the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 21 Mar 2025
Data reduction of incoherent scatter plasma line parameters
Abstract. In the ionosphere, a sustained population of suprathermal electrons arises due to photoionization or electron precipitation. The presence of such a population enhances the scattered power in the plasma line spectrum, thus making it possible to detect them. Plasma line measurements improve the accuracy of electron density and temperature estimates. We investigate plasma line enhancements in EISCAT Tromsø UHF radar observations, using two image processing methodologies for detection: a supervised image morphological processing technique and an unsupervised connected component analysis. The supervised methodology detects more plasma lines, demonstrating higher sensitivity. We determine the times and altitudes with enhancements and model the spectrum with a Gaussian function. The radar beam points in the field-aligned direction for 25 % of the total observational time, is directed east for another 25 % and is oriented in the vertical direction for the remaining 50 %. Plasma lines are detected 26 % of the time when the radar is pointed in the field-aligned direction, 5 % of the time in the east direction and 5 % of the time in the vertical direction. Most plasma lines are detected around the F-region altitude where the electron density is maximum, typically between 230–260 km, with a simultaneous increase in the electron density estimates from the ion line. Plasma line intensity is maximum around noon. It decreases as the aspect angle increases. Both detection methodologies' advantages and disadvantages are discussed, and plasma line intensity variations are analyzed as a function of altitude, aspect angle and phase energy.
Competing interests: The contact author has declared that neither of the authors has any competing interests.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.-
Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
-
Preprint
(5413 KB)
-
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(5413 KB) - Metadata XML
- BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-993', William Longley, 17 Apr 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-993/egusphere-2025-993-RC1-supplement.pdfCitation: https://doi.org/
10.5194/egusphere-2025-993-RC1 - AC1: 'Reply on RC1', Mini Gupta, 03 Oct 2025
-
RC2: 'Comment on egusphere-2025-993', Anonymous Referee #2, 08 Sep 2025
The manuscript "Data reduction of incoherent scatter plasma line parameters"
presents a study of plasma line detection in the EISCAT UHF radar dataset,
using two approaches: a supervised (kind of manually adjusted) and an unsupervised
technique (with the detection based on the statistical parameters of the data
itself).The manuscript is well written and easy to follow. The figures are generally
clear and of good quality. The conclusions are well supported by the data.Minor revisions/clarifications could improve the quality of the manuscript,
which is of high standard already.As the paper provides an important reference for plasma line analysis, it would
be good to mention in the introduction plasma lines associated with instabilities
and turbulence. The interested reader will find this information in e.g. the
review by Akbari et al., but it would be good to mention this fact - and maybe
even add references to key publications.The discussion of Figure 7 is not very clear in lines 224-227. The description
mentions an increase of the plasma line frequency at "about 11:20:15 UT", and
then mentions a "gradual increase" from 10:00-11:20 UT. Both are related to the
Sun, one to the "solar EUV radiation" and the other to "sun exposure". In my
opinion, this description should be consolidated.An interesting phenomenon is observed in Figure 7, namely the undulation of
the location of detected plasma line. This would indicate that the peak of the
profile is moving up and down in altitude. Some quasiperiodic variations of
the lower "boundary" of the F region are seen also in the top panel of figure 6.
While not directly related to main subject of the discussion, the authors
may want to comment on possible nature of the variations (could these be
related to gravity waves? or variations in the ionospheric convection? or
yet something else?). Are these variations of the electron concentration
profile capable of affecting the plasma line enhancement condition?A note on Fig. 6 is that the date of the production of the figure is not
important, and probably should not be included in the plot. For Figure 7
it is a good idea to have a better setup of the time labels, having only
two of them, at 10:29 and 11:30 does not help in pointing out specific times
in the plot. The bottom panel indicates the intensity units in eV, is this
correct? Figure 4 gives intensity in K/kHz, while there is also an extensive
discussion of the phase energy" (eq. 16). In Figure 5 the intensity is
in K, and Figures 10 and 11 present k_B T_p.A minor detail: text predominantly refers to "altitudes", while some of the
figures are marked with "height" (while others with "altitude"). This could
probably be harmonized.The paragraphs in lines 228-236 seem somewhat misplaced. In part they refer
to "similar plots" which are not presented, in contrast to the detailed
discussion of the even presented. They also refer to Figure 10, not to be
presented to the reader until later in paper. The consequences of observing
a narrower interval of the phase energy range than covered by the system is
not very clear at this point. A suggestion would be moving this material to
the discussion (line 257 and onwards), rather than having it in Results.I suggest considering renaming the last section to something like
"Summary and Discussion". Conclusions would be expected to be a concise
summary of the findings, the nature of the presentation here is more of
a discussion (among other aspects, four new figures are presented!).The purpose of showing presenting Figures 8 and 9 in the concluding section
is not very clear (paragraph in lines 254-256). Probably they would fit better
in the analysis section?Line 262-263 "The absence of upshifted plasma lines means that we cannot
