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Preliminary results from the Sprites94 Aircraft Campaign: 1. Red sprites


Abstract and Figures

The dual jet aircraft Sprites94 campaign yielded the first color imagery and unambiguously triangulated physical dimensions and heights of upper atmospheric optical emissions associated with thunderstorm systems. Low light level television images, in both color and in black and white (B/W), obtained during the campaign show that there are at least two distinctively different types of optical emissions spanning part or all of the distance between the anvil tops and the ionosphere. The first of these emissions, dubbed 'sprites' after their elusive nature, are luminous structures of brief (less than 16 ms) duration with a red main body that typically spans the latitude range 50-90 km, and possessing lateral dimensions of 5-30 km. Faint bluish tendrils often extend downward from the main body of sprites, occasionally appearing to reach cloud tops near 20 km. In this paper the principal characteristics of red sprites as observed during the Sprites94 campaign are described. The second distinctive type of emissions, 'blue jets,' are described in a companion paper (Wescott et al., this issue).
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Preliminary results from the Sprites94 aircraft
campaign: 1. Red sprites
D.D. Sentman, E.M. Wescott, D.L. Osborne, D.L. Hampton, and M.J. Heavner
Geophysical Institute, University of Alaska Fairbanks, AK 99775-7320
Abstract. The dual jet aircraft Sprites94 campaign yielded
the first color imagery and unambiguously triangulated
physical dimensions and heights of upper atmospheric
optical emissions associated with thunderstorm systems.
Low light level television images, in both color and in black
and white (B/W), obtained during the campaign show that
there are at least two distinctively different types of optical
emissions spanning part or all of the distance between the
anvil tops and the ionosphere. The first of these emissions,
dubbed "sprites" after their elusive nature, are luminous
structures of brief (< 16 ms) duration with a red main body that
typically spans the altitude range 50-90 km, and possessing
lateral dimensions of 5-30 km. Faint bluish tendrils often
extend downward from the main body of sprites, occasionally
appearing to reach cloud tops near 20 kin. In this paper the
principal characteristics of red sprites as observed during the
Sprites94 campaign are described. The second distinctive
type of emissions, "blue jets," are described in a companion
paper [Wescott et al., this issue].
Introduction and Background
Accounts of brief optical emissions above thunderstorms
go back more than a century [see, e.g., Boys, 1926; Malan,
1937; Vaughan and Vonnegut, 1989], and Wilson [1956] has
discussed the possibility of lightning discharges extending
upward from cloud tops. However, it has not been until the
past few years that images of discharge events have been
obtained. Franz et al. [1990] recorded the first low light level
television images of these events, and estimated that they
extended to altitudes of 34 km or higher. Following this
observation Vaughan et al. [1992] and Boeck et al. [1994]
reported television observations from the space shuttle of a
number, now approaching twenty, of what appear to be similar
events above thunderstorms on the limb of the planet.
During the summers of 1993-1994 there occurred a marked
increase in the quantity and quality of reports of this
phenomenon. Using a low light level All Sky television
system, Sentman and Wesco, [1993] imaged nineteen
examples of these events during a single flight of NASA's DC-
8 Airborne Laboratory over thunderstorms in Iowa, Nebraska
and .Kansas in July, 1993. They estimated the most probable
terminal heights of the events to be 60 km, with error bars
extending to 100 km. The duration was estimated to be 16 ms
or less, and the brightness was calculated from comparison
with stellar brightness to be 25-50 kR, roughly that of
moderately bright aurorae. The occurrence rate was estimated
Copyright 1995 by the American Geophysical Union.
Paper number 95GL00583
0094-8534/95/95GL-00583 $03.00
to be approximately 1 for every 200-300 cloud-to-ground
In a more sustained ground-based program, Lyons
[1994 a,b] obtained B/W images of high altitude flashes
above storm systems in Nebraska and Kansas in July and
August, 1993, increasing the inventory of recorded events to
more than six hundred. Similarly, Winckler [1994], using low
light level B/W cameras, recorded about 150 events above
intense thunderstorm systems to the south of his recording
station in Minnesota in July-August, 1993. Recent summaries
of observations before the summer campaigns of 1994 are
given by Boeck et al. [1994] and Lyons [1994a].
The high altitude luminous structures imaged in the above
reports have been variously referred to in the literature as
upward or cloud-to-ionosphere lightning, cloud-to-ionosphere
or cloud-to-stratosphere discharges. Such appellations suggest
possibly unwarranted parallels to normal tropospheric
electrical discharge activity, or imply specific production
mechanisms about which at present little is known. We
therefore adopted the non judgmental name "sprites" for these
events after their elusive qualities. Hence, the name
"Sprites94" for our observation campaign.
In this paper we report preliminary results of observations
of sprites recorded during the Sprites94 aircraft campaign of
June-July, 1994. The principal objectives of the research were
to obtain color images of the events, to triangulate their
dimensions and terminal altitudes accurately, to record their
optical waveforms and emission spectra, and to study their
ELF/VLF electromagnetic signatures. During the campaign a
second type of emission, distinct from sprites, was also
unexpectedly observed. In a companion paper Wesco, et al.
