Parallel electric fields produced by the ionospheric injection

Saka, Osuke

doi:https://doi.org/10.5194/angeo-2023-1

Preprints

https://doi.org/10.5194/angeo-2023-1

Preprints

12 Jan 2023

| 12 Jan 2023

Status: a revised version of this preprint is currently under review for the journal ANGEO.

Parallel electric fields produced by the ionospheric injection

Osuke Saka

Abstract. It is well known that there exists a thin layer in lower boundary of the ionosphere between altitudes of 80 km and 140 km in which collisional ions and collisionless electrons mix. Local breakdown of charge neutrality may be initiated in this layer by electric fields from the magnetosphere as well as by electric fields generated there by the local neutral winds. The breakdown may be momentarily canceled by the Pedersen currents, but a complete neutralization is prevented because some ionospheric plasmas are released as outflows by parallel electric fields. Those parallel electric fields are produced by inherent plasma processes in the polar ionosphere and act as auroral drivers in the topside ionosphere.

Received: 01 Jan 2023 – Discussion started: 12 Jan 2023

Osuke Saka

Status: final response (author comments only)

RC1:
'Comment on angeo-2023-1', Anonymous Referee #1, 01 Apr 2023

General comments:
The paper proposes a scenario of field-aligned electric potential generation. The author hypothesizes the existence of an electric field pointing downward to the ionosphere due to the breakdown of charge neutrality at a thin layer around altitude of 80km to 140km. This electric field may cause shifting of the electron mirror point to larger L shell (higher altitude), which leads to much less electron loss than the protons in the flux tube. The author uses a 1D model to demonstrate that the charge imbalance of the electron and protons could cause an electric field parallel to the electric field.
As a general opinion from the reviewer, this paper has a few major flaws, in both science merit and in scientific writing quality, which makes the paper unable to meet the standard of publication.
Major weakness 1: The main idea of the paper is based on an assumption of the existence of a thin layer where charge neutrality breaks down which leads to a vertical potential within the layer. However, this assumption is unfounded. The author didn’t provide any evidence or cite related work in either observation or simulation indicating the proposed scenario could be real.
Major weakness 2: The example cases are against common sense and observations. In the deduction of the parallel electric field, the author simply chose two cases of half empty and entirely empty loss cone. However, these two cases can hardly happen or the author didn’t point it out under what time scale this could happen. As a matter of fact, during the substorm or storm, electron and ion fluxes keep coming across the plasma sheet and wave-particle interaction scatters particles and refills the loss cone constantly. The author needs to provide evidence that the proposed cases could actually happen. Furthermore, if the ions get lost through the loss cone much more than the electrons as like the author suggests, then we should have observed much stronger ion precipitation than the electrons, but in reality, it is quite the opposite.
Major weakness 3: The language of the paper could be improved to make the idea clearer to the reader. Some sentences are very vague and confusing to the reviewer. The writer could use figure or diagram to help describe the idea.
Specific comments:
Line 37-40: What is the exact direction mentioned in the “one direction”? Where do the electrons accumulate? The reviewer finds these descriptions quite confusing. It will be very helpful to put a diagram of all the mentioned species and variable so reader can get the idea much clearer.
Line 53-54: The author should define “vertical”, “downward”, etc., in a scientific way, e.g., by providing the description of a coordinate system.
Line 59: The author derives the parallel electric field following Persson 1963, but the storm/substorm time condition may not applicable to Persson’s scenario. The half empty or entirely empty loss cone is very unlikely to persist, because during substorm or storm time, the electron/ion flux keeps coming into the inner magnetosphere and wave-particle interaction refills the flux tube constantly.
Line 122-125: The description is unclear. The author needs to mark x1, x2 in a figure or a diagram.
Technical corrections:
Line 81-87: What does the alpha mean here in the equations? The alpha was the pitch angle in the paragraph above, but now it becomes a ratio.

