The Joule heat production rate and the particle energy injection rate as a function of the geomagnetic indices AE and AL

Ahn, B.‐H.; Akasofu, S.‐I.; Kamide, Y.

doi:10.1029/ja088ia08p06275

Cited by 183 publications

(226 citation statements)

References 21 publications

Supporting

Mentioning

211

Contrasting

Order By: Relevance

“…Finding similar simple expressions for hemispheric auroral precipitation power has appeared to be challenging, because different dependencies are achieved from different measurement technologies. The empirical rule from space-based X-ray imager data by Østgaard et al (2002) yield a larger power value for a given AE than the model by Spiro et al (1982) from satellite precipitation data, which again is larger than the estimate based on incoherent scatter radar measurements (Ahn et al 1983). …”

Section: The Official Ae-indicesmentioning

confidence: 57%

On the Usage of Geomagnetic Indices for Data Selection in Internal Field Modelling

et al. 2016

View full text Add to dashboard Cite

We present a review on geomagnetic indices describing global geomagnetic storm activity (Kp, am, Dst and dDst/dt) and on indices designed to characterize high latitude currents and substorms (PC and AE-indices and their variants). The focus in our discussion is in main field modelling, where indices are primarily used in data selection criteria for weak magnetic activity. The publicly available extensive data bases of index values are used to derive joint conditional Probability Distribution Functions (PDFs) for different pairs of indices in order to investigate their mutual consistency in describing quiet conditions. This exercise reveals that Dst and its time derivative yield a similar picture as Kp on quiet conditions as determined with the conditions typically used in internal field modelling. Magnetic quiescense at high latitudes is typically searched with the help of Merging Electric Field (MEF) as derived from solar wind observations. We use in our PDF analysis the PC-index as a proxy for MEF and estimate the magnetic activity level at auroral latitudes with the AL-index. With these boundary conditions we conclude that the quiet time conditions that are typically used in main field modelling (P C < 0.8, Kp < 2 and |Dst| < 30 nT ) correspond to weak auroral electrojet activity quite well: Standard size substorms are unlikely to happen, but other type of activations

show abstract

Section: The Official Ae-indicesmentioning

confidence: 57%

On the Usage of Geomagnetic Indices for Data Selection in Internal Field Modelling

et al. 2016

View full text Add to dashboard Cite

show abstract

“…The main dissipation is the Joule heating in the ionosphere; it is computed on the basis of the ionospheric current distribution. The other dissipation process, the ionospheric ionization, is about 10% of the Joule dissipation (Ahn et al 1983). In this calculation, the resistivity (or conductivity) of the ionosphere was determined on the basis of incoherent scatter radar data (the electron density) and the simultaneous ground-based magnetometer data in Alaska.…”

Section: Joule Heat Production Ratementioning

confidence: 99%

“…In order to confirm this method, satellite images of the auroral distribution was used in inferring the conductivity Fig. 24 Variations of the Joule heat production in the ionosphere during a substorm time, including a quiet period prior to expansion onset (Ahn et al 1983) …”

Section: Joule Heat Production Ratementioning

confidence: 99%

Auroral Substorms: Search for Processes Causing the Expansion Phase in Terms of the Electric Current Approach

Akasofu

2017

Space Sci Rev

View full text Add to dashboard Cite

Auroral substorms are mostly manifestations of dissipative processes of electromagnetic energy. Thus, we consider a sequence of processes consisting of the power supply (dynamo), transmission (currents/circuits) and dissipations (auroral substorms-the end product), namely the electric current line approach. This work confirms quantitatively that after accumulating magnetic energy during the growth phase, the magnetosphere unloads the stored magnetic energy impulsively in order to stabilize itself. This work is based on our result that substorms are caused by two current systems, the directly driven (DD) current system and the unloading system (UL). The most crucial finding in this work is the identification of the UL (unloading) current system which is responsible for the expansion phase. A very tentative sequence of the processes leading to the expansion phase (the generation of the UL current system) is suggested for future discussions.(1) The solar wind-magnetosphere dynamo enhances significantly the plasma sheet current when its power is increased above 10 18 erg/s (10 11 w). (2) The magnetosphere accumulates magnetic energy during the growth phase, because the ionosphere cannot dissipate the increasing power because of a low conductivity. As a result, the magnetosphere is inflated, accumulating magnetic energy. (3) When the power reaches 3-5 × 10 18 erg/s (3-5 × 10 11 w) for about one hour and the stored magnetic energy reaches 3-5 × 10 22 ergs (10 15 J), the magnetosphere begins to develop perturbations caused by current instabilities (the current density ≈3 × 10 −12 A/cm 2 and the total current ≈10 6 A at 6 Re). As a result, the plasma sheet current is reduced. (4) The magnetosphere is thus deflated. The current reduction causes ∂B/∂t > 0 in the main body of the magnetosphere, producing an earthward electric field. As it is transmitted to the ionosphere, it becomes equatorward-directed electric field which drives both Pedersen and Hall currents and thus generates the UL current system. (6) The substorm intensity depends on the location of the energy accumulation (between 4 Re and 10 Re), the closer the location to the earth, the more intense substorms becomes, because the capacity of holding the energy is higher at closer distances. The convective flow toward the earth brings both the ring current and the plasma sheet current closer when the dynamo power becomes higher.This proposed sequence is not necessarily new. Individual processes involved have been considered by many, but the electric current approach can bring them together systematically and provide some new quantitative insights.

