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Artificial St. Elmo’s Fire
by Reinhard Nitze
What it is about
St. Elmo’s fire is a natural form of electrostatic discharge. It belongs to the so-called electrometeors and appears as a self-luminous corona discharge. It usually occurs during thunderstorms, but can also appear in winter weather conditions (especially during solid precipitation).
Direct observations of St. Elmo’s fire have become very rare in recent decades due to increasing light pollution and sometimes unpleasant or even dangerous weather conditions. However, it is frequently recorded by automated photo webcams. There, it often appears as small blue glowing tufts. These are always attached to pointed objects, usually at the ends of poles, masts, antennas, and similar structures.
If such a mast is covered with ice crystals, these act as attractors and can, in extreme cases, form a kind of “flag” of St. Elmo’s fire. It has also been observed on sharp rock ridges and at the tips of tree branches [1].
Background
At the spring seminar 2022 of the “Arbeitskreis Meteore,” the phenomenon described above was the subject of two presentations (“News about St. Elmo’s Fire” by Rainer Timm and “Unusual St. Elmo’s Fire during the night of 03/04 November 2021 over the Alps” by Claudia Hinz). These talks, together with images of electrostatic discharges on clothing and blankets shown afterwards, inspired the idea of artificially generating and photographing St. Elmo’s fire.
Back home, Reinhard Nitze (the author) began experimenting. After some initial thoughts and preliminary tests, the first results appeared when a PVC pipe was rubbed with a piece of cotton cloth in complete darkness. Weak, colorless, lightning-like emissions became visible (through the cloth), accompanied by the typical crackling sounds of electrical discharge.
Capturing these discharges with a digital camera proved difficult. Only long exposure with a high ISO setting made the “St. Elmo’s fire” visible as a diffuse blue “force field,” caused by motion blur. However, the first test images were mostly not convincing, with one exception.
Left: This PVC pipe was used for the first successful “St. Elmo’s fire” tests.
Middle: One of the first successful images of artificial St. Elmo’s fire in these experiments, appearing as a blue “force field.”
Right: The exception: Numerous individual discharges recorded indirectly under a cloth while rubbing the PVC pipe. The only directly visible discharge is the slightly violet tip originating from a finger holding the pipe (faintly visible).
Improving the experiment
Acrylic glass provided a solution. A sheet covered with protective film on both sides was used. A short test by rubbing the sheet with a cloth produced audible crackling, proving electrostatic discharges.
After dark, experiments began. The sheet was electrically charged by rubbing and then held above or moved along a test object. Depending on the shape and material of the object, the desired light emissions appeared—mostly as individual feather-like flashes or small bundles of flashes. The results were significantly better than those achieved with the PVC pipe. This made it possible to create a proper photo series. The first images of artificial St. Elmo’s fire comparable to natural observations were produced.
After many experiments, the protective film on the sheet began to peel off at the corners. When it was removed in the dark, continuous electrostatic light phenomena appeared along the separation line between film and sheet—vertical, parallel, constantly flickering light fibers accompanied by typical crackling sounds.
This observation led to the method still used by the author today, described below.
The best method
In the “forearm–thigh clamping method,” an acrylic glass sheet is pressed against bare skin between the forearm and thigh so that it can still be moved back and forth. When performing this motion, electrostatic charging usually occurs after a short time. This is noticeable through tingling on the skin, hair standing up, audible crackling, and—most importantly—light emissions along the contact line between the sheet and the skin.
These emissions typically appear as small, tuft-like flashes. Their strength and frequency depend on the level of charge, the pressure between arm and leg, and the speed of movement. With the right combination, the “St. Elmo’s fire” can even appear continuously during motion. It takes some time to reach full intensity. A dry environment and low humidity are essential. If charging does not occur, sweating or high humidity is usually the cause. Ventilating the room often helps.
Grease films (fingerprints, skin oils) also reduce effectiveness and should be removed regularly. Floor conditions and shoe soles (if standing) may also influence charging. If no charging occurs, changing location or footwear (especially if antistatic) may help.
Because the light emissions are very faint, they are only visible in darkness—the darker, the better. They are typically colorless, sometimes slightly greenish or bluish after dark adaptation. Strong discharges may briefly show pink or violet tones. In long-exposure digital photography, however, intense colors appear—mainly blue, with violet, pink, and white in the center of the discharge tufts. The discharges can reach several centimeters in length and often originate where body hairs are present. They frequently form tufted or flame-like structures.structures.