Citation: https://doi.org/10.5194/angeo-2023-1-RC1
- AC1: 'Reply on RC1', Osuke Saka, 09 Apr 2023
  
  Author Comment to Referee 1
  
  AC to RC1
  A variation of ionospheric potential may appear in the global current circuit of ionosphere-atmosphere-earth system. The currents in this circuit are generated in the atmosphere by charge separation processes in tropical convective storms. Nevertheless, the current influenced by the ionospheric potential can be picked up in this global circuit by monitoring vertical component (Bz) of the ground magnetometer data. Bz on the ground was reduced in association with the decrease of atmospheric electric field on the ground [Minamoto and Kadokura, 2011]. Such correlation would occur in association with the potential drop of the ionosphere at above the ground station [Saka, abstract presented in JpGU 2021].
  
  References
  Minamoto, Y., and Kadokura, A.: Extracting fair-weather data from atmospheric electric-field observations at Syowa Station, Antarctica, Polar Sci., 5, 313-318, 2011.
  Saka, O., Effects of auroral Ionosphere on atmospheric electricity, PEM11-P06, Abstract presented in JpGU2021.
  
  AC to RC2
  It is assumed that localized ionospheric potential drop and associated vertical electric fields directed into the ionosphere (downward) grows in the polar ionosphere prior to the auroral evolution arising out of the onset arc. When the downward electric field amplitudes become sufficient, the electric fields displaced mirror point of electrons to higher altitudes. Disagreed pitch angle distributions between electron and ions produced space charge along the field lines. Deposited space charges produce parallel electric fields pointing out of the ionosphere, i.e., upward electric fields. The upward electric fields initiate auroral evolution. Downward electric fields are shielded by the space charge deposited. The lifetime of the downward electric fields may be of the order of few second, bounce periods of electrons. However, upward electric fields produced at the onset are steady-state solutions in converging field geometries [Persson, 1966; Knight, 1973; Chiu and Schulz, 1978]. Upward fields may persist as far as ionospheric generator is activated and trapped populations exceed those in the loss cone. Populations in loss cone are assumed to be empty or filled one-half of the trapped ones. This may happen prior to the onset of upward electric fields.
  
  References
  Persson, H.: Electric field parallel to the magnetic field in a low-density plasma, Phys. Fluids, 9, 1090-1098, 1966.
  Knight, S.: Parallel electric fields, Planet. Space Sci., 21, 741-750, 1973.
  Chiu, Y.T., and Schulz, M.: Self-consistent particle and parallel electrostatic field distributions in the Magnetospheric-Ionospheric auroral region, J. Geophys. Res., 83, 629-642, 1978.
  
  AC to RC3
  To study in more realistic conditions, we considered negative charge sheet (1280km in longitudes and 128km in latitudes) grew in the polar ionosphere. The thickness of the sheet is assumed to be 60km corresponding to the thickness of the ionosphere (80km – 140km). Emerged charge density was 5x10^2 m^-3 in the sheet. Vertical electric fields generated by this negative sheet is directed into the ionosphere or downward. Altitude profiles of the downward electric fields at the center of the sheet is presented in Red in Figure 1(A-1). For references, magnetic mirror force in mV/m is presented in Black. Magnetic moment for this case is calculated assuming 1keV_perp at 1Re. Force arising from electrostatic fields exceed the magnetic mirror force below 3643km in altitudes. When the spatial scale of the negative charge sheet decreased to 640km x 64km, the crossover altitudes of two forces decreased to 1830km (Figure 1(B-1)).
  
  As a result of the downward electric field, electrons moving toward the ionosphere change their pitch angle trajectories by decelerating the parallel velocities. Mirror height moved to 1407km (Figure 1(A-2)). For the smaller scale charge sheet, new mirror height is 590km (Figure 1(B-2)). Pitch angle trajectories (sin^2(alf)-X plots) with new mirror height bend clockwise as shown in Figure 1(A-2 and B-2)) in Red.
  
  From this new mirror height, electrons start bouncing. Ions do not change their pitch angle because ions that moved mirror point to lower altitudes enter the loss cone. As a result, there appeared three regions in the pitch-angle plane in Figure 1(A-2, B-2); (A) electrons and ions are in loss cone, (B) ions are trapped but electrons from loss cone decelerated by downward electric fields filled this region due to magnetic mirroring, (C) electrons and ions are trapped. In these localized potential cases, pitch-angel disagreement appears in region (B).
  