[this issue] describe these "blue jets." Sentman and Wescott
[1994] have previously released a short Video containing
selected sequences of television images obtained during the
The Sprites94 Aircraft Campaign
Two jet aircraft were used as imaging platforms •to provide
the high altitude observing vantages and angular separation
necessary for triangulation studies. Flight missions were
conducted out of Oklahoma City after dusk on the dates listed
in Table 1 to areas of active thunderstorm activity in the
Midwest. The dates of the campaign interval were chosen to
provide for moon down observing conditions necessary for
low light camera operation during 2200-0200 Local Time
when thunderstorm activity was at a maximum.
Aircraft. The two corporate jet aircraft used to make the
observations were a Rockwell Jet Commander and an Israel
Aircraft Industries Westwind 2, both leased from Aero Air, Inc.
of Hillsboro, Oregon. Observations were conducted at altitudes
40,000-42,000 ft (12.2-12.8 kin) at speeds of 425 knots (790
km/hr). On a typical flight mission the aircraft flew in a loose
Table I Sprites94 Flight Missions (1994)
UT Date Area of Tl•nderstorm Observation Hr. Data
29 Jun Colorado, Texas P•handl• 1.0
30 Jun Oklahoma to Nabraska 2.5
1 Jul Central Arkansas 2.0
3 Jul Gulf Coast, Florida Panhandle 3.0
4 Jul New Mexico t•o Kansas 3.0
5 Jul Nebraska to Colorado 1.25
6 Jul Oklahoma to Texas Panhandle 2.7 5
7 Jul Iowa, N•braska, Colorado 2.0
10 Jul Texas Panhandle 2.0
11 Jul South Dakoda 2.0
12 Jul Eastern/Central Texas 1.2 5
13 Jul Eastern Colorado 2.0
trail formation, with the Jet Commander leading the Westwind
2 by 10-75 km.
Instrumentation. The aircraft were both fitted on the
right side with factory new plastic windows. Above 450 nm
their transmissivity was about 90%, and at 400 nm and 390
nm the transmissivity fell to 75% and 51%, respectively. The
primary camera systems utilized during the campaign are
described below. Additionally, the Jet Commander had a pair
of baffled photomultiplier tubes to detect flash waveforms and
propagation velocity, and a television slit spectrograph. The
Westwind 2 carried an intensified B/W All Sky camera as a
backup system. Finally, an ELF/VLF detector was deployed on
the ground northwest of Oklahoma City to record
electromagnetic wave forms associated with sprites.
Both aircraft were equipped with Trimble model Six-Vee 6
Global Positioning Satellite (GPS) navigation systems to
track aircraft position and speed. GPS information was
recorded directly onto the video images using a Horita model
GPS-2 SMPTE time code generator. The GPS signals were fed
to a master sync generator to synchronize the horizontal and
vertical sweeps of all camera systems. This permi.tted accurate
triangulation and stereoscopic visualization of images
simultaneously captured from the separate aircraft. Position,
altitude, and dimension measurements of the sprites
subsequently obtained from triangulation calculations were
accurate to about 2-3 km. Measured: GPS timing and camera
synchronization accuracy was +32 •, absolute.
The measurements reported here were obtained using the
following instruments.
Wide Anele Low Light Level Black and White C•tncr• We
used Dage-MTI VE-1000 SIT B/W cameras, which have a
sensitivity of 1.6 x 10 '7 W-m '2 at 550 nm and 300 lines
resolution. The cameras were equipped with Kinoptik 5.7 mm
f/1.8 TEGEA wide angle lenses, with 92øH x 69øV fields of
view (FOV). One Dage camera was on each aircraft. The video
images from these cameras were recorded at 60 fields per
second (fps) on Sony U-Matic 3/4 inch tape recorders, along
with GPS timing and navigational information.
Intensified Color Camera The color camera on the
Westwind 2 was an Ikegami HL-51S with 2,000,000 ISO
equivalent and sensitivity of approximately 2 kR [lkegami,
1984; Hallinan, 1988]. The camera has three separate SIT
subsystems with red, green and blue responses that maximize
at approximately 600 nm, 530 nm, and 450 nm, respectively
[see Wescott et al., this issue]. For Sprites94 the camera was
equipped with a Canon PV 10X 12B2 12-120 mm zoom lens,
operated at 12 mm and f/2.0, yielding a 55øH x 43øV FOV.
The images from the Ikegami camera system were recorded at
60 fps on a Sony Betacam SP recorder, along with GPS timing
and navigation information.
A ground support station was established at the National
Severe Storms Laboratory (NSSL) for the Sprites94 campaign
to provide real-time updates from the National Lightning
Detection NetwOrk (NLDN). Radar and GOES 7 infrared weather
maps from Weather Services, International (WSI) and
lightning maps from the NLDN were collected periodically and
uploaded to the Jet Commander via the AGRAS and SKYHOOK
communications systems.
Preliminary Results
An estimated 500 separate upper atmospheric optical events
were recorded during the twelve flight missions listed in Table
1. More than half of these events were imaged simultaneously
from both aircraft, and more than half by the color camera.
Figure 1 shows two events recorded during the campaign.
One of the first newly documentable results of the
observations, as shown here in the right panels, is that the
main upper portion of sprites is predominantly red. In the
images from the color camera the main body of the sprite
registers primarily in the red channel. Very weak or no
signatures are present in the blue and green channels.
