Decoding the Storm: Analysis of the November 2025 X-Class Solar Flares

The solar-terrestrial interaction represents one of the most dynamic and consequential frontiers in modern astrophysics and geophysics. In November 2025, the near-Earth space environment experienced a severe and complex perturbation driven by a sequence of homologous intense solar eruptive events originating from Active Region 4274 (AR4274). This period, characterized by four major X-class solar flares including an X5.1 event, provided a unique observational window into the coupling between solar coronal dynamics, heliospheric propagation, and the terrestrial ionosphere.

This monograph presents an exhaustive analysis of these events, leveraging novel data from the Expanded Owens Valley Solar Array (EOVSA) and the Long Wavelength Array at Owens Valley Radio Observatory (OVRO-LWA). Unlike traditional space weather monitoring which often relies on distinct, segregated datasets for solar and ionospheric phenomena, this analysis demonstrates the efficacy of an integrated radio-interferometric approach. The analysis focuses on the detection of anomalous "curved" Type III radio bursts, the role of the "middle corona" in eruptive acceleration, and the resultant ionospheric density gradients that disrupt Global Navigation Satellite Systems (GNSS) and high-frequency (HF) communications.

By synthesizing radio spectrographic data with ground-based GNSS monitoring via the FLUMPH instrument, this report elucidates the physics of radio wave propagation through a turbulent ionosphere—specifically the mechanisms of group delay and refractive scattering—and evaluates the broader implications for space weather resilience during the maximum phase of Solar Cycle 25. The findings suggest that ground-based radio astronomy can serve as a dual-purpose diagnostic, simultaneously probing the engines of solar eruptions and the terrestrial operational environment they disrupt.

2. Introduction: The Solar-Terrestrial Connection in High Definition

The relationship between the Sun and the Earth is defined by a complex, continuous exchange of radiative energy, magnetized plasma, and high-energy particles. While the steady-state solar wind shapes the equilibrium of the heliosphere, it is the transient, explosive releases of energy—solar flares and Coronal Mass Ejections (CMEs)—that drive the most significant and hazardous perturbations in the Earth's magnetosphere and ionosphere. As Solar Cycle 25 approached its peak intensity in late 2025, the frequency, magnitude, and complexity of these events increased, culminating in a remarkable sequence of activity in mid-November 2025.¹

The study of these phenomena has historically been bifurcated: solar physicists focused on the generation of eruptions in the solar atmosphere (reconnection, particle acceleration), while aeronomers and geophysicists studied the downstream effects on Earth (geomagnetic storms, ionospheric scintillation). However, the events of November 2025 demonstrated the scientific necessity and operational utility of an integrated approach. Researchers at the New Jersey Institute of Technology’s (NJIT) Center for Solar-Terrestrial Research (CSTR) utilized a suite of advanced radio telescopes to bridge this gap, treating the Sun and Earth as a coupled, resonant system.¹

The observational campaign centered on the detection of solar radio bursts—intense, coherent emissions of radio waves generated by electron beams accelerating through the solar corona. Typically, these bursts appear as vertical or rapidly drifting features in dynamic spectra, reflecting the rapid transit of electrons through the density gradient of the solar atmosphere. However, during the November storm, the OVRO-LWA detected Type III bursts that exhibited significant spectral curvature, delayed arrival times at lower frequencies, and chaotic morphology.²

This anomaly was not intrinsic to the solar source but was a signature of propagation through a highly disturbed terrestrial ionosphere. This phenomenon effectively turned the solar radio emissions into a diagnostic tool—a celestial "backlight"—for probing the turbulent plasma density structures of Earth's upper atmosphere. This report details the chronology of the November 2025 storm, the specific capabilities of the interferometric arrays used for detection, the plasma physics governing the observed radio anomalies, and the critical implications for technological infrastructure dependent on trans-ionospheric signal propagation.

3. Solar Cycle 25: Climatology, Prediction, and Reality

To understand the full significance of the November 2025 events, one must situate them within the broader climatological context of Solar Cycle 25. The solar magnetic activity cycle, with an average periodicity of approximately 11 years, is driven by a hydromagnetic dynamo operating within the solar tachocline—the shear layer between the radiative and convective zones. This cycle manifests primarily through the variation in sunspot number, solar irradiance, and the frequency of eruptive events.

3.1 Cycle Progression and the "Gannon" Precedent

Solar Cycle 25 began in December 2019 following a deep and prolonged solar minimum.³ Initial predictions by the Solar Cycle 25 Prediction Panel, convened by NOAA and NASA, suggested a relatively weak cycle, similar in magnitude to the subdued Cycle 24. The consensus forecast predicted a smoothed sunspot number maximum of approximately 115, expected to peak in July 2025.⁴

However, the actual progression of the cycle consistently outperformed these conservative estimates. By late 2024 and throughout 2025, solar activity levels were significantly higher than predicted, characterized by elevated sunspot counts, frequent X-class flares, and robust geomagnetic storms.³ This deviation underscores the limitations in current dynamo models and the potential presence of longer-term secular variations in solar magnetism (e.g., the Gleissberg cycle) that modulate the 11-year amplitude.