  Normalized density difference and parallel electric fields calculated by integrating the density difference along field lines are presented in Figure 1(A-3, B-3) and Figure 1(A-4, B-4), respectively. To evaluate the parallel electric fields, we assumed that trapped electrons repelled from both hemispheres would build up the electron rich regions in the magnetosphere.
  
  Specific comments
  “One direction”
  Motions of electron/ion differed in a thin layer composed of collisionless electrons and collisional ions. “One direction” indicates ExB direction in such an anisotropic medium.
  
  “Vertical, downward”
  Please refer to AC to RC2.
  
  “Persson’s scenario”
  Please refer to AC to RC2.
  
  “X1 and X2”
  Marks X1 and X2 are removed because there are no figures related to X1 and X2.
  Technical corrections
  It is corrected, and numbers are added to the equations.
  
  Citation: https://doi.org/10.5194/angeo-2023-1-AC1
- AC3: 'Reply on RC1', Osuke Saka, 12 Apr 2023
  
  Author Comment to Referee 1
  
  AC to RC1
  A variation of ionospheric potential may appear in the global current circuit of ionosphere-atmosphere-earth system. The currents in this circuit are generated in the atmosphere by charge separation processes in tropical convective storms. Nevertheless, the current influenced by the ionospheric potential can be picked up in this global circuit by monitoring vertical component (Bz) of the ground magnetometer data. Bz on the ground was reduced in association with the decrease of atmospheric electric field on the ground [Minamoto and Kadokura, 2011]. Such correlation would occur in association with the potential drop of the ionosphere at above the ground station [Saka, abstract presented in JpGU 2021].
  
  References
  Minamoto, Y., and Kadokura, A.: Extracting fair-weather data from atmospheric electric-field observations at Syowa Station, Antarctica, Polar Sci., 5, 313-318, 2011.
  Saka, O., Effects of auroral Ionosphere on atmospheric electricity, PEM11-P06, Abstract presented in JpGU2021.
  
  AC to RC2
  It is assumed that localized ionospheric potential drop and associated vertical electric fields directed into the ionosphere (downward) grows in the polar ionosphere prior to the auroral evolution arising out of the onset arc. When the downward electric field amplitudes become sufficient, the electric fields displaced mirror point of electrons to higher altitudes. Disagreed pitch angle distributions between electron and ions produced space charge along the field lines. Deposited space charges produce parallel electric fields pointing out of the ionosphere, i.e., upward electric fields. The upward electric fields initiate auroral evolution. Downward electric fields are shielded by the space charge deposited. The lifetime of the downward electric fields may be of the order of few seconds, bounce periods of electrons. However, upward electric fields produced at the onset are steady-state solutions in converging field geometries [Persson, 1966; Knight, 1973; Chiu and Schulz, 1978]. Upward fields may persist as far as ionospheric generator is activated and trapped populations exceed those in the loss cone. Populations in loss cone are assumed to be empty or filled one-half of the trapped ones. This may happen prior to the onset of upward electric fields.
  
  References
  Persson, H.: Electric field parallel to the magnetic field in a low-density plasma, Phys. Fluids, 9, 1090-1098, 1966.
  Knight, S.: Parallel electric fields, Planet. Space Sci., 21, 741-750, 1973.
  Chiu, Y.T., and Schulz, M.: Self-consistent particle and parallel electrostatic field distributions in the Magnetospheric-Ionospheric auroral region, J. Geophys. Res., 83, 629-642, 1978.
  
  AC to RC3
  To study in more realistic conditions, we considered negative charge sheet (1280km in longitudes and 128km in latitudes) grew in the polar ionosphere. The thickness of the sheet is assumed to be 60km corresponding to the thickness of the ionosphere (80km – 140km). Emerged charge density was 5x10^2 m^-3 in the sheet. Vertical electric fields generated by this negative sheet is directed into the ionosphere or downward. Altitude profiles of the downward electric fields at the center of the sheet is presented in Red in Figure 1(A-1). For references, magnetic mirror force in mV/m is presented in Black. Magnetic moment for this case is calculated assuming 1keV_perp at 1Re. Force arising from electrostatic fields exceed the magnetic mirror force below 3643km in altitudes. When the spatial scale of the negative charge sheet decreased to 640km x 64km, the crossover altitudes of two forces decreased to 1830km (Figure 1(B-1)).
  