Variations of the experiment
To create this “St. Elmo’s fire” on other objects, several methods can be used:
Method 1: Hold the charged sheet and move it close (max. ~10 cm) to the object.
Advantage: Any accessible object can be tested; photography is relatively easy.
Disadvantage: Some loss of charge reduces effectiveness.
Method 2: Move the object over the charged sheet.
Advantage: Easy for small objects; slightly more efficient.
Disadvantage: Difficult to photograph.
Method 3 (best): Place the object next to the thigh and expose it directly during charging.
Advantage: Minimal energy loss; best for photography.
Disadvantage: Object size is limited; risk of contact with the sheet.
Experimental goals / observations
The main question—whether St. Elmo’s fire can be artificially produced—can clearly be answered: yes.
Various materials can be tested:
- Natural objects:
- Stones
- Plants
- Self-experiment
- Artificial objects:
- Metallic objects
- Non-metallic objects
All test objects should have sharp points or edges, as these act as attractors for electrostatic energy.
Description of experiments
Artificial St. Elmo’s fire on stones and minerals:
Left: Lava from Tenerife · Right: Rock crystal tip
Calcite (crystalline limestone), with and without additional lighting
Left: Fluorite with quartz, dry and moistened · Right: Galena (lead ore)
Artificial St. Elmo’s fire on plants and plant parts:
Chestnuts in their spiky husks are excellent for producing artificial St. Elmo’s fire. Multiple “flames” can often appear simultaneously. Both positive and negative St. Elmo’s fire can be observed. Literature describes positive discharge as tufted or flame-like, and negative as point-like glowing. In the chestnut images, the positive discharge appears at the top, while the negative appears as glowing points near the ground. Positive discharge is generally more visually impressive, but negative discharge is also interesting and best observed in macro photography.
All four images show negative St. Elmo’s fire in macro view on chestnut spikes. It appears spherical or candle-like. The last image is unusual, likely showing a polarity reversal during exposure.
Pear stem with St. Elmo’s fire
Apple stem with St. Elmo’s fire
Bouquet with St. Elmo’s fire
Turkish hazelnut
Acorn on flint from Rügen
Oak leaves
Fir branch
Artificial St. Elmo’s fire on metallic objects
Left: copper wire; Right: cut ends of galvanized chicken wire
Close-up (macro) of cut chicken wire
Left: Created “in a moment of beer inspiration”
Right: Natural St. Elmo’s fire on a metal rod (likely with ice crystals), photographed on 03 Nov 2021 in Axamer Lizum near Innsbruck, Tyrol (Photo: panomax.com)
Artificial St. Elmo’s fire on non-metallic objects
Left: Negative and positive discharge on the magazine “Meteoros” · Right: On the spout of a plastic measuring cup
Conclusion
With the right technique, it is quite easy to generate St. Elmo’s fire or similar corona discharges. The required equipment is minimal: an acrylic glass sheet (other plastics may also work, but were not tested) and proper handling.
Surprisingly, many materials proved suitable, including ones not expected due to their electrical properties—such as quartz crystals and paper.
Electrical conductivity influenced the behavior:
- Poor conductors produced stronger but more isolated discharges.
- Good conductors produced more continuous but weaker-looking discharges in long exposures.
Most generated discharges were positive (tufted), while only a small fraction were negative (point-like glowing). The reason is unclear but likely related to humidity.
Higher humidity (e.g., due to sweating) can reduce charging and lead to weaker glow discharges.
Side effects / Disclaimer
These experiments are generally harmless, but electrostatic voltages of several thousand volts can occur. There is always a risk of electric shocks, which can sometimes be surprisingly strong.
People who are sensitive, have pre-existing health conditions, or rely on electronic medical devices (e.g., pacemakers) should not perform these experiments.
Additionally:
- Static electricity can ignite flammable gases, vapors, or dust mixtures.
- Electronic components may be damaged by electrostatic discharge (ESD).
Anyone repeating these experiments does so at their own risk. The author assumes no responsibility for any damage or consequences.