show abstract

“…Near midnight, hj/he•½c is about 2 and rises slightly toward dawn to about 3. In the late afternoon, hj/helec is 10-15, and UARS/PEM' 1993 Day 308 It is customary to evaluate the relative contributions of particle and Joule heating in the ionosphere in terms of the ratio of their hemispheric dissipation rates, Hj/Hdec [e.g., Ahn et al, 1983]. Using statistical models of ionospheric conductivity to infer particle precipitation input and an extensive ground magnetometer network to infer the Pedersen currents, Ahn et al [ 1983] estimated Hs/Helec to be close to 3.…”

Section: Electron Energy Depositionmentioning

confidence: 99%

“…The global energy input to regions of the high-latitude atmosphere provided by Joule dissipation of electric currents is thought to exceed the input due to energetic particle precipitation by about a factor of 3 [Ahn et al, 1983;Lu et al, 1996]. This disparity persists during major magnetic storms for which the Joule heating rate can surpass the solar EUV input at ionospheric altitudes [e.g., Cooper et al, 1995].…”

Section: Introductionmentioning

confidence: 99%

UARS observations of Birkeland currents and Joule heating rates for the November 4, 1993, storm

Anderson¹,

Gary²,

Potemra³

et al. 1998

J. Geophys. Res.

View full text Add to dashboard Cite

Abstract. Magnetic field and particle observations from the Upper Atmosphere Research Satellite particle environment monitor (UARS/PEM) are used to estimate field-aligned currents, electron precipitation energy flux, ionospheric conductivities, and Joule heating rates during the main phase of the November 4, 1993, geomagnetic storm. From 0300 to 1200 UT on November 4 the auroral oval expanded equatorward of 65 ø magnetic latitude (MLAT), and UARS encountered the polar cap on seven consecutive passes during the storm main phase. These passes provide data appropriate to determine field-aligned currents and estimate ionospheric Joule heating. For this storm, UARS sampled the midnight to dawn sector in the northern hemisphere and the noon to dusk sector in the southern hemisphere. The maximum net currents on the dayside and nightside are comparable and reach 1 A/m for several hours. The average Joule heating rates are comparable at midnight, early morning, and noon, where they are 9.2, 6.6, and 7.7 GW/h, respectively, but have a strong peak in the late afternoon, where they are 25.6 GW/h. In contrast, the electron precipitation energy deposition is highest near midnight at 5.6 GW/h but drops to less than half this level to 2.4 GW/h and 1.9 GW/h in the early morning and at dusk, respectively, but is very small near noon, only 0.24 GW/h. The Joule to particle energy deposition rate ratio thus varies by roughly an order of magnitude with local time, being over 40 near noon, about 20 at dusk, 3 near dawn, and 2 at midnight. The hemispherical Joule and electron precipitation heating rates, Hj and Helec, are estimated to have been 290 GW and 50 GW, respectively, giving Hj/Helec = 4.5 and Hj + Helec = 340 GW. Differences between these averages and assimilative mapping of ionospheric dynamics (AMIE) results, Hj = 200 GW and He•ec = 80 GW, reflect time variability during the storm and are largely resolved when AMIE results only at the times of UARS passes are considered.

show abstract

The Joule heat production rate and the particle energy injection rate as a function of the geomagnetic indices AE and AL

Abstract: indices. Our present estimates give t•e following relationshi•s: Uj • 2.3 times 10 v ß AE, U A • 0.6 times 10 8 ß AE and U I = 2.9 times 108 ß AE; Uj -3.0 times 108 ß AL U -0.8 times 108 ß AL, and U I -3.8 times 10 • -AAL. Injection Rate

Cited by 183 publications

References 21 publications

On the Usage of Geomagnetic Indices for Data Selection in Internal Field Modelling

On the Usage of Geomagnetic Indices for Data Selection in Internal Field Modelling

Auroral Substorms: Search for Processes Causing the Expansion Phase in Terms of the Electric Current Approach

UARS observations of Birkeland currents and Joule heating rates for the November 4, 1993, storm

Contact Info

Product

Resources

About