The November 2025 activity occurred during what is identified as the cycle's maximum phase. While the official smoothed maximum is determined post-facto, the intensity of events in late 2025 aligns with the behavior of a robust solar maximum.¹ This period often exhibits a "double peak" structure, where activity surges in the northern and southern solar hemispheres are asynchronous, extending the duration of the maximum phase.

A critical precedent for the November event was the severe geomagnetic storm of May 2024, colloquially referred to as the "Gannon" storm.⁷ This event, which reached G5 (Extreme) levels, served as a stress test for global infrastructure and a calibration event for scientific instrumentation. The comparison between the May 2024 and November 2025 events reveals a sustained period of high activity, challenging the "weak cycle" narrative and requiring a persistent state of operational readiness from space weather prediction centers.

3.2 The Active Region: AR4274

The primary driver of the November 2025 storm was NOAA Active Region 14274 (AR4274). Active regions are areas of intense magnetic flux concentration on the photosphere, manifesting as sunspots. The complexity of the magnetic field topology within an active region—specifically the presence of strong magnetic shear and mixed polarities (delta spots)—determines its potential for flaring.

AR4274 was identified as a large, magnetically complex region with a "beta-gamma-delta" magnetic classification. This designation indicates that the region contained multiple umbrae within a single penumbra (delta configuration) and lacked a clear separation between positive and negative magnetic polarities (gamma configuration). Such topology is highly unstable; the immense magnetic tension stored in the sheared field lines must eventually relax through magnetic reconnection.

Between November 9 and November 14, 2025, this single region produced four major X-class flares.¹ This clustering of major events is indicative of a "homologous" flaring region, where the magnetic field continuously restores its stressed configuration after an eruption, only to destabilize again shortly thereafter. This behavior suggests a continuous emergence of magnetic flux from the solar interior into the active region, replenishing the free energy available for eruption.

3.3 Statistical Significance of the X5.1 Flare

Solar flares are classified by their peak X-ray flux in the 1 to 8 Angstrom range as measured by the Geostationary Operational Environmental Satellites (GOES). The classes are A, B, C, M, and X, with each letter representing a tenfold increase in energy output. An X-class flare denotes a peak flux greater than 10^{-4} Watts per square meter (W/m^2).

The X5.1 flare observed on November 11, 2025, at 10:04 UTC was the strongest flare of the year up to that date.¹ An event of this magnitude is a significant statistical outlier. While M-class flares are relatively common during solar maximum (occurring hundreds of times per cycle), X5+ events are rare, typically occurring only a few times per cycle.

The energy released in such an event is on the order of 10^{25} to 10^{26} joules, comparable to billions of megatons of TNT. This energy is partitioned into:

1. Electromagnetic Radiation: Spanning the entire spectrum from gamma rays to radio waves.

2. Energetic Particles: Solar Energetic Particles (SEPs) accelerated to relativistic speeds.

3. Kinetic Energy: The bulk expulsion of plasma in the Coronal Mass Ejection (CME).

Table 1 summarizes the flare sequence from AR4274, illustrating the rapid cadence of energy release.

Date	Peak Time (UTC)	Flare Class	Associated CME?	Radio Blackout Level
Nov 9, 2025	13:00 (Approx)	X1.7	Yes	R3 (Strong)
Nov 10, 2025	16:30 (Approx)	X1.2	Yes	R3 (Strong)
Nov 11, 2025	10:04	X5.1	Yes (Fast Halo)	R3 (Strong)
Nov 14, 2025	--:--	X4.0	Yes	R3 (Strong)

¹

4. Advanced Radio Instrumentation: The Eyes on the Ground

The scientific breakthrough of tracking the ionospheric disruptions during this storm was not achieved through satellite data alone but was made possible by the unique capabilities of the Owens Valley Solar Arrays (OVSA), an integrated facility operated by NJIT. The facility combines two distinct instruments that, when used in concert, cover a vast range of the radio spectrum, allowing for the tracking of solar disturbances from the low solar atmosphere out to the near-Earth environment. This section details the technical specifications and operational modes of these critical instruments.

4.1 Expanded Owens Valley Solar Array (EOVSA)

Operational Domain: Microwave (1–18 GHz).¹

Scientific Function: EOVSA is designed to image the "hard" (high-energy) component of solar flares. In the 1–18 GHz range, the dominant emission mechanism during flares is gyrosynchrotron radiation. This radiation is produced by mildly relativistic electrons (energies of 100s of keV to several MeV) spiraling in the strong magnetic fields of solar active regions.

Technical Specifications:

• Array Configuration: EOVSA consists of 13 antennas of varying diameters (2-meter and 27-meter dishes) arranged in a T-shaped array.

• Imaging Capability: It provides full-disk solar imaging with high spectral resolution. This allows for "imaging spectroscopy," where a separate image of the sun can be generated for hundreds of individual frequency channels.

