Topic
Electrojet
About: Electrojet is a research topic. Over the lifetime, 1904 publications have been published within this topic receiving 51614 citations.
Papers published on a yearly basis
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Papers
TL;DR: The spatial distribution and magnitudes of field-aligned currents at 800-km altitude over northern high latitudes were determined from Triad magnetometer data recorded at College, Alaska, during the period from July 1973 to October 1974 as mentioned in this paper.
Abstract: The spatial distribution and magnitudes of field-aligned currents at 800-km altitude over northern high latitudes were determined from Triad magnetometer data recorded at College, Alaska, during the period from July 1973 to October 1974. The characteristics that were determined include the following: (1) Large-scale field-aligned currents are concentrated in two principal areas encircling the geomagnetic pole: region 1, located near the poleward part of the field-aligned current region; and region 2, located near the equatorward part. (2) In region 1 during moderately disturbed conditions (2− ≤ Kp ≤ 4+) the largest current densities occur on the forenoon sector, with currents flowing into the ionosphere (with a peak value of ∼2 µA/m² between 0700 and 0800 MLT), and in the afternoon sector, with currents flowing away from the ionosphere (with a peak value of ∼1.8 µA/m² between 1500 and 1600 MLT). These areas of maximum current density in region 1 are approximately coincident with the location of the foci of the Sqp current system. (3) In region 2 for 2− ≤ Kp ≤ 4+ the largest current densities occur on the night side where auroral electrojets are usually most active, namely, in the evening to premidnight sector, with currents flowing into the ionosphere (with a peak value of ∼ 1 µA/m² between 2100 and 2300 MLT), and in the midnight to morning sector, with currents flowing away from the ionosphere (with a peak value of ∼ 1.3 µA/m² between 0200 and 0300 MLT). (4) The currents in region 1 are statistically larger than the currents in region 2 at all local times except for the sector near midnight (∼2100–0300 MLT), where the region 2 currents are comparable to or slightly larger than the region 1 currents. (5) The region 2 currents in the midnight to morning sector are correlated with the intensity of the westward electrojet, and the region 2 currents in the evening to premidnight sector are correlated with the intensity of the eastward electrojet. (6) The region 1 currents appear to persist, especially on the day side, even during very low geomagnetic activity with a value of current density ≳0.6 µA/m² for Kp = 0. We suggest that the magnetosphere-ionosphere current system which contains field-aligned currents consists of two distinct parts: a permanent part with field-aligned currents in region 1 and the other part having field-aligned currents in region 2, which is an important element of the auroral electrojets.
1,190 citations
TL;DR: Auroral electrojet index and universal time variations, discussing polar disturbance statistics are discussed in this paper, where the authors also discuss the effect of time variations on polar disturbances and their correlation.
Abstract: Auroral electrojet index and universal time variations, discussing polar disturbance statistics
899 citations
TL;DR: In this paper, a theory of the two-stream ion wave instability in a plasma is developed that takes into account both the effect of collisions of the ions and electrons with neutral particles and the presence of a uniform magnetic field.
Abstract: A theory of the two-stream ion wave instability in a plasma is developed that takes into account both the effect of collisions of the ions and electrons with neutral particles and the presence of a uniform magnetic field. Applying the results to the ionosphere, it is found that irregularities of ionization density should arise spontaneously in regions in which a sufficiently strong current is flowing normal to the magnetic field lines. These irregularities will be strongly aligned with the magnetic field and may have a wide range of wavelengths. The various predictions of the theory are in agreement with the observed characteristics of certain field-aligned irregularities found in the equatorial ionosphere that are associated with the equatorial electrojet. Similar irregularities often appear in the polar ionosphere during auroral displays; it seems very likely that these are caused by the auroral electrojet. (auth)
687 citations
TL;DR: The characteristics of field-aligned currents at an altitude of 800 km in the dayside highlatitude region over the northern hemisphere were determined from the Triad satellite magnetometer data recorded at College, Alaska, from January 1973 to October 1974 as mentioned in this paper.