References
[1] Obermayer, A. v. (1889) Elmsfeuererscheinungen in den Alpen. Zeitschrift des Deutschen und (des) Österreichischen Alpenvereins, Jahrgang 1889, (Band XX), S. 94–101.
[2] Elster, J. & Geitel, H. (1892) Elmsfeuerbeobachtungen auf dem Sonnblick. Akademie d. Wissenschaften Wien 1892
[3] Bosshard, E. (1897) Elmsfeuer und Blitzgefahr im Gebirge. SAC-Jahrbuch 1897
[4] Hinz, C. & Timm, R. (2021) Elmsfeuer in der Geschichte und der Gegenwart. METEOROS 11-12/2021
[5] Hinz, C. & Timm, R. (2022) Fachausschuss Amateurmeteorologie: Elmsfeuer in der Geschichte und der Gegenwart. Mitteilungen DMG 1/2022
[6] Timm, R. & Hinz, C. (2022) Neues vom Elmsfeuer. METEOROS 04/2022
A multi-split rainbow from south-east China, August 12th, 2014
Yulong river, Guangxi province, August 12th, 2014, 17:18 Chinese standard time
Twinned rainbows are rare sightings, in the sense that one may see on average only one per year in Central Europe even when paying close attention. Much rarer still, and maybe restricted to regions closer to the equator, are multi-split rainbows. Only few cases have been documented so far [1, 2, 3], though more snapshots can be found on image sharing platforms labeled as “triple rainbow” etc. It is always a very favorable situation if an archivist and analyst like myself can establish direct communication with a skilful observer, who recorded details of a rainbow display that provide some insight beyond the pretty pictures.
In April 2019 I emailed Mr. Ji Yun, who manages a Facebook group dedicated to atmospheric optical phenomena in China, asking about a spectacular photograph of a multi-split rainbow which had been shared there. He kindly relayed my request to Mr. Liu Hai-Cheng, the original observer. Mr. Liu agreed to answer a long list of questions and I also received two sets of photographs from August 12th, 2014, one from his Sony NEX-5C camera (equipped with a Nikon AF 28mm f/2.8 lens) and the other from his cell phone (Coolpad 8720L). The camera clock’s time stamps were calibrated with respect to the actual local time by comparing camera and cell phone pictures, and assuming the cell phone clock to be synchronized over the network. All time data are given here in Chinese standard time (UTC+8h).
Mr. Liu observed this rainbow rarity in the beautiful landscape of the karst mountains near the Yulong bridge (Yangshuo County, Guilin City, Guangxi province, about 400 km northwest of Hong Kong, 24.8° N, 110.4° E) during a boat trip on the Yulong river. He remembers that it was very hot that afternoon. It began to rain before he passed through the tunnel of the bridge (at about 16:50), with some heavier rain lasting for about 25 minutes. There was no lightning, thunder or strong wind.
Judging from the photos, the rainbow appeared at about 17:10 within 30 s or less. Already on the early photographs there are hints of the unusual splitting of the primary:
17:11
However, Mr. Liu’s visual impression was that the splitting became prominent only later, after the (seemingly ordinary) primary and secondary bow had appeared successively. He also noted that the visibility of the split branches changed over time, while the main primary could always be seen clearly.
Towards the end of the shower, the display reached its peak quality. The following pictures cover the full right-hand side of the rainbow and some of the left. They are presented without additional filtering to allow for a better assessment of the natural contrast conditions.
17:18 (unfiltered version of the title image)
17:18
17:19
For a deeper analysis, I chose the title picture, recorded at 17:18. In the contrast-enhanced version, three primary branches are directly visible, with the most intense one in the center. The secondary rainbow, as far as it is included in the frame, does not exhibit any anomalies. This is a typical feature in (almost) all split rainbow observations known so far. My goal was now to transform the photograph into the scattering angle vs. clock angle coordinate system (in equirectangular projection), as I did on previous occasions [1, 4]. The scattering angle is the angular distance from the sun, and the clock angle the azimuth around the rainbow’s circumference, with the 0° position corresponding to its top.
The sun’s position is easily obtained from standard astronomy software (giving an elevation of 25.4°, and azimuth of 275.4°). Additionally, the precise focal length of the lens (in pixel units) and distortion characteristics need to be known, as well as the camera pointing direction in elevation and azimuth, and the angle describing the rotation of the sensor’s pixel grid with respect to the vertical.