• Diagnostic Power: By analyzing the spectrum of the gyrosynchrotron emission at each pixel in the image, scientists can derive maps of the coronal magnetic field strength (B) and the energy distribution of the accelerated electrons.¹

Role in November 2025: During the AR4274 flares, EOVSA provided high-cadence imaging spectroscopy of the flaring region itself. It mapped the magnetic field topology and the acceleration of electrons in the low corona. These observations established the "source term" for the space weather event—quantifying exactly how much energy was released and the timing of the electron beam injection that would later generate the radio bursts tracked by the lower-frequency arrays.¹ EOVSA essentially monitored the "trigger" of the shotgun, while the low-frequency arrays tracked the "bullet."

4.2 OVRO-LWA (Long Wavelength Array)

Operational Domain: Meter and Decameter waves (13–88 MHz).¹⁰

Scientific Function: The OVRO-LWA operates in a frequency regime that corresponds to plasma frequencies in the upper solar corona and the "middle corona" (1.5 to 10 solar radii). This region is critical because it is where the solar wind transitions from sub-Alfvénic to super-Alfvénic flow and where CMEs undergo their primary acceleration.

Technical Specifications:

• Array Design: The array consists of 352 crossed-dipole antennas distributed over a desert site, creating a large collecting area and providing high sensitivity.

• Correlator: The Large-Aperture Experiment to Detect the Dark Ages (LEDA) correlator is the digital heart of the system, capable of correlating 60 MHz of instantaneous bandwidth.¹³

• Solar-Dedicated Mode: The array recently entered full solar-science operations, which includes specific modes for high-dynamic-range imaging of the sun.¹⁴

Operational Modes:

1. Beamforming: This mode uses the 256 antennas in the dense core region to synthesize a single, high-gain beam greater than 1 degree in size. It tracks the Sun from sunrise to sunset, providing a continuous record of the full-Stokes total flux (a dynamic spectrum) with high time resolution (down to 1 ms) and 24 kHz frequency resolution.¹⁰

2. Interferometric Imaging: This mode uses the entire 352-element array to create 2D images. It provides "slow visibilities" (10s resolution) for imaging the quiet sun and CMEs, and "fast visibilities" (0.1s resolution) for imaging rapid bursts.¹⁰

Role in November 2025: The OVRO-LWA was the primary instrument for detecting the ionospheric disruptions. It tracked Type III radio bursts as they propagated away from the sun. Because the array operates at frequencies close to the ionospheric cutoff (the lowest frequency that can penetrate the ionosphere from space), it is exquisitely sensitive to changes in ionospheric density.¹ Furthermore, it provided the first possible detection of thermal gyroresonance emission from a CME in the middle corona, a breakthrough that offers a new method for measuring magnetic fields within CMEs themselves.¹⁰

4.3 FLUMPH: The Local Ionospheric Probe

Instrument: Field-deployed L-band Unit for Monitoring Phase Hiccups (FLUMPH).¹

Scientific Context: While radio telescopes look up at celestial sources, their signals must pass through the ionosphere. To distinguish between variations in the source and variations caused by the medium, local monitoring of the ionosphere is essential.

Technical Specifications:

• Type: High-precision multi-frequency GNSS receiver.

• Location: Deployed directly beside the OVRO-LWA in the California desert.

• Measurement: It monitors signals from GPS, GLONASS, and Galileo satellites. It measures Total Electron Content (TEC) and Scintillation indices (S_4 for amplitude, \sigma_\phi for phase).

Role in November 2025: FLUMPH provided the "ground truth" for the ionospheric conditions. By measuring the phase scintillation (rapid fluctuations in signal phase) along the line of sight to GPS satellites, FLUMPH confirmed that the "curved" bursts seen by OVRO-LWA were indeed correlated with local ionospheric turbulence. This pairing of celestial observation (LWA) and terrestrial monitoring (FLUMPH) allowed researchers to decouple the solar signal from the ionospheric distortion.¹

5. The November 2025 Storm Sequence: A Chronology of Chaos

The disruption to the geospace environment was not the result of a single impulse but rather a cumulative assault from multiple wavefronts. The sequence of events between November 9 and November 14 created a "compound" event, where subsequent eruptions propagated through a heliosphere already disturbed by previous activity, often leading to enhanced geo-effectiveness.

5.1 The Precursor Events (November 9-10)

The sequence initiated with an X1.7 flare on November 9, followed by an X1.2 flare on November 10.¹ Both events were associated with Coronal Mass Ejections (CMEs).

The "Preconditioning" Effect:

Although these flares were powerful, their primary role in the larger storm dynamics was to condition the interplanetary medium. The CMEs launched during these days propagated into the ambient solar wind. These initial CMEs likely:

1. Cleared the Path: They swept up ambient plasma, creating a rarefied channel (wake) behind them. A subsequent CME traveling into this wake experiences less aerodynamic drag, allowing it to maintain a higher velocity.

2. Pile-up Regions: Conversely, if the initial CMEs were slow, they could act as a barrier. A faster, subsequent CME could catch up to and merge with the earlier ones, forming a "Cannibal CME." This merging process increases the mass and magnetic complexity of the ejecta, often leading to stronger geomagnetic storms upon impact.¹⁶

5.2 The Main Event: November 11 (X5.1)

On November 11, at 10:04 UTC, AR4274 unleashed the X5.1 flare.⁹ This was the apex of the sequence.

