the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 15 Sep 2023
Difference spectrum fitting of the ion-neutral collision frequency from dual-frequency EISCAT measurements
Abstract. Plasma-neutral coupling in the mesosphere/lower thermosphere strongly depends on the ion-neutral collision frequency across that region. Most commonly, the collision frequency profile is calculated from the climatologies of atmospheric models. However, previous measurements indicated that the collision frequency can deviate notably from the climatological average. Direct measurement of the ion-neutral collision frequency with multifrequency Incoherent Scatter Radar (ISR) measurements has been discussed before, though actual measurements have been rare. The previously applied multifrequency analysis method requires a special simultaneous fit of the two Incoherent Scatter spectra which is not possible with standard ISR analysis software. The difference spectrum method allows inferring ion-neutral collision frequency profiles from multifrequency ISR measurements based on standard Incoherent Scatter analysis software such as the GUISDAP software package. In this work, we present the first results by applying the difference spectrum method. Ion-neutral collision frequency profiles obtained from several multifrequency EISCAT ISR campaigns are presented. The profiles obtained with the difference spectrum method are compared to previous collision frequency measurements, both from multifrequency ISR and other measurements, as well as results from empirical and comprehensive atmosphere models. Ion-neutral collision frequency measurements can be applied to improve first-principle ionospheric models.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-1495', Anonymous Referee #3, 16 Sep 2023
This manuscript presented the application of the difference spectrum method to analyze the EISCAT multifrequency measurements in three campaigns to directly obtain ion-neutral collision frequency profiles. The fitting results is acceptable. Due to the lack of ion-neutral collision frequency measurement in the dynamo region, the method presented here is highly valuable.
This manuscript is well structured with careful writing. And the results and conclusions presented are clear and acceptable. I recommend this manuscript to publish without further revisions.
Citation: https://doi.org/10.5194/egusphere-2023-1495-RC1 -
AC1: 'Reply on RC1', Florian Günzkofer, 19 Oct 2023
We thank the Referee for taking the time to read our manuscript and for their positive feedback.
Citation: https://doi.org/10.5194/egusphere-2023-1495-AC1
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AC1: 'Reply on RC1', Florian Günzkofer, 19 Oct 2023
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RC2: 'Comment on egusphere-2023-1495', Anonymous Referee #2, 06 Oct 2023
The paper applied the difference spectrum method to obtain the Ion-neutral collision frequency profiles by actual measurements. The results were compared to previous measurements and models. It is a good work to verify the theory to measure collision frequency profiles by ISR. I recommend the paper to be published. Although I have some questions:
1. As you mentioned in the paper, you compare the difference of the scaling parameter β depending on the altitude. Do you analyze its change with time? What is the suitable strategy to choose the scaling parameter β?
2. If the frequency of two ISRs is close. Does the frequency difference of ISR effect the measurements?
Citation: https://doi.org/10.5194/egusphere-2023-1495-RC2 -
AC2: 'Reply on RC2', Florian Günzkofer, 19 Oct 2023
We thank the Referee for taking the time to review our paper. Please find the responses to your questions below.
Referee:
As you mentioned in the paper, you compare the difference of the scaling parameter β depending on the altitude. Do you analyze its change with time? What is the suitable strategy to choose the scaling parameter β?
Authors:
We determine the β parameter profile for each 60s integration window separately. The β profiles shown in Figure 4 are the median profiles of the respective campaigns. The β value does not show a significant trend over the course of one campaign (few hours) at any altitude. Since the β parameter is introduced to account for technical differences between the UHF and VHF systems, changes within a few hours are not expected. However, there are distinct outliers for some integration windows, presumably during which one of the instruments failed to measure a clear ISR spectrum allowing for analysis. Therefore, median statistics was chosen as the appropriate strategy to determine the scaling parameter β.
Referee:
If the frequency of two ISRs is close. Does the frequency difference of ISR effect the measurements?
