiguity.
Detection limited by network spacing
H5900. A travelling ionospheric disturbance with a wavelength shorter than twice the station spacing is aliased by the network into a longer apparent wavelength, so reported wavelengths are biased upward. The bias is set by the array geometry. Comparing wavelengths from a dense subarray with those from the full network would show the bias.
Status and plan
100 of 1,000. Each was written individually and given its own logical form; the labels are printed so that a reader can see the arguments differ structurally, not only topically. The seven sections are grouping conveniences, not claims that the mechanisms respect the boundaries between them.
The remaining entries will follow the same way, a hundred at a time, with the forms tracked so that repetition stays visible. None has been tested; the value of a hypothesis list is the ideas, and the value of a test is separate.
If one of these is worth an experiment, it is H5879 — that the geoelectric field inferred from a single observatory is uncertain by a factor of about two because the conductivity profile is not unique, and that a two-profile comparison bounds the uncertainty without new hardware.
Incoprea Research · hand-considered hypotheses 5801–5900 · 3 November 2026 · ~/Desktop/Nov3/