The luminous regions appear to range from small single or
multiple vertically elongated spots to spots with faint
extensions above and below, to bright groupings which
extend from the cloud tops to altitudes up to 95 km. The
concentration of the luminosity into distinctive spatial
features tend to occur within a limited range of altitudes and is
sufficiently repeatable to warrant consideration as "unit"
elements. We refer to these unit elements as "sprites" for
reasons mentioned above.
A preliminary anatomy of sprites may be constructed based
on these features. Results of detailed triangulations of the
positions of the features of 29 separate sprites or clusters of
sprites reveal that the brightest region, the "head," lies within
the bracketed range of altitudes 66-74 km (+ 4 km). Above the
head there is often a faint red glow or wispy structure ("hair")
separated from the bright head by a dark band ("hairline"), and
extending to 88:•.5 km. On two of the sprite clusters studied in
detail the terminal height of the hair exceeded 95 km. The hair
may occasionally exhibit a weak horizontal dark bar•. •t 79+4
km. On some of the brighter sprites, as shown in ?'•igure 1,
there is a dark band ("collar") beneath the head at 66ñ 4 km,
below which extend tendril-like filamentary forms. The color
of the tendrils is red just below the collar, gradually merging
into blue with distance downward. The tendrils have been
triangulated to reach downward to as low as 40 km, below
which Rayleigh scattering and camera blooming from
intracloud lightning prevents identification of structural detail
necessary to perform a triangulation. Figure 2 shows our
preliminary anatomy of the basic sprite form, and its altitude
relationship to atmospheric temperature and typical night
time electron density profiles.
Sprites rarely appear singly, usually occurring in clusters of
two, three or more. Some of th e very large events, such as in
Figure 1, seem to be tightly packed clusters of many individual
sprites. The brightest regions of these "compound sprites"
typically saturated the B/W images, and in some cases the
color images, as well (e.g., the white central portion of the
sprites in Figure 1). Many sprite events consist of multiple,
! 0354:12(26) Jet Corn UT 0354:12(26) W W 2 UT 0354:12(26)
4 Jul 94 4 Jul 94 4 Jul 94
U Ma U Ma
b c b
U Ma
100 km
UT 0400:20(0) Jet Com UT 0400:20(0) W W 2 UT 0400:20(0)
0 4 Jul 94 4 Jul 94 4 Jul 94
U Ma e
t UMa
-- Kt
c d
a b c d
Figure 1. Two separate sprite events observed on 4 July, 1994. On each row the left-hand B/W image was taken from the
Jet Commander, while the center B/W image and the fight hand color images show the same event from the Westwind 2
aircraft. Selected stars within the respective fields of view have been labeled. The altitude scale in the color image refers t o
the brightest feature. Top Row UT 0345:12(video frame 25). A cluster of sprites. The parallax of stars in the constellation
Ursa Major relative to the sprites may be seen by comparing the B/W images. Bottom Row UT 0400:20(video frame 0)
This large compound sprite was one of the largest observed. Note the blue/purple tendrils. Aircraft separation for both
events was about 50 km.
spatially distinct sprites, which may be laterally distributed
across distances 40 km or more. Figure 3 shows an example of
a cluster of three distinct sprites that were imaged
simultaneously from the two aircraft while studying a storm
over the Texas panhandle on the night of 6 July, 1994. The
point on the ground below each of the individual sprites is
indicated in the accompanying map. The sprites occurred on
the backside of the frontal storm system that was moving
100 --'
80 --
60 --
Anatomy of a Sprite
Optical Brightness -40 kR
Optical Energy 1-5 kJ
Optical Power 0.3-1.5 MW
Thllnderstorm ' -.-'-::
T osphere
Nighttime /
Figure 2. Anatomy of a "unit" sprite and its altitude
relationship to atmospheric temperature and typical
night time electron density profiles. More
complicated compound sprites and sprite clusters
consist of groupings of the unit sprite at various
Texas Oklahoma
UT 0529:52(25)
a b
", .,'! .i .. ++. ..' ": ..
'.".:•'X ' .:':: :'i"2 " '. • ,
.l': .I. ß . ß • J• ' :• -• ' '•,,•:. '.
,.' .::..'.. ,",• . .,½- •. '- .•. ".,
.• -..,, ... -.-, • ?- '•-..,_
'" :•' ß . '1•. ß - -=- r ß
ß .:.: . :..-r - - "-"-'"L .,..;,..
ß $' ,' ß a' ,r . ."1 .'-' '
ß . ,•..•.. -1..,, ,_ . ,-..