Authors:
The important parameter here is not the difference of radar frequencies but their ratio ξ. As described in Equation 3, the simultaneous UHF and VHF measurements are similar to two UHF measurements at νin and ξνin. This causes the difference of the two spectra. For a ξ ratio close to unity, the difference spectrum is extremely weak and overshadowed by measurement uncertainties. Inferring the ion-neutral collision frequency is therefore only possible for an ξ ratio distinctly larger than 1 (4.2 for the EISCAT systems).
Citation: https://doi.org/10.5194/egusphere-2023-1495-AC2
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AC2: 'Reply on RC2', Florian Günzkofer, 19 Oct 2023
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-1495', Anonymous Referee #3, 16 Sep 2023
This manuscript presented the application of the difference spectrum method to analyze the EISCAT multifrequency measurements in three campaigns to directly obtain ion-neutral collision frequency profiles. The fitting results is acceptable. Due to the lack of ion-neutral collision frequency measurement in the dynamo region, the method presented here is highly valuable.
This manuscript is well structured with careful writing. And the results and conclusions presented are clear and acceptable. I recommend this manuscript to publish without further revisions.
Citation: https://doi.org/10.5194/egusphere-2023-1495-RC1 -
AC1: 'Reply on RC1', Florian Günzkofer, 19 Oct 2023
We thank the Referee for taking the time to read our manuscript and for their positive feedback.
Citation: https://doi.org/10.5194/egusphere-2023-1495-AC1
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AC1: 'Reply on RC1', Florian Günzkofer, 19 Oct 2023
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RC2: 'Comment on egusphere-2023-1495', Anonymous Referee #2, 06 Oct 2023
The paper applied the difference spectrum method to obtain the Ion-neutral collision frequency profiles by actual measurements. The results were compared to previous measurements and models. It is a good work to verify the theory to measure collision frequency profiles by ISR. I recommend the paper to be published. Although I have some questions:
1. As you mentioned in the paper, you compare the difference of the scaling parameter β depending on the altitude. Do you analyze its change with time? What is the suitable strategy to choose the scaling parameter β?
2. If the frequency of two ISRs is close. Does the frequency difference of ISR effect the measurements?
Citation: https://doi.org/10.5194/egusphere-2023-1495-RC2 -
AC2: 'Reply on RC2', Florian Günzkofer, 19 Oct 2023
We thank the Referee for taking the time to review our paper. Please find the responses to your questions below.
Referee:
As you mentioned in the paper, you compare the difference of the scaling parameter β depending on the altitude. Do you analyze its change with time? What is the suitable strategy to choose the scaling parameter β?
Authors:
We determine the β parameter profile for each 60s integration window separately. The β profiles shown in Figure 4 are the median profiles of the respective campaigns. The β value does not show a significant trend over the course of one campaign (few hours) at any altitude. Since the β parameter is introduced to account for technical differences between the UHF and VHF systems, changes within a few hours are not expected. However, there are distinct outliers for some integration windows, presumably during which one of the instruments failed to measure a clear ISR spectrum allowing for analysis. Therefore, median statistics was chosen as the appropriate strategy to determine the scaling parameter β.
Referee:
If the frequency of two ISRs is close. Does the frequency difference of ISR effect the measurements?
Authors:
The important parameter here is not the difference of radar frequencies but their ratio ξ. As described in Equation 3, the simultaneous UHF and VHF measurements are similar to two UHF measurements at νin and ξνin. This causes the difference of the two spectra. For a ξ ratio close to unity, the difference spectrum is extremely weak and overshadowed by measurement uncertainties. Inferring the ion-neutral collision frequency is therefore only possible for an ξ ratio distinctly larger than 1 (4.2 for the EISCAT systems).
Citation: https://doi.org/10.5194/egusphere-2023-1495-AC2
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AC2: 'Reply on RC2', Florian Günzkofer, 19 Oct 2023
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Cited
Florian Günzkofer
Gunter Stober
Dimitry Pokhotelov
Yasunobu Miyoshi
Claudia Borries
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(1721 KB) - Metadata XML