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AMPERE Observations of the Asymmetry Toward Stronger Birkeland Currents in the Northern Hemisphere.

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Title: AMPERE Observations of the Asymmetry Toward Stronger Birkeland Currents in the Northern Hemisphere.
Authors: Coxon, John C.1 (AUTHOR) work@johncoxon.co.uk, Vines, Sarah K.2 (AUTHOR), Mo, Wenli3 (AUTHOR), Townson, Matthew J.1 (AUTHOR), Watt, Clare E. J.1 (AUTHOR), Rae, I. Jonathan1 (AUTHOR), Bloomfield, D. Shaun1 (AUTHOR), Smith, Andrew W.1 (AUTHOR), Milan, Stephen E.4 (AUTHOR), Anderson, Brian J.3 (AUTHOR), Patrick, Atlas M.1 (AUTHOR), Hasler, Maria C.1 (AUTHOR)
Source: Journal of Geophysical Research. Space Physics. May2026, Vol. 131 Issue 5, p1-22. 22p.
Subject Terms: *Magnetic storms, Electric currents, Artificial satellites, Interplanetary magnetic fields, Data pipelining, Time-frequency analysis, Scientific experimentation
Geographic Terms: Northern Hemisphere, Southern Hemisphere
Abstract: We quantify the asymmetry between the Birkeland currents (also known as field‐aligned currents) in the Northern and Southern Hemispheres. We use data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) in 2010–2024 inclusive for both hemispheres, compute the observed asymmetry, and then subtract the modeled asymmetry. We use Block 1 data (based on the original Iridium constellation) and NEXT data (based on Iridium‐NEXT spacecraft), and compare the effect of changing the data processing pipeline on the latter (yielding NEXT v1 and NEXT v2 subdatasets). We find that the asymmetry is significantly smaller in NEXT v2 data (4±2%) $(4\pm 2\%)$ than in Block 1 (21±2%) $(21\pm 2\%)$ or NEXT v1 data (19±3%) $(19\pm 3\%)$. The previously reported asymmetry seen in Swarm is ∼12% ${\sim} 12\%$, indicating that the new data processing pipeline goes from approximately twice the Swarm asymmetry to approximately half. This may indicate that the new AMPERE processing pipeline overestimates the amount of current flowing in the Southern Hemisphere, whereas the old one underestimated this quantity. We use frequency analysis to find that the asymmetry varies with frequencies corresponding to seasonal effects, CME occurrence, Iridium constellation orbit precession, and geomagnetic storms. We find a correlation with IMF BY ${B}_{Y}$, indicating that more current flows in the Northern Hemisphere during positive BY ${B}_{Y}$ and vice versa. We find that Block 1 data in 2010–2017 shows correlations with AL, AU, Kp $Kp$, PCN, and PCS index which indicate that the asymmetry is less pronounced when Dungey Cycle convection is stronger, but NEXT data in 2019–2024 do not show this. Plain Language Summary: Gigantic electric currents flow into and out of Earth's atmosphere in circles around the North and South Pole, and these currents are called Birkeland currents. Maps of Birkeland current in the Northern and Southern Hemispheres can be made by using data from the Iridium satellite constellation, which comprises 66 satellites in orbit around the Earth. We take the maps over a 12‐year period and calculate how much current is flowing over the course of a day, and then we calculate the asymmetry between the two hemispheres. We also use a computer model to estimate the same quantity. We find that there is more current flowing in the Northern Hemisphere and that this is not predicted by the model, but we also find that a new version of the data set disagrees with the older version in interesting ways. Key Points: NEXT v2 data show a ∼5× ${\sim} 5\times $ reduced hemispheric asymmetry compared to NEXT v1 but are still significantly stronger in the Northern HemisphereNEXT v1 data have approximately double the asymmetry seen by Swarm; NEXT v2 data have approximately half the asymmetry seen by SwarmThe power spectral density of the asymmetry has peaks at frequencies related to CMEs, geomagnetic storms, and Earth's orbit around the Sun [ABSTRACT FROM AUTHOR]
Copyright of Journal of Geophysical Research. Space Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: AMPERE Observations of the Asymmetry Toward Stronger Birkeland Currents in the Northern Hemisphere.
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  Data: <searchLink fieldCode="AR" term="%22Coxon%2C+John+C%2E%22">Coxon, John C.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> work@johncoxon.co.uk</i><br /><searchLink fieldCode="AR" term="%22Vines%2C+Sarah+K%2E%22">Vines, Sarah K.</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Mo%2C+Wenli%22">Mo, Wenli</searchLink><relatesTo>3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Townson%2C+Matthew+J%2E%22">Townson, Matthew J.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Watt%2C+Clare+E%2E+J%2E%22">Watt, Clare E. J.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Rae%2C+I%2E+Jonathan%22">Rae, I. Jonathan</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Bloomfield%2C+D%2E+Shaun%22">Bloomfield, D. Shaun</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Smith%2C+Andrew+W%2E%22">Smith, Andrew W.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Milan%2C+Stephen+E%2E%22">Milan, Stephen E.</searchLink><relatesTo>4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Anderson%2C+Brian+J%2E%22">Anderson, Brian J.</searchLink><relatesTo>3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Patrick%2C+Atlas+M%2E%22">Patrick, Atlas M.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Hasler%2C+Maria+C%2E%22">Hasler, Maria C.</searchLink><relatesTo>1</relatesTo> (AUTHOR)
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  Data: <searchLink fieldCode="JN" term="%22Journal+of+Geophysical+Research%2E+Space+Physics%22">Journal of Geophysical Research. Space Physics</searchLink>. May2026, Vol. 131 Issue 5, p1-22. 22p.