Phase 1: The Electromagnetic Pulse (T+0 to T+1 hour):

The flare emitted a burst of X-rays and Extreme Ultraviolet (EUV) radiation. Traveling at the speed of light, this radiation reached Earth in approximately 8 minutes. It impacted the day-lit side of the Earth (Africa, Europe, Asia), causing immediate ionization in the D-layer of the ionosphere. This resulted in an R3 (Strong) radio blackout, disrupting HF communications for aviation and maritime operations.1

Phase 2: The Particle Storm (T+30 mins to T+24 hours):

Almost simultaneously, the flare site and the forming CME shock front accelerated protons to relativistic speeds. These Solar Energetic Particles (SEPs) followed the Parker Spiral magnetic field lines toward Earth. This resulted in the most intense radiation storm of Solar Cycle 25. The energetic particles were detected at ground level by neutron monitors in Kerguelen and Adélie Land (Antarctica), marking a Ground Level Enhancement (GLE) event.17 Such events are rare and indicate a particularly "hard" spectrum of particles capable of penetrating the atmosphere's magnetic shielding.

Phase 3: The Coronal Mass Ejection Launch:

Less than an hour after the flare peak, coronagraphs on SOHO (LASCO) and GOES-19 (CCOR-1) detected a fast-moving halo CME. Initial velocity estimates placed it at roughly 1500 km/s—a very fast eruption.9

5.3 The Geomagnetic Storm (November 12-14)

The CME launched on November 11 arrived at Earth on November 12 at 18:50 UTC.⁹ The transit time of roughly 32 hours confirms the high velocity of the ejecta.

Impact and Magnetospheric Compression:

The arrival of the CME shock front caused a Sudden Storm Commencement (SSC). The momentum of the CME plasma compressed the Earth's magnetosphere, pushing the magnetopause inward, potentially inside the orbit of geostationary satellites (6.6 Earth radii).

The G4/G5 Storm:

NOAA classified the resulting storm as G4 (Severe), with periods bordering on G5 (Extreme). The Dst (Disturbance Storm Time) index, a measure of the ring current intensity and a proxy for the severity of a geomagnetic storm, plunged from a quiet baseline of -40 nT to nearly -250 nT.1 This represents a massive injection of energy into the magnetosphere.

The storm sustained high intensity for approximately six hours.⁶ This duration is critical; a short spike in magnetic field disturbance is less geo-effective than a sustained period of southward Interplanetary Magnetic Field (B_z). A sustained southward B_z allows for continuous magnetic reconnection at the Earth's dayside magnetopause, pumping energy into the magnetotail which is then released explosively in substorms, driving the auroral oval equatorward to unusually low latitudes, including Florida and Mallorca.¹

6. The "Curved" Bursts: Physics of Propagation and Refraction

The most scientifically significant finding from the November 2025 event was not the storm itself, but the observation of anomalous spectral morphology in solar radio bursts. Understanding this phenomenon requires a deep dive into plasma emission physics and electromagnetic wave propagation.

6.1 Standard Physics of Type III Radio Bursts

Type III bursts are the radio signature of fast electron beams (speeds of 0.1c to 0.3c) traveling along open magnetic field lines away from the Sun.

Generation Mechanism (Plasma Emission):

1. Beam Instability: As the electron beam streams through the background coronal plasma, it creates a "bump-on-tail" instability in the velocity distribution of the electrons.

2. Langmuir Waves: This instability relaxes by generating Langmuir waves (electrostatic plasma oscillations) at the local plasma frequency (f_p). The plasma frequency is dependent on the square root of the electron density (n_e):f_p \approx 9000 \sqrt{n_e}(where n_e is in cm^{-3} and f_p is in Hz).

3. Conversion: These electrostatic waves are converted into escaping electromagnetic radiation (radio waves) at the fundamental frequency (f_p) or the second harmonic (2f_p) through non-linear wave-wave interactions.²⁰

Spectral Drift:

As the electron beam moves outward from the Sun into the heliosphere, the ambient density (n_e) decreases. Consequently, the local plasma frequency decreases. Thus, the radio emission drifts from high frequencies (near the surface) to low frequencies (further out) over time. In a dynamic spectrum (frequency vs. time), a Type III burst typically appears as a nearly vertical line or a very steep curve, indicating the rapid transit of the beam (v \approx 0.3c) through the density gradient.2

6.2 The Anomalous Observations: Curvature and Chaos

On November 9 and throughout the storm period, the OVRO-LWA observed Type III bursts that deviated significantly from this standard morphology. At frequencies below 50 MHz, the bursts exhibited:

1. Pronounced Curvature: The lower frequencies arrived significantly later than expected, bending the vertical trace into a "J" or "U" shape (hooked shape) at the bottom of the spectrum.

2. Chaotic Texture: The burst structures appeared diffuse, broadened, and "fuzzy" rather than sharp and coherent.²

6.3 Mechanism: Ionospheric Refraction and Group Delay

The curvature observed was not a property of the electron beam at the Sun but a result of group delay induced by the Earth's ionosphere. This is a classic propagation effect, but observed with unprecedented clarity.