  As a result of the downward electric field, electrons moving toward the ionosphere change their pitch angle trajectories by decelerating the parallel velocities. Mirror height moved to 1407km (Figure 1(A-2)). For the smaller scale charge sheet, new mirror height is 590km (Figure 1(B-2)). Pitch angle trajectories (sin^2(alf)-X plots) with new mirror height bend clockwise as shown in Figure 1(A-2 and B-2)) in Red.
  
  From this new mirror height, electrons start bouncing. Ions do not change their pitch-angle trajectories because of a large mass ratio (M/m). As a result, there appeared three regions in the pitch-angle plane in Figure 1(A-2, B-2); (A) electrons and ions are in loss cone, (B) ions are trapped but electrons from loss cone decelerated by downward electric fields filled this region due to magnetic mirroring, (C) electrons and ions are trapped. In these localized potential cases, pitch-angel disagreement appears in region (B).
  
  Normalized density difference and parallel electric fields calculated by integrating the density difference along field lines are presented in Figure 1(A-3, B-3) and Figure 1(A-4, B-4), respectively. To evaluate the parallel electric fields, we assumed that trapped electrons repelled from both hemispheres would build up the electron rich regions in the magnetosphere.
  
  Specific comments
  “One direction”
  Motions of electron/ion differed in a thin layer composed of collisionless electrons and collisional ions. “One direction” indicates ExB direction toward lower latitudes where electrons accumulate. Please refer schematic illustration of ionospheric injection scenario in [Saka, O.: Ionospheric control of space weather, Ann Geophys., 39, 455-460, 2021]. This is presented in the supplement (Figure 2).
  
  “Vertical, downward”
  Please refer to AC to RC2.
  
  “Persson’s scenario”
  Please refer to AC to RC2.
  
  “X1 and X2”
  Marks X1 and X2 are removed because there are no figures related to X1 and X2.
  Technical corrections
  It is corrected, and numbers are added to the equations.
  
  Citation: https://doi.org/10.5194/angeo-2023-1-AC3
- AC5: 'Reply on RC1', Osuke Saka, 12 Apr 2023
  
  Please delete AC1. New comment AC3 is posted.
  
  Citation: https://doi.org/10.5194/angeo-2023-1-AC5
RC2:
'Comment on angeo-2023-1', Anonymous Referee #2, 02 Apr 2023

Since I have the pricilege of reading the 1. reviewers paper I see no need to provide a new synopsis of the paper; the 1. referee did a fine job.
I also agree with the first referee's assessment. However, I thik it should be stronger. Specifically:
1. The argujmentation is circular. Supposedly, the primary electric field (whatever cause) would cause charge separation that sustains those fields (line 39ff). Electrostatic fields work exactly the opposite way, i.e., forces on the cahrged particles are such as to reduce the charge separation.
2. As pointed out by the other referee, the assumptions for the equations (which should be numbered) have no basis. They are completely arbitrary and may lead to any result one desires. The use of the quantity alpha is not defined, or differently in different places. It remains unclear what it means on line 86.
3. Discussion: What injection? How would plasma be injected onto auroral field lines? And what is a 'local breakdow?' The entire meager discussion is nothing but handwaving. There is no discussion of prior work. In particular, parallel electric fields on ionosphere field lines are understood to be the result of FAC, and the theory has been worked out in detail by Knight, Lyuon, and others, but there is no reference here.
The paper is fundamentally flawed and should not be published.