, .. '-. v ß
..... •" ß ' UT 6 July, 1994 0440-0540 - ,,.,I '. '-',.-,,•...t r
, .' National Lightning Detection Network
Figure 3. Spatial location of the individual sprites in
the event of UT July 6 0529:52(video frame 25). The
location of the sprites, indicated by large red dots, is
projected onto a time/polarity color coded map of
cloud to ground lightning as recorded by the National
Lightning Detection Network. Positive ground
strokes are indicated by pluses, negative strokes by
dots. Strokes occurring, relative to the time the map
was stored (UT 0540), are coded as white (0-15 min),
yellow (15-30 min) or red (30-60 min). The sprites
are seen to be laterally distributed over distances
comparable to the terminal heights of the events
(-100 km).
through the Texas panhandle. The majority of sprites observed
were similarly located well behind the associated storm fronts,
in regions where positive cloud-to-ground strokes were
The red, bright portions of sprites and their extensions
above and below occur predominantly within the altitude range
50-95 km, thus making sprites primarily a mesospheric D-
Region phenomenon. The lateral dimension of "unit" sprites
is typically 5-10 km, corresponding to volumes that may
exceed 103 km 3. Compound sprites and sprite clusters may
occupy volumes greater than 104 km 3.
Detailed analysis of the apparent brightness of several
separate unit sprites determined by comparison to stellar
brightness references [Wescott et al., this issue] yields a
maximum brightness of roughly 600 kR within the sprite.
When averaged over the dimmer outer portions of the sprite
the mean brightness is about 50 kR, consistent with our
original brightness estimates [Sentman and Wescott, 1993] of
10-50 kR. If we assume the optical emission is centered at
600 nm and spatially distributed uniformly throughout a mean
estimated emission volume of 2000 km 3, this translates into a
total optical energy of 1-5 kJ per event. Assuming a duration
of 3 ms the instantaneous optical power of these unit sprites is
therefore in the range 0.3-1.5 MW. Energy and instantaneous
optical power of large sprite clusters and compound sprites my
exceed these figures by an order of magnitude or more, i.e., 10-
50 kJ and 3-15 MW, respectively.
Results of the present study may be summerized as follows.
1. Sprites are a mesospheric/D-region phenomenon. They
reach upward to an average maximum height of
approximately 88 km, with an rms altitude spread of
about 5 km. In the largest and brightest examples
observed terminal heights exceeded 95 km, placing the
tops of these events firmly within the lower regions of
the ionospheric E-region.
2. Sprites are predominantly red. The brightest region of a
unit sprite, its "head," lies between characteristic
altitudes of 66 km and 74 km. Above the head there is
often a dark band ("hairline") above which a faint, wispy
red glow ("hair") is observed to splay upward and outward
toward terminal altitude. Beneath the head there
sometimes occurs a dark band ("collar") at 66+ 4 km
below which faint tendrils may extend downward to
altitudes of 40-50 km, changing from red near the collar
to blue at their lowest extremities.
3. Sprites may occur singly, but more typically occur in
clusters of two or more. Clusters may be tightly packed
together into large structures 40 km or more across, or
loosely spread out into distended structures of spatially
separated sprites. Onset of luminance occurs
simultaneously (within video resolution, 16 ms) across
the cluster as a whole, coincident with the occurrence of
cloud lightning below. All elements of the cluster
typically decay in unison over 3-5 video frames (100-160
ms), but most of this decay time may be attributed to
image lag of the SIT cameras.
4. Sprites seem preferentially to occur on the backside of
frontal storm systems, and occur in regions of positive
lightning ground strokes.
5. The total optical energy in a typical unit sprite is
power of compound sprites and sprite clusters may exceed
these values by an order of magnitude.
Acknowledgments: We thank Mary Mellott and Rick Howard of Code
SS, NASA Headquarters, for support and encouragement in this project,
and Andy Cameron of the Earth Sciences Office for his invaluable
assistance. We thank Aero Air, Inc., Hillsboro, Oregon for use of their
aircraft; the enthusiasm and professional skills of Jeff Tobolski, Norm
Ralston, Mark Satterwhite, and Chuck McWilliams made the success of
the aircraft operations possible. We thank Dave Rust of the National
Severe Storms Laboratory, Norman, Oklahoma for his assistance and
ground station support. We are grateful to H. Stenbaek-Nielsen for
providing us with triangulation routines. Finally, we acknowledge useful
discussions with Walter Lyons, ASTER, Inc., Ft. Collins Colorado, and
Earle Williams, MIT. This research was supported by NASA Grant
NAG5-5019 and National Science Foundation Grant ATM-9217161.
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Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK
estimated to be 1-5 kJ, and the corresponding (Received November 11, 1994;revised February6, 1995;
instantaneous power is 0.5-2.5 MW. The energy and acc'epted February 17, 1995)
... The altitudes of sprites have been well established using different techniques and high-speed cameras. The sprites top altitude has been observed to vary from 73 to 96 km, whereas the altitude of the sprites brightest region has been found to span from 50 to 84.1 km (Füllekrug et al., 2019;Luque et al., 2016;Mashao et al., 2021;Malagón-Romero et al., 2020;Sentman et al.,1995;Stenbaek-Nielsen et al., 2010;Wescott et al., 1998). Mashao et al. (2021) found that the average sprites top altitude in South Africa occurred at approximately 84.3 km. ...
... Mashao et al. (2021) found that the average sprites top altitude in South Africa occurred at approximately 84.3 km. Other authors found sprite top altitudes at 88 km (Sentman et al., 1995), 86.4 km (Wescott et al., 1998), and79-96 km (Stenbaek-Nielsen et al., 2010). Mashao et al. (2021) found that the average altitude of maximum brightness in South Africa occurred at approximately 69 km. ...