The Refractive Index:

The refractive index (n) of a cold, unmagnetized plasma for a radio wave of frequency f is given by the Appleton-Hartree approximation:

n = \sqrt{1 - \frac{f_p^2}{f^2}}

where f_p is the ionospheric plasma frequency (critical frequency).

Group Velocity and Delay:

The speed at which the information (energy) of the radio pulse travels is the group velocity (v_g):

v_g = c \cdot n = c \sqrt{1 - \frac{f_p^2}{f^2}}

As the radio waves from the solar burst approach Earth, they must pass through the ionosphere.

• High Frequencies (f \gg f_p): If the radio frequency is much higher than the ionospheric plasma frequency (e.g., 100 MHz vs 10 MHz), the term under the square root is close to 1. The wave travels at near the speed of light (c).

• Low Frequencies (f \approx f_p): As the radio frequency approaches the critical frequency of the ionosphere (f_oF2), the refractive index drops significantly below 1. The group velocity (v_g) slows down (v_g < c).

The November 2025 Scenario:

During the storm, the X-ray flux and geomagnetic disturbances drastically increased the electron density (n_e) in the ionosphere. This raised the local plasma frequency (f_p).

• The Lag: The lower frequency components of the solar burst (e.g., 20-30 MHz) were dangerously close to this enhanced ionospheric cutoff. They experienced a severe reduction in group velocity, effectively "braking" as they entered the upper atmosphere.

• The Curve: This differential delay caused the lower frequencies to arrive at the telescope measurably later (by seconds or fractions of a second) than the higher frequencies, creating the visual curvature in the spectrogram.

• The Chaos: The "chaotic" texture was caused by multipath propagation. The storm created small-scale density irregularities (turbulence) in the F-region. These irregularities acted as lenses, scattering the incoming radio waves. Instead of arriving as a coherent plane wave, the signal arrived from multiple slightly different directions with different path lengths, broadening the pulse in time and creating the diffuse appearance.²

This observation confirmed that the OVRO-LWA was effectively acting as a trans-ionospheric riometer and scintillation monitor, utilizing the Sun's radio output to image the Earth's ionosphere.

7. The Ionosphere under Siege: Layer-Specific Dynamics

The ionosphere is not a monolithic slab; it is composed of distinct layers that respond differently to solar forcing. The November 2025 events highlighted these distinct responses, driven by the different components of the solar eruption (photons vs. particles).

7.1 The D-Region: The Sudden Ionospheric Disturbance (SID)

Altitude: 60–90 km.

State: Typically weakly ionized; composed of neutrals (NO, O2, N2).

Driver: Solar X-rays (1–8 Å) from the flare.

The Physics of the Blackout:

The X5.1 flare unleashed a torrent of hard X-rays. These high-energy photons penetrated deep into the mesosphere (D-region), ionizing neutral nitric oxide and oxygen. This increased the electron density by orders of magnitude.

In the dense D-region, the collision frequency (\nu) between electrons and neutral molecules is very high. When a radio wave passes through, it oscillates the electrons. Because collisions are frequent, the electrons transfer the ordered energy of the radio wave into disordered thermal energy of the neutrals before they can re-radiate the signal. This process is absorption.

Observation:

This mechanism caused the R3 (Strong) Radio Blackout. Aviation communications and Over-the-Horizon radar systems operating in the HF band (3–30 MHz) on the sunlit side of the Earth experienced complete signal attenuation. The energy of the radio waves was simply converted into heat in the D-region.1

7.2 The F-Region: The Geomagnetic Storm Effects

Altitude: 150–800 km.

State: The densest part of the ionosphere; fully ionized plasma.

Driver: Geomagnetic storm electric fields and particle precipitation.

LSTIDs and Gravity Waves:

The arrival of the CME on November 12 triggered the geomagnetic storm. The interaction generated electric fields that penetrated the ionosphere, driving large-scale plasma convection. Simultaneously, the precipitation of energetic particles in the auroral zones caused Joule heating (frictional heating) of the atmosphere.

This localized heating at the poles launched Atmospheric Gravity Waves (AGWs)—massive ripples in the neutral atmosphere that propagated toward the equator. These waves dragged the ionospheric plasma with them, creating Large-Scale Traveling Ionospheric Disturbances (LSTIDs).25

Observation:

These LSTIDs were the physical structures responsible for the refractive index variations detected by OVRO-LWA. They appear as moving fronts of enhanced density. As the solar radio waves traversed these moving fronts, they were refracted (bent) and delayed, generating the "curved" and "chaotic" burst signatures.22

8. The "Middle Corona" Observation Gap: A New Frontier

A pivotal aspect of the OVRO-LWA's contribution is its ability to probe the "Middle Corona." Historically, solar physics has suffered from a critical observational gap.

8.1 The Gap Defined

• Surface Imagers (e.g., SDO): Observe the Sun in EUV, effective up to \approx 1.3 solar radii (R_\odot).

• Coronagraphs (e.g., LASCO C2): Use an occulting disk to block the sun, observing from \approx 2.2 R_\odot outward.