Citation: https://doi.org/10.5194/angeo-2023-1-RC2
- AC2: 'Reply on RC2', Osuke Saka, 09 Apr 2023
  
  Author Comment to Referee 2
  
  Two types of electrostatic fields:
  It is assumed that localized ionospheric potential drop and associated vertical electric fields directed into the ionosphere (downward) grows in the polar ionosphere (referred to as local breakdown of the ionosphere) prior to the auroral evolution arising out of the onset arc. When the downward electric field amplitudes become sufficient, the electric fields displaced mirror point of electrons to higher altitudes. Disagreed pitch angle distributions between electron and ions produced space charge along the field lines. Deposited space charges produce parallel electric fields pointing out of the ionosphere, i.e., upward electric fields. The upward electric fields initiate auroral evolution. Downward electric fields are shielded by the space charge deposited. The lifetime of the downward electric fields may be of the order of few second, bounce periods of electrons. However, upward electric fields produced at the onset are steady-state solutions in converging field geometries [Persson, 1966; Knight, 1973; Chiu and Schulz, 1978]. Upward fields may persist as far as ionospheric generator is activated and trapped populations exceed those in the loss cone.
  
  References
  Persson, H.: Electric field parallel to the magnetic field in a low-density plasma, Phys. Fluids, 9, 1090-1098, 1966.
  Knight, S.: Parallel electric fields, Planet. Space Sci., 21, 741-750, 1973.
  Chiu, Y.T., and Schulz, M.: Self-consistent particle and parallel electrostatic field distributions in the Magnetospheric-Ionospheric auroral region, J. Geophys. Res., 83, 629-642, 1978.
  
  Equations and the use of the quantity alpha
  All equations are numbered. The equation, sin^2(alf)=B/Br is a key equation in the ionospheric driver scenario. This equation shows that if reflection point changes, pitch-angle at any point B also changes, i.e., a change of reflection point generates space charges.
  Transient downward electric fields change the reflection point and yield space charges along the field lines. Space charges generate parallel electric field out of the ionosphere (upward), opposite to the transient ones. Upward electric fields are steady-state solutions in the converging field geometry [Persson, 1966; Knight, 1973; Chui and Schulz, 1978].
  Populations in loss cone are assumed to be empty or filled one-half of the trapped ones. This may happen prior to the onset of upward electric fields.
  
  Discussion of prior work and meaning of ionospheric injection:
  Generators that build up space charges are supposed to exist in the distant magnetosphere. Parallel potentials related to the magnetospheric driver scenario were discussed by Knight [1973], Chiu and Schulz, 1978, Lyons [1980], and [Stern, 1981 and references therein].
  In the polar ionosphere, the Cowling channel becomes ionospheric generator when the Pedersen currents closed to the field-aligned currents [Baumjohann, 1983]. Part of upward field-aligned currents are carried by ions injected out of the ionosphere to avoid complete neutralization of the ionospheric plasmas. The downward field-aligned currents are carried by the electrons injected out of the ionosphere, from the positive potential rise.
  
  References
  Baumjohann, W.: Ionospheric and field-aligned current systems in the auroral zone: a concise review, Adv. Space Res., 2, 55-62, 1983.
  Chiu, Y.T., and Schulz, M.: Self-consistent particle and parallel electrostatic field distributions in the Magnetospheric-Ionospheric auroral region, J. Geophys. Res., 83, 629-642, 1978.
  Knight, S.: Parallel electric fields, Planet. Space Sci., 21, 741-750, 1973.
  Lyons, L.R.: Generation of large-scale regions of auroral currents, electric potentials, and precipitation by the divergence of the convection electric field, J. Jeophys. Res., 85, 17-24, 1980.
  Stern, D.P.: One-dimensional models of quasi-neutral parallel electric fields, J. Geophys. Res., 86, 5839-5860, 1981.
  