use our data to calculate ionospheric currents." - what this ever the
intension in this work?Figures 10 and 11 present k_B T_p in eV. These would correspond to
temperatures well in excess of those shown in Fig. 5 (left panel). I suspect
that the numbers are not directly comparable, but it would be helpful with a
clarification in the paper on how they should relate to each other.It would be interesting to discuss how the choice of the dataset affects
the results. The observations are from several days in a row in January,
all during daytime. How would the observations look in a different seasons
and/or time of the day?Citation: https://doi.org/10.5194/egusphere-2025-993-RC2 - AC2: 'Reply on RC2', Mini Gupta, 03 Oct 2025
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-993', William Longley, 17 Apr 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-993/egusphere-2025-993-RC1-supplement.pdf
- AC1: 'Reply on RC1', Mini Gupta, 03 Oct 2025
-
RC2: 'Comment on egusphere-2025-993', Anonymous Referee #2, 08 Sep 2025
The manuscript "Data reduction of incoherent scatter plasma line parameters"
presents a study of plasma line detection in the EISCAT UHF radar dataset,
using two approaches: a supervised (kind of manually adjusted) and an unsupervised
technique (with the detection based on the statistical parameters of the data
itself).The manuscript is well written and easy to follow. The figures are generally
clear and of good quality. The conclusions are well supported by the data.Minor revisions/clarifications could improve the quality of the manuscript,
which is of high standard already.As the paper provides an important reference for plasma line analysis, it would
be good to mention in the introduction plasma lines associated with instabilities
and turbulence. The interested reader will find this information in e.g. the
review by Akbari et al., but it would be good to mention this fact - and maybe
even add references to key publications.The discussion of Figure 7 is not very clear in lines 224-227. The description
mentions an increase of the plasma line frequency at "about 11:20:15 UT", and
then mentions a "gradual increase" from 10:00-11:20 UT. Both are related to the
Sun, one to the "solar EUV radiation" and the other to "sun exposure". In my
opinion, this description should be consolidated.An interesting phenomenon is observed in Figure 7, namely the undulation of
the location of detected plasma line. This would indicate that the peak of the
profile is moving up and down in altitude. Some quasiperiodic variations of
the lower "boundary" of the F region are seen also in the top panel of figure 6.
While not directly related to main subject of the discussion, the authors
may want to comment on possible nature of the variations (could these be
related to gravity waves? or variations in the ionospheric convection? or
yet something else?). Are these variations of the electron concentration
profile capable of affecting the plasma line enhancement condition?A note on Fig. 6 is that the date of the production of the figure is not
important, and probably should not be included in the plot. For Figure 7
it is a good idea to have a better setup of the time labels, having only
two of them, at 10:29 and 11:30 does not help in pointing out specific times
in the plot. The bottom panel indicates the intensity units in eV, is this
correct? Figure 4 gives intensity in K/kHz, while there is also an extensive
discussion of the phase energy" (eq. 16). In Figure 5 the intensity is
in K, and Figures 10 and 11 present k_B T_p.A minor detail: text predominantly refers to "altitudes", while some of the
figures are marked with "height" (while others with "altitude"). This could
probably be harmonized.The paragraphs in lines 228-236 seem somewhat misplaced. In part they refer
to "similar plots" which are not presented, in contrast to the detailed
discussion of the even presented. They also refer to Figure 10, not to be
presented to the reader until later in paper. The consequences of observing
a narrower interval of the phase energy range than covered by the system is
not very clear at this point. A suggestion would be moving this material to
the discussion (line 257 and onwards), rather than having it in Results.I suggest considering renaming the last section to something like
"Summary and Discussion". Conclusions would be expected to be a concise
summary of the findings, the nature of the presentation here is more of
a discussion (among other aspects, four new figures are presented!).The purpose of showing presenting Figures 8 and 9 in the concluding section
is not very clear (paragraph in lines 254-256). Probably they would fit better
in the analysis section?Line 262-263 "The absence of upshifted plasma lines means that we cannot
use our data to calculate ionospheric currents." - what this ever the
intension in this work?Figures 10 and 11 present k_B T_p in eV. These would correspond to
temperatures well in excess of those shown in Fig. 5 (left panel). I suspect
that the numbers are not directly comparable, but it would be helpful with a
clarification in the paper on how they should relate to each other.It would be interesting to discuss how the choice of the dataset affects
the results. The observations are from several days in a row in January,
all during daytime. How would the observations look in a different seasons
and/or time of the day?Citation: https://doi.org/10.5194/egusphere-2025-993-RC2 - AC2: 'Reply on RC2', Mini Gupta, 03 Oct 2025
Peer review completion
Journal article(s) based on this preprint
Data sets
Plasma line analysis MATLAB functions Mini Gupta https://doi.org/10.5281/zenodo.14135585
Model code and software
Plasma line analysis MATLAB functions Mini Gupta https://doi.org/10.5281/zenodo.14135585
Viewed
| HTML | XML | Total | BibTeX | EndNote | |
|---|---|---|---|---|---|
| 1,624 | 146 | 28 | 1,798 | 90 | 123 |
- HTML: 1,624
- PDF: 146
- XML: 28
- Total: 1,798
- BibTeX: 90
- EndNote: 123
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
Patrick Guio
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(5413 KB) - Metadata XML