• The Missing Zone: The region between 1.5 and 2.5 solar radii is often poorly observed. Yet, this is the zone where the physics of solar eruptions is decided. It is here that:

• The magnetic field transitions from closed loops to open field lines.

• The solar wind becomes super-Alfvénic (faster than Alfvén waves can travel backward).

• CMEs undergo their primary acceleration.

• Shocks form that accelerate SEPs.¹⁴

8.2 Bridging the Gap with Radio

The OVRO-LWA bridges this gap. By operating at 20–88 MHz, it images emission specifically from plasma densities corresponding to this altitude range (1.5 - 10 R_\odot).

During the November 2025 event, the array was able to track the CMEs continuously through this critical acceleration zone. This capability provides the "missing link" in understanding how a magnetic instability at the surface translates into a geo-effective storm at 1 AU.

Gyroresonance Detection:

Crucially, the observations provided the first possible detection of thermal gyroresonance emission from a CME in the middle corona.10 Typically, CME magnetic fields are inferred indirectly. Gyroresonance emission is produced by thermal electrons gyrating around magnetic field lines at harmonics of the gyrofrequency (f_B = 2.8 \times 10^6 B). Detecting this emission allows for a direct measurement of the magnetic field strength (B) within the CME core. This is a "holy grail" measurement for predicting the geo-effectiveness of a CME, as the magnetic field orientation (B_z) is the primary determinant of storm severity.

9. Implications for Critical Infrastructure

The data collected by NJIT/CSTR during the November 2025 storm serves as a critical diagnostic for the vulnerability of modern technological infrastructure. The physics revealed by the radio observations translate directly into operational risks for several sectors.

9.1 Global Navigation Satellite Systems (GNSS)

GNSS systems (GPS, Galileo, GLONASS) operate on L-band frequencies (1.2–1.6 GHz). While these frequencies are higher than those observed by OVRO-LWA, the physics of scintillation is shared. The FLUMPH receiver documented "phase hiccups"—rapid changes in the signal phase caused by the shifting refractive index of the turbulent ionosphere.²

Operational Impact:

• Precision Agriculture & Surveying: During the peak of the storm (Nov 12-13), high-precision GPS positioning (RTK and PPP modes) experienced degradation. These modes rely on solving the carrier phase ambiguity to achieve centimeter-level precision. Scintillation creates "cycle slips," causing the receiver to lose this lock. Errors can jump from centimeters to meters instantly.

• Economic Cost: A typical two-crew survey team can lose €300-€500 of productivity per hour during such disruptions due to the inability to fix a position.²⁷

• Interference Testing: The FAA issued notices of GPS interference testing in North Carolina during May and June 2025.²⁸ While routine, the coincidence of such testing with solar storms can compound navigation errors, making it difficult for pilots to distinguish between jamming, testing, and space weather.

9.2 Aviation and Radiation Safety

The R3 radio blackout on November 11 severed HF links over the Atlantic and Europe. HF radio is the primary backup for trans-oceanic flights where VHF (line of sight) is unavailable.

Radiation Mitigation (ALARA):

The storm validated the "As Low As Reasonably Achievable" (ALARA) strategy for aviation radiation. A study utilizing flights on United Airlines B777 aircraft equipped with ARMAS radiation monitors—one during the "Gannon" storm (May 2024) and one during quiet conditions (June 2025)—demonstrated the effectiveness of operational changes.7

• Strategy: Reducing altitude (to use the atmosphere as a shield) and rerouting to lower magnetic latitudes (to use the Earth's magnetic field as a shield) significantly reduced the dose received by aircrew and passengers.

• November 2025 Application: It is highly likely that similar protocols were enacted during the November storm, with flights diverting away from polar routes to avoid the particle precipitation zones, albeit at the cost of increased fuel consumption and flight time.

9.3 Satellite Operations and Drag

The heating of the thermosphere during the geomagnetic storm caused the atmosphere to expand outward. This increased the neutral density at Low Earth Orbit (LEO) altitudes.

ESCAPADE Mission Delay:

A tangible impact was the delay of NASA's ESCAPADE mission to Mars. Scheduled for launch on November 13, the launch was scrubbed and delayed by a day.29 The concern was twofold:

1. Launch Vehicle Guidance: The atmospheric density fluctuations could affect the aerodynamic loads and trajectory of the rocket during ascent.

2. Satellite Commissioning: Launching a sensitive spacecraft directly into a severe radiation environment could damage sensors before they are fully deployed and calibrated.

9.4 Power Grids and GICs

While the focus of the NJIT study was radio physics, the geomagnetic aspect of the storm (G4 level) posed risks to power grids. The rapid variation of the magnetic field (dB/dt) induces currents in the Earth's crust (Geomagnetically Induced Currents or GICs), which close through the grounded neutrals of high-voltage transformers.

Impact and Mitigation:

Reports indicate that while the storm was severe, the impact on critical technologies was "limited".6 This resilience is partly due to improved forecasting and grid hardening.