Abstract: The characteristics of field-aligned currents at an altitude of 800 km in the dayside high-latitude region over the northern hemisphere were determined from the Triad satellite magnetometer data recorded at College, Alaska, from January 1973 to October 1974. The field-aligned currents discussed here are located poleward of the large-scale field-aligned currents reported earlier and referred to as 'region 1 field-aligned currents' by the authors (Iijima and Potemra, 1976). These high-latitude field-aligned currents are most often observed in the dayside sector between 0930 and 1430 MLT and are statistically distributed between 78/sup 0/ and 80/sup 0/ invariant latitude during weakly disturbed conditions as indicated by westward electrojet activity (abs. value of AL < 100..gamma..). Although these high-latitude field-aligned currents show complicated variations, they generally flow away from the ionosphere in the forenoon hours (0930--1200 MLT) and into the ionosphere in the afternoon hours (1200--1430 MLT). These flow directions are opposite to the quasi-permanent region 1 field-aligned currents related to the S/sub q//sup p/ currents previously discussed by the authors. The directions and spatial distribution of these field-aligned currents are consistent with the antisolarward equivalent ionospheric current near 1200 MLT deduced from simultaneous ground-based magnetograms at approx.81/sup 0/ invariant latitude. The intensitymore » of these high-latitude field-aligned currents increases as the interplanetary magnetic field increases in the southward direction. These field-aligned currents are located within the region associated with the dayside magnetospheric cusp, and their relationship to geomagnetic activity, especially interplanetary magnetic field variations, suggests that they may play an important role in the coupling between the interplanetary medium and the magnetosphere. (AIP)« less
687 citations
TL;DR: In this article, the authors used magnetometer chains collaborating with SuperMAG to derive SME, a generalization of the auroral electrojet indices calculated from 100 or more sites instead of the 12 used in the official AU(12) − AL(12), and investigated how these various indices relate to nightside auroral power by using both particle (DMSP) and image (Polar Ultraviolet Imager (UVI)) data.
Abstract: [1] We use magnetometer chains collaborating with SuperMAG to derive SME, a generalization of the auroral electrojet indices calculated from 100 or more sites instead of the 12 used in the official auroral electrojet indices, AE(12) = AU(12) − AL(12). We investigate how these various indices relate to nightside auroral power by using both particle (DMSP) and image (Polar Ultraviolet Imager (UVI)) data. The best correlation is between SME and total nightside auroral power, namely, r = 0.86. Hence, nearly 3/4 of the minute-by-minute variance in nightside power can be determined by SME alone. Interestingly, although the geophysical meaning of AE(12) has sometimes been challenged, we show that even that index correlates at the r = 0.81 level, or 2/3 of the variance, in nightside power. Most auroral power stems from the diffuse aurora, with a linear relationship between the auroral electrojet indices and nightside diffuse power. Thus, SME has a clear geophysical meaning: It samples the thermal portion of the magnetotail plasma sheet. We study how well SML (the generalization of AL) identifies substorms in two types of tests. The first is a comparison with a set of 1081 substorms determined from Polar UVI in 1997–1998, and the second is the use of DMSP particle precipitation data for superposed epoch analysis. The same algorithm applied to SML is much more likely (about 50% more likely) to identify an onset seen by UVI than is AL(12). Even when both indices can be used to identify onsets, the median delay after imaging onset until the AL indicator is less than half using SML (about 4 min versus 8 min). There are 10,719 onsets in the SML data between 1 January 1997 and 31 December 2002, of which 5084 are isolated. Isolated SML onsets behave almost identically to the onsets determined by global imagers. Specifically, they represent the same sharp spike in auroral power, which is most pronounced in broadband (wave) precipitation, with the same duration and subsequent recovery. However, recurrent substorms (those following less than 2 h after a previous onset) rise from a higher baseline by a smaller percentage but with the same absolute change in auroral power, thus reaching a higher peak power.
592 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2025 | 15 |
| 2024 | 41 |
| 2023 | 56 |
| 2022 | 75 |
| 2021 | 22 |
| 2020 | 23 |