... We found that TLEs top altitudes vary from 71 to 90.5 km, with an average and standard deviation of 79.8 and 5.2 km, respectively. The TLEs top altitudes are in the altitude range previously reported in the literature (Füllekrug et al., 2019;Luque et al., 2016;Mashao et al., 2021;Malagón-Romero et al., 2020;Sentman et al.,1995;Stenbaek-Nielsen et al., 2010;Wescott et al., 1998). The analyzed TLEs brightest region altitude ranged from 50 to 73 km, with an average and standard deviation of 61.5 and 6.4 km, respectively. ...
Transient Luminous Events (TLEs) above thunderclouds have been previously associated with variables such as the lightning Charge Moment Change (CMC), charge height, charge transfer, and lightning current rise-time. We show for the first time a comparison of the CMC, rise-time, fall-time, peak electric field, and peak current of the lightning discharges associated with 11 column, 11 carrot, and 18 sprites with halo. We found that carrot sprites are induced by a lightning discharge with CMC, peak electric field, and peak current greater and less than that for column sprites and sprites with halo, respectively. Sprites with a halo are initiated by a lightning discharge with a longer rise-time and fall-time than that for column and carrot sprites. Column sprites top altitude and carrot sprites brightest region altitude positively correlate with lightning rise-time. For carrot sprites top altitude, the results suggest that the electrical breakdown region decreases in altitude for a longer fall-time, greater peak electric field, and greater peak current. For the altitude of the sprites brightest region, column sprites correlate negatively with lightning fall-time, peak electric field, and CMC, and column sprites top altitude also correlates negatively with lightning peak electric field. For sprites with a halo top altitude increased with lightning fall-time and peak current, and sprites with a halo brightest altitude increased with an increase in lightning CMC. Halo diameters correlate positively with lightning fall-time, peak electric field, and peak current. The investigated lightning parameters can be used to identify the initiated sprites morphological type when optics are not available.
... Most of the articles published in this area of knowledge over the past three decades are devoted to sprites. [2][3][4][5][6][7][8][9][10][11][12][13][14][15] The first documentary confirmation of the observation of sprites in the form of a black-and-white photograph is given in Ref. 11. In subsequent years, color images of red sprites of various shapes appeared already in various sources (articles, magazines, the Internet), which are photographed by employees of ground laboratories, 11 from aircraft, 12 from satellites, 13 from the International Space Station, 14,15 as well as created by professional photographers. ...
... [2][3][4][5][6][7][8][9][10][11][12][13][14][15] The first documentary confirmation of the observation of sprites in the form of a black-and-white photograph is given in Ref. 11. In subsequent years, color images of red sprites of various shapes appeared already in various sources (articles, magazines, the Internet), which are photographed by employees of ground laboratories, 11 from aircraft, 12 from satellites, 13 from the International Space Station, 14,15 as well as created by professional photographers. 16 Physical processes that occur during the development of sprites, and which determine their initiation, shape, color, and emission spectrum, have been studied by a large number of scientific groups around the world. ...
Results of experimental studies of red-colored plasma diffuse jets are presented. Such jets are initiated by a capacitive discharge in air or nitrogen at pressures of 0.2–3 Torr fed by voltage pulses with an amplitude of 5–7 kV following with a frequency of 21 kHz. They can be considered as a lab analog of a columnar sprite. The jet is formed by successive ionization waves (streamers). A significant effect of the reduced electric field strength E/N on the color (emission spectrum) of a plasma diffuse jet has been established. It is shown that the transition from red to blue as the jet approaches the additional electrodes and the end flange of the discharge tube is due to an increase in E/N in these regions. This, in turn, explains the change in color of sprites as they approach the top of the storm clouds. An assumption about the influence of noctilucent clouds on the formation of the beaded structure of sprites is made. The plasma parameters (electron Te, vibrational Tv, rotational Tr, and translational Ttr temperatures, as well as E/N) in the region of the capacitive discharge and along the plasma diffuse jet were measured by optical emission spectroscopy. The measurements have shown that with the increase in distance from the electrode assembly, E/N decreases from ∼3500 to ∼200 Td, while Te changes from ∼50 to 3 eV. The gas temperature varies slightly from 400 to 360 K. The measurement results are compared with those of natural red sprites.
... The properties of plasma discharges are largely affected by the fundamental physical processes, operating conditions, and discharge modes and can thus be classified based on characteristic parameters, such as length and pressure scales. As shown in Fig. 1, natural discharge phenomena, such as red sprite and lightning (Franz et al. 1990;Franz 2009;Sentman et al. 1995), have dimension scales exceeding tens of kilometres, and such phenomena are almost impossible to reproduce in experimental investigations. Downscaled models of this kind of discharge are desired to further explore their characteristics. ...
... However, it was not until 1989 that such discharges were photographed for the first time accidentally by scientists at the University of Minnesota (Franz et al. 1990). From June to July 1994, during the thunderstorm season in Oklahoma in the midwestern United States, Sentman and his colleagues took two jet planes over twelve days and performed a series of imaging studies on sprites at an altitude of 12,000 km (Sentman et al. 1995). The parameters of the sprites, such as the scale, height, waveform, and spectrum, were accurately determined. ...