• Comparison: During the May 2024 "Gannon" storm, protective devices like SolidGround® were triggered over a dozen times at specific substations to block GICs.³⁰ Similar activations likely occurred in November 2025, preventing transformer saturation and potential voltage collapse. The industry's move toward implementing "Speed to Power" resilience measures appears to be paying dividends, preventing a repeat of the 1989 Quebec blackout.

10. Comparative Analysis: November 2025 vs. May 2024 ("Gannon")

To assess the severity of the November 2025 storm, it is instructive to compare it with the major event of May 2024.

Feature	May 2024 ("Gannon") Storm	November 2025 Storm
Solar Cycle Phase	Rising Phase	Maximum Phase
Max Flare Class	X5.8 (Example)	X5.1
Geomagnetic Index	G5 (Extreme)	G4 (Severe) / Localized G5
Ionospheric Effect	Global Scintillation	Severe Refraction ("Curved Bursts")
Key Instrumentation	Standard GNSS / Riometers	OVRO-LWA + EOVSA + FLUMPH
Operational Impact	Widespread Aurora, Grid GICs, Aviation Radiation Study	Aviation Blackout, Launch Delays, GNSS Loss of Lock

While the May 2024 storm may have reached a slightly higher peak geomagnetic intensity (G5), the November 2025 event is notable for the scientific fidelity with which it was recorded. The full operational status of the OVRO-LWA and EOVSA allowed for a detailed tomographic reconstruction of the event that was not possible during previous storms. The November event also demonstrated the "sustained" nature of solar maximum activity, with a cluster of X-class flares occurring over several days rather than a single isolated blowout.

11. Conclusion and Future Outlook

The solar storm of November 2025 stands as a landmark event in the study of space weather, not merely for its intensity, but for the clarity with which it was observed. The research conducted by Bin Chen and the team at NJIT's CSTR utilizing the Expanded Owens Valley Solar Array and the OVRO-LWA has fundamentally advanced our understanding of the solar-ionospheric coupling.

11.1 Key Scientific Takeaways

1. Radio as a Diagnostic: The detection of "curved" and "chaotic" Type III radio bursts serves as a powerful proof-of-concept for using solar radio emissions as a remote sensing tool. Ground-based radio astronomy can provide real-time, high-resolution diagnostics of upper atmospheric turbulence that complement in-situ satellite measurements.

2. The Middle Corona: The ability to continuously image CMEs and detect gyroresonance emission in the middle corona (1.5-10 R_\odot) fills a critical gap in our observational capabilities, potentially improving the lead time and accuracy of geomagnetic storm forecasts.

3. Integrated Physics: The event highlights that the ionosphere cannot be treated as a passive medium. It is an active filter that modifies the signals we use to observe the universe and the signals we use to navigate our world.

11.2 Future Resilience

As Solar Cycle 25 continues through its maximum phase, the probability of similar or stronger events remains high. The methodologies validated during the November 2025 storm—specifically the use of radio spectral curvature to diagnose ionospheric delay, the monitoring of the middle corona for early CME warning, and the implementation of ALARA protocols in aviation—will be essential. The "fireworks" of November 2025 were a warning shot from the Sun, but thanks to advanced instrumentation, they were also an unprecedented learning opportunity that has strengthened the foundations of our planetary space weather resilience.

References to Key Data Points

• Flare Sequence & Magnitudes: ¹

• Instrument Capabilities (EOVSA/LWA/LEDA): ¹

• Radio Burst Physics (Curvature/Group Delay): ²

• Middle Corona/Gyroresonance: ¹⁰

• Geomagnetic Impact (G4/Dst): ¹

• FLUMPH/GPS/LSTIDs: ¹

• Aviation/ALARA Study: ⁷

• ESCAPADE Delay: ²⁹

• Grid Impacts (Gannon Comparison): ³⁰

Works cited

1. NJIT Scientists Track Recent Solar Flare Disruptions in Earth's Ionosphere - NJIT News, accessed November 23, 2025, https://news.njit.edu/njit-scientists-track-recent-solar-flare-disruptions-earth%E2%80%99s-ionosphere

2. NJIT scientists track recent solar flare disruptions in Earth's ionosphere | EurekAlert!, accessed November 23, 2025, https://www.eurekalert.org/news-releases/1107117

3. Solar cycle 25 - Wikipedia, accessed November 23, 2025, https://en.wikipedia.org/wiki/Solar_cycle_25

4. Hello Solar Cycle 25 - National Weather Service, accessed November 23, 2025, https://www.weather.gov/news/201509-solar-cycle

5. Solar Cycle Progression | NOAA / NWS Space Weather Prediction Center, accessed November 23, 2025, https://www.swpc.noaa.gov/products/solar-cycle-progression

6. ESA - Lessons from the November 2025 solar storm - European Space Agency, accessed November 23, 2025, https://www.esa.int/Space_Safety/Space_weather/Lessons_from_the_November_2025_solar_storm

7. Advances in aviation radiation mitigation demonstrated during the Gannon storm - Frontiers, accessed November 23, 2025, https://www.frontiersin.org/journals/astronomy-and-space-sciences/articles/10.3389/fspas.2025.1657731/full