  Citation: https://doi.org/10.5194/angeo-2023-1-AC2
- AC4: 'Reply on RC2', Osuke Saka, 12 Apr 2023
  
  Author Comment to Referee 2
  
  Two types of electrostatic fields:
  It is assumed that localized ionospheric potential drop and associated vertical electric fields directed into the ionosphere (downward) grows in the polar ionosphere (referred to as local breakdown of the ionosphere) prior to the auroral evolution arising out of the onset arc. When the downward electric field amplitudes become sufficient, the electric fields displaced mirror point of electrons to higher altitudes. Disagreed pitch angle distributions between electron and ions produced space charge along the field lines. Deposited space charges produce parallel electric fields pointing out of the ionosphere, i.e., upward electric fields. The upward electric fields initiate auroral evolution. Downward electric fields are shielded by the space charge deposited. The lifetime of the downward electric fields may be of the order of few seconds, bounce periods of electrons. However, upward electric fields produced at the onset are steady-state solutions in converging field geometries [Persson, 1966; Knight, 1973; Chiu and Schulz, 1978]. Upward fields may persist as far as ionospheric generator is activated and trapped populations exceed those in the loss cone.
  
  References
  Persson, H.: Electric field parallel to the magnetic field in a low-density plasma, Phys. Fluids, 9, 1090-1098, 1966.
  Knight, S.: Parallel electric fields, Planet. Space Sci., 21, 741-750, 1973.
  Chiu, Y.T., and Schulz, M.: Self-consistent particle and parallel electrostatic field distributions in the Magnetospheric-Ionospheric auroral region, J. Geophys. Res., 83, 629-642, 1978.
  
  Equations and the use of the quantity alpha
  All equations are numbered. The equation, sin^2(alf)=B/Br is a key equation in the ionospheric driver scenario. This equation shows that if reflection point changes, pitch-angle at any point B also changes, i.e., a change of reflection point generates space charges if electrons and ions differed.
  Transient downward electric fields change the reflection point of electrons and yield space charges along the field lines. Space charges generate parallel electric field out of the ionosphere (upward), opposite to the transient ones. Upward electric fields are steady-state solutions in the converging field geometry [Persson, 1966; Knight, 1973; Chui and Schulz, 1978].
  Populations in loss cone are assumed to be empty or filled one-half of the trapped ones. This may happen prior to the onset of upward electric fields.
  
  Discussion of prior work and meaning of ionospheric injection:
  Generators that build up space charges are supposed to exist in the distant magnetosphere. Parallel potentials related to the magnetospheric driver scenario were discussed by Knight [1973], Chiu and Schulz, 1978, Lyons [1980], and [Stern, 1981 and references therein].
  In the polar ionosphere, the Cowling channel becomes ionospheric generator when the Pedersen currents closed to the field-aligned currents [Baumjohann, 1983]. In the present scenario, part of upward field-aligned currents is carried by ions injected out of the ionosphere from negative potential region. The downward field-aligned currents are carried by the electrons injected out of the ionosphere, from positive potential.
  
  References
  Baumjohann, W.: Ionospheric and field-aligned current systems in the auroral zone: a concise review, Adv. Space Res., 2, 55-62, 1983.
  Chiu, Y.T., and Schulz, M.: Self-consistent particle and parallel electrostatic field distributions in the Magnetospheric-Ionospheric auroral region, J. Geophys. Res., 83, 629-642, 1978.
  Knight, S.: Parallel electric fields, Planet. Space Sci., 21, 741-750, 1973.
  Lyons, L.R.: Generation of large-scale regions of auroral currents, electric potentials, and precipitation by the divergence of the convection electric field, J. Jeophys. Res., 85, 17-24, 1980.
  Stern, D.P.: One-dimensional models of quasi-neutral parallel electric fields, J. Geophys. Res., 86, 5839-5860, 1981.
  
  Citation: https://doi.org/10.5194/angeo-2023-1-AC4
- AC6: 'Reply on RC2', Osuke Saka, 12 Apr 2023
  
  Please delete AC2. New comment AC4 is posted.
  
  Citation: https://doi.org/10.5194/angeo-2023-1-AC6

Osuke Saka

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Short summary

Transverse electric fields transmitted from the magnetosphere and those generated there by the neutral winds yield a local breakdown of the charge neutrality at the boundaries between thermosphere and mesosphere. The breakdown may create parallel electric fields in the thermosphere to produce spiral auroras and outflows. This explanation supposes an auroral generator located not in distant space but rather in our much nearer upper atmosphere.


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