To precisely determine these quantities, a rather extensive calibration must be carried out. Here I had to try some reasonable guessing: There is a nominal focal length in mm, the sensor data (pixel pitch) can be looked up, as well as some distortion information for this specific lens. From aerial pictures showing the river and individual mountains, the viewing direction can be estimated. The appearance of the water surface gives some clues about the camera rotation. In combination, all these estimations allow for a plausible transformation:
Assuming this reconstruction to be not too far off, it is immediately obvious that the bright central branch does indeed fit to the conventional primary rainbow locus at a constant scattering angle of about 138°. As expected, the secondary ends up at about 129°, also as a straight line. The lower branch (i.e. at higher scattering angles) can in principle be explained by aerodynamically flattened raindrops, following a long tradition in rainbow physics [5, 6, 7, 8, 4]. However, the upper branch penetrating into Alexander’s dark band requires elongated raindrops, whose existence cannot be accounted for by aerodynamics alone. Electrostatic fields [9] can elongate raindrops, but in the absence of any lightning activity it is speculative if any higher fields were present. Elongated shapes do also occur as transitory states during oscillations of larger drops in the appropriate (axisymmetric) modes [10].
The problematic element in this explanation is, however, that in the case of the rainbow we deal with a large number of contributing raindrops and a temporal average due to the finite exposure time. So we need an argument why contributions from transitory states are not simply wiped out. The resonance frequencies of the individual drops depend on their size, so no singular event such as an acoustic shock wave from thunder (if there had been any at all) can synchronize the oscillations. The only plausible idea for a formation of stable rainbow branches by drop oscillations in a stochastic ensemble might be that the two extremal states of the oscillation (flattened and elongated) are encountered with a higher probability than intermediate ones, as the momentary velocity decreases to zero at the turning points of any classical oscillation. Admittedly, this requires a rather narrow distribution of amplitudes throughout the ensemble (at least in the dominant drop size range), as otherwise the branches will be wiped out again due to the spread in extremal axis ratios. To my knowledge, there is not enough data on the statistical properties of oscillations in large ensembles of natural raindrops published yet to draw a definitive conclusion here.
Some further details of this observation are worth to be noted: The three branches of the primary bow appear each in a distinct fashion: The lowest is broad and rather diffuse, the middle one is bright and shows the features of a typical primary rainbow, the top one is narrow with a sharp uppermost outer rim. Moreover, it gives the impression of having developed a downward sub-branch in the –10°…+5° clock angle interval, resulting in a four-fold split bow there.
Rainbows certainly go on fascinating people all over the world, and rightfully so: Even in the 21st century, some outstanding displays occur from time to time that still challenge our understanding. Maybe those in hotter climates with intense rain showers have better chances of catching such rarities. In any case, we have to go out and take a look and a picture at the right time.
Halo Blog is back
We have reactivated the separate Halo Blog so that it can serve as an international forum for observations of halo phenomena and for discussions about halo theory.
We hope for an interesting exchange!
Reflected pillar & rays in windows
On April 9th, 2014, Uwe Bachmann observed a pillar of light, produced by sunlight falling onto the building of the European Central Bank (EZB) in Frankfurt. He was observing from the German Weather Service’s (DWD) headquarters in Offenbach, i.e. from a distance of 3 kilometers.
For his first photo taken at 6.17 UTC, the sun was at an elevation of 13.9° and at an azimuth of 94.8°. The upward beam of light is thought to be produced by reflection from the building’s front, which is at an angle of 9° to the vertical, with scattering from aerosol producing the luminous pillar.
With the rising of the sun and the changing of its azimuth, this pillar is “cut down” subsequently. The second photo shows the situation at 06.35 UTC for a solar elevation 16.8° and an azimuth of 98.4°. The skewness of the reflected beam of light at an angle of 45° is evident.
The last photo taken at 06.52 UTC for a solar elevation 19.5° and an azimuth of 101.8° shows the beam being reflected almost at a right angle. Here, the azimuth of the sun is almost coincident with the observer’s.
Author: Michael Großmann,Kämpfelbach & Uwe Bachmann DWD, Offenbach, Germany
Atmospheric Phenomena 