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Similarity theory and scaling laws determine how physical laws remain the same when control parameters are changed, which is essential for the correlation, prediction, and optimization of discharge plasma parameters under varied conditions. Over the past hundred years, similarity and scaling methods have been broadly explored for low-temperature plasma discharges driven by direct current, alternating current, and pulsed power supplies. Combining scaling laws with similarity theory can greatly reduce the complexity of designing and optimizing plasma devices, especially for geometrically similar discharges of different dimensional scales. This approach further allows extrapolation of plasma discharges to novel parameter regimes without solving equations or conducting experiments. In this review, the establishment and historical development of similarity laws are revisited, and the theoretical interpretation and derivation of similarity theory for different plasma regimes are presented. The similarity properties are demonstrated for various discharge types, including glow discharges, pulsed discharges, streamers, radio-frequency discharges, and microdischarges. The similarity results for plasma discharges from experimental diagnostics, numerical simulations, and theoretical analysis are summarized, and the state-of-the-art progress in the breakdown scaling and dynamical similarities is discussed. Violation mechanisms of the similarity laws, such as nonlinear collision processes, are also elaborated. Finally, the applications, limitations, and future development of similarity theory and scaling laws are discussed.
... The hypothesis about their existence was first put forward in 1925 [16]. The first color images of these phenomena were published only at the end of the twentieth century [17]. Sprites occur at altitudes of 70-80 km and consist of red colored jets propagating in both towards and away from the Earth's surface [2], [8], [15]. ...
... At the altitude of ~50 km from the Earth's surface the color of sprites changes from red to blue [3], [15]. The progress that is currently being observed in the field of TLEs research, in particular red sprites, is due to the use of modern high-resolution devices installed on board aircraft [17] and on the International Space Station [11]. ...
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The paper is devoted to the study of a pulsed streamer discharge, similar to that in the Earth’s upper atmosphere. An experimental setup providing the formation of two ionization waves propagating in opposite directions from a region filled with a plasma formed by the capacitive discharge in low-pressure atmospheric air was created. In a physical experiment, the process of propagation of red ionization waves (streamers) was simulated. It was established that the average propagation velocities of their fronts correspond to those of red sprites. This was shown as a result of spectral studies that at air pressures of 0.4-3 Torr, the radiation color radiation observed visually and captured on an integral photograph from the region of passage of ionization waves is determined by the spectral transitions of the first positive system (FPS) of nitrogen molecules, similar to what occurs for red sprites. In this case, the spectral energy density of radiation in the most intense band of the second positive system (SPS) of the nitrogen molecule with a wavelength of 337.13 nm is an order of magnitude or higher than that in the most intense band of the FPS with the wavelength of 775.32 nm. Using the emission spectra and methods of optical emission spectroscopy (OES), the main parameters of the discharge plasma are estimated. Thus, the created setup makes it possible to simulate the process of the formation of red sprites propagating in opposite directions under laboratory conditions.
... Page 5 of 14 Wang and Chang Terrestrial, Atmospheric and Oceanic Sciences (2023) 34:4 In the calculation of ν α , the ion-electron collision frequency ν αe is obtained from ν eα in Eq. (4) as ν αe = (m e /m α ) 1/2 ν eα (e.g., Hsieh 1968), where m α is the mass of ion species α. The ion-neutral collision frequency ν αn is obtained from including both nonresonant and resonant collision frequencies as discussed in Schunk and Nagy (2009) and Ieda (2020). The ion-ion collision frequency ν αα are much smaller than ν αe . ...
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The characteristics of whistlers generated from an observed gigantic jet (GJ) are assessed and possible locations to detect these waves are deduced. Modeling is based on disturbances in the electric field, as measured by NCKU ELF/VLF station, associated with a tree-like GJ event over typhoon Lionrock. The power spectrum of GJ differs from that of common cloud-to-ground lightning; therefore, this study also investigates differences between GJ-generated signals and common lightning-generated whistlers. Detectability is evaluated by considering the absorption of amplitudes resulted from collisional damping associated with the propagation of generated waves. Our results show that in the ionosphere the waves are subject to greater attenuation as the frequency increases; however, a reversal occurs at lower frequencies of a few hundred Hz. The calculated waveforms show that the whistlers generated by the tree-like GJs are preceded by small fluctuations at high frequencies generated by the initiating lightning. Overall, the amplitudes increase with the passage of time; however, they are more randomly-distributed over time for whistlers generated from common lightning. The amplitudes decrease again when lower-frequency components below a few hundred Hz arrive. The amplitudes drop to the order of 1 mV/m as the waves propagate in the ionosphere, which puts them within a range detectable by the instruments on most satellites. Based on the locations of tree-like GJ events observed by ISUAL (Imager of Sprites and Upper Atmospheric Lightning), regions of the western and southeastern Pacific Ocean, as well as northern Africa region are the most likely locations to detect these whistlers.
... However, recent studies have found that the proportion of sprites caused by a negative polarity discharge can reach ∼18% [25,28] or even ∼25% [10]. Based on the optical observation data, the morphologies of sprites are typically a column or a carrot type [42,53,8]. Less common morphologies include angel type, firework type, and dancing type [29,47,8]. In addition, the morphology of sprites varies in different regions and seasons. ...