– Name: Subject
  Label: Subject Terms
  Group: Su
  Data: *<searchLink fieldCode="DE" term="%22Magnetic+storms%22">Magnetic storms</searchLink><br /><searchLink fieldCode="DE" term="%22Electric+currents%22">Electric currents</searchLink><br /><searchLink fieldCode="DE" term="%22Artificial+satellites%22">Artificial satellites</searchLink><br /><searchLink fieldCode="DE" term="%22Interplanetary+magnetic+fields%22">Interplanetary magnetic fields</searchLink><br /><searchLink fieldCode="DE" term="%22Data+pipelining%22">Data pipelining</searchLink><br /><searchLink fieldCode="DE" term="%22Time-frequency+analysis%22">Time-frequency analysis</searchLink><br /><searchLink fieldCode="DE" term="%22Scientific+experimentation%22">Scientific experimentation</searchLink>
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  Label: Geographic Terms
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  Data: <searchLink fieldCode="DE" term="%22Northern+Hemisphere%22">Northern Hemisphere</searchLink><br /><searchLink fieldCode="DE" term="%22Southern+Hemisphere%22">Southern Hemisphere</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: We quantify the asymmetry between the Birkeland currents (also known as field‐aligned currents) in the Northern and Southern Hemispheres. We use data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) in 2010–2024 inclusive for both hemispheres, compute the observed asymmetry, and then subtract the modeled asymmetry. We use Block 1 data (based on the original Iridium constellation) and NEXT data (based on Iridium‐NEXT spacecraft), and compare the effect of changing the data processing pipeline on the latter (yielding NEXT v1 and NEXT v2 subdatasets). We find that the asymmetry is significantly smaller in NEXT v2 data (4±2%) $(4\pm 2\%)$ than in Block 1 (21±2%) $(21\pm 2\%)$ or NEXT v1 data (19±3%) $(19\pm 3\%)$. The previously reported asymmetry seen in Swarm is ∼12% ${\sim} 12\%$, indicating that the new data processing pipeline goes from approximately twice the Swarm asymmetry to approximately half. This may indicate that the new AMPERE processing pipeline overestimates the amount of current flowing in the Southern Hemisphere, whereas the old one underestimated this quantity. We use frequency analysis to find that the asymmetry varies with frequencies corresponding to seasonal effects, CME occurrence, Iridium constellation orbit precession, and geomagnetic storms. We find a correlation with IMF BY ${B}_{Y}$, indicating that more current flows in the Northern Hemisphere during positive BY ${B}_{Y}$ and vice versa. We find that Block 1 data in 2010–2017 shows correlations with AL, AU, Kp $Kp$, PCN, and PCS index which indicate that the asymmetry is less pronounced when Dungey Cycle convection is stronger, but NEXT data in 2019–2024 do not show this. Plain Language Summary: Gigantic electric currents flow into and out of Earth's atmosphere in circles around the North and South Pole, and these currents are called Birkeland currents. Maps of Birkeland current in the Northern and Southern Hemispheres can be made by using data from the Iridium satellite constellation, which comprises 66 satellites in orbit around the Earth. We take the maps over a 12‐year period and calculate how much current is flowing over the course of a day, and then we calculate the asymmetry between the two hemispheres. We also use a computer model to estimate the same quantity. We find that there is more current flowing in the Northern Hemisphere and that this is not predicted by the model, but we also find that a new version of the data set disagrees with the older version in interesting ways. Key Points: NEXT v2 data show a ∼5× ${\sim} 5\times $ reduced hemispheric asymmetry compared to NEXT v1 but are still significantly stronger in the Northern HemisphereNEXT v1 data have approximately double the asymmetry seen by Swarm; NEXT v2 data have approximately half the asymmetry seen by SwarmThe power spectral density of the asymmetry has peaks at frequencies related to CMEs, geomagnetic storms, and Earth's orbit around the Sun [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Journal of Geophysical Research. Space Physics is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
PLink https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=8gh&AN=194052532
RecordInfo BibRecord:
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    Identifiers:
      – Type: doi
        Value: 10.1029/2026JA035162
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 22
        StartPage: 1
    Subjects:
      – SubjectFull: Magnetic storms
        Type: general
      – SubjectFull: Electric currents
        Type: general
      – SubjectFull: Artificial satellites
        Type: general
      – SubjectFull: Interplanetary magnetic fields
        Type: general
      – SubjectFull: Data pipelining
        Type: general
      – SubjectFull: Time-frequency analysis
        Type: general
      – SubjectFull: Scientific experimentation
        Type: general
      – SubjectFull: Northern Hemisphere
        Type: general
      – SubjectFull: Southern Hemisphere
        Type: general
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      – TitleFull: AMPERE Observations of the Asymmetry Toward Stronger Birkeland Currents in the Northern Hemisphere.
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            – D: 01
              M: 05
              Text: May2026
              Type: published
              Y: 2026
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