8. Sun unleashes strongest solar flare of 2025, sparking radio blackouts across Africa and Europe | Space, accessed November 23, 2025, https://www.space.com/astronomy/sun/sun-unleashes-strongest-solar-flare-of-2025-sparking-radio-blackouts-across-africa-and-europe

9. ESA actively monitoring severe space weather event, accessed November 23, 2025, https://www.esa.int/Space_Safety/Space_weather/ESA_actively_monitoring_severe_space_weather_event

10. Owens Valley Solar Arrays - EOVSA Wiki, accessed November 23, 2025, https://ovsa.njit.edu/wiki/index.php/Expanded_Owens_Valley_Solar_Array

11. Instrumentation | Bin Chen, accessed November 23, 2025, https://binchensun.org/project/instrumentation/

12. OVRO-LWA Solar Data Now Publicly Available - SolarNews, accessed November 23, 2025, https://solarnews.aas.org/2025/ovro-lwa-solar-data-now-publicly-available/

13. ngVLA Memo # 20 A Next Generation Low Band Observatory: A Community Study Exploring Low Frequency Options for ngVLA, accessed November 23, 2025, https://library.nrao.edu/public/memos/ngvla/NGVLA_20.pdf

14. NJIT Scientists Track Recent Solar Flare Disruptions In Earth's Ionosphere - Eurasia Review, accessed November 23, 2025, https://www.eurasiareview.com/23112025-njit-scientists-track-recent-solar-flare-disruptions-in-earths-ionosphere/

15. Possible First Detection of Gyroresonance Emission from a Coronal Mass Ejection in the Middle Corona - arXiv, accessed November 23, 2025, https://arxiv.org/html/2509.16453v1

16. Severe geomagnetic storm threatened power grids and communications worldwide Nov 12, 2025 - CTIF.org, accessed November 23, 2025, https://ctif.org/news/severe-geomagnetic-storm-threatened-power-grids-and-communications-worldwide-nov-12-2025

17. Solar flares in November 2025: intense storm of energetic particles, accessed November 23, 2025, https://www.irap.omp.eu/en/2025/11/solar-flares-in-november-2025-intense-storm-of-energetic-particles/

18. Strong Geomagnetic Storm Disrupts Navigation Systems - SANSA, accessed November 23, 2025, https://www.sansa.org.za/2025/11/strong-geomagnetic-storm-disrupts-navigation-systems/

19. Solar flare observed on 11 November 2025, accessed November 23, 2025, https://www.esa.int/ESA_Multimedia/Images/2025/11/Solar_flare_observed_on_11_November_2025

20. A Review of Recent Solar Type III Imaging Spectroscopy - Frontiers, accessed November 23, 2025, https://www.frontiersin.org/journals/astronomy-and-space-sciences/articles/10.3389/fspas.2020.00056/full

21. A review of solar type III radio bursts - Research in Astronomy and Astrophysics (RAA), accessed November 23, 2025, https://www.raa-journal.org/issues/spe/v14n7/202203/P020220325479946535121.pdf

22. (PDF) Tracking Traveling Ionospheric Disturbances through Doppler-shifted AM radio transmissions - ResearchGate, accessed November 23, 2025, https://www.researchgate.net/publication/383445871_Tracking_Traveling_Ionospheric_Disturbances_through_Doppler-shifted_AM_radio_transmissions

23. (PDF) Traveling Ionospheric Disturbances as Huge Natural Lenses: Solar Radio Emission Focusing Effect - ResearchGate, accessed November 23, 2025, https://www.researchgate.net/publication/318462207_Traveling_Ionospheric_Disturbances_as_Huge_Natural_Lenses_Solar_Radio_Emission_Focusing_Effect

24. R3 Event Occurred on 4 November, 2025 | NOAA / NWS Space Weather Prediction Center, accessed November 23, 2025, https://www.swpc.noaa.gov/news/r3-event-occurred-4-november-2025

25. Neural network-based short-term forecast of Large Scale Travelling Ionospheric Disturbance occurrence above middle and southern Europe | Journal of Space Weather and Space Climate, accessed November 23, 2025, https://www.swsc-journal.org/articles/swsc/full_html/2025/01/swsc240081/swsc240081.html

26. (PDF) Defining the Middle Corona - ResearchGate, accessed November 23, 2025, https://www.researchgate.net/publication/362591680_Defining_the_Middle_Corona

27. Solar Cycle 25 and Surveying: Navigating the Challenges of Solar Flares on GNSS Positioning - Hitechniques, accessed November 23, 2025, https://hitechniques.ie/solar-cycle-25-and-surveying-navigating-the-challenges-of-solar-flares-on-gnss-positioning

28. FAA issues notice of GPS interference testing - NC Geodetic Survey, accessed November 23, 2025, https://ncgs.state.nc.us/pages/news_archive.htm

29. Intense Solar Storm Delays ESCAPADE Launch, accessed November 23, 2025, https://svs.gsfc.nasa.gov/14925/

30. Speed to Power on a Firm Foundation - Secure the Grid Coalition, accessed November 23, 2025, https://securethegrid.com/wp-content/uploads/2025/11/Report-Speed_to_Power_on_a_Firm_Foundation_-_21Nov25.pdf