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We present a catalog of 525 sprites detected over the Sea of Japan and a northeast part of the Pacific Ocean from Sagamihara between September 2016 and March 2021. We analyze the morphology of 525, estimate the location of 441, and calculate the accurate top height of 15 sprites. More than half of our samples occurred in winter, while only 11% were in summer. In terms of morphology, 52% to 60% column type sprites took place in spring, autumn, and winter, while only 15.5% in summer. Therefore, summer thunderstorms are more likely to produce sprites with complex structures like carrots. Furthermore, sprites in summer are almost all located on the main island of Japan, and their spatial distributions are significantly different from the other seasons. Finally, from the perspective of the time distribution, the number of sprites is the largest at 1:00 JST. In addition, the morphology of sprites tends to be simple (e.g., a column type) at midnight JST.
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This document provides guidelines for the terrestrial environment that are specifically applicable in the development of design requirements/specifications for NASA aerospace vehicles, payloads, and associated ground support equipment. The primary geographic areas encompassed are the John F. Kennedy Space Center, FL; Vandenberg AFB, CA; Edwards AFB, CA; Michoud Assembly Facility, New Orleans, LA; John C. Stennis Space Center, MS; Lyndon B. Johnson Space Center, Houston, TX; George C. Marshall Space Flight Center, Huntsville, AL; and the White Sands Missile Range, NM. This document presents the latest available information on the terrestrial environment applicable to the design and operations of aerospace vehicles and supersedes information presented in NASA-HDBK-1001 and TM X-64589, TM X-64757, TM-78118, TM-82473, and TM-4511. Information is included on winds, atmospheric thermodynamic models, radiation, humidity, precipitation, severe weather, sea state, lightning, atmospheric chemistry, seismic criteria, and a model to predict atmospheric dispersion of aerospace engine exhaust cloud rise and growth. In addition, a section has been included to provide information on the general distribution of natural environmental extremes in the conterminous United States, and world-wide, that may be needed to specify design criteria in the transportation of space vehicle subsystems and components. A section on atmospheric attenuation has been added since measurements by sensors on certain Earth orbital experiment missions are influenced by the Earth’s atmosphere. There is also a section on mission analysis, prelaunch monitoring, and flight evaluation as related to the terrestrial environment inputs. The information in these guidelines is recommended for use in the development of aerospace vehicle and related equipment design and associated operational criteria, unless otherwise stated in contract work specifications. The terrestrial environmental data in these guidelines are primarily limited to information below 90 km altitude. Subject Terms: environment criteria, terrestrial environment, surface extremes, wind, temperature, humidity, precipitation, density, pressure, atmospheric electricity, cloud cover, control systems, geology, sea state, severe storms, constituents, radiation, diffusion, models
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Plain Language Summary Sprites are lightning‐induced optical transient emissions in the mesosphere. The morphological features of sprites are observed to be quite complex but closely related to the polarity of their causative cloud‐to‐ground (CG) lightning strokes. In our previous studies, the polarity of sprite‐producing CG lightning strokes has been determined for hundreds of events with the concurrent ground‐based measurement of associated lightning sferics. Based on the machine learning method, we develop a model to identify the polarity of sprite‐producing CG lightning strokes for events observed by the Imager of Sprites and Upper Atmospheric Lightning (ISUAL) mission. With such a model, the polarity of sprite‐producing CG lightning strokes without ground‐based observations can be recognized. In total, 258 sprites produced by negative CG lightning strokes, roughly 17% of the whole data set (1522) are identified. The proportion of sprites produced by negative CG lightning strokes greatly varies with latitude and sea‐land distribution, and it is greater in the tropical regions below 20° latitude and also larger over the sea. Moreover, the proportion of sprites produced by negative CG lightning strokes over Africa and North America is much smaller than that over the rest of the continents and the sea.
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Initial observations of a newly documented type of optical emission above thunderstorms are reported. 'Blue jets', or narrowly collimated beams of blue light that appear to propagate upwards from the tops of thunderstorms, were recorded on B/W and color video cameras for the first time during the Sprites94 aircraft campaign, June-July, 1994. The jets appear to propagate upward at speeds of about 100 km/s and reach terminal altitudes of 40-50 m. Fifty six examples were recorded during a 22 minute interval during a storm over Arkansas. We examine some possible mechanisms, but have no satisfactory theory of this phenomenon.
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An experiment was conducted in which an image-intensified, low-light video camera systematically monitored the stratosphere above distant (100-800 km) mesoscale convective systems over the high plains of the central U.S. for 21 nights between 6 July and 27 August 1993. Complex, luminous structures were observed above large thunderstorm clusters on eleven nights, with one storm system (7 July 1993) yielding 248 events in 410 minutes. Their duration ranged from 33 to 283 ms, with an average of 98 ms. The luminous structures, generally not visible to the naked, dark-adapted eye, exhibited on video a wide variety of brightness levels and shapes including streaks, aurora-like curtains, smudges, fountains and jets. The structures were often more than 10 km wide and their upper portions extended to above 50 km msl.
The thundercloud is regarded as a great influence machine, the ionization currents associated with it being the agents by which its electromotive force is developed and maintained. The moving ions which constitute these currents may be intercepted by solid or liquid cloud elements so that it becomes possible for them to be carried against the field and so increase an existing electromotive force. The early stages in its growth are due to the ionization current within the cloud initiated by the earth's fine-weather field. Later it is the external currents due to the thundercloud's own field which are effective. Lightning discharges may themselves contribute to the electromotive force of the thundercloud.
During the night of 9-10 August 1993 more than 150 luminous cloud-ionosphere discharges (CIs) were observed above a thunderstorm complex moving SE across the state of Iowa. Images of the CIs were obtained through clear air by intensified CCD TV cameras at the O'Brien Observatory of the University of Minnesota located about 60 km NE of Minneapolis and 250-500 km from the storm center. The discharges consisted of bright vertical striations extending from 50-80 km altitude, often covering tens of kilometers laterally, with tendrils of decreasing intensity visible for the brighter events down to cloud tops below 20 km altitude. All the more intense CIs were coincident with a VLF sferic in the 300Hz-12kHz range, but small events often did not yield a detectable sferic. There is no unambiguous evidence that CIs were sources of sferics. Some of the CIs were observed to be coincident with a cloud brightening and with a cloud-ground stroke recorded by the National Lightning Detection Network. The duration of the images was generally less than one TV field (< 16.7 ms). Many of these discharges have now been observed by the space shuttle, by aircraft-borne TV cameras and a large number by a ground-based camera observations in Colorado. The present results are compared with these observations and recent theoretical ideas related to the CI events are discussed. It is proposed that CIs arise from intense bursts of cloud electrification and may follow the preexisting paths of cloud-to-ionosphere thunderstorm currents.
Data from 36 Ba shaped-charge releases carried out at an angle of less than 25 deg to the magnetic field, by the technique of Wescott et al. (1972) and Michel (1974), were examined for evidence of a sustained rate of ionization in excess of that attributable to sunlight. In four of the experiments, the time constant for the decay of the neutrals was measured using an ultrasensitive color TV camera and was found to have a value of about 30 sec, consistent with slow (solar) ionization. Although the qualitative appearance of most jets was found to be consistent with a slow process of ionization, some releases produced a thin confined jet that was suggestive of rapid ionization. Two of these jets were analyzed in detail, but no evidence of anomalous ionization was produced. The data obtained in this work agree with the geometrical predictions of the Swift model.
I HAVE to thank Dr. Perrine for his observations on my article on ``Progressive Lightning.'' They are interesting as indicating some difference in the appearance of lightning in the Argentine, where the strokes are exceptionally strong, and that of lightning in Great Britain. Here without any question the appearance of the multiple flash is found when the distance is as little as a kilometre, and I certainly believe much less. In Cordoba Dr. Perrine only observes this when the flashes are so distant that thunder is barely beard. Such a distance here is from sixteen to twenty kilometres. I suppose here, with a flash near enough, even if it were multiple, the eye would be so dazzled by the primitive flash as not to be able to see those that follow, but it is difficult to account in this way for the great distance implied by the faint audibility of the thunder. I have seen a large number of photographs taken with an ordinary camera held in the hand, and not intentionally moved as Dr. Hoffert's was, but nevertheless not really fixed, which show the multiple flash, and the size of the flashes on the plates indicates that they must have been fairly near. At any distance such as sixteen kilometres the flash would occupy but a small portion of the plate.
Short-duration upper atmospheric optical flashes were recorded on the night of 8 July, 1993 (9 July UT) from the NASA DC-8 Airborne Laboratory flying over the American Midwest. All-sky video images from an intensified silicon intensified target (ISIT) camera revealed 19 upper atmospheric flashes occurring over a period of approximately 100 min. The flashes were similar in appearance to previously reported ground and shuttle-based video observations. Detailed analysis of 12 of the events yielded these parameters: (1) duration less than or = 17 ms; (2) brightness 10-50 kR, roughly that of bright aurorae; (3) terminal heights 30-100 km, with a mean of approximately 60 km; (4) horizontal extent 10-50 km; and (5) emission volume greater than 1000 km(sup 3). The relative frequency of the optical flashes was (6) 1:200-1:400 compared to negative cloud-to-ground discharges and 1:20-1:40 compared to positive cloud-to-ground discharges.
An examination and analysis of video images of lightning, captured by the payload bay TV cameras of the space shuttle, provided a variety of examples of lightning in the stratosphere above thunderstorms. These images were obtained on several recent shuttle flights while conducting the Mesoscale Lightning Experiment (MLE). The images of stratospheric lightning illustrate the variety of filamentary and broad vertical discharges in the stratosphere that may accompany a lightning flash. A typical event is imaged as a single or multiple filament extending 30 to 40 km above a thunderstorm that is illuminated by a series of lightning strokes. Examples are found in temperate and tropical areas, over the oceans, and over the land.
A letter of inquiry to a magazine read by airplane pilots has elicited 15 new observations of a rare form of lightning that comes out of the cloud top, goes up vertically, and terminates in the clear air above. These confirm previous observations showing that this phenomenon usually occurs above very large and energetic thunderclouds. However, small clouds with tops at 15,000 feet have been observed to have this rare form of lightning also. One of the more spectacular observations was made over the severe storm that produced the devastating Xenia, Ohio, tornadoes of April 1965.